Quiz 4: Structure and function of plasma membranes

What would likely occur if a stable red blood cell is placed in a solution of distilled water?

• The red blood cell will change color to blue.
• The red blood cell will remain unchanged.
• The red blood cell will shrink and become smaller.
• The red blood cell will swell and likely burst.

Tags

NGSS.HS-LS1-3

Phagocytosis is a means of exocytosis that involves bringing fluids into the cell.

• True

• False

Answer explanation

Phagocytosis is a type of endocytosis, not exocytosis.

Which of the following is not an apt descriptor for active transport?

• moves from area of high concentration to low concentration

• moves against a concentration gradient

• requires metabolic energy to conduct

• collectively called pumps

Which characteristic of a phospholipid membrane contributes to the fluidity of the membrane?

• double bonds in the fatty acid tail

• a saturated fatty acid tail

• its phosphate glycerol head

• cholesterol molecules interspersed

Answer explanation

The fluidity of a phospholipid membrane is mainly due to unsaturated fatty acid tails, which have kinks that prevent tight packing. Cholesterol also helps maintain fluidity by stabilizing the membrane.

The primary means of fueling active transport is often

• concentration regulation

• H2O

• ATP
• Glucose

Answer explanation

ATP is an energy-storing molecule in cells. It releases energy when it loses a phosphate group, powering processes like muscle contraction and biochemical reactions.

Tags

NGSS.HS-LS1-7

Plasma membranes are symmetrical, the interior and exterior being identical.

• true

• false

Answer explanation

Plasma membranes are asymmetrical; the interior (cytoplasmic side) and exterior (extracellular side) have different compositions and functions. This asymmetry is important for various cellular processes, including signaling and transport.

How does the sodium-potassium pump make the interior of the cell negatively charged?

• by expelling more cations than are taken in

• by pulling in anions

• by expelling more cations than are taken in

• by taking in and expelling an equal number of cations

Which of the following accurately describes the cell membrane?

• Fatty membrane only letting certain substances out and in

• Semipermeable membrane only allowing fluids osmotically in or out of the cell

• Selectively permeable membrane composed of lipids, proteins, and carbohydrates.

• Diffusion based lipid layer allowing for entrance and exit of cellular products.

Answer explanation

The statement is wrong because it simplifies the cell membrane. It's not just a "fatty membrane"—it's made of fats and has special proteins that help control what goes in and out. These proteins act like doors and messengers, making the membrane more than just a barrier.

Carrier proteins are specifically designed for a specific protein.

• true

• false

The principal force driving movement in diffusion is the __________.

• particle size

• concentration gradient

• membrane surface area

• temperature

Tags

NGSS.HS-PS1-5