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Medical Biochemistry Exam 1 Questions
and Correct Answers/ Latest Update /
Already Graded
Oxidoreductase
Ans: Catalyze oxidation-reduction reactions. Use NAD, FAD, or
metals as cofactors.
Transferases
Ans: Catalyze transfer of C-, N-, P- containing groups. Example
- Kinase, aminotransferases, methyltransferases,
acetyltransferases.
Hydrolases
Ans: Catalyze cleavage of bonds by addition of water. Example
- Esterases, nucleases, phosphatases, glycosides, serine
proteases
Lyases
Ans: Catalyze cleavage of C-C, C-S, and certain C-N bonds
without water. Example - Decarboxylases, aldolases, synthases.
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Isomerases
Ans: Catalyze rearrangement of optical or geometric isomers.
Example - Racemases, epimerases, isomerases
Ligases
Ans: Catalyze formation of bonds between carbon and O, S, N
coupled to hydrolysis of high-energy phosphates. Example -
Synthetases, carboxylases.
Riboflavin (B2) & Niacin (B3)
Ans: Oxidoreductase cofactors. Important to pyruvate
dehydrogenase complex.
NAD and NADP
Ans: Accept only one electron
FAD & FMN
Ans: Exists as partially reduced (semiquinone, FADH) and fully
reduced form FADH2
Cofactors linked to lysine
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Ans: Pyridoxal phosphate, lipoic acid, biotin (all form covalent
bonds to the epsilon active site on lysine). Sometimes referred
to as prosthetic groups since they are covalently bound
(stronger).
Pyridoxine (B6)
Ans: Binds covalently to lysine. Converted to pyridoxal
phosphate and then is bound to lysine on enzyme. Link forms
Schiff's base (easily broken). Used in transamination and
decarboxylation reactions. Important for synthesis and
degradation of AA and neurotransmitters.
Lipoate
Ans: Part of pyruvate dehydrogenase complex. Important for
acyl transfer and electron transfer. Contain sulfurs in its ring
(novel chemical group). Available in liver, kidney, spinach, and
broccoli.
Biotin (B7)
Ans: Used in enzymes that add carboxyl groups to substrate -
carboxylases. Is converted to carboxybiotin before it binds
covalently to epsilon group on lysine.
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Thiamine (B1)
Ans: Deficient in beriberi. Important cofactor in
decarboxylation reactions. Must be converted to thiami ne
pyrophosphate and is important in the pyruvate dehydrogenase
complex. Has thiazolium ring (not present in other AA).
Pantothenic Acid (B5)
Ans: Incorporated into coenzyme A. CoA is essential for acetyl
group transport, energy from fats, carbs, and proteins. Makes
thioester bond to acetyl groups that facilitate catalysis.
Coenzyme A is required in larger abundance than most
cofactors. Plays a role in regulation of proteins (acetylation),
synthesis of cholesterol, and steroid hormones. Part of
pyruvate dehydrogenase complex.
Pyruvate dehydrogenase complex
Ans: pyruvate dehydrogenase, dihydrolipoyl transacetylase,
dihydrolipoyl dehydrogenase
cofactors of pyruvate dehydrogenase complex
Ans: 1. TPP- thiamine derived - B1
2. lipoic acid
3. FAD+ (Riboflavin) B2
All rights reserved © 2025/ 2026 |
Medical Biochemistry Exam 1 Questions
and Correct Answers/ Latest Update /
Already Graded
Oxidoreductase
Ans: Catalyze oxidation-reduction reactions. Use NAD, FAD, or
metals as cofactors.
Transferases
Ans: Catalyze transfer of C-, N-, P- containing groups. Example
- Kinase, aminotransferases, methyltransferases,
acetyltransferases.
Hydrolases
Ans: Catalyze cleavage of bonds by addition of water. Example
- Esterases, nucleases, phosphatases, glycosides, serine
proteases
Lyases
Ans: Catalyze cleavage of C-C, C-S, and certain C-N bonds
without water. Example - Decarboxylases, aldolases, synthases.
All rights reserved © 2025/ 2026 |
, Page |2
Isomerases
Ans: Catalyze rearrangement of optical or geometric isomers.
Example - Racemases, epimerases, isomerases
Ligases
Ans: Catalyze formation of bonds between carbon and O, S, N
coupled to hydrolysis of high-energy phosphates. Example -
Synthetases, carboxylases.
Riboflavin (B2) & Niacin (B3)
Ans: Oxidoreductase cofactors. Important to pyruvate
dehydrogenase complex.
NAD and NADP
Ans: Accept only one electron
FAD & FMN
Ans: Exists as partially reduced (semiquinone, FADH) and fully
reduced form FADH2
Cofactors linked to lysine
All rights reserved © 2025/ 2026 |
, Page |3
Ans: Pyridoxal phosphate, lipoic acid, biotin (all form covalent
bonds to the epsilon active site on lysine). Sometimes referred
to as prosthetic groups since they are covalently bound
(stronger).
Pyridoxine (B6)
Ans: Binds covalently to lysine. Converted to pyridoxal
phosphate and then is bound to lysine on enzyme. Link forms
Schiff's base (easily broken). Used in transamination and
decarboxylation reactions. Important for synthesis and
degradation of AA and neurotransmitters.
Lipoate
Ans: Part of pyruvate dehydrogenase complex. Important for
acyl transfer and electron transfer. Contain sulfurs in its ring
(novel chemical group). Available in liver, kidney, spinach, and
broccoli.
Biotin (B7)
Ans: Used in enzymes that add carboxyl groups to substrate -
carboxylases. Is converted to carboxybiotin before it binds
covalently to epsilon group on lysine.
All rights reserved © 2025/ 2026 |
, Page |4
Thiamine (B1)
Ans: Deficient in beriberi. Important cofactor in
decarboxylation reactions. Must be converted to thiami ne
pyrophosphate and is important in the pyruvate dehydrogenase
complex. Has thiazolium ring (not present in other AA).
Pantothenic Acid (B5)
Ans: Incorporated into coenzyme A. CoA is essential for acetyl
group transport, energy from fats, carbs, and proteins. Makes
thioester bond to acetyl groups that facilitate catalysis.
Coenzyme A is required in larger abundance than most
cofactors. Plays a role in regulation of proteins (acetylation),
synthesis of cholesterol, and steroid hormones. Part of
pyruvate dehydrogenase complex.
Pyruvate dehydrogenase complex
Ans: pyruvate dehydrogenase, dihydrolipoyl transacetylase,
dihydrolipoyl dehydrogenase
cofactors of pyruvate dehydrogenase complex
Ans: 1. TPP- thiamine derived - B1
2. lipoic acid
3. FAD+ (Riboflavin) B2
All rights reserved © 2025/ 2026 |
