Question 1

Which of the following best describes the amphipathic nature of phospholipids in the plasma membrane?

Accepted Answer

Phospholipids have both hydrophilic and hydrophobic regions, enabling them to form a bilayer that separates aqueous compartments.

Question 2

A cell is placed in a solution with a higher solute concentration than inside the cell. What will happen to the cell, and what is the term for this type of solution?

Accepted Answer

The cell will lose water and shrink; the solution is hypertonic.

Question 3

Which equation correctly represents the relationship between solute concentration and water potential in osmosis?

Accepted Answer

$\Psi = \Psi_s + \Psi_p$

Question 4

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membranes with unsaturated hydrocarbon tails remain fluid at lower temperatures due to kinks that prevent tight packing.

Question 5

Which type of transport protein is responsible for the facilitated diffusion of water across the plasma membrane?

Accepted Answer

Aquaporins

Question 6

A plant cell is placed in a hypotonic solution. What is the expected outcome?

Accepted Answer

The cell will become turgid as water enters, which is the healthiest state for most plant cells.

Question 7

Which process requires energy input from the cell and moves substances against their concentration gradient?

Accepted Answer

Active transport

Question 8

The sodium-potassium pump in animal cells exchanges which ions across the plasma membrane, and in what direction?

Accepted Answer

It pumps $3$ Na$^+$ out and $2$ K$^+$ in, using ATP.

Question 9

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Synthesis of DNA

Question 10

Familial hypercholesterolemia is caused by a defect in which cellular process?

Accepted Answer

Receptor-mediated endocytosis of LDL cholesterol

Question 11

Which type of cell signaling involves hormones traveling long distances through the bloodstream to reach target cells?

Accepted Answer

Endocrine signaling

Question 12

What is the role of protein kinases in signal transduction pathways?

Accepted Answer

They transfer phosphate groups from ATP to proteins, activating them.

Question 13

Which of the following is a common second messenger in signal transduction pathways?

Accepted Answer

Cyclic AMP ($cAMP$)

Question 14

Which equation best represents the conversion of ATP to cyclic AMP by adenylyl cyclase?

Accepted Answer

$ATP \xrightarrow{adenylyl\ cyclase} cAMP + PP_i$

Question 15

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It speeds up the passive movement of molecules down their concentration gradient without energy input.

Question 16

Which type of membrane receptor is directly involved in the nervous system by allowing ions to pass through when activated by a ligand?

Accepted Answer

Ligand-gated ion channel

Question 17

What is the main difference between passive and active transport across membranes?

Accepted Answer

Passive transport does not require energy and moves substances down their concentration gradient, while active transport requires energy and moves substances against their gradient.

Question 18

Which process allows large molecules such as proteins to enter the cell in bulk, and what is one specific type of this process?

Accepted Answer

Endocytosis; phagocytosis

Question 19

Which of the following best explains why the plasma membrane is described as a 'fluid mosaic'?

Accepted Answer

It consists of a mosaic of protein molecules floating in a fluid bilayer of phospholipids.

Question 20

Which of the following is a real-life example of cotransport in plant cells?

Accepted Answer

The use of a proton gradient to drive the active transport of nutrients into the cell.

Membrane Transport and Cell Signaling: Study Notes (Campbell Biology in Focus, Chapter 5)

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