Q: Which of the following equations correctly represents the stoichiometry of the sodium-potassium pump?

$$3\ \mathrm{Na}^+_{\text{(in)}} + 2\ \mathrm{K}^+_{\text{(out)}} + \mathrm{ATP} \rightarrow 3\ \mathrm{Na}^+_{\text{(out)}} + 2\ \mathrm{K}^+_{\text{(in)}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 1

Which of the following best describes the structure of the plasma membrane according to the fluid mosaic model?

Accepted Answer

A double layer of phospholipids with embedded proteins that move freely, and carbohydrates attached to the outer surface.

Question 2

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which type of solution was the cell placed in, and what is the underlying mechanism?

Accepted Answer

Hypotonic; water moves into the cell due to lower solute concentration outside.

Question 3

Which of the following is a function of integral membrane proteins?

Accepted Answer

Forming channels and carriers for transport, acting as receptors, and participating in signal transduction.

Question 4

A patient with severe burns is at risk of losing fluids and electrolytes rapidly. Which property of the plasma membrane is compromised in this scenario?

Accepted Answer

Selective permeability

Question 5

Which of the following best explains why oxygen and carbon dioxide can diffuse directly through the plasma membrane?

Accepted Answer

They are nonpolar and lipid-soluble, allowing them to pass through the hydrophobic core.

Question 6

A cell is observed to engulf bacteria by extending its plasma membrane around the particle. Which process is being described, and what is the resulting vesicle called?

Accepted Answer

Phagocytosis; phagosome

Question 7

Which of the following equations correctly represents the stoichiometry of the sodium-potassium pump?

Accepted Answer

$$3\ \mathrm{Na}^+_{	ext{(in)}} + 2\ \mathrm{K}^+_{	ext{(out)}} + \mathrm{ATP} ightarrow 3\ \mathrm{Na}^+_{	ext{(out)}} + 2\ \mathrm{K}^+_{	ext{(in)}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 8

Which of the following best describes the role of the glycocalyx in cell biology?

Accepted Answer

It serves as a specific biological marker for cell-to-cell recognition and allows the immune system to distinguish self from nonself.

Question 9

A scientist observes that a cell is able to move glucose into the cytoplasm against its concentration gradient, but only when sodium ions are also present and moving down their gradient. Which type of transport is this, and what is the underlying mechanism?

Accepted Answer

Secondary active transport (symport); sodium gradient created by ATP-driven pumps is used to co-transport glucose.

Question 10

Which of the following best explains why animal cells are more susceptible to osmotic imbalances than plant cells?

Accepted Answer

Animal cells lack a cell wall to limit hydrostatic pressure, making them prone to swelling or shrinking.

Question 11

Which of the following scenarios best illustrates the function of tight junctions in epithelial tissue?

Accepted Answer

Preventing digestive enzymes from leaking between cells lining the stomach.

Question 12

A mutation causes a cell to lack functional lysosomal enzymes. Which disease is most likely to result, and what is the underlying cellular defect?

Accepted Answer

Tay-Sachs disease; accumulation of undigested glycolipids in nerve cells.

Question 13

Which of the following best describes the process of osmosis?

Accepted Answer

Movement of water molecules from low solute concentration to high solute concentration through a selectively permeable membrane.

Question 14

Which of the following is a correct statement about the resting membrane potential (RMP) in most animal cells?

Accepted Answer

RMP is established mainly by the movement of $$\mathrm{K}^+$$ ions out of the cell, making the inside more negative.

Question 15

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

Accepted Answer

Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Question 16

A cell is observed to have an extensive smooth endoplasmic reticulum (ER). Which function is this cell most likely specialized for?

Accepted Answer

Lipid metabolism and detoxification of chemicals.

Question 17

Which of the following best explains the role of microvilli on the surface of intestinal epithelial cells?

Accepted Answer

They increase the surface area for absorption of nutrients.

Question 18

During which phase of the cell cycle does DNA replication occur, and what is the result of this process?

Accepted Answer

S phase; two identical DNA molecules are produced, each with one old and one new strand.

Cells: The Living Units – Structure, Function, and Membrane Transport

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