FREE BACE Chemistry and Biochemistry Questions and Answers 2

Question 1

What is the chemical basis for enzyme catalysis?

Accepted Answer

Enzymes lower the activation energy of reactions increasing the reaction rate without being consumed

Answer

Enzymes change the equilibrium constant of reactions making unfavorable reactions thermodynamically possible

Answer

Enzymes increase the temperature of the microenvironment around substrates to accelerate reactions

Answer

Enzymes supply energy (ATP) directly to drive otherwise endergonic reactions

Question 2

What is the difference between an agonist and an antagonist in the context of receptor pharmacology?

Accepted Answer

An agonist binds and activates a receptor; an antagonist binds but blocks receptor activation

Answer

An agonist inhibits receptor signaling; an antagonist activates receptor signaling

Answer

An agonist is a small molecule; an antagonist is always a large protein

Answer

An agonist is natural; an antagonist is always synthetic

Question 3

What is the Michaelis-Menten constant (Km) a measure of?

Accepted Answer

The substrate concentration at which the reaction rate is half of Vmax reflecting the affinity of the enzyme for its substrate

Answer

The maximum rate of an enzyme-catalyzed reaction when substrate is saturating

Answer

The rate at which an enzyme-substrate complex dissociates back to free enzyme and substrate

Answer

The optimal pH at which an enzyme has maximum activity

Question 4

What type of chemical bond holds the two strands of the DNA double helix together?

Accepted Answer

Hydrogen bonds between complementary base pairs

Answer

Covalent phosphodiester bonds

Answer

Ionic bonds between negatively charged phosphates and positive ions

Answer

Disulfide bonds between cysteine residues in the DNA structure

Question 5

What is the primary structure of a protein?

Accepted Answer

The linear sequence of amino acids linked by peptide bonds

Answer

The three-dimensional folded conformation of the complete polypeptide chain

Answer

The coiled or sheet-like local structure formed by hydrogen bonding of the backbone

Answer

The arrangement of multiple polypeptide subunits into a functional complex

Question 6

What is the function of NADH and FADH2 in cellular respiration?

Accepted Answer

They are electron carriers that donate electrons to the mitochondrial electron transport chain driving ATP synthesis

Answer

They directly phosphorylate ADP to ATP in the cytoplasm

Answer

They are cofactors required for glycolysis reactions in the cytoplasm

Answer

They transport carbon dioxide from cells to the lungs for exhalation