Cell Membrane, Membrane Transport, and Membrane Potential 1

Question 1

What are the functions of the plasma membrane?

Answer 1

1. separate cytoplasm from ECF
2. regulate exchange between ECF and cytoplasm
3. communicate with other cells
4. provide structural attachments between cells or between cells and extracellular matrix

Question 2

What are the organic molecules that make up the plasma membrane?

Answer 2

-phospholipids
-steroids
-proteins
-carbohydrates

Question 3

What is the consistency of plasma membranes at body temp?

Answer 3

of a thick oil

Question 4

Why is the plasma membrane the consistency of a thick oil?

Answer 4

because it needs to be flexible enough to allow things to pass through

Question 5

What are the characteristics of phospholipids?

Answer 5

amphipathic and organized into a bilayer

Question 6

What substances are able to move through the plasma membrane?

Answer 6

hydrophobic substances, small non-polar, and lipophilic substances
-WATER IS

Question 7

What are some examples of things that can pass through the plasma membrane?

Answer 7

gases (O2 and CO2) , fatty acids, steroids, ethanol, and water

Question 8

What substances are not able to move through the plasma membrane?

Answer 8

larger molecules, polar molecules, charged substances

Question 9

What are some examples of things that can not pass through the plasma membrane?

Answer 9

glucose, amino acids, ions, and proteins

Question 10

What is the role of cholesterol in the plasma membrane?

Answer 10

help keep the membrane fluid over a wide range of temperatures and help to make membrane water tight

Question 11

If the plasma membrane were a pure phospholipid bilayer, what would happen?

Answer 11

water would be able to pass through very easily without much control

Question 12

What are some factors that alter protein shape?

Answer 12

mutations, pH, temperature, osmolarity, and covalent/allosteric modulation

Question 13

What determines a protein’s function?

Answer 13

its shape

Question 14

What are the structural classifications of proteins?

Answer 14

transmembrane, integral, and peripheral

Question 15

What are transmembrane proteins?

Answer 15

travel throughout the entire length of the membrane

Question 16

What are integral proteins?

Answer 16

proteins that are embedded in the membrane but do not travel the entire length

Question 17

What are peripheral proteins?

Answer 17

proteins that are associated with the heads of the phospholipids but do not actually enter the bilayer
-can be in the cytoplasm of the ECF

Question 18

What are the properties of receptors?

Answer 18

-specificity
-saturation
-competition

Question 19

What do receptors do?

Answer 19

bind to a specific chemical signal (ligand) and transmit information into the cytoplasm

Question 20

What is signal transduction?

Answer 20

the process where a ligand receptor complex causes an intracellular response

Question 21

What is specificity?

Answer 21

the idea that the shape of the binding site determines what can bind

Question 22

Do proteins interact with many different substances?

Answer 22

no, typically receptors will only interact with one substance or one class of substance

Question 23

What is the active site?

Answer 23

the site where the ligand interacts with the receptor

Question 24

What is saturation?

Answer 24

the idea that there are a set number of proteins within the body so there is a set number of binding sites for those proteins

Question 25

What does it mean if something is saturated?

Answer 25

all of the binding sites are full

Question 26

What does saturation refer to?

Answer 26

the fraction of total binding sites that are occupied at any given time

Question 27

What is saturation dependent on?

Answer 27

concentration of protein and the concentration of the substance

Question 28

What is transport rate proportional to?

Answer 28

substrate concentration until the carriers are saturated

Question 29

What is an exogenous ligand?

Answer 29

something is put into our body from outside

Question 30

What is an endogenous ligand?

Answer 30

something that comes from inside the body

Question 31

What is a competitive inhibitor?

Answer 31

chemical substance (exogenous ligand) that binds to the active site of the protein and blocks the endogenous ligand from binding

Question 32

What do competitors do?

Answer 32

they do not produce an effect

Question 33

What is the level of inhibition dependent on?

Answer 33

the concentration of protein, endogenous ligand, ad competitive inhibitor

Question 34

When there is an inhibitor, what happens to the rate of the reaction?

Answer 34

it decreases because some of the binding sites are blocked and not producing the same effect

Question 35

What are some examples of competitors?

Answer 35

penicillin, ACE inhibitors, and beta blockers

Question 36

If there is no receptor, what happens to the response?

Answer 36

there is no response

Question 37

If two different ligands bind to the same receptor what happens?

Answer 37

(as long as neither is an inhibitor) they will both cause the same response

Question 38

If one ligand can bind to two different receptors, what happens?

Answer 38

there will be two different effects based on the receptor that is being bound to

Question 39

What is receptor affinity?

Answer 39

the strength/ease of ligand-receptor binding

Question 40

What is receptor affinity directly proportionate to?

Answer 40

the number of ligands bound to receptors at any given concentration of ligands

Question 41

What is Kd?

Answer 41

concentration of ligand where 1/2 of the receptors are bound

Question 42

Low affinity = what kind of Kd?

Answer 42

higher Kd