Membranes II: Passive and Active Transporters

Water molecules are unable to pass directly through a biological membrane because

• a.they have partial positive and partial negative charges.
• b.they do not have a charge.
• c.they are too large.
• d.the fatty acids inside the membrane are too close together.

Active transporters do not require an input of energy to allow molecules to pass through them.

• a.true
• b.false

Channels allow specific molecules to flow

• a.from areas of low concentration to areas of high concentration.
• b.from areas of high concentration to areas of low concentration.
• c.in either direction across a membrane.
• d.out of a cell, in order to build the concentration gradient.

People who suffer from chronic heartburn or indigestion may take a drug to reduce the discomfort. These drugs work by

• a.allowing ions to pass quickly through the cell’s membrane.
• b.completely blocking ions from passing through the cell’s membrane.
• c.slowing down the proton pumps in the stomach walls.
• d.speeding up the proton pumps in the stomach walls.

The sodium/potassium pump (Na⁺/K⁺ pump) actively moves these two different ions in opposite directions. This is known as a(n)

• a.gate.
• b.ATP.
• c.analgesic.
• d.antiport.

Acetylcholine is a neurotransmitter that causes muscles to contract by

• a.stimulating the sodium pump.
• b.inhibiting the potassium pump.
• c.opening sodium gates.
• d.stimulating the Na⁺/K⁺ pump.

In all cells of the human body, the concentration of _______ is higher inside the cells and the concentration of ________ is higher outside the cells.

• a.potassium; sodium
• b.sodium; ATP
• c.ATP; sodium
• d.protons; ATP

Which term is not related to active transport?

• a.ATP
• b.energy
• c.facilitated diffusion
• d.pumps