Membrane Transport and the Role of Lipid Bilayer

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Which of the following is true about the lipid bilayer?

It is impermeable to most water-soluble molecules (correct)
It allows movement of charged and polar solutes
It is semipermeable
It contains membrane transport proteins

What determines the rate of simple diffusion across a protein-free bilayer?

Concentration gradient
Size and solubility (correct)
Membrane potential
Presence of carrier proteins

Which statement about membranes and water permeability is true?

Membranes are equally permeable to water and small ions
Membranes are a billion times more permeable to water than to small ions (correct)
Membranes are impermeable to water
Membranes are selectively permeable to water

Which of the following is true about transporters and channels?

Transporters transfer solutes at a much slower rate than channels (B) Signup and view all the answers

What are the two means for movement across a selectively permeable membrane?

Diffusion and active transport (C) Signup and view all the answers

Which of the following is true about diffusion?

Diffusion is a passive process (D) Signup and view all the answers

What is the role of membrane transport proteins?

To prevent loss of charged and polar solutes (D) Signup and view all the answers

What are the characteristics of transporters?

They undergo conformational changes (C) Signup and view all the answers

What is the main difference between channels and transporters?

Channels undergo conformational changes while transporters open or close (B) Signup and view all the answers

What is the main function of the lipid bilayer?

To act as a selectively permeable barrier (A) Signup and view all the answers

Which of the following is a major category of gated ion channels?

Voltage-gated channels (B) Signup and view all the answers

What is the driving force for the movement of solutes across the membrane by passive transport?

Electrochemical gradient (D) Signup and view all the answers

What is the measure of polarity and solubility in a nonpolar solvent/water for a molecule?

Partition coefficient (B) Signup and view all the answers

Which of the following processes allows substances to move across membranes directly through the lipid bilayer?

Simple diffusion (B) Signup and view all the answers

What type of transport is characterized by binding to a membrane-spanning protein that changes its shape?

Facilitated transporters (B) Signup and view all the answers

What is the selectivity filter for ion specificity in a potassium channel?

Carbonyl groups (C) Signup and view all the answers

What determines the direction in which each solute will flow across the membrane by passive transport?

Electrochemical gradient (D) Signup and view all the answers

What causes the release of neurotransmitter molecules?

Influx of Ca2+ (C) Signup and view all the answers

Which of the following is NOT a process by which substances move across membranes?

Active transport (A) Signup and view all the answers

What type of transport is characterized by opening and closing due to ligand binding?

Ligand-gated channels (B) Signup and view all the answers

Which of the following is true about active transport?

Active transport moves molecules from low to high concentration (C) Signup and view all the answers

What is the purpose of the Na+/K+-ATPase pump?

To establish gradients needed for nerve-muscle impulses (C) Signup and view all the answers

What does the Na+/K+-ATPase pump do to the net charge on each side of the membrane?

Makes the inside of the cell more positive and the outside more negative (B) Signup and view all the answers

How does the Na+/K+-ATPase pump change shape?

Through phosphorylation (A) Signup and view all the answers

What is the purpose of the glucose transporter?

To import glucose into the cell (D) Signup and view all the answers

How does the Na+/glucose cotransporter work?

It moves glucose up its gradient as Na+ flows down its gradient (D) Signup and view all the answers

What is the role of coupled transporters?

To carry >1 type of solute (C) Signup and view all the answers

How many Na+ ions are transported into the cell for every glucose molecule?

2 Na+ ions (C) Signup and view all the answers

What does the movement of 2 moles of Na+ ions into a cell generate?

A glucose concentration that is 30,000 times higher inside than out (D) Signup and view all the answers

What is the purpose of the Na+/H+ exchanger?

To exchange Na+ for H+ (D) Signup and view all the answers