Cell theory

1. All living things are composed of cells

2. Cells are the basic units of structures and function in living things.

3. New cells are produced from preexisting cells.

2 types of _

Prokaryotes/Eukaryotes

Prokaryote

Single-celled organisms; Lack internal struggles; no membrane bound organelles (no nucleus); DNA is in cytoplasm.

Example: Bacteria

Eukaryote

Single-celled and multicellular organisms with internal membrane-bound organelles (true nucleus)

Example: Protists, Fungi, Plants Animal

How are prokaryotes and eukaryotic similar?

• Both cells carry DNA and rDNA (ribosomal DNA)

• Both prokaryotic cells and eukaryotic cells have vesicles.

Both prokaryotes and eukaryotes may be single-celled organisms.

Unicellular/multicellular

Unicellular

Single cell.

Examples: E.coli, Yeast, Amoeba.

Multicellular

Some cells are specialized

Examples: Mold, Red Maple, Coral, Human.

Cell structure

of Organization

• Atom

• Molecule

• Organelle

• Cell

• Tissue

• Organ

• Organ System

• Organism

Cytoplasm/Cytosol

• The cytoplasm consists of cytosol: a gel-like substance that contains other matter: cell organelles; smaller cell-like bodies bound by separate membranes; and cytoplasmic inclusions; insoluble molecules that store energy and are not surrounded by any layer.

• The cytoplasm is a colorless and has about 80% water along with other various nutrients required for the cell.

• It is known to have the properties of both viscous matters as well as elastic matter. Under it elastically, cytoplasm helps in the movement of materials inside the cell by a process termed cytoplasmic streaming.

Cell Wall

• In a plant cell, the cell wall is made up of cellulose, hemicellulose, and proteins while in a fungal cell, it is composed of chitin

• A cell wall is multilayered with a middle lamina, a primary cell wall, and a secondary cell wall.

• Middle lamina contains polysaccharides that provide adhesion and allows binding of the cells to one another.

• After middle lamina is the primary cell wall which is composed of cellulose. The last layer, which is not always present, is the secondary cell wall made of cellulose and hemicellulose

Cell membrane/Plasma membrane

• Structurally, it consists of a phospholipid bilayer along with two types of proteins viz. embedded proteins and peripheral proteins that function in providing shape and allowing the movement of particles in and out of the cell.

• The most abundant lipid which is present in the cell membrane is a phospholipid which contains a polar head group attached to two hydrophobic fatty acid tails.

• The embedded proteins act as channels for the transfer of particles across the cell with some proteins acting as receptors for the binding of various components.

• The peripheral proteins function as to provide fluidity as well as mechanical support to the structure of the cell.

Nucleus and Nucleolus

• Structurally, the nucleus consists of a nuclear envelope, chromatin, and nucleolus.

• The nuclear envelope is similar to the cell membrane in structure and composition. It has pores that allow the movement of proteins and RNA in and outside the nucleus. It enables the interaction with other cell organelles while keeping nucleoplasm and chromatin within the envelope.

• The chromatin in the nucleus contains RNA or DNA along with nuclear proteins, as genetic material that is responsible for carrying the genetic information from one generation to another. It is present in a sense and compact structure which might be visible as chromosome under powerful magnification.

• The nucleolus is like a nucleus within the nucleus. It is a membrane-less organelle that is responsible for the synthesis of rRNA and assembly of ribosomes required for protein synthesis.

Centrosome (contains centrioles)

• A centriole consists of a cylindrical structure made with nine triplets microtubules that surround the periphery of the centriole while the center has a Y-shaped linker and a barrel-like structure that stabilizes the centriole.

• Another structure called cartwheel is present in a centriole which is made up of a central hub with nine spokes/filaments radiating from it. Each of these filaments/spokes is connected to the microtubules through a pinhead.

Microtubules

• They are long hollow, beaded tubular structure of diameter of about 24nm.

• The wall of the microtubules consists of globular subunits present at a helical array of a and b tubulin.

• Similar to microfilaments, the ends of microtubules also have a defined polarity with one end being positively charged while the other being negatively charged.They are long hollow, beaded tubular structure of diameter of about 24nm.

• The wall of the microtubules consists of globular subunits present at a helical array of a and b tubulin.

• Similar to microfilaments, the ends of microtubules also have a defined polarity with one end being positively charged while the other being negatively charged.

• They are long hollow, beaded tubular structure of diameter of about 24nm.

• The wall of the microtubules consists of globular subunits present at a helical array of a and b tubulin.

• Similar to microfilaments, the ends of microtubules also have a defined polarity with one end being positively charged while the other being negatively charged.

Microfilaments(Cytoskeleton)

• Around three different classes of fibers make up the cytoskeleton which is: microtubules, microfilaments, and intermediate filaments.

• These are separated based on a protein present in them.

  The filaments are present either in cross-linked forming networks or as bundles. The chains of protein remain twisted around each other in a helical arrangement.

• One of the polar ends of the filament is positively charged and barbed, whereas the other end is negatively charged and pointed.

Rough Endoplasmic Reticulum

• Endoplasmic Reticulum exists in three forms viz. cisternae, vesicles, and tubules.

• Cisternae are sac-like flattened, unbranched structures that remain stacked one on top of another.

• Vesicles are spherical structures that carry proteins throughout the cell.

• Tubules are tubular branched structures forming a connection between cisternae and vesicles

Ribosome(s)

• The ribonucleoprotein consists of two subunits.

• In the case of prokaryotic cells, the ribosomes are of the 70S with the larger subunit of 50S and the smaller one of 30S.

• Eukaryotic cells have 80S ribosomes with 60S larger subunit and 40S smaller subunit.

• Ribosomes are short-lived as after the protein synthesis, the subunits split up and can be either reused or remain broken up.

Smooth Endoplasmic Reticulum

• Endoplasmic Reticulum exists in three forms viz. cisternae, vesicles, and tubules.

• Cisternae are sac-like flattened, unbranched structures that remain stacked one on top of another.

• Vesicles are spherical structures that carry proteins throughout the cell.

• Tubules are tubular branched structures forming a connection between cisternae and vesicles

Golgi Apparatus/Golgi Body/Golgi Complex/Golgi

• The structure of the Golgi Complex is pleomorphic; however, it typically exists in three forms, i.e. cisternae, vesicles, and tubules.

• The cisternae, which is the smallest unit of Golgi Complex, has a flattened sac-like structure which is arranged in bundles in a parallel fashion.

• Tubules are present as tubular and branched structures that radiate from the cisternae and are fenestrated at the periphery.

• Vesicles are spherical bodies that are divided into three groups as transitional vesicles, secretory vesicles, and clathrin-coated vesicles.

Vesicle

• A vesicle is a structure containing liquid or cytosol which is enclosed by a lipid bilayer.

• The outer layer enclosing the liquid is called a lamellar phase which is similar to the plasma membrane. One end of the lipid bilayer it hydrophobic whereas the other end is hydrophilic.

Endosomes

• There are different types of endosomes based on morphology and the time it takes for the endocytosed materials to reach them.

• The early endosomes are made with the tubular-vesicular network while the late endosomes lack tubules but contain many close-packed intraluminal vesicles. The recycling endosomes are found with microtubules and are mainly composed of tubular structures.

Lysosome/Lysozymes

• The shape of lysozymes is irregular or pleomorphic; however, mostly, they are found in the spherical or granular structure.

• Lysozymes are surrounded by a lysosomal membrane that contains the enzymes within the lysosome and protects the cytosol with the rest of the cell from the harmful action of the enzymes.

Peroxisome

• Peroxisome consists of a single membrane and granular matrix scattered in the cytoplasm.

• They exist either in the form of interconnected tubules or as individual peroxisomes.

• The compartments within every peroxisome allow the creation of optimized conditions for different metabolic activities.

• They consist of several types of enzymes with major groups being urate oxidase, D-amino acid oxidase, and catalase.

Mitochondria/Mitochondrion

• A mitochondrion contains two membranes with the outer layer being smooth while the inner layer is marked with folding and finger-like structures called cristae.

• The inner mitochondrial membrane contains various enzymes, coenzymes, and components of multiple cycles along with pores for the transport of substrates, ATP, and phosphate molecules.

• Within the membranes is a matrix that contains various enzymes of metabolic processes like Kreb’s cycle.

• In addition to these enzymes, mitochondria are also home to single or double-stranded DNA called mtDNA that is capable of producing 10% of the proteins present in the mitochondria.

Chloroplast

• It is a double-membraned structure with its own DNA which is inherited from the previous chloroplast.

• These are usually lens-shaped with shape and number varying according to cells. They have an outer membrane, an inner membrane, and a thylakoid membrane that enclosed the gel-like matric called the stroma.

• The outer and inner membrane is porous and allows transport of materials while the stroma contains DNA, chloroplast ribosomes, proteins, and starch granules.

Vacuole (Central Vacuole)

• The vacuole is surrounded by a membrane called tonoplast, which encloses fluid containing inorganic materials like water and organic materials like nutrients and even enzymes.

• These are formed by the fusion of various vesicles, so vacuoles are very similar to vesicles in structure4

Cilia and Flagella

• Cilia are hair-like projections that have a 9+2 arrangement of microtubules with a radial pattern of 9 outer microtubule doublet that surrounds two singlet microtubules. This arrangement is attached to the bottom with a basal body.

• Flagella is a filamentous organelle, the structure of which, is different in prokaryotes and eukaryotes.

• In prokaryotes, it is made up of the protein called flagellin wrapped around in a helical manner creating a hollow structure at the center throughout the length.

• In eukaryotes, however, the protein is absent and the structure is replaced with microtubules

Microvili

• Microvilli are bundles of protuberances loosely arranged on the surface of the cell with little or no cellular organelles.

• These are surrounded by a plasma membrane enclosing cytoplasm and microfilaments.

• These are bundles of actin filaments bound by fimbrin, villin, and epsin.

Cell Functions

Cytoplasm/Cytosol

• Most of the vital cellular and enzymatic reactions like cellular respiration and translation of mRNA into proteins occur in the cytoplasm.

• It acts as a buffer and protects genetic materials as well as other organelles from damage due to collision or change in the pH of the cytosol.

• The process called cytoplasmic streaming helps in the distribution of various nutrients and facilitates the movement of cell organelles within the cell.

Cell Wall

• The critical function of the cell wall is protecting and maintaining the shape of the cell. It also helps the cell withstand the turgor pressure of the cell.

• It initiates cell division by providing signals to the cell and allows the passage of some molecules into the cell while blocking others.

Cell membrane/Plasma membrane

• The cell membrane provides mechanical support that facilities the shape of the cell while enclosing the cell and its components from the external environment.

• It regulates what can be allowed to enter and exit the cell through channels, acting as a semi-permeable membrane, which facilities the exchange of essential compounds required for the survival of the cell.

• It generates and distributes signals in and outside of the cell for the proper functioning of the cell and all the organelles.

• It allows the interaction between cells required during tissue formation and cell fusion.

Nucleus and Nucleolus

• The nucleus is responsible for storage as well as the transfer of genetic materials in the form of DNA or RNA.

• It aids in the process of transcription by the synthesis of mRNA molecules.

• The nucleus controls the activity of all other organelles while facilitating processes like cell growth, cell division and synthesis of proteins.

Centrosome(contains centrioles)

• During cell division, centrioles have a crucial role in forming spindle fibers which assist the movement of chromatids towards their respective sides.

• They are involved in the formation of cilia and flagella.

Microtubules

• As a part of the cytoskeleton, they provide shape and movement to the cell.

• Microtubules facilitate the movement of other cell organelles within the cell through binding proteins.

Microfilaments(Cytoskeleton)

• The critical function of the cytoskeleton is to provide shape and mechanical support to the cell against deformation.

• It allows the expansion and contraction of the cell which assists in the movement of the cell.

• It is also involved in intracellular and extracellular transport of materials.

• It generates the strength for the structure and movement of the cell in association with myosin protein.

• They help in cell division and are involved in the products of various cell surface projections.

Rough Endoplasmic Reticulum

• ER contains many of the enzymes required for several metabolic processes, and the surface of the ER is essential for other operations like diffusion, osmosis, and active transport.

• One of the crucial functions of ER is the synthesis of lipids like cholesterol and steroids.

• Rough ER allows for the modification of polypeptides emerging out of the ribosomes to prepare secondary and tertiary structures of the protein.

• ER also synthesizes various membrane proteins and has a crucial role in preparing the nuclear envelope after cell division..

Ribosome(s)

• Ribosomes are the site of biological protein synthesis in all living organisms.

• They arrange the amino acids in the order indicated by tRNA and assist in protein synthesis.

Smooth Endoplasmic Reticulum

The primary function of Smooth E.R. is synthesis of lipids

Golgi Apparatus/Golgi Body/Golgi Complex/Golgi

• Golgi Complex has an essential purpose of directing proteins and lipids to their destination and thus, act as the “traffic police” of the cell.

• They are involved in the exocytosis of various products and proteins like zymogen, mucus, lactoprotein, and parts of the thyroid hormone.

• Golgi Complex is involved in the synthesis of other cell organelles like a cell membrane, lysozymes, among others.

• They are also involved in the sulfation of various molecules.

Vesicle

• Vesicles facilitate the storage and transport of materials in and outside the cell. It even allows the exchange of molecules between two cells.

• Because vesicles are enclosed inside a lipid bilayer, vesicles also function in metabolism and enzyme storage.

• They allow temporary storage of food and also control the buoyancy of the cell.

Endosomes

Endosomes allow the sorting and delivery of internalized materials from the cell surface and transport of materials to the Golgi or the lysosomes.

Lysosome/Lysozymes

• These organelles are responsible for intracellular digestion where the larger macromolecules are degraded into smaller molecules with the help of enzymes present in them.

• Lysozymes also perform the critical function of the autolysis of unwanted organelles within the cytoplasm.

• Besides these, the lysosome is involved in various cellular processes, including secretion, plasma membrane repair, cell signaling, and energy metabolism.

Peroxisome

• Peroxisomes are involved in the production and elimination of hydrogen peroxide during biochemical processes.

• Oxidation of fatty acids takes place within peroxisomes.

• Additionally, peroxisomes are also involved in the synthesis of lipid-like cholesterol and plasmalogens.

Mitochondria/Mitochondrion

• The primary function of mitochondria is the synthesis of energy in the form of ATP required for the proper functioning of all the cell organelles.

• Mitochondria also help in balancing the amount of Ca+ ions within the cell and assists the process of apoptosis.

• Different segments of hormones and components of blood are built within mitochondria.

• Mitochondria in the liver have the ability to detoxify ammonia.

Chloroplast

• The chloroplast is the primary center for light-dependent and light-independent reactions during photosynthesis.

• Different proteins present in chlorophyll are involved in the regulation of photorespiration.

Vacuole(Central Vacuole)

• Vacuoles act as a storage for nutrients as well as waste materials to protect the cell for toxicity.

• They have an essential function of homeostasis as it allows the balance of pH of the cell by influx and outflow of H+ ions to the cytoplasm.

• Vacuoles contain enzymes that play an important role in different metabolic processes.

Cilia and Flagella

• The most critical role of cilia and flagella is movement. These are responsible for the movement of the organisms as well as for the movement of various particles present around the organisms.

• Some cilia present in some particular organs may have the function of sense. The cilium in the blood vessels, which helps in controlling the flow of blood is an example.

Microvili

• Microvilli increase the surface area of the cell, thus, enhancing the absorption and secretion functions.

• The membrane of microvilli is packed with enzymes that allow the break down of larger molecules into smaller allowing more effective absorption.

• Microvilli act as an anchoring agent in white blood cells and in sperms during fertilization.

Cell definitions

Cytoplasm/Cytosol

Cytoplasm refers to everything present inside the cell except the nucleus.

Cell wall

An additional non-living layer present outside the cell membrane in some cells that provides structure, protection, and filtering mechanism to the cell is the cell wall.

Cell membrane/Plasma membrane

A plasma membrane is composed of lipids and proteins where the composition might fluctuate based on fluidity, external environment, and the different stages of development of the cell.

Nucleus and Nucleolus

• The nucleus is a double membrane-bound structure responsible for controlling all cellular activities as well as a center for genetic materials, and it’s transferring.

• It is one of the large cell organelles occupying 10% of total space in the cell.

• It is often termed the “brain of the cell” as it provides commands for the proper functioning of other cell organelles.

• A nucleus is clearly defined in the case of a eukaryotic cell; however, it is absent in prokaryotic organisms with the genetic material distributed in the cytoplasm.

Centrosome(contains centrioles)

Centrioles are tubular structures mostly found in eukaryotic cells which are composed mainly of the protein tubulin.

Microtubules

Microtubules are also a part of the cytoskeleton differing from microfilaments in the presence of tubulin protein

Microfilaments(Cytoskeleton)

A number of fibrous structures are present in the cytosol that helps give shape to the cell while supporting cellular transport.

• Microfilaments are a part of the cytoskeleton of a cell made up of actin protein in the form of parallel polymers.

• These are the smallest filaments of the cytoskeleton with high rigidity and flexibility, providing strength and movement to the cell.

Endoplasmic Reticulum (rough and smooth)

• Endoplasmic Reticulum (ER) is present as an interconnection of tubules that are connected to the nuclear membrane in eukaryotic cells.

• There are two types of ER based on the presence or absence of ribosomes on them:

  • Rough ER (RER) with ribosomes attached on the cytosolic face of Endoplasmic Reticulum and thus is involved in protein synthesis

  • Smooth ER (SER)which lacks ribosomes and has a function during lipid synthesis.

Ribosome(s)

• Ribosomes are ribonucleoprotein containing equal parts RNA and proteins along with an array of other essential components required for protein synthesis.

• In prokaryotes, they exist freely while in eukaryotes, they are found either free or attached to the endoplasmic reticulum.

Golgi Apparatus

The Golgi Apparatus is the cell organelle mostly present in eukaryotic cells which is responsible for the packaging of macromolecules into vesicles so that they can be sent out to their site of action.

Vesicle

• Vesicles are structures present inside the cell which are either formed naturally during processes like exocytosis, endocytosis or transport of materials throughout the cell, or they might form artificially, which are called liposomes.

• There are different types of vesicles like vacuoles, secretory and transport vesicles based on their function

Endosomes

• Endosomes are membrane-bound compartments within a cell originating from the Golgi network

Lysosome/Lysozymes

• Lysozymes are membrane-bound organelles that occur in the cytoplasm of animal cells.

• These organelles contain an array of hydrolytic enzymes required for the degradation of various macromolecules.

• There are two types of lysozymes:

  • Primary lysosome containing hydrolytic enzymes like lipases, amylases, proteases, and nucleases.

  • Secondary lysozyme formed by the fusion of primary lysozymes containing engulfed molecules or organelles.

Peroxisome

• Peroxisomes are oxidative membrane-bound organelles found in the cytoplasm of all eukaryotes.

• The name is accredited due to their hydrogen peroxide generating and removing activities.

Mitochondria/Mitochondrion

• Mitochondria are double membrane-bound cell organelles responsible for the supply and storage of energy for the cell.

• The oxidation of various substrates in the cell to release energy in the form of ATP (Adenosine Triphosphate) is the primary purpose of mitochondria.

Chloroplast

• A chloroplast is a type of plastic that is involved in photosynthesis in plants and algae.

• Chloroplast contains an essential pigment called chlorophyll necessary to trap sunlight for the production of glucose.

Vacuole(Central Vacuole)

Vacuoles are membrane-bound structures varying in size in cells of different organisms.

Cilia and Flagella

Cilia and Flagella are tiny hair-like projections from the cell made of microtubules and covered by the plasma membrane.

Microvili

Microvilli are tiny finger-like structures that project on or out of the cells. These exist either on their own or in conjunction with villi.

Simpler definitions

Smooth E.R.

The organelle that helps produce and metabolize lipids

Lysosomes

Organelle that contains digestive enzymes, allowing a “clean up” of the cell

Nucleolus

A spherical structure found in the nucleus, it synthesizes ribosomal RNA, creating Ribosomes

Vesicles

Individual sacs made from cell membrane material that contains materials for transport into or out of the cell.

Central Vacuole

A large structure in plant cells, containing mostly water, when the plant is adequately hydrated.

Ribosomes

Small, complex proteins that assemble other proteins from amino acids.

Chloroplasts

The organelle responsible for photosynthesis where energy from the sun is converted into chemical energy for growth.

Flagella/Cilia/Pili

Made of protein filaments, they allow cells to move, or to push items along.

Golgi Apparatus

Packages proteins into vesicles for movement out of or around the cell.

Cell Wall

Not found in animals, this provides rigidity and support to cells.

Mitochondria

With a double membrane, this organelle performs cellular respiration, synthesizes ATP for energy in the cell.

Nucleus

Contains the genetic material and “instructions” for the cell.

Rough E.R

Synthesizes cellular material into ribosomes, that are visible along its surface.

Centrosome

Organelle present in an animal cell that acts as the micro tubule organizing center of the cell.

Centrioles

A clynderic organism near the nucleus in animal cells, involved in development of spindle fibers in cell division.

Cytoskeleton

Large network of protein fibers that give shape and structure to the cell.

Chlorophyll

Pigment that gives plants green color and helps in photosynthesis

Small Vacuoles

In animal cells, small and help sequester waste product.

Picture examples

Cytoplasm/Cytosol

Cell Wall

Cell membrame/Plasma membrane

Nucleus and Nucleolus

Centrosome

microtubules

Microfilaments

Rough Endoplasmic Reticulum

Ribosome(s)

Smooth ER

Golgi Apparatus

Vesicle

Lysosome

Peroxisome

Mitochondria/Mitochondrion

Chloroplast

Flagella

Pili

Cilia

Link:

Vocab

Homeostasis- stable environment

Cell Membrane- controls what goes in and out of the cell (regulated homeostasis)

Polar= unequal sharing of electrons among atoms

Non-polar= equal sharing of electrons among atoms

Structure of a cell membrane

• Phospholipid: Bilayer(2)

• Head is polar

• Tail is non-polar

Passive transport

• no energy needed

• Concentration gradient

  • Concentration gradient is low density to high density.

Simple Diffusion

• No energy needed so it is a passive transport that goes with the concentration gradient

• Non-polar molecules can go directly into the cell

• Examples of these molecules include oxygen and carbon dioxide.

Facilitated diffusion

• Proteins in membranes are the transport proteins.

• They can:

  • Act as channels

    • Change shape

      • Open/close

• No energy so passive transport

• Proteins are helping things pass the membrane

• Charged Ions used protein channels.

• Glucose and Osmosis(for a faster rate) use Aquaporins.

They CAN go low to high even without energy.

Active transport

Think about this: What if the concentration in the cell is higher than in the environment? The cell would still need those materials and that is where Active transport comes in.

• It uses energy (ATP)

• Just think. Active TransPort

• A=A T=T P=P ATP=Active TransPort

Endocytosis

• Molecules going inside the cell

• three types

Phagocytosis

type of endocytosis that stretches out around molecule and pulls into vacuole

Receptor Mediated Endocytosis

type of endocytosis that is picky. incoming substances bind to receptors

Pinocytosis

type of endocytosis that takes in fluids.

Exocytosis

Exit.

• Used to get rid of cell waste

• It also gets important materials out of the cell.

Transport + Cell Membrane

Transport uses the cell membrane

Things to remember about the cell membrane

• It is semi-permeable (selectively permeable)

• Structure: Fluid Mosaic Model (Lipid Bilayer); double layer of proteins (hydrophilic) & phospholipids (hydrophobic)

• Function:  Regulates what enters & leaves the cell to maintain HOMEOSTASIS; Protection

Homeostasis

Maintains proper concentration of substances inside the cell.

Cell transport

Cells transport materials like oxygen, carbon dioxide, and glucose between intracellular and extracellular spaces.

• Intracellular means that something is inside the cell membrane

• Extracellular means that something is outside the cell membrane.

Why is cell transport important?

In order for a cell to maintain homeostasis, or a stable internal environment, it needs to regulate the movement of molecules from one side of the membrane to the other. 

Cell transport helps cells to:

• Maintain homeostasis

• Bring in crucial molecules needed for survival

• Get rid of cell waste

• Survive

What is a concentration gradient?

• movement of molecules from one concentration to another concentration through the cell membrane.

• They occur when there is an uneven distribution of a specific solute between intracellular and extracellular region.

• Cytoplasm in cells has many different substances dissolved in water.

• In any solution, solute particles move constantly and spread out randomly.

• HIGH TO LOW

Passive vs active

Passive

moves with concentration gradient and energy is not used

Active

moves against the gradient and energy is used

Passive transport (in depth)

Passive transport is the movement of materials across the cell membrane WITHOUT using energy.

Examples

• Diffusion: movement of molecules from high to low concentration

• Osmosis: movement of WATER across a semipermable membrane from high to low concentration

Vocab

Equilibrium- state in which concentration gradient is equal in all areas; even distribution

Diffusion-movement of molecules from higher to lower concentration

Example: Dye

Osmosis-movement of water from higher to lower concentration; trying to reach equilibrium by moving water

Simple diffusion

• Particles move from a high concentration to a low concentration without using energy. These particles are typically small and uncharged. 

• Particles will cross the cell membrane to achieve an equal concentration between extracellular and intracellular regions. 

• Even when equilibrium is reached, particles still move randomly in both directions.

Faciliated diffusion

Facilitated diffusion: the process in which molecules cannot directly diffuse across the membrane and must pass through protein channels in order to cross.

• Ions and large molecules like glucose pass through cell membranes quickly through protein channels.

• Protein channels act as passageways for larger molecules. 

• Although facilitated diffusion is fast and specific, it still is diffusion, and does NOT require any additional use of cell energy.

Faciliated diffuusion pt 2

Molecules move across membrane with help of transport proteins

Example: Using a carrier protein to move a sugar molecule in

Osmosis

• The water moves not the solutes

• “Water likes to party”

• Will move against gravity or even leave the body to get to the “party”

• Goes to where there is more solutes and less water

Hypertonic

• type of osmosis

• concentration of solute is greater outside cell

• example: Plasmolysis- water LEAVES vacuole in a salt solution

• plasmolyzed

Hypotonic

• type of osmosis

• concentration of solute is less outside cell

• example: water going INTO a cut stem

• Turgid

• In animal cell will burst but good for plant cells

Isotonic

• Type of osmosis

• concentration of solute is EQUAL on both sides of membrane

• example: RBC in blood

• Flaccid

Osmostic Pressure

• Osmotic pressure is a force driven by the difference in solute concentration and the movement of water in and out of a cell. 

• This pressure can cause cells to swell or shrink. 

• Because cells contain sugars, proteins, salts, and other dissolved molecules they are generally hypertonic to freshwater. 

Water tends to move quickly into a cell that is not buffered by isotonic solutions, such as blood or other fluids.

Active transport (in depth)

Diffusion is powerful, but sometimes not powerful enough! 

• Active transport is the movement of materials across the cell membrane against the concentration gradient.

• This is an active process and uses energy.Active transport is typically carried out by transport proteins, or protein pumps, in the membrane, also know as molecular transport. 

• Large materials can also be transported 

• in bulk across the membrane by endocytosis and exocytosis. 

• This sometimes involves changes in the shape of the cell membrane.

• Uses energy to transport molecules against concentration gradient: USE proton pumps (channel proteins): ATP

Example: Sodium-potassium Pump

Moleculea Transport

• Proteins act as pumps to carry small molecules and ions across the cell membrane. 

  • Ex: calcium, potassium, and sodium. 

This process allows cell to concentrate substances in a specific location even when the forces of diffusion try to move them in an opposite direction.

Bulk transport

Large molecules and solid clumps of materials are actively transported in bulk in or out of the cell. 

Cells form pockets of the cell membrane to form a vesicle or vacuole within the cytoplasm to transport materials in or out. 

Endocytosis: Materials move IN the cell

Exocytosis: Materials move OUT of the cell

Endocytosis:

• Membrane forms a pocket around the material. It then pinches off and breaks loose from the outer portion of the cell membrane to form a vesicle within the cytoplasm.

• Phagocytosis: “Cell Eating”  

  • Cells ingest food or other large solid materials. 

• Pinocytosis: “Cell Drinking”

• Cells ingestl iquid from the environment

Bulk (Macromolecules) transport-active ENDOCYTOSIS

Engulfing large particles IN using the cell membrane and vesicle: uses energy

• Endocytosis

A.  Phagocytosis

• Endocytosis of solid material    Ex. WBC eating bacteria

B. Pinocytosis

• Endocytosis of liquid material  Ex. Hormone

Exocytosis

The membrane of the vacuole surrounding material inside the cell fuses with the cell membrane and forces the contents out of the cell. 

This helps cells get rid of waste or excess materials that it does not need. 

Bulk Transport-Active EXOCYTOSIS

Cell secretes large particles OUT via membrane bound sacs, vesicles from Golgi Apparatus; uses energy.