BIO Exam 2 Review

Structures in only plant cells

chloroplast, a large central vacuole, and plant cell walls

Plastids

contains own DNA and has molecular machinery for gene expression and synthesis of proteins on ribosomes

Examples of plastids

chloroplasts, amyloplasts, and chromoplasts

Chloroplast

found in only plant cells; have an outer boundary membrane and an inner boundary membrane to enclose the stroma; inside the stroma is the thylakoids that are stacked in grana

What do thylakoid membranes contain and what do they do

chlorophyll, the pigment that absorbs light and converts it to chemical energy

Central vacuoles

found only in plant cells; 90% or more of the cell’s volume may be taken up by this; acts as storage, contains enzyme for breakdown of macromolecules, and contains molecules for chemical defense

Cells walls

found only in plant cells; consists of cellulose fibers

Parts of a cell wall

primary cell wall- soft and flexible

secondary cell wall- additional layers of cellulose fibers and branched carbs

Middle lamella

what walls of adjacent cells are held together by; is a layer of polysaccharides (pectin)

Plasmodesmata

communication junctions in plant cells; what primary and secondary cell walls are perforated by

What do plasmodesmatas allow

they allow ions and small molecules to move from one cell to another through the cytosol

What structures are on the surface of animal cells

cell adhesion molecules, cell junctions, and extracellular matrix

Cell adhesion molecules

glycoproteins in the plasma membrane that bind to specific molecules on other cells; they make the initial connection between cells in early embryonic development

What do cancer cells lack and what does it allow them to do?

cell adhesion molecules; it allows for them to break loose and migrate towards other areas of the body (metastasis)

What are cell adhesion molecules occasionally targeted by?

bacteria and viruses

Anchoring junctions

spots on cells that “weld” adjecent cells together; most common tissues that are subject to stretching and other mechanical forces

Desmosomes

anchoring junctions with intermediate filaments that anchor the junction in underlying cytoplasm

Adherens junctions

microfilaments (actin) are the anchoring cytoskeleton component

Tight junctions

regions of tight connections between membranes of adjacent cells; they seal spaces between cells in cell layers that cover internal organs, outer surface of the body, or layers that line the internal cavities and ducts

How are tight junctions formed

direct fusion of proteins on the outer surfaces of plasma membranes of adjacent cells

Gap junctions

open direct channels that allow ions and small molecules to pass directly from one cell to another (they are like plasmodesmata in plants); communicate between cells within a tissue

Extracellular matrix

forms the mass of skin, bones, tendons, and many high specialized extracellular structures; also affect cell division, adhesion, motility, and embryonic development

main component of ECM

glycoproteins

Collagen

the most abundant ECM glycoprotein

Fibronectin

bind to receptor proteins (integrins) in plasma membrane

Proteoglycans

what the consistency of the ECM depend on; surrounds collagen fibers

What are 2 major lipids in membranes

phospholipids and sterols

Structure of phospholipids

glycerol + 2 fatty acids

Sterols

have nonpolar carbon rings with a nonpolar side chain at one end and a single polar group at other end; align with the nonpolar interior while the polar side extends into polar surface

Main sterol in animal membranes

cholesterol

Fluid mosaic models

membranes consist of fluid phospholipid bilayer where proteins are embedded and move freely

• fluid- refers to phospholipid molecules that constantly move and exchange places within the same layer

• mosaic- refers to membrane proteins that either float in lipid bilayer or are attached to cytoskeleton

Integral proteins

embedded in the phospholipid bilayer

Peripheral protein

held to membrane surfaces by noncovalent bonds

Lipid anchor proteins

anchored to bilayer via lipid molecules

Purpose of membrane proteins

transport, recognition, receptors, and cell adhesion

How do membrane proteins contribute to transport?

to form channels that allow selected polar molecules and ions to pass across a membrane

How do membrane proteins contribute to recognition?

in the plasma membrane identify a cell as part of the same individual or as foreign

How do membrane proteins contribute to receptors?

recognize and bind molecules from other cells that act as chemical signals (like hormones)

How do membrane proteins contribute to cell adhesion?

bind cells together by recognizing and binding receptors or chemical groups on other cells

_________ acid chains in membrane phospholipids help keep membranes fluid at low temperatures

unsaturated fatty acid

At low temperature, cholesterol . . .

intercalates between hydrocarbon tails and prevent them from stiffening => maintains fluidity

At high temperatures, cholesterol . . .

stabilizes the membrane and decreases fluidity

Hibernation

double bonds in fatty acids and cholesterol content increase to prevent membrane from freezing

What is the take away from Frye’s and Edidin’s experiment?

the mixing of membrane proteins in the fused human-mouse cells shows that membrane proteins move in the phospholipid bilayer, indicating that the membrane is fluid

Selective permeability

• hydrophobic molecules move freely through bilayer

• hydrophilic molecules move through slowly (impeded by hydrophobic core)

• charged atoms and molecules are blocked

Passive transport

uses energy from concentration gradient

Active transport

uses energy from ATP and other forms of energy

Simple Diffusion

diffusion through lipid part of a biological membrane

• depends solely on molecular size and lipid solubility

• nonpolar inorganic cases (o2, n2, and co2) and organic molecules are transported this way

Facilitated diffusion

diffusion of polar and charged molecules through transport proteins

Channel proteins

integral membrane proteins that form hydrophilic channels in the membrane through which water and ions can pass

Aquaporins

channel proteins that transport water

Ion channels

facilitate transport ions (Na+, K+, Ca2+, Cl-); most are gated channels

Gated channels

switch between open ,closed, or intermediate states

Carrier proteins

transport ions and other solutes across the plasma membranes

• physically binds molecules on one side of the membrane and releases them on the other

• this protein undergoes conformational change

• is specific, passive, and can become saturated if there are too few of them to handle solute molecules

Osmosis

diffusion of water across a selectively permeable membrane in response to concentration gradients; less solutes (high water concentration) to more solutes (less water concentration)

Osmotic pressure

force needed to stop osmotic flow; cell walls can counterbalance this but animal cells can burst

Tonicity

property of a solution with respect to a particular membrane

Hypotonic

solution around cell has a low concentration of solutes outside cell => water enters and cell swells

Hypertonic

solution around cell has high concentration of solutes outside cell => water leaves and cell shrinks

Isotonic

concentration outside and inside cell are balanced

Turgor pressure

what plants cells use to keep cells rigid and plants standing

Active transport

substances move against concentration gradient & requires energy

Functions of active transport

uptake of essential nutrients from fluid surrounding cells, removal of secretory or waste materials, and maintenance of intracellular concentrations (H+ Na+, K+, and Ca2+)

Membrane potential

active transport ions contribute to electrical charge difference across plasma membrane

Primary active transport

uses ATP; moves low to high; requires use of carrier proteins

Sodium-potassium pump

moves Na3+ out of cell and 2K+ into cell

• atp is used

• affinity of carrier protein for either Na or K changes so the ions can be carried across the membrane

  • positive charge accumulates outside membrane and negative inside, so a membrane potential of -50 to -200 mV is made

Calcium pump

moves Ca2+ from cytoplasm to cell exterior and from cytosol to vesicles of ER

• regulates secretion, microtubule assembly, and muscle contraction

  • in muscle contraction, CA2+ released=> leads to contraction

Symport

solute moves through membrane channel in same direction as driving ion

Driving ion

ion that generates energy to power other molecules to move against the gradient

Antiport

solute and driving ion move through membrane channel in opposite directions

Coupled transport

uses energy released from molecules in diffusion to supply energy to activate transport of a different molecule; a symporter is used

Endocytosis

proteins and other substances are trapped in pit-like inward depressions from plasma membrane

Non-specific endocytosis

aka bulk endocytosis; pinocytosis is a type where cells take in only fluids (nonspecific)

Specific endocytosis

aka receptor mediated endocytosis; specific molecules (signal molecules) are taken in after they bind to a receptor

What is the process of receptor mediated endocytosis

1. target molecules are bound to receptor proteins on outer cell surface (they recognize and bind only specific molecules in ECF)

2. receptors with target molecules collect in a depression in plasma membrane called the coated pit (a network of clathrin)

3. the pit pinches free from the membrane to form endocytic vesicles which fuse with lysosome in cytoplasm

4. enzymes in lysosome digest the contents of the vesicle

5. membrane proteins are recycled to plasma membrane

Phagocytosis

specific form of endocytosis; where surface receptors bind to materials taken in through extending cytoplasmic lobes around the material

Mutation in aquaporin causes. . .

inability to make concentrated urine because the aquaporin is a channel proteins that transports water

Aerobic respiration

oxygen is reactant in ATP producing process; form of cellular respiration in many eukaryotes and prokaryotes

Anaerobic respiration

molecule other than oxygen (nitrate or sulfate) is used as the final electron acceptor ; form of cellular respiration in some prokaryotes

Fermentation

final electron acceptor is an organic molecule

Stages of glucose oxidation

glycolysis, pyruvate oxidation, kreb’s cycle, and ETC/chemiosmosis

Where does the breakdown of glucose occur in eukaryotes

cytosol- glycolysis

mitrochondrial matrix- pyruvate oxidation and krebs

inner mitochondrial membrane- ETC/chemiosmosis

yield of glycolysis

2 ATP, 2 NADH, 2 pyruvate

yield of pyruvate oxidation

2 NADH, 2 Acetyl-CoA

yield of krebs cycle

6 NADH, 2 FADH2, 2 ATP

Feedback inhibition in glycolysis

• ATP allosterically inhibits phosphofructokinase; excess citrate and NADH will inhibit this enzyme as well

• pyruvate kinase is inhibited by high levels of ATP and acetyl-CoA, and activated by high levels of fructose, 1,6- bisphosphate

Feedback inhibition in pyruvate oxidation

pyruvate dehydrogenase inhibited by high levels of NADH

Feedback inhibition in citric acid cycle

citrate synthase inhibited by high levels of ATP and citrate

Electron Transport Chain

series of membrane bound electron carriers; embedded in inner mitochondrial membrane

Which are the 3 major protein complexes

complex I, III, IV

Where does NADH enter

complex I

Where does FADH enter

complex II

What role do the moving electrons have

forms a proton gradient across the inner mitochondrial membrane

• high proton concentration in intermembrane compartment

• low proton concentration in matrix

What role does the proton gradient have

supplies energy that drives ATP synthesis by mitochondrial ATP synthase

Which electron carriers are in between complexes

cytochrome c and ubiquinone

What electron carriers are in complex I

FMN (flavin mononucleotide) and Fe/S (iron-sulfur)

What electron carriers are in complex III

cytochrome b, Fe/S, and cytochrome c1

What electron carriers are in complex IV

cytochrome a and cytochrome a3

Chemiosmosis

chemiosmotic hypothesis; ATP synthase uses proton-motive forces to add phosphate to ADP to make ATP