Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

4. Biomolecules

Proteins

General Biology

4. Biomolecules

Proteins

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0:54 minutes

Problem 14

Textbook Question

What are the two types of secondary structures found in polypeptides, and what maintains them?
What stabilizes the tertiary structure of a polypeptide?

Verified step by step guidance

The two types of secondary structures found in polypeptides are the alpha-helix (α-helix) and the beta-pleated sheet (β-sheet). These structures are formed by the folding of the polypeptide chain in specific patterns.

The secondary structures are maintained by hydrogen bonds. In the α-helix, hydrogen bonds form between the carbonyl oxygen (C=O) of one amino acid and the amide hydrogen (N-H) of another amino acid four residues away. In the β-sheet, hydrogen bonds form between the carbonyl oxygen and amide hydrogen of amino acids in adjacent strands.

The tertiary structure of a polypeptide refers to its three-dimensional shape, which is formed by the folding and interactions of the secondary structures.

The tertiary structure is stabilized by various interactions, including hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges. Disulfide bridges are covalent bonds formed between the sulfur atoms of two cysteine residues.

These interactions collectively contribute to the overall stability and functionality of the protein, allowing it to perform its biological role effectively.

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Key Concepts

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

Secondary Structure of Proteins

The secondary structure of proteins refers to the local folded structures that form within a polypeptide due to hydrogen bonding between the backbone atoms. The two most common types are alpha helices, which are coiled structures, and beta sheets, which are flat, sheet-like arrangements. These structures are crucial for the overall shape and function of proteins.

Hydrogen Bonds

Hydrogen bonds are weak interactions that occur between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom. In the context of protein secondary structures, these bonds stabilize the alpha helices and beta sheets by forming between the carbonyl oxygen of one amino acid and the amide hydrogen of another. This interaction is essential for maintaining the integrity of the protein's structure.

Tertiary Structure of Proteins

The tertiary structure of a protein is its overall three-dimensional shape, formed by the interactions between the side chains of the amino acids. This structure is stabilized by various forces, including hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges. The tertiary structure is critical for the protein's functionality, as it determines how the protein interacts with other molecules.

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Related Practice

Textbook Question

Based on what you know of the peptide bonds that link together amino acid residues, why would proline's side chain reduce the flexibility of the backbone?

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Textbook Question

Which structural level of a protein would be least affected by a disruption in hydrogen bonding?

a. Primary structure

b. Secondary structure

c. Tertiary structure

d. Quaternary structure

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Textbook Question

Make a concept map that relates the four levels of protein structure and shows how they can contribute to the formation of hemoglobin. Your map should include the following boxed terms: Primary structure, Secondary structure, Tertiary structure, Quaternary structure, Amino acid sequence, R-groups, αα-helices, and ββ-pleated sheets.

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Textbook Question

Most proteins are soluble in the aqueous environment of a cell. Knowing that, where in the overall three-dimensional shape of a protein would you expect to find amino acids with hydrophobic R groups?

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Textbook Question

How can a cell make many different kinds of proteins out of only 20 amino acids?

Of the myriad possibilities, how does the cell 'know' which proteins to make?

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Textbook Question