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

4. Protein Structure

Quaternary Structure

Biochemistry

4. Protein Structure

Quaternary Structure

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Multiple Choice

Why is the hemoglobin molecule considered to have a quaternary protein structure?

Because it has a single polypeptide chain folded into a globular shape.

Because it is composed of four polypeptide subunits that interact to form a functional protein complex.

Because it is stabilized solely by hydrogen bonds within one polypeptide chain.

Because it contains both alpha-helices and beta-sheets within a single polypeptide chain.

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Verified step by step guidance

Understand the concept of protein structure levels: Proteins have four levels of structure—primary, secondary, tertiary, and quaternary. Quaternary structure refers to the arrangement and interaction of multiple polypeptide chains (subunits) in a protein complex.

Analyze the hemoglobin molecule: Hemoglobin is composed of four polypeptide subunits—two alpha chains and two beta chains. These subunits interact to form a functional protein complex.

Recognize the significance of subunit interaction: The quaternary structure of hemoglobin is stabilized by various interactions, including hydrogen bonds, ionic bonds, and hydrophobic interactions between the subunits.

Compare the incorrect options: The statement about a single polypeptide chain folded into a globular shape describes tertiary structure, not quaternary. Similarly, stabilization solely by hydrogen bonds within one chain and the presence of alpha-helices and beta-sheets within a single chain are characteristics of secondary and tertiary structures, not quaternary.

Conclude why hemoglobin has quaternary structure: Hemoglobin's functional complexity arises from the cooperative interaction of its four subunits, making it a classic example of a protein with quaternary structure.