Q: Which equation best describes the net movement of molecules during passive diffusion across a membrane?

Net movement $$= D \times (C_{high} - C_{low})$$

Question 1

Which of the following best explains why electron microscopes provide higher resolution than light microscopes?

Accepted Answer

Electron microscopes use electrons, which have a shorter wavelength than visible light, allowing for greater resolution.

Question 2

A scientist wants to study the movement of living cells without killing them. Which microscopy technique should they use?

Accepted Answer

Phase-contrast microscopy

Question 3

During cell fractionation, which cellular component will be found in the first pellet after centrifugation?

Accepted Answer

Nuclei

Question 4

Which of the following statements about the surface area-to-volume ratio in cells is correct?

Accepted Answer

Small cells have a higher surface area-to-volume ratio, allowing for more efficient exchange of materials.

Question 5

A mutation causes ribosomes to be unable to attach to the rough ER. Which cellular process would be most directly affected?

Accepted Answer

Synthesis of proteins destined for secretion or membrane insertion

Question 6

Which organelle is primarily responsible for converting glucose into ATP in animal cells?

Accepted Answer

Mitochondrion

Question 7

According to the endosymbiont theory, which evidence supports the idea that mitochondria and chloroplasts were once independent prokaryotes?

Accepted Answer

They contain their own circular DNA and double membranes.

Question 8

Which cytoskeletal component is most directly involved in muscle contraction and amoeboid movement?

Accepted Answer

Microfilaments (actin filaments)

Question 9

A plant cell is placed in pure water. Which structure prevents it from bursting due to water uptake?

Accepted Answer

Cell wall

Question 10

Which type of cell junction allows for direct exchange of ions and small molecules between adjacent animal cells?

Accepted Answer

Gap junctions

Question 11

Which property of phospholipids is essential for the formation of the cell membrane's bilayer structure?

Accepted Answer

Amphipathic nature (having both hydrophilic and hydrophobic regions)

Question 12

How does cholesterol affect the fluidity of the cell membrane at different temperatures?

Accepted Answer

It decreases fluidity at high temperatures and prevents solidification at low temperatures.

Question 13

Which equation best describes the net movement of molecules during passive diffusion across a membrane?

Accepted Answer

Net movement $$= D 	imes (C_{high} - C_{low})$$

Question 14

A cell needs to import glucose against its concentration gradient. Which transport mechanism is most likely used?

Accepted Answer

Active transport via carrier proteins

Question 15

The Na⁺/K⁺ pump in animal cells moves sodium and potassium ions against their gradients. Which equation represents the energy requirement for this process?

Accepted Answer

Energy required $$= \Delta G = RT \ln \left( \frac{[Na^+]_{out}}{[Na^+]_{in}} \right) + zF\Delta \Psi$$

Question 16

Which process is responsible for the uptake of large particles, such as bacteria, by immune cells?

Accepted Answer

Fagocytosis

Question 17

A patient with severe diarrhea is treated with an oral rehydration solution (ORS) containing glucose and salt. Which transport mechanism is primarily responsible for the absorption of these nutrients?

Accepted Answer

Cotransport (symport) of Na⁺ and glucose

Question 18

Which sequence correctly represents the three steps of cellular signal transduction?

Accepted Answer

Reception → Transduction → Response

Question 19

Which type of receptor is most likely to be activated by steroid hormones such as aldosterone?

Accepted Answer

Intracellular receptor

Question 20

Which molecule acts as a second messenger in the signal transduction pathway initiated by adrenaline, leading to glycogen breakdown?

Accepted Answer

cAMP (cyclisch AMP)

Cell Biology: Structure, Function, and Communication of Cells

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