Question 1

Which of the following best describes the effect of an enzyme on a chemical reaction?

Accepted Answer

It lowers the activation energy but does not change the overall free energy change $$\Delta G of $$the reaction.

Question 2

A pharmaceutical company is designing a drug that must rapidly enter cells by passive diffusion. Which property should the drug molecule have to maximize its rate of diffusion across the plasma membrane?

Accepted Answer

Small and nonpolar

Question 3

During aerobic respiration, how many molecules of carbon dioxide ($$\mathrm{CO}_2) $$are produced from the complete oxidation of one molecule of glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$)?

Accepted Answer

Six

Question 4

Which of the following best explains why small ions such as $$\mathrm{K}^+$$ and $$\mathrm{H}^+$$ require transport proteins to cross the plasma membrane?

Accepted Answer

They are charged and cannot easily pass through the hydrophobic core of the membrane.

Question 5

In the Calvin cycle, how many turns are required to produce one molecule of glyceraldehyde-3-phosphate (G3P)?

Accepted Answer

Three

Question 6

A mutation prevents the formation of vesicles during receptor-mediated endocytosis. Which cellular process would be most directly affected?

Accepted Answer

Uptake of specific ligands bound to cell surface receptors

Question 7

Which sequence correctly describes the pathway of a secreted protein from synthesis to secretion?

Accepted Answer

Rough endoplasmic reticulum $$\rightarrow$$ Golgi apparatus (cis to trans) $$\rightarrow$$ vesicle $$\rightarrow$$ plasma membrane

Question 8

If a cell is exposed to a toxin that blocks all transport proteins, which molecule would be LEAST affected in its ability to cross the plasma membrane?

Accepted Answer

Oxygen ($$\mathrm{O}_2)$$

Question 9

Which of the following statements about exocytosis is correct?

Accepted Answer

Vesicle contents are released outside the cell when the vesicle fuses with the plasma membrane.

Question 10

A scientist labels the three carbons of a G3P molecule with a radioactive isotope. After one turn of the citric acid cycle, how many of these labeled carbons would be released as $$\mathrm{CO}_2$$?

Accepted Answer

All three

Question 11

Which of the following best explains why large polar molecules diffuse slowly across the plasma membrane?

Accepted Answer

They are both large and hydrophilic, making it difficult to pass through the hydrophobic lipid bilayer.

Question 12

Which of the following is true regarding the fate of carbon atoms during cellular respiration?

Accepted Answer

All six carbons from glucose are eventually released as $$\mathrm{CO}_2.$$

Question 13

Which step in the secretory pathway is responsible for sorting and packaging proteins for export from the cell?

Accepted Answer

Trans face of the Golgi apparatus

Question 14

A cell is engineered to lack receptors on its surface. Which process would be most directly impaired?

Accepted Answer

Receptor-mediated endocytosis

Question 15

Which of the following best describes the role of activation energy in enzyme-catalyzed reactions?

Accepted Answer

Enzymes lower the activation energy, allowing reactions to proceed faster without changing $$\Delta G.$$

Question 16

Which of the following molecules would diffuse most slowly across a biological membrane without the help of a transport protein?

Accepted Answer

Potassium ion ($$\mathrm{K}^+)$$

Question 17

If the Calvin cycle is disrupted after two turns, how many molecules of G3P will have been produced?

Accepted Answer

Less than one

Question 18

Which of the following is a key difference between receptor-mediated endocytosis and exocytosis?

Accepted Answer

Receptor-mediated endocytosis brings specific molecules into the cell, while exocytosis releases molecules out of the cell.

Question 19

A patient has a genetic disorder that prevents vesicle fusion with the plasma membrane. Which process would be most directly affected?

Accepted Answer

Exocytosis

Question 20

Which of the following statements about the flow of carbon in photosynthesis is correct?

Accepted Answer

Three turns of the Calvin cycle are required to produce one G3P molecule.

Key Concepts in Enzymes, Membrane Diffusion, Carbon Flow, and Cellular Transport

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