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

Which of the following statements about protein structure is correct?

The α-helix is stabilized primarily by ionic interactions between amino acid R groups.

Disulfide bond formation can only form between adjacent cysteine residues in a sequence.

The stability of quaternary structure in all proteins is primarily due to covalent bonds between subunits.

The denaturation of a protein always leads to irreversible loss of secondary & tertiary structure.

Quaternary subunits complex primarily through hydrophobic interactions between chains.

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Verified step by step guidance

Understand the levels of protein structure: primary, secondary, tertiary, and quaternary. Each level has distinct characteristics and types of interactions that stabilize them.

Review the α-helix structure: It is a type of secondary structure stabilized by hydrogen bonds between the backbone atoms, not by ionic interactions between R groups.

Consider disulfide bonds: These are covalent bonds that can form between cysteine residues, but they do not need to be adjacent in the sequence. They can form between cysteines that are brought close together in the folded protein.

Examine quaternary structure: This level involves the assembly of multiple polypeptide chains (subunits). The stability of quaternary structures is often due to non-covalent interactions, such as hydrophobic interactions, hydrogen bonds, and ionic interactions, rather than covalent bonds.

Understand protein denaturation: Denaturation involves the unfolding of a protein, which can lead to loss of secondary and tertiary structures. However, denaturation is not always irreversible; some proteins can refold back to their native state under the right conditions.