Question 1

Which of the following best describes the mechanism of skeletal muscle contraction at the biochemical level?

Accepted Answer

Calcium ions bind to troponin, causing tropomyosin to move and expose myosin-binding sites on actin, allowing cross-bridge formation.

Question 2

Which immunoglobulin class is primarily responsible for mediating allergic reactions and defense against parasitic infections?

Accepted Answer

IgE

Question 3

Which of the following best defines an enzyme?

Accepted Answer

A protein that acts as a biological catalyst, increasing the rate of a reaction without being consumed.

Question 4

Given the Michaelis-Menten equation $$v = \frac{V_{max}[S]}{K_M + [S]}$$, what does $$K_M$$ represent?

Accepted Answer

The substrate concentration at which the reaction rate is half of $$V_{max}.$$

Question 5

If a Lineweaver-Burk plot is drawn for an enzyme with $$V_{max} = 100$$ µmol/min and $$K_M = 10$$ µM, what is the equation of the line?

Accepted Answer

$$\frac{1}{v} = \frac{K_M}{V_{max}} \frac{1}{[S]} + \frac{1}{V_{max}}$$

Question 6

Which type of enzyme inhibition results in a decrease in $$V_{max}$$ but no change in $$K_M$$?

Accepted Answer

Noncompetitive inhibition

Question 7

Chymotrypsin catalyzes peptide bond hydrolysis by which mechanism?

Accepted Answer

Formation of a covalent acyl-enzyme intermediate followed by nucleophilic attack by water.

Question 8

Which of the following is NOT a mechanism of enzyme regulation?

Accepted Answer

Hydrolysis of ATP by the enzyme

Question 9

According to the first law of thermodynamics, which statement is correct regarding biological systems?

Accepted Answer

Energy can be transformed from one form to another, but cannot be created or destroyed.

Question 10

Which term describes a reaction in which the change in free energy ($$\Delta G) is $$negative?

Accepted Answer

Exergonic

Question 11

How can an endergonic reaction ($$\Delta G \u003e 0) $$proceed in a biological system?

Accepted Answer

By coupling it to an exergonic reaction ($$\Delta G \u003c 0$$), such as ATP hydrolysis.

Question 12

Which molecule acts as the primary 'energy currency' of the cell, transferring free energy from exergonic to endergonic processes?

Accepted Answer

ATP

Question 13

If a redox reaction has a positive redox potential ($$E^0$$), what does this indicate about the direction of electron flow?

Accepted Answer

Electrons will flow spontaneously from the donor to the acceptor with higher $$E^0.$$

Question 14

Which of the following best describes a polysaccharide?

Accepted Answer

A polymer composed of many monosaccharide units linked by glycosidic bonds.

Question 15

Which type of isomerism is exhibited by glucose and galactose?

Accepted Answer

Epimerism

Question 16

Which disaccharide is formed by the glycosidic linkage between glucose and fructose?

Accepted Answer

Sucrose

Question 17

During anaerobic glycolysis in muscle, which product is formed to regenerate NAD+?

Accepted Answer

Lactate

Question 18

Which enzyme is bypassed in gluconeogenesis by the action of fructose-1,6-bisphosphatase?

Accepted Answer

Phosphofructokinase-1

Question 19

Which pathway provides NADPH for biosynthetic reactions and ribose for nucleotide synthesis?

Accepted Answer

Pentose phosphate pathway

Question 20

Which citric acid cycle intermediate is withdrawn for gluconeogenesis and replenished by anaplerotic pathways?

Accepted Answer

Oxaloacetate

Comprehensive Study Guide: Enzymes, Thermodynamics, Carbohydrates, and Metabolic Pathways in Biochemistry

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