Membrane Transport 1

Question 1

What is the primary function of membrane transport proteins?

Answer 1

They regulate the movement of molecules across cellular and intracellular membranes to maintain homeostasis.

Question 2

What are the main lipid components of the plasma membrane?

Answer 2

Phospholipids (~49%), cholesterol (~49%), and glycolipids (~2%).

Question 3

What is passive diffusion?

Answer 3

The movement of molecules down their concentration gradient without energy input.

Question 4

How does facilitated diffusion differ from simple diffusion?

Answer 4

Facilitated diffusion requires a carrier or channel protein, whereas simple diffusion does not.

Question 5

What is the role of aquaporins?

Answer 5

They are specialized water channels that allow rapid water movement across membranes.

Question 6

Membrane transport proteins are essential for

Answer 6

cellular survival and function.

Question 7

Diffusion is always down a

Answer 7

concentration gradient.

Question 8

Ion channels can be

Answer 8

gated (ligand, voltage, or mechanosensitive).

Question 9

Facilitated diffusion involves carrier proteins and shows

Answer 9

saturation kinetics.

Question 10

Primary active transport requires ATP to

Answer 10

move substances against their gradient.

Question 11

The Na⁺/K⁺-ATPase exchanges 3 Na⁺ out for 2 K⁺ in, maintaining the

Answer 11

resting membrane potential.

Question 12

The Goldman equation estimates membrane potential based on

Answer 12

ion permeability.

Question 13

The plasma membrane is impermeable to all molecules.

Answer 13

False (It is selectively permeable, allowing specific molecules to pass through via transport proteins.)

Question 14

Ion channels transport ions up their concentration gradient.

Answer 14

False (Ion channels facilitate passive movement down the gradient.)

Question 15

Carrier-mediated transport is always passive.

Answer 15

False (It can be passive (facilitated diffusion) or active (requiring ATP).)

Question 16

The Na⁺/K⁺-ATPase directly contributes to the resting membrane potential.

Answer 16

True (It maintains the electrochemical gradient essential for cell function.)

Question 17

The ______ is a lipid bilayer that acts as a selective barrier for the cell.

Answer 17

Plasma membrane

Question 18

______ diffusion requires no transport proteins and occurs directly across the lipid bilayer.

Answer 18

Simple

Question 19

Water moves through cell membranes via specialized channels called ______.

Answer 19

Aquaporins

Question 20

Active transport requires ______ to move substances against their concentration gradient.

Answer 20

ATP

Question 21

______ transporters move two solutes in opposite directions, while ______ transporters move them in the same direction.

Answer 21

Antiport, Symport

Question 22

Which of the following is NOT a type of membrane transport?
A) Simple diffusion
B) Facilitated diffusion
C) Active transport
D) Osmotic endocytosis

Answer 22

D) Osmotic endocytosis (not a recognized transport mechanism)

Question 23

Which factor affects the rate of passive diffusion?
A) Steepness of the concentration gradient
B) Number of channel proteins
C) Temperature
D) All of the above

Answer 23

D) All of the above

Question 24

How does the Na⁺/K⁺-ATPase contribute to cellular function?
A) Generates ATP for cellular energy
B) Exchanges sodium and potassium ions to maintain membrane potential
C) Facilitates osmosis by creating a hypotonic environment
D) Actively transports glucose into the cell

Answer 24

B) Exchanges sodium and potassium ions to maintain membrane potential

Question 25

Which statement about ion channels is TRUE? A) They transport ions against their concentration gradient. B) They are always open. C) They can be ligand-gated, voltage-gated, or mechanically gated. D) They require ATP to function.

Answer 25

C) They can be ligand-gated, voltage-gated, or mechanically gated.

Question 26

Scenario 1: A patient has a genetic mutation in their CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) gene. How might this affect membrane transport in their cells?

Answer 26

Answer: The CFTR protein is an ATP-binding cassette (ABC) transporter that facilitates chloride ion transport. A mutation could lead to defective chloride transport, resulting in thick mucus production, as seen in cystic fibrosis.

Question 27

Scenario 2: A researcher is measuring electrical currents in a neuron and notices rapid ion movement through a channel protein. What type of transport is occurring, and what technique could confirm this?

Answer 27

Answer: Ion channels are facilitating passive transport. The patch-clamp technique can measure ion flow and confirm the presence of active ion channels.

Question 28

Scenario 3: A muscle cell is exposed to insulin, leading to an increase in glucose uptake. What membrane transport mechanism is being upregulated?

Answer 28

Answer: Insulin increases GLUT4 transporters in muscle cells, enhancing facilitated diffusion of glucose.

Question 29

Passive diffusion:

Answer 29

Movement of molecules from high to low concentration without energy input.

Question 30

Facilitated diffusion:

Answer 30

Transport of molecules via carrier proteins, still down the gradient.

Question 31

Active transport:

Answer 31

Energy-dependent transport moving substances against the gradient.

Question 32

Ion channels:

Answer 32

Pore-forming proteins that allow ions to pass through the membrane.

Question 33

Aquaporins:

Answer 33

Channel proteins that facilitate rapid water transport.

Question 34

Na⁺/K⁺-ATPase:

Answer 34

Enzyme that actively transports sodium and potassium ions to maintain membrane potential.

Question 35

Symport:

Answer 35

Transporter moving two molecules in the same direction.

Question 36

Antiport:

Answer 36

Transporter moving two molecules in opposite directions.