biol 302 exam 3

whoop whoop

cell membranes act as ______

selective barriers

what do cell membranes do?

allow for the molecular composition of a cell to differ from its environment

eukaryotic cells have additional ____ ______ that inclose individual organelles

internal membranes

what are 4 functions of a cellular membrane?

bring nutrients in, pump wastes out, protect internal organelles, sense changes in the extracellular environment

what is the phospholipid bilayer composed of?

hydrophobic and hydrophilic regions

what is the most common phospholipid in the bilayer?

phosphatidylcholine

what is phosphatidylcholine made of?

choline, phosphate, and 2 hydrocarbon chains

different types of lipids are _______ (containing hydrophobic and phyllic regions)

amphipathic

true/false: the plasma membrane and internal membranes are self sealing

true

what are liposomes?

closed, spherical formations of pure phospholipids that can form spontaneously

what is the fluidity of the the lipid bilayer influenced by?

temperature, phospholipid composition, saturated vs unsaturated cells, short tails, and unsaturated fatty acid tails

what do scramblases do?

scramble up the phospholipid bilayer so its more symmetrical, its completely random

what do flippases do?

maintain asymmetry of the plasma membrane

what does cholesterol do in the cell membrane?

helps provide structure by stiffening the membrane

what are 4 types of membrane proteins?

anchors, receptors, enzymes, transporters

what do anchor membrane proteins do?

keep things in place to do their jobs

what do receptor membrane proteins do?

communicate things from inside and outside the cell

what do transporter membrane proteins do?

help things go in and out of the membrane

what do enzyme membrane proteins do?

build or break down covalent bonds

what are the 4 ways membrane proteins associate with the lipid bilayer?

transmembrane, monolayer, lipid linked, and protein attached associations

how can the lipid bilayer be broken up?

by using a detergent to solubize it

what are detergents commonly used in the lab?

SDS and Triton X 100

what does the cell cortex do?

determines the shape of a cell and its mechanical properties

human red blood cells are made up of a meshwork of _______

spectrin dimers

what are some ways plasma membrane proteins are restricted?

tethered to the cell cortex, tethered to ECM molecules outside the cell, tethered to proteins on another cell, diffusion barriers restrict movement

the eukaryotic cell surface is coated with ______ attached to lipids and proteins in the extracellular face

sugars

why is sugar coated euakryotic cell surfaces important?

they help with cell-cell recognition and adhesion, absorb water, provides a slimy outer coating to help the cell slide and squeeze into places, and protects the cell from chemical damages

what is photobleaching used for?

to study the rates of lateral diffusion in membrane proteins

membrane proteins can be tagged with ________ to observe fluorescence over time

GFP

faster fluorescence recovery after photobleaching (FRAP) indicates….

more movement

single particle tracking (SPT) is used for?

tracking the movement of single particles across the membrane

how do differences in ion composition btw a cells interior and exterior affect cellular processes?

it influences activity of nerve cells and atp production

what molecules are able to diffuse through the membrane w no aid?

small hydrophobic molecules, small uncharged polar molecules, larger uncharged poplar moleculeswhatwhat

what are two types of proteins that help larger molecules across the cellular membrane?

channel and transporter proteins

what is a channel protein?

a hydrophilic pore across the lipid bilayer where specific ions can diffuse through

what is a transporter protein?

a membrane protein that undergoes conformational changes to transfer molecules across the lipid bilayer

passive transport

movement across the membrane that requires no energy

active transport

movement across the membrane that requires energy

what are the 2 types of passive transport?

simple diffusion - no transport protein required

facilitated diffusion - transport protein required

a molecule moving from an area of high to low concentration is moving…

down the concentration gradient

a molecule moving from an area of low to high concentration is moving…

up the concentration gradient

what are the two stages of conformational changes?

stage 1 - binding site exposed on the outside of the membrane (attractive)

stage 2 - site is exposed on the other side of the membrane (repulsive)

what two things drive passive transport?

concentration gradients and electrical forces

what is the electrochemical gradient determined by?

concentration gradient of an ion and membrane potential

what are the 3 types of active transport?

coupled transport, ATP driven pump, light driven pump

coupled transport

Process where the movement of one substance is coupled to the movement of another substance across a membrane.

atp driven pump

the movement of a molecule up the concentration gradient is coupled to the hydrolysis of ATP to ADP (most common)

light driven pump

movement of one molecule up the concentration gradient coupled to light energy (bacteria)

why must high levels of Na+ be maintained on the extracellular side?

bc its used for coupled transport

why is K+ on the cytoplasmic side important?

for nervous system function

what are the steps of the Na+-K+ pump?

1. 3 sodium ions bind to the intracellular site
2. phosphate group is transferred by ATP hydrolysis
3. pump undergoes conformational change and transports sodium across
4. 2 potassium binding sites are exposed
5. phosphate is released, pump returns to its original state
6. K+ is moved across the membrane

what does the calcium pump require to function?

atp

why must calcium concentrations be kept low?

intracellular signaling requires an increase in calcium

symport movement

same direction

antiport direction

opposite directions

uniport transport

one molecule is transferred across the membrane

the transport of glucose is is conducted by…

the symport protein which uses the Na+ electrochemical gradient

osmosis

diffusion of water

diffusion

movement from high to low concentrations

what are some qualities of potassium channels?

a selectivity filter to control ion transport, highly selective pores, opposite charges work best

gated ion channels

switch between open and closed and very in the conditions that influence their opening

voltage gated channel

controlled by membrane potential and voltage sensors, transmits signals between nerve cells

ligand gated channel

controlled by the binding of a ligand to the channel protein

stress activated channel

controlled by mechanical forces, sounds trigger the opening of ion channels in the ear

membrane potential

voltage differences across a membrane due to slight excess of positive ions on one side and negative ions on the other

what does membrane potential do?

its sued for transmitting signals between cells, especially muscle and neurons

what are neurons made of?

a cell body, axons, dendrites, and nerve terminals

signals in the nervous system travel long distances, what keeps these signals from fading?

action potentials

action potentials

a local stimulus causes a large change in membrane potential that provides a strong enough signal to get to the next nerve cell

how is action potential stimulated?

ligated channels open temporarily which causes depolarization of the plasma membrane, the membrane potential becomes less negative, and the depolarization opens voltage gated Na+ channels

ion flow dictates the __ and ___ of an action potential

rise and fall

how do neurons transmit signals?

an electrical signal is converted into a chemical signal at a nerve terminal by ion gated channels at a synapse, then the signal is transmitted across the synapse

excitatory neurotransmitters

activate ion channels that allow the passage of Na+

inhibitory neurotransmitters

activate ion channels that allow the passage of Cl-

the breakdown of chemical bonds that produces energy creates what molecules?

ATP, NADH and other activated carrier molecules

what are the 3 stages of cellular metabolism?

1. breakdown of large food molecules into simple subunits
2. breakdown of small subunits into acetyl coa, limited amounts of ATP and NADH are produced
3. complete oxidation of acetyl group to H2O and CO2, large amounts of ATP and NADH are produced in the inner mitochondrial membrane

LEO the lion goes GER

lose an electron - oxidize

gain an electron - reduce

what are the net products of glycolysis?

2 pyruvate, 2 ATP, 2 NADH

what are the 3 main stages of glycolysis?

1. energy investment
2. cleavage of 6-C sugars into 2 3-C sugars (pyruvate)
3. energy generation

which steps of glycolysis are irreversible?

steps 1, 3, and 10

what enzyme is involved in step 1 or glycolysis?

hexokinase

what enzyme is involved in step 3 of glycolysis?

phosphofructokinase

what enzyme is involved in step 10 of glycolysis?

pyruvate kinase

what is the difference between the way NADH+ is generated in yeast cells and in muscle cells?

in muscle cells pyruvate is converted to lactate, in yeast cells pyruvate is converted to CO2 and ethanol

pyruvate is oxidized by acetyl coa and CO2 by dehydrogenase in the _____ __.__ this produces _______

mitochondrial matrix, NADH+

fatty acids are converted to acetyl coa in the mitochondria by trimming __ __(#)__ _____ off at a time from the carboxyl end

2 carbons

each turn of the fatty acid to acetyl coa cycle produces…

1 acetyl coa, 1 NADH, 1 FADH2

what are the net products of the citric acid cycle (TCA cycle)?

3 NADH, 1 FADH2, 1 GTP, 2 CO2

what is the purpose of the citric acid cycle?

to convert the acetyl group of acetyl coa into H2O and CO2

what is step 1 of the TCA cycle?

the conversion of 4C Oxaloacetate into 6C citrite through the addition of acetyl coa

glycolysis and the tca cycle provide the precursors needed to ______________

synthesize biological molecules

anabolic pathways can convert different substrates into ___ *,* __, ______, and _______

amino acids, lipids, nucleotides, other small molecules

to maintain order in cells, all organisms must constantly replenish ______ through sugar or fat oxidation

ATP

glycogenesis

a process by which blood glucose is synthesized from lactate, pyruvate or amino acids reverse reactions from glycolysis

where does glycogenesis mainly occur? (type of cell)

liver cells

how is the irreversible 3rd step of glycolysis bypassed in glycogenesis?

by transferring a phosphate group from ATP

step 3 of glycolysis is catalyzed by _____ and ________ reverses it

phosphofructokinase, fructose 1-6 biphosphate

what is the purpose of glycogen?

to be a way to store sugars for later use, a backup for when more atp is needed

glycogen phosphorylase

catalyzes the breakdown of glycogen to glucose-1-phsophate in liver cells

glycogen synthase

catalyzes glucose to glycogen