bio unit 2: all topics

Cells

Cells

The basic structural and functional units of every organism, bound by a plasma membrane, containing cytosol, chromosomes, and ribosomes.

Plasma membrane (aka cell membrane)

flexible barrier that surrounds the cell, separating its internal functions/environment from the external environment

regulates movement of particles in and out of the cell

Cell wall

rigid structural layer that surrounds the outside of (some) cells that provides the cell with structural support and protection

ONLY found in plant, bacteria, fungi, and algae cells

Prokaryotes

Cells that belong to the domains Bacteria and Archaea, with DNA located in the nucleoid region and generally smaller than eukaryotes.

Eukaryotes

Cells that include protists, fungi, animals, and plants, with DNA contained in a nucleus and membrane-bound organelles.

Chromosomes

genetic information found in nucleus of a cell

Organelles

Membrane-bound structures in eukaryotic cells that perform specific functions.

Endomembrane organelles

nuclear envelope, endoplasmic reticulum, Golgi complex, lysosomes, vesicles/vacuoles, and plasma membrane

Compartmentalization

The organization of cellular functions in different organelles, allowing for increased surface area and prevention reactions from occurring in the same location

Nucleus

The organelle that contains chromosomes and is enclosed by a double membrane called the nuclear envelope, with pores regulating material entry and exit.

Nucleolus

region of nucleus where ribosomal RNA (rRNA) is synthesized

rRNA is combined with proteins to form subunits of ribosomes

Ribosomes

Complexes made of ribosomal RNA (rRNA) and protein that synthesize proteins

translate messages found on mRNA into the primary structure of proteins/polypeptides

found in the cytosol (FREE RIBOSOMES)

or bound to the endoplasmic reticulum/nuclear envelope (secreted from cell, leave via transport vesicles)

Endoplasmic Reticulum (ER)

A network of membranous sacs and tubes that synthesizes membranes and compartmentalizes the cell

includes rough ER (with ribosomes bound to ER membrane) keep proteins separate from those free ribosomes

and smooth ER (without ribosomes) synthesizes lipids, metabolizes carbohydrates, and detoxifies cell

Golgi Complex

An organelle that modifies, sorts, and packages materials received from the ER into transport vesicles for secretion or delivery to other locations (leaves via exocytosis)

Cisternae

sacs in golgi complex that are separated from cytosol

have DIRECTIONALITY

Cis face: RECEIVES vesicles from the ER

Trans face: SENDS vesicles back into cytosol to other locations

Lysosomes

Membranous sacs containing hydrolytic enzymes that hydrolyze macromolecules in animal cells and recycle organic materials through autophagy

Autophagy

lysosomes can recycle their own cell’s organic materials; allows cell to renew itself

Peroxisomes

similiar to lysosomes; membrane bound metabolic compartment

catalyze reactions that produce H2O2 (break down into water)

Vacuoles

Large vesicles that stem from the ER and Golgi and involved in selective transport; types include:

food vacuoles (form via cell eating and are digested by lysosomes)

contractile vacuoles (maintain water level in cells)

central vacuoles (found in PLANTS ONLY, contains inorganic ions and water, regulate turgor pressure)

Energy organelles

mitochondria, chloroplast; involved in energy production

Endosymbiont Theory

The theory that explains the similarities between mitochondria and chloroplasts to prokaryotes, suggesting that an early eukaryotic cell engulfed a prokaryotic cell (BECAME ONE FUNCTIONAL ORGANISM)

prokaryotic cell then became an endosymbiont (cell within another cell)

evidence: double membrane, ribosomes, circular DNA, capable of functioning by themselves

Mitochondria

Organelles that are the site of cellular respiration, characterized by a double membrane:

smooth outer membrane

inner membrane folded into cristae: divides the mitochondria into TWO internal compartments and increases surface area (compartmentalization)

amount of mitochondria in a cell correlates with metabolic activity: high metabolic activity=more mitochondria

Intermembrane

space between inner and outer membrane in mitochondria

Mitochondrial matrix

enclosed by inner membrane

location for the KREBS CYCLE

contains: enzymes to catalyze cellular respiration and produce ATP, mitochondrial DNA, ribosomes

Electron transport chain

a collection of proteins bound to the inner mitochondrial membrane where electrons pass through in a series of redox reactions, and release energy (ATP)

Krebs Cycle

sequence of reactions that occur in cells to produce energy which takes place in mitochondria

nutrients are broken down to release energy: energy produced is then stored as ATP and waste products are released

Chloroplast

Specialized organelles in photosynthetic organisms that contain chlorophyll (green pigment) and are the site of photosynthesis, with thylakoids and stroma.

Thylakoids

membranous sacs that can organize into stacks called grana (light dependent reactions occur here)

Stroma

fluid AROUND thylakoids

location for CALVIN CYCLE

contains: chloroplast DNA, ribosomes, enzymes

Calvin Cycle

the chemical reactions of photosynthesis that occur inside the cell using the stored by light dependent reactions (use of sunlight+carbon CO2) to form glucose (sugars)

Light reactions

photochemical reactions involved in photosynthesis that allow the plant cells to create and store energy/food

Photosynthesis

process in which plants synthesize food and energy using sunlight, water, and carbon dioxide (also involved chlorophyll)

Cytoskeleton

A network of fibers throughout the cytoplasm that provides structural support, anchors organelles, and facilitates movement of vesicles/cells

movement of cells/vesicles depends on interaction with motor proteins

Type of fibers (3)

microtubules, microfilaments, and intermediate filaments

Microtubules

Hollow rod-like structures made of tubulin (a protein, grows from centrosome) that assist in organelle movement, chromosome separation, and cell motility (cilia and flagella)

Cilia

membrane bound, sensory organelle that appears on most eukaryotic cell

hair-like structure on outside of cells to move particles across the cell surface

Flagella

microscopic hair-like structures that help the cell move; found on many different types of cells

Microfilaments

Thin solid rods made of actin (a protein) that maintain cell shape, assist in muscle contraction, and are involved in animal cell division.

Intermediate Filaments

Fibrous proteins that provide permanent structural support, maintain cell shape, and anchor the nucleus and organelles

form the nuclear lamina which lines the linear envelope

Review questions + connecting ideas

questions for 2.1, 2.2, 2.10, and 2.11

(2.1) what organelles are in animal cells but NOT plant cells?

lysosomes, centrosomes, flagella

what organelles are in plant cells but NOT animal cells?

cell wall, chloroplast, vacuoles, plasmodesmata (in cell wall)

how do ribosomes help carry out instructions encoded in the DNA?

before DNA leaves the nucleus, it is transcribed into mRNA (messenger RNA) and then sent to the cytoplasm. there, the ribosomes translate the messages from mRNA and form chains of amino acids (forming proteins)

DNA —> mRNA in nucleus —> ribosomes —> amino acid chains —> protein

if a cell has a high rate of protein synthesis, what organelle would you expect it to have a large number of? why?

ribosomes because they are the sites for protein synthesis

differentiate between the rough and smooth ER

rough: contains ribosomes, keep proteins separate from free ribosomes

smooth: NO ribosomes, synthesizes lipids, metabolizes carbohydrates, detoxifies cell

what are the main differences between prokaryotic and eukaryotic cells?

prokaryotic: mainly in bacteria, generally smaller, DNA found in nucleoid, DO NOT have membrane bound organelles

eukaryotic: found in plants, animals, fungi, and protists, DNA in nucleus, DO have membrane bound organelles

describe the endomembrane system

network of membranes present in the cytoplasm of a eukaryotic cell that divide the cell into compartments, or organelles. the system helps to send, receive, modify, and sometimes synthesize proteins/lipids in the cell.

organelles include: nuclear envelope, ER, golgi complex, lysosomes, vesicles, vacuoles, plasma membrane (cell membrane)

trace the path of a protein, from mRNA to modifications to final function.

DNA can only leave nucleus as mRNA so it can be read by ribosomes. mRNA goes into cytoplasm after it is modified inside nucleus and translated/read by ribosomes to be made into long chains of amino acids, which then form the proteins. proteins then go on to perform many different functions in the cell including (but not limited to): maintaining structure, replicating and transcribing DNA, transporting materials/molecules to other organelles, regulate what materials come in and out of the cell, etc.

compare the main functions of microtubules, microfilaments, and intermediate filaments

microtubules: (hollow rods, tubulin) structural support, separation of chromosomes, cell motility

microfilaments: (solid rods, actin) maintain cell shape, muscle contraction, division of animal cells

intermediate filaments: (form in nuclear lamina, lines nuclear envelope) maintain fell shape and anchor nucleus/organelles

Plants have a cell wall, therefore they do not have a plasma membrane. Is this true or false?

this is false; even though plant cells have a cell wall and animal cells do not, they both still have plasma membranes (cell membranes) that help to regulate which particles travel in and out of the cell

(2.2) compare the golgi complex to a warehouse/mail facility. how is the function similar?

the golgi complex, like a warehouse/mail facility, receives transport vesicles with materials from the ER. they then modify the material, sort the material, add molecular tags, and then package the material into new transport vesicles that exit the membrane. it receives, modifies, sorts, tags, and then sends out information, similar to what a mail facility like do with an income of mail

plant cells get their energy from photosynthesis, therefore they do not have mitochondria. do you agree or disagree with this statement? Why?

disagree; plant cells still have mitochondria even though they perform photosynthesis for energy. photosynthesis is not always a reliable way for the plants to make their energy (the sunlight is not always available), so they need mitochondria to use the sugar from the chloroplast to produce ATP through cellular respiration when sunlight is not available (during the night)

describe the roles of mitochondria and chloroplast

mitochondria: site of cellular respiration and the Krebs Cycle

chloroplast: site of photosynthesis and the Calvin Cycle (also for other light dependent reactions)

differentiate between the light dependent reactions and the Calvin cycle in the chloroplast

light dependent reactions: occur in grana in thylakoids. uses sunlight to produce energy in ATP and NADPH form

Calvin cycle: occur in stroma. uses the energy formed in the light dependent reactions (ATP and NADPH) to convert CO2 into sugar molecules

differentiate between the Krebs cycle and the electron transport chain in the mitochondria

Krebs cycle: occurs in mitochondrial matrix. chemical reactions that produce high-energy electron carriers like NADH

electron transport chain (ETC): uses energy electron carriers produced in the Krebs cycle to form protein chains that are eventually used to generate ATP

identify the location where each process occurs:

1. light dependent reactions

2. calvin cycle

3. krebs cycle

4. ATP synthesis

5. electron transport chain (ETC)

1. light dependent reactions: chloroplast, grana (thylakoids)

2. calvin cycle: chloroplast, stroma

3. krebs cycle: mitochondrial matrix

4. ATP synthesis: mitochondrial matrix

5. electron transport chain (ETC): intermembrane

why are pigments, like chlorophyll, important to plants?

chlorophyll is important to plants because they are involved in processes such as photosynthesis and other energy-producing processes needed for the plant to survive. they give the plant the ability to capture light from the sun and they help to transform the light energy into chemical energy

(2.10) why is compartmentalization important in cells? (use lysosomes as an example to support your reasoning)

because it allows different reactions in the cell to occur at different places by increasing the surface area. it prevents the possibility of reactions occurring in the same location. lysosomes are one example of why compartmentalization is so important; they break down cellular macromolecules and cell waste with enzymes that would otherwise harm other functions occurring in the cell. their functions need to be compartmentalized in order to keep the cell/cytoplasm from distructive enzymes

discuss how the mitochondria and chloroplast compartmentalize processes (be specific)

both the mitochondria and chloroplast compartmentalize their processes by using a double membrane. it allows them to separate different chemical processes that happen within each respective organelle. it makes it easier for each organelle to separate the different functions they perform and the enzymes needed for each function

mitochondria: outer membrane = smooth, inner membrane = cristae folds that divides mitochondria into tow compartments and increases surface area (useful for compartmentalization to prevent different reactions from occurring in the same place)

chloroplast: thylakoids (grana) for light dependent reactions, stroma for Calvin cycle; need to happen in two separate places in order for the energy for the cell to be made properly and then used in the Calvin cycle

how does compartmentalization affect surface area?

increases surface area to ensure a surface are to volume ratio that allows for the most space (and therefore ensuring that interfering reactions do not occur in the same place within the organelle)

why is the mitochondria highly folded? (i.e. what is it producing?)

because the folds (cristae) increase the surface area to maximize the amount of space available for chemical reactions to occur. it allows the mitochondria to synthesize/produce the most amount of ATP/energy that it can

how do eukaryotic and prokaryotic cells differ in terms of compartmentalization?

because eukaryotic cells contain membrane bound organelles, compartmentalization is essential to ensure that their functions do not interfere with each other. because prokaryotic cells usually lack membrane bound organelles, most of their processes occur in open spaces rather than specific organelles. (therefore compartmentalization is not as needed in prokaryotic cells)

(2.11) describe the endosymbiotic theory in your own words

theory that proves how the mitochondria and chloroplast are similiar to a prokaryote. uses claim that an eukaryotic cell surrounded a prokaryotic cell and therefore became an endosymbiotic cell (one cell that lives in another) and one cohesive functional organism. used to explain existence/origin of chloroplast and mitochondria

what evidence is there to support the endosymbiont theory?

1. double membranes

2. ribosomes

3. ciruclar DNA

4. capability of functioning on their own

mitochondria and chloroplasts can still be found as free-living prokaryotes (i.e. not in a symbiotic relationship with a eukaryote). True or False?

false: they cannot live freely outside of an eukaryotic cell. they originated from prokaryotic cells that were then engulfed by eukaryotic cells in order to become organelles and function inside the eukaryotic cells. this means that they could not live freely as a prokaryote outside the cell because they need the eukaryotic cell to function

cell size

dictates the cell function; cellular metabolism depends on cell size. at a certain size, the cell cannot effectively regulate what comes it and what goes out of the plasma membrane

surface area and volume

cells need a high surface area-to-volume ratio to optimize the exchange of materials through the membrane

**when the SA:V ratio is HIGHER, it optimizes the cell’s ability to exchange material through the plasma membrane

types of formulas

formulas for CUBIODAL cells and SPHERICAL cells

**note: all formulas are given on this quiz and on the AP test as well

SA:V ratio significance?

SMALL cells have a HIGH SA:V ratio (optimizes exchange of materials)

LARGE cells have a LOWER SA:V ratio (lose efficiency in exchanging materials, demand for resources increases and rate of heat exchange decreases)

plasma membrane

separates internal cell environment from external environment. comprised mainly of phospholipids

phospholipids

type of lipid molecule that is amphipathic (have hydrophilic heads and hydrophobic tails) and form a bilayer in the membrane.

phospholipids are made up of a phosphate group, glycerol, a hydrophilic head, and a hydrophobic tail (tails are either saturated or unsaturated)

amphipathic

having both hydrophilic and hydrophobic parts

hydrophilic heads

oriented TOWARD aqueous environments (facing outwards in the bilayer)

hydrophobic tails

oriented inwards AWAY from aqueous environments (facing inwards in the bilayer)

selective permeability

ability of membranes to regulate the substances that enter and exit the cell

fluid mosaic model

model to describe the structure of cell membranes

fluid

membrane is held together by weak hydrophobic interactions and can therefore move and shift (flexible)

affects on fluidity

temperature, unsaturated hydrocarbon tails (maintain fluidity), kinked tails PREVENT tight packing of phospholipids,

cholesterol

helps maintain fluidity at high and low temps

high temp: reduces movement

low temp: reduces tight packing of phospholipids

mosaic

comprised of many macromolecules, TWO major proteins in the membrane

integral proteins (transmembrane proteins)

are embedded into the lipid bilayer; amphipathic

peripheral proteins

NOT embedded into the lipid bilayer; loosely bonded to the surface

membrane carbohydrates

important for cell-to-cell recognition; TWO types: glycolipids and glycoproteins

glycolipids

carbohydrates bonded to lipids

glycoproteins

carbohydrates bonded to proteins; most abundant membrane carbohydrates

plant cells

have a CELL WALL that covers their plasma membranes: extracellular structure that are NOT found in animal cells)

composed of cellulose and plasmodesmata

functions of the cell wall

shape/structure, protection, regulation of water intake (VERY IMPORTANT FOR PLANTS)

plasmodesmata

hole like structures in the cell wall filled with cytosol that connect adjacent cells

polar

molecule that has an uneven distribution of electrical charge: one side of the molecule has a slightly positive charge and one side has a slightly negative charge

hydrophilic head of a phospholipid is POLAR

nonpolar

molecule whose charges (electron density) are more or less evenly distributed

hydrophobic tail of a phosphlipid is NONPOLAR

charged

referring to a molecule/ion that has a specific electron charge (attract or repel other charged matter)

positively charged ion= cation

negatively charged ion= anion

Describe how the surface area-to-volume ratio should be in order for cells to optimize the exchange of material through the plasma membrane (2.3)

cells need a HIGH surface area-to-volume ratio; the size dictates the function. when there is a high surface area-to-volume ratio, it maximizes the amount of space inside the cell for the organelles to carry out their individual functions effectively.

Propose problems that would occur if a single cell were to keep getting larger and larger over time

if a cell gets too large, it could potentially effect the cell’s ability to regulate what comes in and what goes out of the plasma membrane; cellular METABOLISM depends on the cell SIZE. this could lead to unwanted substances to enter the cell, wanted substances to be blocked out of the cell, or limit the cell’s ability to get rid of excess waste/thermal energy.

The following lists compare the surface area-to-volume ratio of three cells. Identify the ratio of the cell that will have the most efficient exchange across its cell membrane :

1. 2.0; 0.9; 1.2

2. 0.9; 0.6; 1.1

3. 0.6; 0.7; 0.5

1. 2.0

2. 1.1

3. 0.7

   the highest surface area-to-volume ratios in each scenario will have the most efficient exchange across their cell membranes.

You have a set of data regarding the surface area-to-volume ratios of four cells. Identify the ratio belonging to the cell that would be best suited for storage:

1. 4.5

2. 7.2

3. 3.1

4. 5.5

3. 3.1: larger cells normally have a LOWER surface area-to-volume ratio. This means that it most likely has more room to store substances. It could also mean that because larger cells have a more difficult time exchanging materials through the plasma membrane, this cell would be a better source of storage rather than constant function/interaction.

Calculate and compare the SA:V ratios of the cubes. Then identify which will have the best exchange of material through the plasma membrane.

cube #2 (SA:V= 3) because the ratio is higher and therefore better at exchanging materials through the plasma membrane

Why is the plasma membrane often referred to as a fluid mosaic model? (2.4)

because of the specific properties and macromolecules that the plasma membrane has.

fluid: membrane held together by weak hydrophobic interactions (hydrophobic tails of the phospholipids) and therefore can move and shift; plasma membranes are held together by hydrophobic tails of phospholipids and are flexible because of those weak bonds.

mosaic: comprised of many macromolecules; the plasma membrane also contains macromolecules including carbohydrates (glycolipids and glycoproteins) and proteins (integral [embedded into bilayer] and peripheral [NOT embedded into lipid bilayer]).

What is the purpose of the plasma membrane?

the plasma membrane separates the internal environment of the cell from the external environment. it regulates what comes in and what goes out of the cell, allowing the cell to invite wanted substances in and exporting the unwanted substances such as waste.

What is the difference between unsaturated and saturated tails of the phospholipids? (think back to Unit 1)

the saturated tails only have SINGLE bonds between carbon atoms, therefore creating a STRAIGHT chain. this allows for the chain to be tightly packed together, providing more structure and less flexibility.

the unsaturated tails have one of more DOUBLE bonds between carbon atoms, causing a “kink” in the chain; this “kink” results in a BENT chain, making the unsaturated tails less packed together and more ability to be flexible

What causes the kinks in the tails of phospholipids?

the creation of a double bond between carbon atoms; if there is a kink in the chain, that tail can be classified as an unsaturated fatty acid chain