Bio Final

3-1 Macromolecules

Carbon Based Life

• All living things on Earth made up of molecules based on carbon

  • Carbon can bond with many elements to form molecules of life

    • These include hydrogen, oxygen, nitrogen, and phosphorus

  • Carbon atoms able to form long chains of carbon-carbon bonds

    • Due to carbon/s ability to bond with other carbon atoms, it has ability to form millions of different large and complex structures

Macromolecules

• Macromolecules: Large organic compounds that make up living cells

• Forming Macromolecules:

  • Most macromolecules (ex: carbohydrates, nucleic acids, and proteins) formed through process called polymerization

    • Polymerization: Process in which large compounds are built by joining smaller compounds together

      • Monomers: The smaller compounds

      • Polymers: The large compounds

Carbohydrates

• Carbohydrates are the main source of energy used by living things

• Carbohydrates: Compounds made from carbon, hydrogen, and oxygen atoms. (Quick short bursts of energy that come from sugar)

  • Breakdown of sugars by mitochondria serve as main source of energy for cellular activity

    • Animals store excess sugar in polysaccharide called glycogen. When they need sugar they break the glycogen molecules down

    • Plants store excess sugar in polysaccharide called starch

    • Polysaccharides: long chains of carbohydrate molecules

• Plants and some other organisms use carbohydrates for structural purposes

  • EX: Plants using cellulose, a polysaccharide as structural component

  • EX: Fungi, insects, and crustaceans using another polysaccharide, chitin, as structural component in bodies

• Carbohydrate Monomers and Polymers

  • The monomers of carbohydrates are monosaccharides or single sugars

    • EX: Glucose

  • Polysaccharides are large macromolecule carbohydrates

Nucleic Acids

• Nucleic acids: Store and transmit genetic information

  • Two kinds: DNA and RNA

• Nucleic acids are macromolecules that contain carbon, hydrogen, oxygen, nitrogen, and phosphorous

• Nucleic Acid Monomers and Polymers

  • The individual monomers of nucleic acids are nucleotides

    • Each nucleotide has 3 parts: a nitrogenous base, a 5-carbon sugar, and a phosphate group

  • Nucleic acids (DNA & RNA) are large macromolecules assembled from nucleotides

Proteins

•  Proteins: macromolecules that contain carbon, hydrogen, oxygen, and nitrogen

  • Proteins serve diverse array of functions, like forming important cellular or body structures, fighting disease, transport of materials, regulation of cell processes, and acting as enzymes

• Protein Monomers and Polymers

  • Monomers that make up proteins are amino acids

  • When joined together, amino acids form polypeptides, which intern interact with other polypeptides to form proteins

Enzymes:

• Enzymes: Proteins that can speed up the rate of a chemical reaction

  • Living organisms require enzymes to perform chemical reactions that make life possible

  • Changes in temperature, pH, and presence of regulatory molecules can affect rate of enzyme activity

Lipids

• Lipids: The only macromolecules that are not polymer

• Not considered polymers because they are made up of two separate sub-units

  • Can be used to story energy and act as structural components of organisms where they form biological membranes or act as waterproof body coverings

  • Steroids are lipids that serve as chemical messengers

• Lipids are generally made from mostly carbon and hydrogen atoms

  • Lipids consist of two main components: a glycerol and fatty acid

3-2 Enzymes

• Enzymes are proteins that can speed up the rate of a chemical reaction

  • Also called catalysts because they catalyze (speed up) a chemical reaction

  • These chemical reactions used to build and break molecules

    • Sum of all these chemical reactions in a cell called metabolism

• Enzymes are not changed or used up in chemical reaction

Enzyme Function

• Enzymes lower a reaction’s activation energy

  • Activation Energy: The amount of energy needed for a reaction to begin

Steps in a Chemical Reaction

1. The enzyme will bind to a reactant molecule at the enzyme's active site.

Substrate: Reactant molecule

2. When the substrate is bound to the enzyme, it forms the enzyme-substrate complex

3. The chemical reaction occurs, creating the product

4. The product is released from the enzyme’s active site

Enzyme Specificity

• Enzymes are specific for the substance they bind to

• EX: Lock and key - an enzyme's active site is structured to match the specific substrate it binds to

Enzyme Changes

• Changes in temperature, pH, and presence of regulatory molecules can affect rate of enzyme activity 

  • When favorable conditions change, enzyme can be denatured

    • When enzyme is denatured, its shape has changed and it can no longer function correctly to catalyze chemical reactions

  • Enzymes do not die since they are not living, but it can restructure itself and function again

3-3 Energy and Life

Intro

• Energy: the ability to do work

  • Comes in many forms

    • EX: Light, heat, and electricity 

  • Can be stored in chemical bonds

    • When bonds are broken, energy stored in the bonds are released and the atoms reform new, lower-energy bonds

• Life is dependent on ability to obtain and use energy

Chemical Energy and ATP

• ATP: One of the most important compounds that cells use to store and release energy

  • Stands for adenosine triphosphate

  • Consists of the nitrogenous base adenine, a 5-carbon sugar called ribose, and three phosphate groups

Chemical Energy and ATP

• ATP can easily be release and store energy by breaking and forming bonds between its phosphate groups

  • Energy is stored in the bonds connecting the phosphate groups

  • ATP’s ability to store and release energy comes from breaking bond between the 2nd and 3rd phosphate groups

    • When the third phosphate group is broken off the ATP molecule, energy is release and the ATP molecule becomes ADP (Adenosine diphosphate)

    • When cell has energy available it can use that energy to reattach a phosphate group to an ADP molecule, changing it back to ATP

• When there are three phosphate groups energy is stored (ATP) and when there are two (ADP) energy has been released.

Cells and Energy

• Cells use ATP to power several important processes:

  • Active transport

  • Movement 

  • Bioluminescence

  • Protein Synthesis

Drawbacks of ATP

• ATP is important and useful for cells, but it’s not a good molecule for storing large amounts of energy long term

  • Cells use molecules like glucose to store energy in the long term because they are more stable and store more energy

    • The energy in a molecule of glucose can be converted to ATP

Heterotrophs and Autotrophs

• All living things must take in energy to power their life processes

  • Heterotrophs: Must consume other living things in order to obtain energy

  • Autotrophs: Organisms that are able to make their own food

    • Most autotrophs use photosynthesis to convert energy from sun into high-energy carbohydrates

      • In process of photosynthesis, plants convert energy of sunlight into chemical energy stored in bonds of carbohydrates

3-4 Photosynthesis

Intro

• Photosynthesis: Process by which organisms, like plants and other autotrophs, capture light energy and use it to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrate such as sugars and starches

  • Almost all living things on Earth depend on the process of photosynthesis

Chlorophyll and Carotenoids

• Chlorophyll: The primary pigment used by most plants to capture sunlight 

  • Pigment: A light absorbing molecule

• Carotenoids: Red, orange, and yellow pigments. The color imparted by carotenoids is usually only visible when chlorophyll breaks down or is absent

  • Carotenoids CAN absorb sunlight, but chlorophyll mainly does

Chloroplasts and Chlorophyll

• Chloroplasts: Organelles found in the cells of photosynthetic eukaryotes that capture energy from the sun and convert it into chemical energy

• Parts of the Chloroplast:

  • Thylakoids: Saclike photosynthetic membranes found inside chloroplasts

    • Granum: A stack of thylakoids

  • Stroma: The fluid portion of the chloroplast outside the thylakoids

Energy Collection

• Chlorophyll absorbs visible light and transfer the energy in the light to electrons in the chlorophyll molecule (what exists in the chloroplasts to take in light energy)

• The rest of the process of photosynthesis relies on making use of these high-energy electrons to make carbohydrates

Energy Collections

• High energy electrons: High energy electrons that are very reactive and require carrier molecules to transfer them and their energy to another molecule

  • Electron
    carrier: Compound that can accept a pair of high-energy electrons and transfer them and most of their energy to another molecule

    • NADP+: A carrier molecule able to hold two high-energy electrons along with a hydrogen atom 

    • When NADP+ does this,, it is converted to NADPH

      • When you see the +, that means the carrier is empty. When it is full (holding onto two electrons), it is converted to NADPH

An Overview of Photosynthesis

The process of Photosynthesis

• Light dependent reactions: The first set of reactions in the process of photosynthesis

  • These reactions require direct involvement of light and light-absorbing pigments

  • Take place in thylakoid membranes of chloroplasts

    • Thylakoids contain clusters of chlorophyll and proteins known as photosystems

• Photosystems: Absorb sunlight and transfer high-energy electrons to an electron transport chain

  • Electron transport chain: Series of carrier proteins that move high energy electron during the process of making ATP

    • The electrons sent through the electron transport chain come from breaking apart water molecules

• Light-dependent reactions use energy from sunlight to break up water molecules 

  • They produce oxygen and convert ADP and NADP+ into the energy carriers ATP and NADPH

• The light-independent reactions (The Calvin cycle)

  • Cycle that makes use of several different molecules that are regenerated o that the cycle can continue

• Light-independent reactions: Complete the process of photosynthesis and produce the carbohydrates

  • These reactions use the energy in ATP and NADPH as well as carbon dioxide to build carbohydrates

    • During light-independent reactions, the ATP and NADPH produced in the light-dependent reactions are used to produce high-energy sugars from carbon dioxide 

      • Carbon dioxide used in Calvin cycle comes from atmosphere

  • The light-independent reactions take place in the stroma

3-5 Cellular Respiration

Cellular Respiration

• Cellular respiration: Process that releases energy from food in presence of oxygen

  • Can be sumymarized by the following equation

• Oxygen

  • Aerobic: The pathways (or steps) in cellular respiration that require oxygen

  • Anaerobic: The pathways (or steps) in cellular respiration that do not require oxygen

Comparing Cellular Respiration & Photosynthesis

• Photosynthesis and cellular respiration can be seen as opposite processes

  • Cellular respiration removes oxygen from atmosphere and photosynthesis puts it back

  • Photosynthesis removes carbon dioxide from atmosphere and cellular respiration puts it back 

Stages of Cellular Respiration

Occurs in three stages

1. Glycolysis 

2. The Krebs cycle

3. The electron transport chain

Glycolysis

• Glycolysis: The first stage in cellular respiration, takes place in the cytoplasm

  • During glycolysis, 1 molecule of glucose (a 6-carbon compound) is broken into 2 molecules of pyruvic acid ( a 3-carbon compound)

  • Glycolysis also produces 2 NADH molecules that are sent to the electron transport chain

  • NADH: Full electron carrier, anytime there is an H it’s full, and you can differentiate between NADPH because there is no P meaning it's not photosynthesis

  • The goals of glycolysis are the electron carriers NADH and pyruvic acid 

• The ATP of Glycolysis

  • In order to break apart the glucose molecule, th cell must spend 2 ATP molecules

  • The process of glycolysis produces 4 ATP molecules

  • The cell realizes a net gain of 2 ATP molecules 

The Krebs Cycle

• Krebs cycle: The second stage of cellular respiration, takes place in the mitochondria

  • During Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy releasing steps

  • Krebs cycle also produces 8 molecules of NADH and 2 molecules of FADH2 (both are full)  that are sent to the electron transport chain

• The ATP Math of the Krebs Cycle

  • Krebs cycle produces one molecule of ATP for each molecule of pyruvic acid that enters the cycle

    • One molecule of glucose produces 2 molecules of pyruvic acid, thus 2 ATP molecules are produced

The Electron Transport Chain

• Electron transport chain: Uses high energy electrons from glycolysis and the Krebs cycle to convert ADP to ATP

  • High-energy electrons are transferred to the electron transport chain by the carrier molecules NADH and FADH

  • Electron transport chain is located in the inner membrane of the mitochondria

• The electron transport chain produces 32 molecules of ATP

• Purpose of ATP synthase is to catalyze the reaction of making ATP

Summary

• The process of cellular respiration (glycolysis, the Krebs cycle, and the electron transport chain) produce 36 ATP molecules from one molecule of glucose

  • This represents 36% of the total energy available in the glucose molecule, the remaining 64% is lost as heat

3-6 Cell Structure

Cell Structure

Two types of organisms: Prokaryotes and Eukaryotes

• Prokaryotes: Organisms made up of cells that do not have membrane-bound organelles

  • Two groups of prokaryotes, bacteria and archaea

    • Bacteria can be classified as harmful or helpful

      • Bacteria if it causes disease

    • Archaea are unique life form found to live in extreme environments

      • Archaea have been found in hydrothermal vents in ocean, and arctic ice

• Eukaryotes: Organisms made up of cells that have membrane-bound organelles

  • Three groups of eukaryotes are plants, animals, and fungi

• Prokaryotic cells are simple in comparison to eukaryotic cells

Typically, they are single celled organisms

• Eukaryotes are much more complex than prokaryotes, and are multi-celled organisms

Cell Organization

• Eukaryotes and prokaryotes have distinct cell organization

  • Cells can be divided into two main sections: Nucleus/nucleoid and cytoplasm

  • Nucleus and nucleoid

    • In prokaryotic cells, there is no membrane bound nucleus. Instead DNA is stored in region called the nucleoid

    • In eukaryotic cells, there is a membrane bound nucleus. Nucleus stores nearly all of cell’s DNA and controls most of cell’s activity and hold instructions to make proteins

  • Cytoplasm

    • The cytoplasm is the inside of the cell

      • In prokaryotes, everything inside cell is located in cytoplasm because prokaryotes do not have membrane bound organelles

      • In eukaryotes, the majority of cells’ organelles are located in the cytoplasm

        • Organelles: Specialized structures that perform important cellular functions

Storage, Cleanup, and Support

• Eukaryotic cells have organelles responsible for storage, cleanup, and support

  • Vacuoles, lysosomes and cytoskeleton fulfill the roles of storage cleanup, and support in cell

  • Vacuoles and Vesicles

    • Vacuoles: Cellular organelles that store materials like water, salts, proteins, and carbohydrates

    • Vesicles: Smaller membrane enclosed structures that store and move materials between organelles

  • Lysosomes

    • Lysosomes: Small organelles that are filled with enzymes 

      • Enzymes contain in lysosomes break down lipids, carbohydrates, and proteins into small molecules that can be used by rest of cell

  • Cytoskeleton

    • Cytoskeleton: Network of protein filaments in a eukaryotic cell that gives the cell its shape and internal organization and is involved in movement

    • Microfilaments: Thread like structures that support the cell

      • Microfilaments also help cell move

    • Microtubules: Hollow structures that help to maintain cell shape

Cell Movement

• Prokaryotes have flagella and pili are protein-based filaments found on the outer surface of the cell to help prokaryotes move

Building Proteins

• Eukaryotes have organelles responsible for building proteins

  • Cells need to  build new molecules all the time, especially proteins, which catalyze chemical reactions and make up important structures in cell

  • Since proteins carry out many of essential functions in living things, big part of cell is devoted to their production and distribution

• Ribosomes

  • Ribosomes: Small particles of RNA and protein found throughout the cytoplasm in all cells that produce proteins

• Endoplasmic Reticulum:

  • Two types: smooth and rough

    • Endoplasmic reticulum is where lipid components of cell membrane are assembled, along with proteins and other materials that are exported from cell

• Rough endoplasmic reticulum

  • Portion of the ER involved in synthesis of proteins

    • Given this name because ribosomes are found in its surface

    • Newly made proteins leave these ribosomes and are inserted in the rough ER, where they may be chemically modified

• Smooth endoplasmic reticulum

  • Called smooth ER because ribosomes are not found on its surface

    • In many cells, smooth ER contains collections of enzymes that perform specialized tasks, including synthesis of membrane lipids and detoxification of drugs

• Golgi Apparatus

  • Golgi apparatus: Modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or release outside the cell

    • Proteins produced in rough ER move next into golgi apparatus, which appears as stack of flattened membranes 

    • The proteins are bundled into tiny vesicles that bud from the ER and carry them to the Golgi apparatus

Capturing and Releasing Energy

• Eukaryotes have organelles responsible for capturing energy and releasing energy

  • All living things require a source of energy. Most cells are powered by food molecules that are built using energy from sun

  • Chloroplasts and mitochondria both involved in energy conversion process within cell

• Chloroplasts

  • Chloroplasts: Capture energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis

• Mitochondria

  • Mitochondria: Convert the chemical energy stored in food into compounds that are more convenient for the cell to use

Cell Boundaries

• Eukaryotes and prokaryotes are made up of cells with important cell boundaries

  • Cell Walls

    • Main function of cell wall is to provide support and protection for cell

      • Prokaryotes, plants, algae, fungi, and have cell walls

      • Animal cells do not have cell walls

    • Cell walls lie outside the cell membrane and most are porous enough to allow water,, oxygen, carbon dioxide, and certain other substances to pass through easily

• Cell Membrane

  • Cell membrane regulates what enters and leaves the cell and also protects and supports the cell

    • The composition of nearly all cell membranes is a double-layered sheet called a lipid layer, which gives cell membranes a flexible structure and forms a strong barrier between the cell and its surroundings

3-7 Introduction to Homeostasis

The Cell as an Organism

• Homeostasis: The existence and maintenance of a relatively constant environment within the body of an organism

  • To maintain homeostasis, unicellular organisms grow, respond to the environment, transform energy and reproduce

• Unicellular organisms are capable of surviving and performing all life processes on their own

  • Can include both prokaryotes and eukaryotes

• In terms of number of individuals, single-celled organisms make up majority of life on Earth

Multicellular Life

• Cells in multicellular organisms are not capable of surviving on their own. They require the “services” of other cells in order to survive

  • Cells of multicellular organisms become specialized for particular tasks and communicate with one another to maintain homeostasis

    • Different cell types play different roles within the organism

• Specialized cells in multicellular organisms are organized into different levels

  • Cells make up tissues

    • Tissue: Similar group of cells that perform a particular function

  • Tissues make up organs

    • Organ: A group of tissues that work together to carry out complex function

  • Organs make up systems

    • Organ System: A group of organs that work together to carry out complex functions

• Cells in multicellular organisms must communicate to survive

  • This communication is accomplished by means of chemical signals passed from one cell to another

    • These signals can slow down or speed up cellular activity

  • Cells have receptors onto which signaling molecules can bind

Limits to Cell Size

• The larger a cell becomes, the more demands the cell places on its DNA

  • Additionally, a larger cell is less efficient in moving nutrients and waste materials across its cell membrane

• Information Overload

  • Living cells store satirical information in DNA

    • As a cell grows, that info is used to build the molecules needed for growth

    • As cell size increases, the demands on that information grow as well

  • If a cell were to grow without limit, an “information crisis” would occur

Division of the Cell

• Cell division: A cell splitting into two new “daughter cells” before becoming too large

  • Before cell division the cell copies all of its DNa

    • It then divides into two “daughter” cells. Each daughter cell receives a complete set of DNA

• Cell division reduces cell volume

Homeostasis

• Homeostasis: The existence and maintenance of a relatively constant environment within the body of an organism

  • Each cell in the body is surrounded by a small amount of fluid and the normal functioning of the cell is dependent on the maintenance of its environment within a narrow range of conditions

• Like all organisms, animals must maintain homeostasis by:

  • Gathering and responding to information

  • Obtaining and distributing oxygen and nutrients 

  • Collection and eliminating carbon dioxide and other wastes

  • Reproduction

Feedback

• Regulating homeostatic control system

  • Most homeostatic control systems function by negative feedback

    • In negative feedback, a buildup of the end product of the system shut the off

  • Some homeostatic control systems function by positive feedback

    • In positive feedback, a change in some variable that triggers mechanisms that amplify the change (Instead of going back to an end up point, were trying to get to and end goal then shut down the system)

Essential Functions Animals Perform to Survive

• One way homeostasis is maintained is by feedback inhibition

  • Negative Feedback: A system in which the product or result of a process limits the process itself

    • EX: Your house is getting too cold so your thermostat turns on the heat. As the heat warms the house, the thermostat turns the heater off.

    • Body’s thermostat works the same way

    • If you get too cold you shiver, using muscle activity to generate heat. If you get too hot you sweat, which helps you lose heat

    • 
      

• All body systems work together to maintain homeostasis

  • In most animals, repository and digestive system would be useless without circulatory systems to distribute oxygen and nutrients

  • The excretory system needs a circulatory system to collect carbon dioxide and nitrogenous wastes from body tissues and deliver them to the lungs and excretory organs

  • Muscles wouldn't work without a nervous system to direct them and a skeletal system to support them

4-1 Discovering DNA

Intro:

• Many discoveries in science come when scientists are looking for something completely different

  • Discovery of the structure of DNA is an example 

    • In 1928 scientist named Fredrick Grifffth was trying to figure out how bacteria make people sick

Bacterial Transformation

• Griffith’s Experiment:

  • Griffith isolated two different strains of the same bacterial species

    • He then injected mice with both strains of th bacteria

      • Mice that got the S strain got pneumonia and died

      • Mice that got the R strain stayed healthy

  • Girffith then heat killed the strain of bacteria and mixed it with R strain of bacteria and injected it into mice

    • The mice died of pneumonia

    • When he cultured the bacteria in their lung, he found live S strain bacteria

• Griffith’s Reasoning

  • Reasoned that some chemical factor that could change harmless bacteria into disease-causing bacteria was transferred from the heat-killed cells of the S strain into the live cells of the R strain

    • He called this Transformation

      • Transformation: Process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria

        • Concluded that the chemical factor was a gene

• Griffith’s work continued by a group of scientists led by Oswald Avery

  • Avery’s group wanted to determine which molecule was responsible for transformation

• Avery’’s Experiment:

  • In 1944, Avery extracted molecules from the heat killed bacteria and treated them with different chemicals designed to destroy different molecules including proteins, lipids, carbohydrates, and RNA

    • Even after all of these molecules were destroyed transformation still occurred

    • Avery then destroyed the DNA and transformation did not occur

  • Avery’s Conclusion: DNA was the transforming factor

• By observing bacterial transformation, Avery and other scientists discovered that the nucleic acid DNA stores and transmits genetic information from one generation of bacteria to the next

• The Hershey-Chase experiment

• Bacteriophage: A virus that infects bacteria

  • Bacteriophages work by injecting their genetic material into a bacterium. This DNA then hijacks the cell's machinery and produces more viruses. Eventually the cell bursts open and the new viruses burst out and go on to infect other bacteria

• In 1952, Hershey and Chase wanted to determine which part of the virus, the protein cat or DNA core infected the cell

  • Hershey and Chase grew viruses in cultures containing radioactive isotopes of phosphorus-32 (p-32) sulfur-35 (S-35)

• The two scientists mixed the marked viruses with bacterial cells, waited a few minutes for the viruses to inject their genetic material, and then tested the bacteria for radioactivity

  • Nearly all the radioactivity in the bacteria was from phosphorus P-32, the marker found in DNA

• Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein

  • Heryshey and Chase’s experiment with bacteriophage confirmed Avery’s results, convincing many scientists that DNA was the genetic material found in genes - not just living organisms.

Solving the structure of DNA

• Chargaff’s Rule

  • In 1949, Chargaff discovered that the percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA. The same thing is true for the other two nucleotides, guanine [G] and cytosine [C]

  • The observation that [A]=[T] and [G]=[C] became known as “Chargaff’s rules”

• In 1952, Rosalind Franklin used a technique called X-ray diffraction to get information about the structure of the DNA molecule

  • X-ray diffraction revealed an X-shaped pattern showing that the strands in DNA are twisted around each other like the coils of a spring

  • The angle of the X-shaped pattern suggested that there are two strands in the structure

  • Other clues suggest that the nitrogenous bases are near the center of the DNA molecule

• Work of Watson and Crick

  • In 1953, Watson and Crick built 3 dimensional models of DNA

  • The clues in Franklin's X-ray pattern enabled Watson and Crick to build a model that explained the specific structure and properties of DNA

  • Watson and Crick’s breakthrough discovery was the double helix model of DNA

    • In the double helix model two strands of nucleotide sequences are wound around each other - like a spiral staircase

The Double Helix Model

• The Double helix model explains Chargaff’s rule of base pairing and how the two strands of DNa are held together

  • In the double-helix model, the two strand of DNA are “antiparallel”- they run in opposite directions

    • This arrangement enables the nitrogenous bases on both strands to come into contact at the center of the molecule

• Nitrogenous bases are held together by hydrogen bonds

  • Hydrogen bonds are relatively weak chemical forces that allow the two strands of helix to separate

    • The ability of the two strands to separate is critical to DNA’s functions

• Watson and Crick discovered that bases pair in a specific way.

  • The hydrogen bonds needed to hold the nucleotides together only form in specific ways

    • Adenine will only pair with Thymine

    • Cytosine will only pair with Guanine

  • Base pairing is the principle that bonds DNA can form only between adenine and thymine and between cytosine and guanine

Pulse-Chase Primer: The Meselson-Stahl Experiment

• In the 1950s, James Watson and Francis Crick suggested a mechanism for the replication of DNA, which they called the “Semiconservative model of Replication”

  • During replication, each of the two strands of DNA would act as a template for the synthesis of a new strand. The two new DNA molecules would consist of one strand from the original molecule and a newly synthesized strand

  • At the time, scientists were considering three possible replication models

    • Conservative replication

    • Semiconservative replication

    • Dispersive replication

  • In 1958, Matthew Meselson and Franklin Sthal conducted their now-famous pulse-chase experiment to determine which of these three models was correct

  • Their experiment demonstrated that DNA goes through semiconservative replication

4-2 The Structure and Function of DNA

The Components of DNA

• DNA: A nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds

  • Nucleotides are the building blocks of nucleic acids

• Nucleotides are made up of three components:

  • A 5-Carbon sugar

    • In DNA, the 5-carbon sugar is deoxyribose

  • A phosphate group

  • A nitrogenous base

    • Nitrogenous bases are bases that contain nitrogen

      • In DNA there are four nitrogenous bases. These bases are referred to y scientists by the first letter of their name

        • Adenine - A

        • Guanine - G

        • Cytosine - C

        • Thymine - T

• Nucleotides in DNA on the same strand are joined together by covalent bonds

  • Covalent bond: electrons pairs being shared between two atoms

• The nucleotides can be joined together in any order, meaning that any sequence of bases is possible

• Nucleotides in DNA on opposite strands are joined together by hydrogen bonds

  • A bonds with T

  • G bonds with C

The Role of DNA

• The DNA that makes up genes must be able to store, copy, and transmit genetic information in a cell

• DNA has three functions:

1. Storing Information

   • DNA is the molecule of heredity, meaning that its most important job is storing information

   • Genes control patterns of development, which means that the instructions that cause a single cell to develop into an oak tree or a dog must be written into the DNA of each of these organisms

2. Copying Information

   • Before a cell divides, it must make a complete copy of every one of its genes

3. Transmitting Information

   • When a cell divides, each daughter cell must receive a complete copy of the genetic information

DNA Molecule:

RNA

• RNA (ribonucleic acid) is another nucleic acid that has a different structure and a different function than DNA

  • Like DNA, RNA is made up of nucleotides joined into long strands of chains by covalent bonds

• RNA nucleotides are made up of three components 

  • A 5-Carbon sugar

    • 5-Carbon sugar is Ribose

  • A phosphate group

  • A nitrogenous Base

    • Adenine - A

    • Cytosine - C

    • Guanine - G

    • Uracil - U

4-3 Protein Synthesis

Intro to RNA

• Watson & Cricks discovery of the structure of DNA explained how DNA could be copied but not how genes actually work

  • Discovery of RNA explained how the information in the genetic code is put into action

  • RNA is a single stranded nucleic acid that contains the sugar ribose

RNA:

• Nucleotides in DNA are made of a 5 carbon sugar (deoxyribose), a phosphate group and a nitrogenous base

  • Three important differences between DNA and RNA

    • Sugar in RNA is ribose

    • RNA is single stranded (no double helix)

    • Rna contain the nitrogenous base uracil in place of thymine 

The Role of RNA

• DNA is the master plan for the cell and as such is very valuable. If DNA were taken out into the cytoplasm to have it information assessed, it would risk having the information lost or damaged

• RNA is produced so that the DNA can remain safely stored in the nucleus 

• Three types of RNA are involved in taking the information stored in DNA and turning it into proteins

  • Messenger RNA (mRNA):

    • Messenger RNA (mRNA) is the type of RNA that carries copies of instructions for the assembly of amino acid into proteins from DNA to the rest of the cell

      • A set of three bases in mRNA is called a codon, and each codon “codes” for an amino acid

  • Ribosomal RNA (rRNA):

    • Ribosomal RNA (rRNA) is the type of RNA that combines with proteins to form ribosomes

  • Transfer RNA (tRNA):

    • Transfer RNA (tRNA) is the type of RNA that carries each amino acid to a ribosome during protein synthesis 

RNA Synthesis p

• Most of the work in making RNA occurs during a process transcription

• Transcription: The synthesis of an RNA molecule from a DNA template

  • In transcription, segments of the transcribed RNA complement the base sequences of the template of DNA

  • The base sequences of the transcribed RNA compliment the base sequences of the template DNA

The Genetic Code

• First step in decoding the genetic messages is to transcribe DNA to RNA

• Proteins are made by joining together long chains of amino acids

  • Polypeptides: Long chains of amino acids

• The contents of the polypeptide as well as how it is arranged determines the type of protein

  • Different proteins have different functions 

• RNA contains 4 bases: adenine, guanine, cytosine, uracil

  • These four bases make up the alphabet of RNA
    
    

• Combination of bases which make up the language of RNA is known as the genetic code

  • All of the words in this language are made of only three letters

    • Codon: A three letter word in mRNA

  • The genetic code is read three letters at a time, so that each word is three bases long and corresponds to a single amino acid

    • Since there are four different bases in mRNA, 64 codons are possible

• RNA has its own punctuation system which signals protein synthesis to start and stop

  • Methionine is the start of codon

    • The codon from start mRNA is AUG

  • Three different stop codons exist

    • UGA, UAA, and UAG 

    • When a stop codon is reached translation ends

Transcription and Translation

• Transcription: The coding of DNA into RNA

  • In eukaryotes, transcription occurs in the nucleus

  • In prokaryotes, transcription occurs in the cytoplasm

• Translation: The assembling of a protein from mRNA

  • Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptides chains

  • Translation occurs in the cytoplasm

The process of Translation

• After mRNA sequence is transcribed, it enters the cytoplasm and heads for a ribosome to be translate into a protein

• Step 1: Initiation

  • TRanslation begins when a ribosome attaches to an mRNA molecule in the cytoplasm

    • As the ribosome reads the coded molecules 3 bases at a time searching for the start codon, AUG

    • When AUG is read, it directs tRNA ti bring the amino acid to methionine into the ribosome 

• Step 2: Elongation

  • The ribosome shifts the mRNA molecule to the next codon and reads it

    • It directs the tRNA to bring the specified amino acid

      • Each tRNA molecule carries just one kind of amino acid

      • In addition, each tRNA molecule has three unpaired bases, called the anticodon which are complementary to one mRNA codon

    • Once the tRNA molecule has dropped off its amino acid, it moves away from the binding site

• Step 3: Termination

  • The polypeptide chain continues to grow until the ribosome reaches a “stop” codon on the mRNA molecule

    • When the ribosome reaches a stop codon, it releases both the newly formed polypeptide and the mRNA molecule, completing the process of translation

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The Molecular Basis of Heredity

• Gene expression: The process by which a gene produces its product and the product carries out its function

• The central dogma of molecular biology is that information is transferred from DNA to RNA to protein

4-4 Mutations

Intro

• Mutation: Any change in the genetic material of a cell

  • Mutations are heritable changes in genetic information (each new daughter cell will made the mutated cell will have the mutation

  • Not all mutation are inherited from parent to offspring

    • Only those taking place in cells that produce gametes (sperm and egg) will be inherited

Types of Mutations

• Gene mutations: Mutations that produce a change in a single gene

• Chromosomal mutations: Mutations that produce changes in whole chromosomes.

Gene Mutations

• Two types of gene mutations

  • Point mutations

  • Frameshift mutations

• These types of mutations generally occur during DNA replication.

  • If mistake is not caught, mutation will be passed onto every cell that develops from the original one

Point mutations

• Mutations in which a single base pair of DNA has been changed

  • Substitutions: The only point mutation and occur when on base pair is substituted for another

  • Substitutions often affect only one amino acid and sometimes have no effect at all

Frameshift Mutations

• Frameshift mutations: Mutations that shift the reading frame of the genetic message by inserting or deleting nucleotides

  • Frameshift mutations can change every amino acid that follows the point of the mutation and can alter  protein so much that it is unable to perform its normal functions

• Two types of frameshift mutations

  • Insertions

    • EX: ACG but insert a T in between two letters and now its ACTG, which is read as ACT. This could change an amino acid

  • Deletions

    • EX: ACGATT but delete the G, turning the letters into ACATT, possibly changing the amino acid

• If a nucleotide is added or deleted, the bases are still read in groups of three, but now those groupings shift every codon that follows the mutation 

Effects of Mutations

• Genetic material can be altered by natural events or by artificial means

  • Many mutations are produced by eros in genetic processes including mistakes during DNA replication, mitosis or meiosis

  • Some mutations come from mutagens

    • Mutagen: A chemical or physical agent in the environment which causes mutations

      • Chemical mutagens include pesticides, tobacco smoke, environmental pollutants, and certain plant alkaloids

      • Physical mutagens include some forms of electromagnetic radiation, X-rays, gamma rays, UVA & UVB rays are all known mutagens

• Effects of mutations can vary widely. They can be:

  • Silent (or Neutral)

    • The redundancy of genetic code allows for some mutations to not change the final outcome of a protein

  • Beneficial

    • Beneficial mutations are responsible for evolution and contribute to genetic variability within a species 

  • Harmful:

    • Some of most harmful mutations are those that dramatically change protein structure or gene activity

      •  Defective proteins produced by these mutations can disrupt normal biological activities, and result in genetic disorders

      • EX: Some cancers are product of mutations that cause the uncontrolled growth of cells

4-5 Reproductive Strategies

Asexual vs. Sexual Reproduction

• Prokaryotes and eukaryotes differ in reproduction strategies

  • Prokaryotes (and some eukaryotes) go through the process of asexual reproduction

    • In asexual reproduction, a single parent produces offspring that are genetically identical

    • There are three asexual reproduction strategies: binary fission, budding, and fragmentation

  • Binary fission: The parent splits in half to create two new organisms

    • EX: amoeba, paramecium

  • Budding: The parent will create a small cell known as a bud. The bud will grow and develop, and when it’s mature, it will be released as a new organism

    • EX: Yeast, coral

  • Fragmentation: The parent splits into fragments. These fragments will then form into a new organism

    • EX: Sea Star, lichen

• Asexual reproduction is a very fast process, and can be an advantage to many organisms

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• Most eukaryotes go through process of sexual reproduction

  • In sexual reproduction, two parents create genetically unique offspring

  • Parents produce unique cells called gametes that will combine through the process of fertilization to create a new organism called a zygote

    • Each zygote receives half of their mother’s chromosomes and half of their father’s chromosomes

  • The gametes that are needed for sexual reproduction are created through a process called meiosis

Meiosis

• Meiosis: Cell division that creates gametes: sperm and egg cells

  • Sexual reproduction combines gametes from two parents to produce a living organism

  • When gametes are produced, the number of chromosomes just be half

    • The zygote created from sexual reproduction must contain genetic information from the mother and the father, so the gametes must have half of the chromosomes found in normal body cells

  • When two gametes come together at fertilization, the normal amount of chromosomes are found (23+23=46)

4-6 Meiosis

Meiosis

• Meiosis: Cell division that creates gametes: sperm and egg cells

  • Sexual reproduction combines gametes from two parents to produce a living organism

  • When two gametes come together at fertilization, the normal amount of chromosomes are result

Homologous Chromosomes

• Human cells have 23 pairs of chromosomes; each chromosome within a pair is a called homologous chromosome

  • For each of the 23 chromosome pairs, you received one chromosome from your father and one chromosome from your mother. Together they are a homologous pair

    • Alleles: alternate forms of genes found on chromosomes

    • Homologous chromosomes have the same genes, but they may have different alleles

      • Therefore, homologous chromosomes are very similar, but they are not identical

      • The homologous chromosomes are separated when gametes are formed. 

      • Gametes only have 23 chromosomes, not 23 pairs.

Diploid vs. Haploid

• A cell with two sets of chromosomes is diploid

  • Most of the cells in a human body are diploid

• A cell with one set of chromosomes, like a gamete, is haploid

  • Sex cells are haploid

• When a haploid sperm and a haploid egg combine, a diploid zygote will be formed

The process of Meiosis

• Before meiosis begins, DNA replication occurs, so each chromosome contains two sister chromatids that are identical to the original chromosome

• Meiosis is divided into two divisions: Meiosis I and Meiosis II

  • Each division can be divided into the same phases as mitosis: Prophase, metaphase, anaphase, and telophase. Cytokinesis follows telophase each time 

  • Between the two cell divisions, DNA replication does not occur

  • By the end of Meiosis II, one diploid cell will divided into four haploid cells

Meiosis I

• During meiosis 1, the pairs of homologous chromosomes are separated from each other

  • Prophase 1: The homologous chromosomes line up together and exchange genetic information in a process called crossing over. Crossing over forms new combinations of alleles on the resulting chromosome

    • Without crossing over, the offspring would always inherit all of the alleles on one of the homologous chromosomes. The spindle forms, the chromosomes condense as they coil rightly, and the nuclear envelope disappears

  • Metaphase 1: The homologous chromosomes line up in their pairs in the middle of the cell

  • Anaphase 1: The homologous chromosomes are separated, and begin to move to opposite sides of the cell

  • Telophase 1: The spindle fibers dissolve, but a new nuclear envelope does not need to form. This is because after cytokinesis, the nucleus will immediately begin to divide again

Meiosis II

• During meiosis 2, sister chromatids are separated and the gametes are generated.This cell division is similar to mitosis, but results in four genetically unique haploid cells

  • Prophase 2: The chromosomes condense

  • Metaphase 2: The chromosomes line up one on top of each other along the middle of the cell (like in mitosis). The spindle is attached to the centromere of each chromosome 

  • Anaphase 2: The sister chromatids separate and move to opposite ends of the cell

  • Telophase 2: The nuclear envelope forms around the chromosomes in all four cells This is followed by cytokinesis

• Meiosis results in four haploid, genetically unique daughter cells. Each cell has half the DNA of the parent cell.

  • In human cells, the parent cell has 46 chromosomes, so the cells produced by meiosis have 23 chromosomes

Chromosomal Mutations

• Chromosomal mutations: Involve changes in the number or structure of chromosomes. 

  • These mutations can change the location of genes on chromosomes and can change the number of copies of some genes

• Four types of chromosomal mutations:

  • Deletion: The loss of all or part of a chromosome 

  • Duplication: Produces an extra copy of all or part of a chromosome

    • EX: Down syndrome

  • Inversion: Reverses the directions of parts of a chromosome 

  • Translocation: Occurs when part of one chromosome breaks off and attaches to another

4-7 Mendelian Inheritance

Gregor Mendel

• All living things have a set of characteristics that they have inherited from their parents

• Genetics: The scientific study of heredity

  • Heredity is the delivery of a set of characteristics from parent to offspring

• The modern science of genetics was discovered by Gregor Mendel

• Mendel conducted his experiments using pea plants 

  • Pea plants as “model systems”

    • Scientists use model system because they are convenient to study and may tell us how other organisms, including humans, actually function

    • By using peas, Mendel was able to carry out, in just one or two growing seasons, experiments that would have been impossible to do with humans and that would have taken decades 

Mendel’s Conclusions

• Mendel's first conclusion: The Theory of Particulate inheritance

  • An individual’s characteristics are determined by factors that are passed from one parental generation to the next

    • Today scientists call these factors genes

      • Gene: A sequence of DNA that codes for a protein and thus determines a trait

    • Different forms of a gene are called alleles

      • EX: The gene that codes for plant height came in two forms; tall and short

• Mendel’s Second Conclusion: The Principle of Dominance 

  • The principle of dominance states that some alleles are dominant and other recessive

    • If an offspring contains one dominant and one recessive allele it will display the trait of the dominant gene 

    • The only way that the recessive trait will be shown is if no dominant allele is present 

• Mendel’s Third Conclusion: The Principle of Independent Assortment

  • The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes

Probability and Punnett Squares

• Probability: The likelihood that a particular event will occur

  • EX: Coin Flip

• Gene segregation during meiosis is random. This random segregation allows for the principles of probability to be used to predict the outcomes of genetic cross

• Probabilities predict the outcome of a large number of events. The greater the number of events, the closer the results will be to the predicted values

Homozygous and Heterozygous

• Not all organisms with the same characteristics have the same set of alleles 

  • Both TT and Tt allele combinations will produce tall plants

    • Organisms that have two identical alleles for a particular gene are said to be homozygous

    • Organisms that have two different allele for a particular gene are said to be heterozygous

  • Mendel noticed that the F1 generation of plants had the same phenotype as the P generation but had a different genotype 

    • Genotype is the genetic makeup an organism

    • Phenotype is the makeup of an organism

Punnett Squares 

• The punnett square is a tool that can be used to predict the outcome of genetic cross

  • Punnett squares use mathematical probabilities to help predict the genotype and phenotype combinations in a genetic cross

Summarizing Mendel’s Principles

• Mendel’s principles of heredity, observed through patterns of inheritance, form the basis of modern genetics

• The inheritance of biological characteristics is determined by individual units called genes, which are passed from parent to offspring

  • In most sexually reproducing organisms, each adult has two copies of each gene, one from each parent

• Where two or more alleles of the gene for a single trait exist some may be dominant and other recessive

• Alleles for different genes usually segregate independently of one another

4-8 Beyond Mendelian Inheritance

Beyond Dominant and Recessive Alleles

• There are some exceptions to Mendel’s principles: incomplete dominance and codominance 

• Incomplete Dominance

  • Some alleles are neither dominant nor recessive

    • Incomplete dominance: A situation in which one allele is not completely dominant over the other allele

      • In incomplete dominance, the heterozygous phenotype is somewhere between the two homozygous phenotypes

    • Codominance: A situation in which the phenotype produced by both alleles are completely expressed

      • In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens have a color described as “erminette,” speckled with black and white feathers

4-9 Cell Membrane Structure

Cell Membranes

• All cells (whether prokaryotic or eukaryotic) have cell membranes to protect and organize the content of the cell

• Cell membranes regulate what can enter and what can exit a cell

Cell Membrane Composition

• Cell membranes are made up of a double-layered sheet.  This is called a lipid bilayer.

  • The lipid bilayer is important because it gives the cell membrane flexibility and strength

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Cell Membrane Composition 

• The lipid bilayer is made up of phospholipids

  • These molecules are composed of a phosphate group and two fatty acid chains

    • The fatty acid chains are considered hydrophobic, or “water-hating”. They do not come into contact with water and are instead buried in the middle of the membrane. This keeps water from entering or exiting the cell

    • The phosphate groups are considered hydrophilic, or “water-loving”. They are at the ends of the fatty acid chains, and face the inside and outside of the cell

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• The Lipid bilayer is made up of phospholipids

  • The tendency of the fatty acid chains to oppose water, and the phosphate groups to attract water, gives the cell membrane its lipid bilayer arrangement

• Another lipid found in cell membranes is cholesterol. Cholesterol helps to maintain the flexibility of the membrane.

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Permeability if Cell Membranes

• Many substances are able to cross the cell membrane

  • However, substances that are too large or too charged (positive or negative) cannot

• Permeable: If a substance is able to cross the cell membrane, then it is considered permeable to that substance

• Impermeable: If a substance is unable to cross the cell membrane, the cell membrane is considered impermeable to that substance 

  • The term scientists give to cell membranes is selectively permeable

  • Selectively Permeable: Some substances can cross the membrane barrier and others cannot

Fluid Mosaic Model

• Within the cell membrane, there are many different types of molecules that move throughout the phospholipids

  • Protein molecules have a variety of functions. Some are channels or pumps, allowing substances to move across the membrane. Other are involved in a cell’s ability to responds to its environment

    • Carbohydrates molecules are attached to some of these proteins. They are involved in chemical identification, allowing cells to recognize one another. 

      • When a carbohydrate is attached to a protein, it is called a  glycoprotein

• Due to the variety of different molecules, and the molecules ability to move throughout the phospholipid, cell membranes are also referred to as a fluid mosaic model

  • “Fluid” because of the movement, and mosaic because of the variety of molecules

4-10 Passive Cell Transport

Cell Membranes

• Cell membranes control what enters and exits a cell

  • Cell membranes are therefore said to be selectively permeable

  • Some cells require larger amounts of specific substances than other cells and they must have a way of obtaining these materials from extracellular fluids. They do this through the process of membrane transport

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Passive Transport

• Passive transport: A naturally-occurring phenomenon and does not require the cell to use any energy to accomplish the movement of molecules across the cell membrane

• These molecules must be small enough to move through the phospholipids, and are typically uncharged

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• In passive transport, small molecules move from an area of higher concentration to an area of lower concentration

  • A physical space in which there is a range of concentrations of a single molecule has what is called a concentration gradient. 

• Concentration Gradient: The force that allows molecules to move across the cell membrane

  • Equilibrium: Movement across the cell membrane stopping when the molecules are evenly distributed 

• Two main types of passive transport: diffusion and osmosis

Diffusion

• Diffusion is the movement of molecules across the cell membrane. These molecules will move from an area of high concentration to an area of low concentration 

  • This is called moving down their concentration gradient 

• Two types: simple diffusion and facilitated diffusion

  • Simple diffusion: molecules move through the phospholipids

    • These molecules are small and uncharged so they are easily able to move across the cell membrane

  • Facilitated diffusion: Molecules move through protein channels

    • These molecules are too large or are charged (positive or negative) and therefore cannot move through the phospholipids

• Many factors can affect the rate of diffusion, including concentration gradient, size of the particles that are diffusing, and temperature.

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Osmosis

• The cell membrane contains phospholipids made up of hydrophilic phosphate heads and hydrophobic fatty acid chains

  • This composition keeps water from entering or exiting the cell easily 

• In order for water molecules to move across the cell membrane, they must travel through special channels called aquaporins

• The movement of water across the cell membrane is a type of facilitated diffusion known as osmosis

  • Because it is a type of diffusion, water will move from an area of high concentration of low concentration

Tonicity

• Many molecules are too large to move across cell membranes through diffusion so they do not reach equilibrium. However, water can easily move through aquaporins until equilibrium is reached

• The concentration of molecules (called solutes) and the concentration of water (called solvent) are inversely proportional

  • When the concentration of water is 60%, the concentration of solutes is 40%

  • When the concentration of water is 40%, the concentration of solutes is 60%

• While these solute particles are trapped on one side of the cell, water can easily move

• Osmotic pressure: The differences in solute concentration between the two sides of the cell membrane drives the movement of water into and out of the cell. 

• Osmotic pressure leads to three effects of osmosis on cells:

  • Hypertonic: the outside of the cell has more solutes/less water compared to the inside of the cell

    • Water will move down its concentration gradient from inside the cell to outside the cell

      • This causes the cell to shrink

  • Hypotonic: the outside of the cell has less solute/more water compared to the inside of the cell

    • Water will move down its concentration gradient from outside the cell to inside the cell

      • This causes the cell to swell and eventually burst

  • Isotonic: The outside of the cell and the inside of the cell have the same concentration of solute and water (ideal condition of a cell)

    • Water will not move because equilibrium is reached

      • The cell will not change  shape

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4-11 Active Cell Transport

Concentration Gradient

• Diffusion moves molecules across the cell membrane down their concentration gradient. This means movement occurs from an area of high concentration to an area of low concentration

  • Sometimes, the cell needs to move molecules in the opposite direction: from an area of low concentration to an area of high concentration. In this case, movement is against the concentration gradient

• This is called active transport, and it requires ATP to be accomplished

Active Transport

• Active Transport: A process that moves molecules across the cell membrane using energy.

  • This movement is from an area of low concentration to an area of high concentration.

• There are two types of active transport: molecular transport and bulk transport

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Molecular Transport

• Small molecules and charged ions can move across the cell membrane using protein pumps. These pumps push the molecules or charged ions across the cell membrane against their concentration gradient

  • The energy stored in ATP is the force that allows these molecules to move across the cell membrane

  • ATP will bind to the protein pump in the cell membrane, causing the protein to change shape This allows the molecule being transported to bind to the protein pump. It is then released on the other side of the membrane

Bulk Transport

• Unlike molecular transport, bulk transport utilizes vesicles and vacuoles to move molecules across the cell membrane against their concentration gradient.

  • These molecules are too large to be transported through protein pumps

• There are two types of bulk transport: endocytosis and exocytosis

• Endocytosis: The process of moving molecules from outside the cell to inside the cell. This is done by creating pockets in the cell membrane that will break off inside of the cell

  • Two types of endocytosis: pinocytosis and phagocytosis

    • Pinocytosis: Liquid is moved from outside the cell to inside the cell. The membrane will create a pocket filled with fluid that will break off into a vacuole

    • Phagocytosis: Solid particles are moved from outside the cell to inside the cell. The cell membrane will create a pocket filled with solid particles that will break off into a vesicle

  • The vesicles and vacuoles created through endocytosis travel through the cytoplasm to their final destination to be used by the cell

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• Exocytosis: The process of moving molecules from inside the cell to outside the cell. The vacuoles or vesicles inside the cytoplasm will travel to the cell membrane and fuse with it

  • When this fusion occurs, the contents (either liquid or solid) will be transported out of the cell.

•