Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

18. Amino Acids and Proteins

Secondary Protein Structure

GOB Chemistry

18. Amino Acids and Proteins

Secondary Protein Structure

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Problem 74

Textbook Question

Give an example of a protein containing primarily alpha-helices. Is this a fibrous or globular protein?

Verified step by step guidance

Step 1: Understand the structure of alpha-helices. Alpha-helices are a common secondary structure in proteins, characterized by a coiled shape stabilized by hydrogen bonds between the backbone amide hydrogen and carbonyl oxygen atoms.

Step 2: Identify a protein that is known to contain primarily alpha-helices. A classic example is myoglobin, which is a protein that stores oxygen in muscle cells and is composed almost entirely of alpha-helices.

Step 3: Classify the protein as fibrous or globular. Proteins are categorized based on their overall shape and function. Fibrous proteins are elongated and structural, while globular proteins are compact and functional.

Step 4: Determine the classification of myoglobin. Myoglobin is a globular protein because it has a compact, spherical shape and is involved in a functional role (oxygen storage) rather than structural support.

Step 5: Summarize the findings. Myoglobin is an example of a protein containing primarily alpha-helices, and it is classified as a globular protein due to its compact shape and functional role.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Alpha-Helices

Alpha-helices are a common structural motif in proteins, characterized by a right-handed coiled or spiral shape. They are stabilized by hydrogen bonds between the backbone amides of amino acids, typically every fourth residue. This structure contributes to the overall stability and functionality of proteins, influencing their interactions and roles in biological processes.

Fibrous vs. Globular Proteins

Proteins can be classified into two main categories: fibrous and globular. Fibrous proteins, such as collagen and keratin, have elongated structures and are typically involved in providing support and strength. In contrast, globular proteins, like enzymes and antibodies, are more spherical and often function in catalysis and regulation. The arrangement of secondary structures, including alpha-helices, plays a crucial role in determining a protein's classification.

Examples of Alpha-Helical Proteins

An example of a protein that contains primarily alpha-helices is alpha-keratin, found in hair, nails, and skin. This fibrous protein is composed of long chains of amino acids that form a helical structure, providing mechanical strength and resilience. Understanding the specific structure of such proteins helps in distinguishing their functional roles in biological systems.

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Related Practice

Textbook Question

Describe the differences in the shape of an α helix and a β-pleated sheet.

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Textbook Question

For each of the following proteins, note whether the main secondary structure feature is α helix, β-pleated sheet, or both.

a. collagen

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Textbook Question

For each of the following proteins, note whether the main secondary structure feature is α helix, β-pleated sheet, or both.

c. hemoglobin

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Textbook Question

For each of the following proteins, note whether the main secondary structure feature is α helix, β-pleated sheet, or both.

e. hexokinase

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Textbook Question

Globular proteins are water-soluble, whereas fibrous proteins are insoluble in water. Indicate whether you expect the following amino acids to be on the surface of a globular protein or on the surface of a fibrous protein.

a. Ala

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Textbook Question

What is meant by the following terms as they apply to protein structure, and what bonds or molecular interactions stabilize that level of structure?

b. Secondary structure

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Textbook Question

Complete the following two sentences with either globular or fibrous:

a. Proteins with secondary structure composed primarily of alpha-helix are___________ proteins.

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