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

Enzymes

Biochemistry

6. Enzymes and Enzyme Kinetics

Enzymes

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Multiple Choice

Which enzyme is responsible for covalently joining DNA fragments with sticky ends that have already hydrogen bonded to each other?

Restriction endonuclease

DNA polymerase

Helicase

DNA ligase

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Verified step by step guidance

Understand the role of DNA ligase: DNA ligase is an enzyme that catalyzes the formation of covalent bonds between the phosphate group of one nucleotide and the hydroxyl group of another nucleotide, sealing nicks in the DNA backbone.

Recognize the context of sticky ends: Sticky ends are single-stranded overhangs of DNA created by restriction enzymes. These ends can hydrogen bond with complementary sequences, but the DNA backbone remains incomplete until covalently joined.

Differentiate DNA ligase from other enzymes: Restriction endonucleases cut DNA at specific sequences, DNA polymerase synthesizes new DNA strands, and helicase unwinds the DNA helix. None of these enzymes are responsible for sealing DNA fragments.

Identify the specific action of DNA ligase: DNA ligase uses ATP or NAD+ as a cofactor to catalyze the formation of phosphodiester bonds, completing the DNA backbone and ensuring the fragments are permanently joined.

Conclude that DNA ligase is the correct enzyme for covalently joining DNA fragments with sticky ends after they have hydrogen bonded to each other.