L40 Transport Across the Plasma Membrane

Question 1

How do small, nonpolar molecules cross the plasma membrane?

Answer 1

Simple diffusion

e.g. O2, CO2

Question 2

How do large, polar molecules cross the plasma membrane?

Answer 2

Facilitated diffusion

• Uncharged molecules: diffuse down concentration gradient
• Ions: diffuse down electrochemical gradient

Question 3

A carrier protein that can move just a single solute at a time is termed __?__

Answer 3

uniport

Question 4

A carrier protein that can move 2 solutes at a time in the same direction is termed __?__

Answer 4

symport

Question 5

A carrier protein that can move 2 solutes at a time in opposite directions is termed __?__

Answer 5

antiport

Question 6

GLUT1 transporters are found in the membrane of __?__.

Answer 6

Red blood cells

Question 7

Where are the 4 types of glucose transporter found?

Answer 7

GLUT1: RBC membrane

GLUT2: Liver and muscle

GLUT3: Placenta and neuronal cells

GLUT4: Adipose

Question 8

How do channel proteins help facilitate diffusion across a plasma membrane?

Answer 8

Form a hydrophilic passage across the hydrophobic region of the plasma membrane

Question 9

True or false: As they move molecules through the plasma membrane, channel proteins undergo a conformational change in shape.

Answer 9

False.

Carrier proteins change shape, channel proteins do not.

Question 10

What effect does the cystic fibrosis-causing mutation in CFTR gene have on plasma membrane proteins in the lungs?

Answer 10

Ion channels maintain salt balance in cells.

A specific Cl- ion channel maintains conc. in lung epithelial cells.

Mutation in CFTR leads to defective ion channel and results in excessive mucus build up in the lungs.