Table of contents

1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

6. Enzymes and Enzyme Kinetics

Cofactor

Biochemistry

6. Enzymes and Enzyme Kinetics

Cofactor

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Multiple Choice

Which of the following is an example where a vitamin or mineral functions as a cofactor?

ATP serving as an energy source in muscle contraction

Glucose acting as a substrate for glycolysis

Cholesterol forming the backbone of steroid hormones

Magnesium ions (Mg^{2+}) assisting DNA polymerase activity

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Verified step by step guidance

Step 1: Understand the concept of a cofactor. A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst. Cofactors can be organic molecules (coenzymes) or inorganic ions (such as magnesium ions, Mg²⁺).

Step 2: Recognize the role of magnesium ions (Mg²⁺) in enzymatic activity. Magnesium ions often stabilize the structure of enzymes or interact with substrates to facilitate enzymatic reactions. In this case, Mg²⁺ assists DNA polymerase, an enzyme responsible for synthesizing DNA during replication.

Step 3: Compare the other options provided in the question. ATP serving as an energy source in muscle contraction is not a cofactor; it is a molecule that provides energy. Glucose acting as a substrate for glycolysis is also not a cofactor; it is a reactant in the metabolic pathway. Cholesterol forming the backbone of steroid hormones is a structural role, not a catalytic one.

Step 4: Identify why Mg²⁺ is the correct answer. DNA polymerase requires Mg²⁺ to stabilize the negative charges on the phosphate groups of the DNA backbone and to assist in the catalytic addition of nucleotides during DNA synthesis.

Step 5: Conclude that magnesium ions (Mg²⁺) function as a cofactor by directly aiding the enzymatic activity of DNA polymerase, making it the correct example of a vitamin or mineral functioning as a cofactor.