Membrane Transport - Exam Questions

Question 1

How permeable is the cell membrane lipid bilayer to the following
chemicals?
a. Hydrophobic molecules
b. Large uncharged polar molecules
c. Charged polar molecules
d. Small uncharged polar molecules
e. Ions
i. Very permeable
ii. Permeable to a very small degree
iii. Very impermeable

Answer 1

a. i - Cell membrane is very permeable to hydrophobic molecules
b. ii. Membrane is permeable to a very small degree for large uncharged polar molecules
c. iii. Membrane is very impermeable to charged polar molecules
d. i. Membrane is very permeable to small uncharged polar molecules.
e. iii. Membrane is very impermeable to ions.

Question 2

Facilitated diffusion
a. requires energy input
b. is against the electrochemical gradient
c. is required for water transport
d. uses the energy from a down-gradient movement to produce an upgradient
movement
e. is required for glucose transport

Answer 2

e. Facilitated diffusion is required for glucose transport

Question 3

What does a high parittion coefficient (Kow) indicate that a molecule is?

Answer 3

Highly oil soluble

Question 4

What is an aquaporin?

Answer 4

A transmembrane water channel constitutively allowing passive diffusion

Question 5

What is an ion channel which opens when a molecule binds to it?

Answer 5

Ligand gated

Question 6

Two molecules being transported in the same direction across a
membrane is an example of
a. antiport
b. facilitated diffusion
c. symport
d. primary active transport
e. uniport

Answer 6

c. Two molecules being transported in the same direction across a membrane is an example of a symport.

Question 7

What does facilitated diffusion generally require?

Answer 7

A change in conformation of a transmembrane carrier protein

Question 8

Rate of uptake via facilitated diffusion

a. approaches an asymptote which indicates Vmax
b. is maximum at the substrance concentration of Km
c. is directly proportional to substrate concentration
d. approaches an asymptote which indicates Km
e. is inversely proportional to substrate concentration

Answer 8

a. Rate of uptake via facilitated diffusion approached an asymptote which indicates Vmax.

Question 9

What does a low Km for a substrate indicate?

Answer 9

High affinity for its transporter

Question 10

Match the glucose transporter to its tissue distribution

a. GLUT-1
b. GLUT-2
c. GLUT-3
d. GLUT-4
i. liver, pancreatic β cells
ii. brain
iii. muscle, adipocytes
iv. ubiquitous

Answer 10

GLUT-1 = ubiquitous(found everywhere)
GLUT-2 = liver, pancreatic β cells
GLUT-3 = brain
GLUT-4 = muscle and adipocytes

Question 11

What does GLUT-5 transport?

Answer 11

Fructose

Question 12

Via which mechanism do GLUTs 1-4 transporters transport glucuse?

Answer 12

Facilitated diffusion

Question 13

Match the glucose transporter to its features

a. GLUT-1
b. GLUT-2
c. GLUT-3
d. GLUT-4
i. Insulin recruits transporter to membrane
ii. Transports glucose in the brain
iii. High Km and high Vmax for glucose
iv. Low Km for glucose

Answer 13

GLUT-1 = Low Km for glucose
GLUT-2 = High Km and high Vmax for glucose
GLUT-3 = Transports glucose in the brain
GLUT-4 = Insulin recruits transporter to membrane

Question 14

The transporter with a high Km and high Vmax for glucose is useful

a. when glycogenolysis is occurring
b. when blood glucose levels are high
c. in the fasting state
d. when blood glucose levels are normal
e. in starvation

Answer 14

b, The transporter with a high Km and high Vmax for glucose is useful when blood glucose level are high

Question 15

Secondary active transport
a. is also known as facilitated diffusion
b. produces energy which is used to make ATP
c. uses energy from the movement of a molecule down its
electrochemical gradient
d. uses energy from the hydrolysis of ATP
e. is also known as symport

Answer 15

c. Secondary active transport uses energy from the movement of a molecule down its electrochemical gradient

Question 16

What is Na+/K+ -ATPase in the sarcoplasmic reticulum an example of?

Answer 16

Primary active transport

Question 17

The binding of sodium in Na⁺/K⁺-ATPase causes a conformational
change via
a. G-protein activation
b. autophosphorylation of the transporter
c. creation of a potential difference across the membrane
d. mechanical stresses to the transporter caused by the binding
e. activation of adenylate cyclase

Answer 17

b. The binding of Na+/K+ -ATPase causes conformation change via autophosphorylation of the transporter

Question 18

A drug which blocks Na⁺/K⁺-ATPase is

a. suxamethonium
b. propofol
c. propranolol
d. oubain
e. atropine

Answer 18

d. Oubain blocks Na+/K+ -ATPase

Question 19

Heart failure may be helped by bockade of Na⁺/K⁺-ATPase due to

a. a decrease in intracellular Ca²⁺ concentration
b. an increase in intracellular Ca²⁺ concentration
c. an increase in intracellular K⁺ concentration
d. a decrease in intracellular K⁺ concentration
e. a decrease in intracellular Na⁺ concentration

Answer 19

b. Heart failure may be helped by blockase of Na+/K+ -ATPase due to an increase in intracellular Ca2+ concentration

Question 20

What is the importance of the SGLUT transporter?

Answer 20

The absorption of dietary glucose from the lumen of the gut into the blood

Question 21

What does Na+/K+ -ATPase move?

Answer 21

Sodium out, potassium in in a 3:2 ratio

Question 22

What is secondary active transport used for in cholera treatment?

Answer 22

Drives sodium replacement via a high intestinal glucose concentration.

Question 23

Vibrio cholerae causes oversecretion of

a. Ca²⁺
b. K⁺
c. glucose
d. water
e. Cl

Answer 23

e. Vibrio cholerae causes oversecretion of Cl- by constant activation of cyclase enzyme