Question 1

When a membrane protein synthesized in the rough ER is transported to the plasma membrane, how is its orientation maintained during this process?

Accepted Answer

B. The protein's orientation is preserved because vesicle fusion maintains the inner and outer membrane faces established in the ER.

Question 2

A researcher is testing the permeability of a synthetic membrane that mimics a biological phospholipid bilayer. She exposes one side of the membrane to oxygen ($$O_2$$), glucose, and sodium ions ($$Na^+). $$After one hour, only oxygen is detected on the opposite side. Based on these results, which conclusion best evaluates the membrane's selective permeability?

Accepted Answer

A. The membrane selectively allows nonpolar molecules such as oxygen to cross easily, while polar or charged molecules require transport proteins for passage.

Question 3

A freshwater protozoan is placed in a solution with a higher solute concentration than its cytoplasm. Based on principles of osmosis, what will happen to the protozoan's water balance?

Accepted Answer

B. Water will move out of the cell, causing it to shrink as the external solution is hypertonic.

Question 4

A neuron uses the sodium-potassium pump to maintain its resting membrane potential. How does this pump contribute to the cell's electrochemical gradient?

Accepted Answer

B. It actively transports ions against their concentration gradients, creating a charge difference that stores potential energy for cellular work.

Question 5

Both a cell and an engine convert chemical energy into work. Which statement best explains how each accomplishes this conversion?

Accepted Answer

B. Chemical bonds are rearranged, releasing stored potential energy that is transformed into kinetic or usable work.

Question 6

A spontaneous reaction in a cell proceeds very slowly until an enzyme is added. What best explains how the enzyme affects this reaction?

Accepted Answer

A. It lowers the activation energy, allowing the reaction to proceed faster without changing the overall $$\Delta G.$$

Question 7

A metabolic enzyme becomes active only when a small molecule binds to a site separate from its active site. What binding is being described?

Accepted Answer

B. This is allosteric activation, where a molecule binds to a site other than the active site.

Question 8

A researcher measures synthetic activity from a human cell extract and from a purified ('heat-loving') bacterial sample. Both enzymes catalyze the same reaction efficiently under their normal conditions. What would most likely happen if both enzymes were incubated at 80$$^\circC$$?

Accepted Answer

B. The bacterial enzyme would remain active because it is stable at high temperature.

Question 9

When a person eats a meal, how is the chemical energy in food macromolecules made available for cellular work?

Accepted Answer

A. Macromolecules are broken into subunits, which are further oxidized to release energy and provide building blocks for new molecules.

Question 10

If all cellular respiration stopped, energy stored in glucose's chemical bonds transformed into which products? Which process is directly responsible for this transformation?

Accepted Answer

D. Both processes release energy as glucose is oxidized, releasing $$CO_2$$ and driving ATP synthesis.

Question 11

When a muscle cell's demand for energy increases, what happens to ATP production and $$CO_2$$ release during cellular respiration?

Accepted Answer

A. Both increase because more fuel is consumed, producing more $$CO_2$$ and ATP.

Question 12

If a cell has abundant ADP and NADH, how will this affect the citric acid cycle?

Accepted Answer

D. The cycle will speed up because ADP stimulates key enzymes, increasing the rate of ATP production.

Question 13

Pyruvate is reduced directly to ethanol without producing any intermediate compounds. Which process is being described?

Accepted Answer

A. Pyruvate is converted to acetaldehyde and $$CO_2$$, acetaldehyde then accepts electrons from NADH to form ethanol and regenerate NAD$$^+.$$

Question 14

A plant appears orange in color under sunlight. What can you infer about the wavelengths of light absorbed and reflected by its pigments?

Accepted Answer

B. The pigments absorb blue-green wavelengths while reflecting orange and yellow light.

Question 15

How do the light-dependent reactions and the Calvin cycle work together to complete photosynthesis?

Accepted Answer

A. The light-dependent reactions provide ATP and NADPH used by the Calvin cycle to fix $$CO_2$$ into sugar.

Question 16

How do Photosystems I and II work together to convert light energy into the chemical energy needed for ATP?

Accepted Answer

C. Photosystem II splits water and passes electrons through an electron transport chain that produces ATP; Photosystem I uses those electrons and light to form NADPH.

Question 17

If a plant cell is deprived of water, how would this most directly affect photosystem I activity?

Accepted Answer

C. Photosystem I activity would stop or be reduced because electrons supplied by Photosystem II, which depend on water splitting, are lost.

Question 18

A researcher observes that a hormone triggers changes in gene expression only after binding a receptor located inside the cell. Based on this observation, the hormone is most likely classified as which type?

Accepted Answer

B. Lipid-soluble; it crosses the plasma membrane and likely affects the cell via nuclear receptors.

General Biology: Cell Structure, Metabolism, Membrane Transport, and Photosynthesis Study Guide

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