Question 1

If rats inhale radioactive oxygen, which molecule in their cells will first become radioactive, and why?

Accepted Answer

Water, because oxygen is reduced to water at the end of the electron transport chain.

Question 2

Creating non-specific pores for charged molecules in the inner mitochondrial membrane immediately halts ATP synthesis. What is the most logical explanation for this observation?

Accepted Answer

Leakage of hydrogen ions dissipates the proton gradient needed for ATP synthase.

Question 3

If glucose is not available, how can a cell still produce ATP?

Accepted Answer

By carrying out anaerobic respiration or using lipids and proteins as alternative fuels.

Question 4

Which of the following best explains why plant tissues are higher in carbohydrates and undigestible fibers compared to animal tissues?

Accepted Answer

Plant cell walls are made of carbohydrate polymers, while animal ECM is mainly protein.

Question 5

Which statement about plant primary cell walls is NOT true?

Accepted Answer

Plant primary cell walls remain unchanged after they are first made.

Question 6

What is the main function of the middle lamella in plant cells?

Accepted Answer

It provides a gelatinous layer of pectins that glues adjacent cells together.

Question 7

Which of the following is a correct comparison between plant and animal extracellular structures?

Accepted Answer

Plant cell walls are mainly polysaccharides, while animal ECM is mainly proteins and proteoglycans.

Question 8

Which type of cell junction in animal cells provides a water-tight seal between adjacent cells?

Accepted Answer

Tight junctions

Question 9

Destruction of the chondrocyte extracellular matrix in osteoarthritis is associated with a malfunctioning endoplasmic reticulum. What does this suggest?

Accepted Answer

The endoplasmic reticulum is involved in the synthesis of the extracellular matrix.

Question 10

Which of the following best describes the function of gap junctions in animal cells?

Accepted Answer

They allow ions and small molecules to pass directly between adjacent cells.

Question 11

Which of the following is true about receptor proteins involved in cell signaling?

Accepted Answer

They are highly specific for their ligands due to their three-dimensional shape.

Question 12

A ligand binds to a receptor, causing a shape change that initiates a signaling cascade. What is the immediate result of this binding?

Accepted Answer

The receptor switches from an inactive to an active conformation.

Question 13

Which of the following is an example of a receptor that acts as both a transducer and an effector?

Accepted Answer

A ligand-gated ion channel that opens to allow ions to flow through.

Question 14

Which of the following best describes the process of signal amplification in a signaling pathway?

Accepted Answer

A single ligand binding event leads to the activation of many downstream molecules.

Question 15

Which of the following is NOT a function of membrane proteins?

Accepted Answer

DNA replication

Question 16

Which of the following statements about plasmodesmata is correct?

Accepted Answer

They are channels in plant cell walls that connect the cytoplasm of adjacent cells.

Question 17

Which of the following best describes the role of expansins in plant cell walls?

Accepted Answer

They disrupt hydrogen bonds in the cell wall to allow for cell expansion.

Question 18

Which of the following is a real-world example of cell signaling affecting physiology?

Accepted Answer

Insulin binding to its receptor and triggering glucose uptake in muscle cells.

Question 19

Which of the following best explains why mature plant cells secrete lignin into their secondary cell walls?

Accepted Answer

To provide additional strength to withstand gravity and wind.

Question 20

Which of the following is a correct statement about the specificity of receptor-ligand interactions?

Accepted Answer

The three-dimensional shape of the receptor determines which ligand it can bind.

Cell Surfaces, Connections, and Signaling Pathways

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