$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$$

Question 1

Which of the following changes to the lipid composition of a cell membrane would most likely increase its fluidity at low temperatures?

Accepted Answer

Increase the proportion of unsaturated fatty acids in the phospholipids.

Question 2

Which property of mitochondria and chloroplasts best supports the endosymbiotic theory of their origin?

Accepted Answer

They contain their own circular DNA similar to bacterial genomes.

Question 3

A scientist observes that a certain organelle can grow and divide independently of the host cell. Which organelle is most likely being observed?

Accepted Answer

Mitochondrion

Question 4

Which of the following is NOT a function of proteins associated with the cell membrane?

Accepted Answer

DNA replication

Question 5

What is the main structural difference between saturated and unsaturated fatty acids in phospholipids, and how does this affect membrane fluidity?

Accepted Answer

Unsaturated fatty acids have double bonds, causing kinks that increase fluidity.

Question 6

Which of the following best describes the 'fluid mosaic model' of the cell membrane?

Accepted Answer

A double layer of phospholipids with proteins and carbohydrates embedded and able to move laterally.

Question 7

A red blood cell is placed in a hypotonic solution. What will most likely happen to the cell?

Accepted Answer

It will swell and possibly burst as water enters the cell.

Question 8

Which of the following processes requires energy input in the form of ATP?

Accepted Answer

Active transport of Na+ ions from low to high concentration.

Question 9

Which equation best represents the hydrolysis of ATP, which provides energy for primary active transport?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy}$$

Question 10

Which of the following statements about glycosylation of membrane proteins is correct?

Accepted Answer

Glycosylation is important for cell-cell recognition.

Question 11

A cell is placed in a solution and water moves into the cell. Which term best describes the solution relative to the cell?

Accepted Answer

Hypotonic

Question 12

Which of the following best explains why cell membranes are described as 'selectively permeable'?

Accepted Answer

They allow some molecules to pass while restricting others.

Question 13

Which of the following would NOT support the endosymbiotic origin of mitochondria and chloroplasts?

Accepted Answer

Ribosomes in mitochondria and chloroplasts are structurally identical to those in the cytosol.

Question 14

Which of the following best describes the role of cholesterol in animal cell membranes?

Accepted Answer

It decreases membrane fluidity at high temperatures and increases it at low temperatures.

Question 15

Which of the following is an example of secondary active transport?

Accepted Answer

Movement of glucose into a cell using the energy from a sodium gradient.

Question 16

Which of the following best describes the movement of water through aquaporins?

Accepted Answer

Facilitated diffusion

Question 17

A cell uses a proton pump to create a proton gradient across its membrane. Which type of transport is this?

Accepted Answer

Primary active transport

Question 18

Which of the following best explains why plant cells do not burst when placed in a hypotonic solution, while animal cells do?

Accepted Answer

Plant cells have a rigid cell wall that prevents excessive expansion.

Question 19

Which of the following is a correct statement about integral membrane proteins?

Accepted Answer

They span the lipid bilayer and have hydrophobic regions.

Question 20

Which of the following scenarios best illustrates the concept of an electrochemical gradient?

Accepted Answer

A difference in both ion concentration and charge across a membrane.

Cell Membranes and the Origin of Semiautonomous Organelles

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