Question 1

Which statement best describes the First Law of Thermodynamics as it applies to biological systems?

Accepted Answer

Energy is transformed but not created or destroyed; for example, glucose oxidation converts chemical energy to ATP and heat.

Question 2

A reaction has $$\Delta H = +300\ \mathrm{kJ}$$ and $$T\Delta S = +350\ \mathrm{kJ}. $$What is the value of $$\Delta G$$ and what does it indicate about the reaction?

Accepted Answer

$$\Delta G = -50\ \mathrm{kJ}$$; the reaction is spontaneous and entropy-driven.

Question 3

Which of the following best explains why living systems require constant energy input?

Accepted Answer

To continuously drive cellular work and maintain order (low entropy).

Question 4

What is the primary function of the Na+/K+ pump in animal cells?

Accepted Answer

To maintain resting potential, nerve impulse conduction, and osmotic balance by pumping 3 Na+ out and 2 K+ in per ATP hydrolyzed.

Question 5

Which transport process requires ATP and moves molecules against their concentration gradient?

Accepted Answer

Primary active transport

Question 6

A red blood cell is placed in a 10% NaCl solution. What will happen to the cell and why?

Accepted Answer

Water will exit the cell, causing it to shrink (crenation) due to osmosis.

Question 7

Why do phospholipids spontaneously form bilayers in water?

Accepted Answer

Hydrophobic tails aggregate away from water, increasing water's entropy.

Question 8

Which organelle is primarily responsible for energy conversion (ATP synthesis) in eukaryotic cells?

Accepted Answer

Mitochondrion

Question 9

What evidence supports the endosymbiotic theory for the origin of mitochondria and chloroplasts?

Accepted Answer

Presence of double membranes, circular DNA, and bacterial-type ribosomes.

Question 10

If an enzyme is denatured at temperatures above 37°C, what is the most likely consequence for a metabolic reaction it catalyzes?

Accepted Answer

Reaction efficiency and spontaneity are reduced due to loss of enzyme structure.

Question 11

Which of the following best explains why small cells are more efficient at nutrient exchange than large cells?

Accepted Answer

Small cells have a higher surface area to volume ratio, allowing faster diffusion and nutrient exchange.

Question 12

Which scenario describes facilitated diffusion across a cell membrane?

Accepted Answer

Glucose enters a cell via a channel protein, moving down its concentration gradient.

Question 13

What happens to $$\Delta G$$ when entropy ($$S) $$increases in a system at constant temperature?

Accepted Answer

$$\Delta G$$ becomes more negative; reaction more spontaneous.

Question 14

Which of the following is a function of cholesterol in the plasma membrane?

Accepted Answer

It buffers membrane fluidity, preventing rigidity in cold and melting in heat.

Question 15

Which organelle is responsible for protein packaging and secretion in eukaryotic cells?

Accepted Answer

Golgi apparatus

Question 16

A cell stops producing ATP due to mitochondrial dysfunction. Which process will be most immediately affected?

Accepted Answer

Primary active transport of ions across the membrane

Question 17

Which feature distinguishes integral membrane proteins from peripheral membrane proteins?

Accepted Answer

Integral proteins span the bilayer and are involved in transport; peripheral proteins attach loosely for signaling or structure.

Question 18

Which of the following best describes a coupled reaction in cellular metabolism?

Accepted Answer

ATP hydrolysis drives endergonic reactions by phosphorylating molecules, increasing their potential energy.

Question 19

Which two features indicate that mitochondria and chloroplasts share a prokaryotic origin?

Accepted Answer

Double membranes and circular DNA

Question 20

A 2 cm cube cell has a surface area to volume ratio (SAV) of 3:1, while a 4 cm cube cell has a SAV of 1.5:1. What does this imply about the efficiency of nutrient exchange?

Accepted Answer

The 2 cm cell is more efficient at nutrient exchange due to its higher SAV ratio.

Energy Transformations, Membrane Structure, and Cell Biology Study Notes

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