Question 1

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

Accepted Answer

The lateral movement of phospholipids and some proteins within the lipid bilayer.

Question 2

A red blood cell is placed in a hypotonic solution. Which of the following will most likely occur, and why?

Accepted Answer

Water will move into the cell, causing it to swell and possibly burst, because the solution has a lower solute concentration than the cell.

Question 3

Which of the following statements about membrane proteins is correct?

Accepted Answer

Carrier proteins bind to specific molecules and change shape to shuttle them across the membrane.

Question 4

Which of the following molecules can most easily diffuse through a plasma membrane without the help of a transport protein?

Accepted Answer

O$$_2$$

Question 5

A plant cell is placed in a hypertonic solution. What is the most likely consequence?

Accepted Answer

The cell will lose water, and the plasma membrane will pull away from the cell wall (plasmolysis).

Question 6

Which of the following best describes the difference between active transport and facilitated diffusion?

Accepted Answer

Active transport requires energy (often from ATP) to move solutes against their concentration gradient, while facilitated diffusion moves solutes down their gradient without energy input.

Question 7

Which of the following is an example of cotransport in biological membranes?

Accepted Answer

Glucose entering a cell along with Na$$^+$$ ions, using the Na$$^+$$ gradient established by active transport.

Question 8

Which of the following changes would increase the fluidity of a cell membrane at low temperatures?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the membrane.

Question 9

Which statement best describes the Second Law of Thermodynamics as it applies to biological systems?

Accepted Answer

Every energy transfer increases the entropy (disorder) of the universe.

Question 10

Given the equation for Gibbs free energy: $$\Delta G = \Delta H - T\Delta S$$, which of the following scenarios would most likely result in a spontaneous reaction?

Accepted Answer

$$\Delta H is $$negative and $$\Delta S is $$positive.

Question 11

Which of the following best describes the role of ATP in energy coupling within cells?

Accepted Answer

ATP hydrolysis releases energy that can drive endergonic reactions by transferring a phosphate group.

Question 12

Which of the following is NOT a component of ATP?

Accepted Answer

Deoxyribose

Question 13

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy, speeding up reactions without being consumed.

Question 14

A metabolic pathway that breaks down glucose to release energy is best described as:

Accepted Answer

A catabolic pathway

Question 15

Which of the following environmental changes is most likely to decrease the rate of an enzyme-catalyzed reaction in the human body?

Accepted Answer

Lowering the pH from 7.4 to 2

Question 16

Which of the following best describes allosteric regulation of an enzyme?

Accepted Answer

A molecule binds to a site other than the active site, changing the enzyme's shape and activity.

Question 17

Which of the following is an example of feedback inhibition in a metabolic pathway?

Accepted Answer

The end product of a pathway binds to an enzyme early in the pathway, decreasing its activity.

Question 18

Which of the following best explains why Na$$^+$$ ions cannot easily cross the plasma membrane without a transport protein?

Accepted Answer

Na$$^+$$ ions are charged and cannot pass through the hydrophobic interior of the lipid bilayer.

Question 19

A reaction has $$\Delta G = +5$$ kcal/mol. Which of the following statements is true?

Accepted Answer

The reaction is nonspontaneous and requires energy input.

Question 20

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

Accepted Answer

Exergonic reactions have a negative $$\Delta G$$ and release energy; endergonic reactions have a positive $$\Delta G$$ and require energy input.

General Biology Exam 3 Study Guide: Membranes & Metabolism

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