Cell Membrane, Membrane Transport, & Membrane Potential

Question 1

PM function (4)

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 cell and extracellular matrix.

Question 2

PM structure (3)

Answer 2

1. Described by the Fluid Mosaic Model
2. Made up of four different types of Organic Molecules
3. At body temperature has the consistency of a thick oil

Question 3

PM is made up of four different types of Organic Molecules (4)

Answer 3

1. Phospholipids
2. Steroids
3. Proteins
4. Carbohydrates

Question 4

Phospholipids are

Answer 4

amphipathic

Question 5

Phospholipids are organized into a

Answer 5

bilayer

Question 6

functions of phospholipids

Answer 6

creates barrier

Question 7

Permeable (3)

Answer 7

 Hydrophobic substances - 
Small, nonpolar molecules
• Ex. (Gases (O2, CO2), Fatty 
acids, steroids
 Lipophilic substances
• Ex. Ethanol
 Water

Question 8

Non-Permeable (4)

Answer 8

• Larger molecules
• Polar molecules
• Charged substances
• Ex.
– Glucose
– Ions
– Amino acids
– Proteins

Question 9

Cholesterol helps to (2)

Answer 9

keep membrane fluid over a wide range of temperatures

make membrane water tight

Question 10

protein shape determines

Answer 10

function

Question 11

Anything that alters protein shape will also alter

Answer 11

protein function

Question 12

Factors that alter protein shape (3)

Answer 12

1.Mutations – 1⁰ structure
2.pH, T, Osm – Loss of 2⁰, 3⁰, and 4⁰
structure - denaturation
3.Covalent/Allosteric Modulation –
change 2⁰, 3⁰, and 4⁰ structure

Question 13

Structural Classification (3)

Answer 13

 Transmembrane
 Integral
 Peripheral

Question 14

Receptors

Answer 14

Bind to specific chemical signals (ligands) and transmit

that information to the cytoplasm

Question 15

Properties of receptors (3)

Answer 15

1. Specificity
2. Saturation
3. Competition

Question 16

Specificity

Answer 16

Shape of the binding site determines what will bind

Question 17

Each type of protein, in general, will interact with

Answer 17

only one type of 
substance or class of substances

Question 18

Example of specificity (3)

Answer 18

Insulin Receptor only binds to insulin
Enzyme Maltase will only interact with substrate maltose
Glucose transporter will only bind to and transport Glucose

Question 19

Within the solutions of the body there are a set number of proteins and therefore

Answer 19

a set number of binding sites

Question 20

Saturation refers to

Answer 20

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

Question 21

saturation is dependent on (2)

Answer 21

[protein] and the [substance]

Question 22

transport rate is proportional to

Answer 22

substrate until the carriers are saturated

Question 23

A competitive inhibitor is a chemical substance (exogenous ligand) that binds to

Answer 23

the active site of the protein and blocks the endogenous ligand from binding

Question 24

When bound, competitor does not

Answer 24

produce an effect

Question 25

Level of inhibition dependent on (3)

Answer 25

[protein], [endogenous ligand], and [competitive inhibitor]

Question 26

examples of competitive inhibitors (3)

Answer 26

 Penicillin
 ACE Inhibitors
 β Blockers

Question 27

Response of a cell to a chemical signal is — —, not — —

Answer 27

receptor mediated

signal mediated

Question 28

1. No Receptor =

Answer 28

No Response

Question 29

2. Two different ligands binding to same receptor =

Answer 29

same response

Question 30

3. One ligand binding to two different receptors =

Answer 30

two different responses

Question 31

Receptor Affinity

Answer 31

Strength/Ease of ligand-receptor binding

Question 32

Affinity is proportional to

Answer 32

# ligands bound to receptors at any given 
[ligand]

Question 33

Affinity is proportional to (inverse)

Answer 33

1/Kd

Kd=[Ligand] where ½ receptor occupied

Question 34

Transport Proteins

Answer 34

Move hydrophilic substances across the plasma

membrane of cell

Question 35

Three Types of transport proteins

Answer 35

1. Channels
2. Carriers
3. Active transporters

Question 36

Channels

Answer 36

Transmembrane proteins with a 3D shape that forms a tiny

fluid filled pore connecting ECF and Cytoplasm

Question 37

function of channels (2)

Answer 37

Facilitated diffusion of ions into and out of cell (passive;
does not require energy)
Can be somewhat specific (Ca++ channel, Na+ channel, Cl-
channel, cation channel, etc.)

Question 38

Open Channels

Answer 38

Always open and ions freely flow through via facilitated

diffusion

Question 39

open channels creates

Answer 39

“Leak Currents”

Question 40

Gated Channels

Answer 40

Spend most of their time in the closed state, and will

open only when stimulated

Question 41

Three types of gated channels

Answer 41

a. Chemically gated
b. Mechanically gated
c. Voltage gated

Question 42

Carriers

Answer 42

ransmembrane 
protein that moves 
hydrophilic building 
blocks across the 
plasma membrane 
via facilitated 
diffusion (passive; 
does not require 
energy).

Question 43

properties of carriers (3)

Answer 43

1. Specificity
2. Saturation
3. Competition

Question 44

active transport

Answer 44

transmembrane proteins that move ions and hydrophilic building blocks across the membrane via active transport (active, requires energy)

Question 45

active transport exhibits (3) properties

Answer 45

specificity
saturation
competition