Question 1

Which of the following best describes the structure and function of the plasma membrane in eukaryotic cells?

Accepted Answer

It is a dynamic, selectively permeable phospholipid bilayer with embedded proteins that regulates the movement of substances into and out of the cell.

Question 2

Which of the following best explains why phospholipids form a bilayer in aqueous environments?

Accepted Answer

The hydrophilic heads face the aqueous environment, while the hydrophobic tails are sequestered away from water, forming a bilayer.

Question 3

A newly synthesized protein destined for secretion from a eukaryotic cell would follow which correct path?

Accepted Answer

Rough ER → Golgi apparatus → vesicle → plasma membrane

Question 4

Which of the following best describes the function of lysosomes in animal cells?

Accepted Answer

They contain hydrolytic enzymes that break down macromolecules and recycle cellular components.

Question 5

Which of the following statements about mitochondria is correct?

Accepted Answer

Mitochondria contain their own DNA and are the primary site of ATP production via cellular respiration.

Question 6

Which of the following best describes the difference between integral and peripheral membrane proteins?

Accepted Answer

Integral proteins are embedded within the lipid bilayer, while peripheral proteins are attached to the membrane surface.

Question 7

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

Accepted Answer

Water will move into the cell, causing it to swell and possibly burst.

Question 8

Which of the following best describes the function of the Na$^+$/K$^+$-ATPase pump in animal cells?

Accepted Answer

It uses ATP to actively transport Na$^+$ out of the cell and K$^+$ into the cell, maintaining electrochemical gradients.

Question 9

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

Accepted Answer

Na$^+$/glucose symporter using the Na$^+$ gradient established by Na$^+$/K$^+$-ATPase to transport glucose into the cell.

Question 10

Which of the following best explains why enzymes lower the activation energy of a chemical reaction?

Accepted Answer

They provide a surface for reactants to come together and stabilize the transition state.

Question 11

A scientist measures the rate of an enzyme-catalyzed reaction at different pH values and finds that the activity is highest at pH 7, but drops sharply at pH 5 and pH 9. What is the most likely explanation for this observation?

Accepted Answer

The enzyme is denatured at extreme pH values, altering its active site.

Question 12

Which of the following best describes the difference between exergonic and endergonic reactions?

Accepted Answer

Exergonic reactions release energy ($\Delta G < 0$), while endergonic reactions require an input of energy ($\Delta G > 0$).

Question 13

Which of the following best explains why the fluidity of a cell membrane increases at higher temperatures?

Accepted Answer

Phospholipid tails move more rapidly, increasing the distance between molecules and thus increasing fluidity.

Question 14

Which of the following is a function of the Golgi apparatus in eukaryotic cells?

Accepted Answer

Modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.

Question 15

Which of the following best describes the role of microtubules in the cytoskeleton?

Accepted Answer

They provide structural support and serve as tracks for intracellular transport.

Question 16

A mutation causes a cell to lack functional tight junctions. Which of the following would most likely be affected?

Accepted Answer

The cell's ability to prevent the passage of substances between adjacent cells.

Question 17

Which of the following best describes the process of phagocytosis?

Accepted Answer

The cell engulfs large particles or microorganisms by wrapping the plasma membrane around them to form a vesicle.

Question 18

Which of the following best explains why ATP is considered the 'energy currency' of the cell?

Accepted Answer

ATP contains high-energy phosphate bonds that, when hydrolyzed, release energy for cellular work.

Question 19

A cell is placed in an environment with a high concentration of non-permeable solutes. Which of the following best describes the tonicity of the solution and the likely effect on the cell?

Accepted Answer

The solution is hypertonic, and the cell will shrink as water leaves the cell.

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