Question 1

Which of the following organelles is surrounded by a double membrane and is thought to have originated via endosymbiosis?

Accepted Answer

Mitochondrion

Question 2

According to the inside-out theory of eukaryotic origins, which event is proposed to occur first?

Accepted Answer

Outward protrusion of the plasma membrane leading to loss of the cell wall

Question 3

Which organelle is primarily responsible for the synthesis of lipids and detoxification of harmful substances in eukaryotic cells?

Accepted Answer

Smooth endoplasmic reticulum

Question 4

A protein destined for secretion from a eukaryotic cell will follow which correct sequence of organelles?

Accepted Answer

Rough ER → Golgi apparatus → Secretory vesicle → Plasma membrane

Question 5

Which of the following statements about lysosomes is TRUE?

Accepted Answer

They store hydrolases and have a carbohydrate coating that protects their inner membrane.

Question 6

Peroxisomes are especially important in liver and kidney cells because they:

Accepted Answer

Detoxify hydrogen peroxide ($$H_2O_2) by $$converting it to water and oxygen

Question 7

Which of the following best describes the function of the Golgi apparatus?

Accepted Answer

It modifies, sorts, and packages proteins and synthesizes complex polysaccharides.

Question 8

Which of the following is NOT a component of the eukaryotic cytoskeleton?

Accepted Answer

Cisternae

Question 9

Bacterial cell walls are primarily composed of:

Accepted Answer

Peptidoglycans with chains of GlcNAc and MurNAc

Question 10

Which property distinguishes living organisms from viruses?

Accepted Answer

Ability to reproduce independently

Question 11

Which equation correctly represents the Gibbs free energy change for a biochemical reaction?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 12

Enzymes increase the rate of a reaction by:

Accepted Answer

Lowering the activation energy ($$E_a)$$

Question 13

Which of the following amino acids is LEAST likely to be directly involved in enzyme active site catalysis?

Accepted Answer

Valine

Question 14

A cell biologist observes that an enzyme is only active at pH 2. Which of the following is the most likely explanation?

Accepted Answer

The enzyme's active site contains amino acids that require a low pH to maintain their charge and structure.

Question 15

Which of the following is an example of a coenzyme that acts as a prosthetic group in enzyme catalysis?

Accepted Answer

NADH

Question 16

Which catalytic mechanism involves the enzyme temporarily forming a covalent bond with the substrate?

Accepted Answer

Covalent catalysis (electron transfer)

Question 17

The induced-fit model of enzyme activity proposes that:

Accepted Answer

Substrate binding induces a conformational change in the enzyme, optimizing catalysis.

Question 18

Which of the following best explains why increasing temperature beyond the optimal point decreases enzyme activity?

Accepted Answer

The enzyme denatures, losing its three-dimensional structure and active site.

Question 19

Which class of enzymes catalyzes the transfer of functional groups from one molecule to another?

Accepted Answer

Transferases

Question 20

A mutation causes the loss of the carbohydrate coating on the inner membrane of lysosomes. What is the most likely consequence?

Accepted Answer

Lysosomal enzymes may digest the lysosome itself, leading to cellular damage.

Eukaryotic Cell Structure, Endomembrane System, and Organelle Functions

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