GRQ #2 - Membrane Potentials

Question 1

besides phospholipids the main components of the plasma membrane are

Answer 1

membrane proteins - they carry out many of the membrane’s functions

Question 2

how are membrane proteins positioned

Answer 2

their hydrophobic amino acids are in the fatty acid tail portion of the phospholipid bilayer - the middle - and their hydrophilic amino acids are facing the water filled cytosol and/or ECF

Question 3

What is an integral protein?

Answer 3

they typically span the entire width of the membrane and when they do reach both sides of the membrane they are known as transmembrane proteins

Question 4

what are peripheral proteins>

Answer 4

they are found on only one side of the membrane

Question 5

are all integral proteins static?

Answer 5

no - some are anchored in place by the cytoskeleton but many float freely within the plane of the PBL

Question 6

are peripheral proteins static?

Answer 6

no - they are loosely bound to the membrane surface or to integral proteins and many can also move horizontally along the membrane surface

Question 7

what is one structure/function of membrane proteins?

Answer 7

acting as channels. many transmembrane proteins serve as protein channels that allow certain substances to cross the membrane and pass into or out of the cell

Question 8

what is another function of membrane proteins? acting as _

Answer 8

carriers. integral proteins called carrier proteins bind and directly transport substances into and out of the cell - ex. an ion from the ECF binds to a carrier protein which changes shape and releases the ion into the cytosol

Question 9

another function of the membrane proteins is acting as __

Answer 9

receptors. a receptor is a membrane protein that binds to a chemical messenger called a ligand and when a ligand binds to its receptor then changes are triggered within the cell

Question 10

receptor - ligand interactions are an example of __ and are responsible for __

Answer 10

cell-cell communication core principle. They are responsible for much of the physiology of the muscular, nervous, and endocrine systems

Question 11

acting as ___ is another function of membrane proteins

Answer 11

acting as enzymes. enzymes are proteins that speed up chemical reactions and they are vital to plasma membrane structure and function and are often lodged within the membrane

Question 12

enzymes can ___ metabolic reactions are are often found lodged within the ___

Answer 12

catalyze and are found lodged ex. enzymes can catalyze the formation or breakdown of bonds between substrates

Question 13

providing ___ ____ is another function

Answer 13

structural support. membrane proteins may be bound to components of the cytoskeleton and other proteins in the ECF and cytosol which provides the cell with shape and help maintain structural integrity

Question 14

___ ____ cells is another function of membrane proteins

Answer 14

linking adjacent cells. certain membrane proteins can attach to other membrane proteins in adjacent cells, holding the cells in a tissue together - known as “linker proteins” and they can strengthen a tissue or allow adjacent cells to communicate

Question 15

what are other components of the plasma membrane? (4)

Answer 15

several kinds of lipids, glycolipids, glycoproteins (consist of carbohydrate chains called polysaccharides that are covalently attached to either membrane lipids or proteins) and carbohydrates
ex. cholesterol is a lipid

Question 16

what does cholesterol do in the membrane?

Answer 16

it stabilizes the structure of the plasma membrane when the temperature changes - critical because the plasma membrane must maintain a certain state of fluidity to function

Question 17

what is cell recognition?

Answer 17

the ability of our cells to tell one cell type from another - polysaccharides or polymers that are found on the outside of the membrane function in cell recognition

Question 18

the glycoproteins and glycolipids produced by each cell are ___ to that cell type and that ___ and serve as a ___

Answer 18

each cell are unique to that cell type and that organism and serve as a sort of identification tag

Question 19

the plasma membrane acts as a __ between the __ and the __ in our cells

Answer 19

fence between the extracellular fluid and the cytosol in our cells

Question 20

the plasma membrane is ___ ___ and it is a property critical to the cell - it needs to pass things in and out like oxygen, nutrients etc.

Answer 20

selectively permeable - allows certain things to pass through but not others

Question 21

the ECF and cytosol consist largely of ___ with dissolved __ and ____ of varying size & concentration

Answer 21

water with dissolved ions and organic compounds

Question 22

The ECF contains substances the cell ___ while the cytosol contains substances that must ___

Answer 22

needs; leave the cell
ex: ECF = glucose, amino acids, fatty acids, water, oxygen, vitamins
cytosol = CO2, waste products

Question 23

passive transport process

Answer 23

requires no net expenditure of energy from the cell

Question 24

active transport process

Answer 24

do require the cell to expend energy usually in the form of ATP

Question 25

what three variables does whether or not the process is active or passive depend on

Answer 25

1. the type of substance crossing the membrane 2. the membrane's permeability 3. the concentration of that substance both inside and outside the cell

Question 26

what are the two basic types of passive transport?

Answer 26

osmosis and diffusion

Question 27

diffusion is defined as

Answer 27

the movement of solute molecules (those that are dissolved) from an area of higher solute concentration to an area of lower solute concentration

Question 28

what is the basic force that drives diffusion called?

Answer 28

a concentration gradient - it involves a difference in concentration of a substance from one area to another

Question 29

diffusion allows solutes to move into and out of the cell using the ___ ____ of a concentration gradient

Answer 29

potential energy

Question 30

moving from a higher to a lower concentration during the process of diffusion is known as

Answer 30

moving down/with the concentration gradient

Question 31

why do the molecules scatter when the divider is removed>

Answer 31

they move due to their own kinetic energy, which all molecules have as long as thermal energy or heat is present

Question 32

the movement continues until ___ is reached because there is no more __ ___

Answer 32

equilibrium because there is no more potential energy from a gradient to drive it

Question 33

no "net" movement refers to the fact that there is no further change taking place in the solution's concentration, but the molecules are __ even at ___ because of their __ ___

Answer 33

the molecules are moving even at equilibrium because of their kinetic energy

Question 34

rate of diffusion depends on several factors which include

Answer 34

size and phase of the diffusing particles, temperature, size of the concentration gradient

Question 35

___ particles, particles in ___ phase, ___ temperatures and ___ concentration gradients ___ the rate of diffusion

Answer 35

smaller, gaseous phase, higher temps, steeper concentration gradients, increase the rate

Question 36

raising the particles' __ __ will cause them to move __

Answer 36

kinetic energy; move faster

Question 37

the ___ which the particles diffuse and the __ of a barrier are other factors

Answer 37

medium; presence

Question 38

when a barrier exists, the rate of diffusion depends on the properties of the barrier such as __, ___, and ___ to the ___

Answer 38

thickness, surface area and permeability to the particles

Question 39

the barrier to diffusion in and out of the cell is the ___ ___

Answer 39

plasma membrane

Question 40

what are the two types of basic diffusion

Answer 40

facilitated and simple

Question 41

what is simple diffusion

Answer 41

it mostly involves nonpolar solutes (such as hydrocarbons and lipids and gases like O2 and CO2) that pass straight through the phospholipid bilayer without assistance from a membrane protein

Question 42

facilitated diffusion involves:

Answer 42

charged or polar solutes (such as ions and glucose) that cross the bilayer with the help of a membrane protein

Question 43

nonpolar molecules in simple diffusion have properties similar to those of the nonpolar fatty acid tail region therefore they can ___

Answer 43

easily cross into or out of the cell with their concentration gradients

Question 44

fatty acid tails don't want to react with the polar solutes and ions making it ___ for them to cross the membrane unassisted

Answer 44

difficult

Question 45

what two types of membrane proteins do the polar solutes rely on to transport in and out of the cell?

Answer 45

channels and carriers

Question 46

when using the protein channels,

Answer 46

the hydrophilic amino acids in the protein are orientate toward the interior of the channel which forms the passageway through which charged polar solutes can pass ; most channels are specific for an individual solute

Question 47

facilitated diffusion using carrier proteins works in that ...

Answer 47

the carriers bind one or two specific solutes and "carry" them into or out of the cell - when a solute binds to the carrier protein, the protein changes shape allowing the solute to move across the membrane

Question 48

three types of carrier proteins are:

Answer 48

1. uniporter 2. antiporter 3. symporter

Question 49

a uniporter:

Answer 49

transports a single solute

Question 50

a antiporter:

Answer 50

transports two different solutes in opposite directions - one in the cell and one out

Question 51

a symporter:

Answer 51

moves two solutes in the same direction

Question 52

facilitated diffusion is a type of ___ transport even though it requires the ___

Answer 52

passive; requires the help of membrane proteins

Question 53

both facilitated and simple diffusion rely on the __ __ of the __ __ to drive each solute's movement

Answer 53

potential energy of the concentration gradient to drive the solute's movement

Question 54

active transport requires ___ because solutes are moving ___

Answer 54

cells to expend energy in the form of ATP because solutes are moving against their concentration gradient

Question 55

they move from ___ concentration to ___

Answer 55

low to high concentration

Question 56

energy must be supplied from the ___ of ___ because the gradient does not provide ___ to drive the movement

Answer 56

hydrolysis of ATP because gradient doesn't provide energy to drive movement

Question 57

active transport requires carrier proteins called __

Answer 57

pumps - they bind and transport a solute across the membrane

Question 58

pumps can be __ , ___, or ___ and they are all ___ so they are also enzymes that catalyze the reaction that breaks down ATP into ADP and a phosphate

Answer 58

uniporter, antiporter or symporters and they are all ATPases

Question 59

what are the two types of active transport that move substances across the plasma membrane?

Answer 59

primary active transport and secondary active transport

Question 60

in the process of primary active transport:

Answer 60

a pump binds a solute and transports it against its concentration gradient using energy from the hydrolysis of ATP

Question 61

the major primary active transport pump in the body is the ___ pump known as the ___

Answer 61

the antiport pump known as the sodium-potassium pump

Question 62

critical to maintain the concentration gradients of sodium and potassium ions as they are required for __ __

Answer 62

skeletal muscles to contract, the heart to beat, nerves to send impulses, cells to maintain their osmotic balance and more

Question 63

the pump maintains this steep concentration gradient by transporting __ sodium ions ___ of the cell for every __ potassium ions it moves __ the cell

Answer 63

3 sodium ions out of the cell for every 2 potassium ions it moves into the cell - both against their concentration gradient

Question 64

sequence of events of the sodium potassium pump:

Answer 64

1. the pump binds 3 sodium ions from the cytosol 2. ATP is hydrolyzed, phosphate binds to pump and pump changes shape 3. the pump releases the three sodium ions into the ECF and binds 2 potassium ions 4. the phosphate detaches and the pump changes back to original shape 5. the pump releases the two potassium ions into the cytosol

Question 65

secondary active transport is the process of:

Answer 65

using ATP indirectly. the cell first uses ATP to create a concentration gradient by pumping one substance across the plasma membrane and then once the first gradient is established the cell harnesses that potential energy to power the active transport another substance against its gradient ; the active transport of one substance is coupled with the passive transport of a second substance