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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2:32 minutes

Problem 7

Textbook Question

Why are proteins not considered to be a good candidate for the first living molecule?
a. Their catalytic capability is not sufficient for most biological reactions.
b. Their amino acid monomers were not likely present in the prebiotic soup.
c. They cannot serve as a template for replication.
d. They could not have polymerized from amino acid monomers under early Earth conditions.

Verified step by step guidance

Understand the role of proteins in biological systems: Proteins are essential macromolecules that perform a wide range of functions, including catalysis of biochemical reactions, structural support, and transport of molecules.

Consider the requirements for the first living molecule: The first living molecule would need to have the ability to store information, replicate, and catalyze reactions.

Evaluate the ability of proteins to serve as a template for replication: Proteins are composed of amino acids linked by peptide bonds, but they do not have the ability to store genetic information or serve as a template for replication like nucleic acids (DNA or RNA) do.

Assess the presence of amino acids in the prebiotic environment: While amino acids are the building blocks of proteins, their availability and the conditions required for polymerization into proteins under prebiotic conditions are uncertain.

Analyze the catalytic capabilities of proteins: Although proteins can act as enzymes to catalyze reactions, the first living molecule would need to have a broader range of capabilities, including self-replication, which proteins alone cannot achieve.

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Key Concepts

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

Catalytic Capability of Proteins

Proteins are known for their role as enzymes, catalyzing a wide range of biological reactions. However, the catalytic capability of proteins alone is not sufficient for the origin of life, as they require a pre-existing system to synthesize and fold them into functional structures. This limitation suggests that proteins may not have been the first self-replicating molecules necessary for life.

Amino Acid Availability in Prebiotic Soup

The prebiotic soup theory posits that early Earth had a mixture of organic compounds from which life originated. However, the specific amino acids required to form proteins may not have been abundantly available or in the right conditions to spontaneously form complex proteins, making them unlikely candidates for the first living molecules.

Template for Replication

For a molecule to be considered a candidate for the first living molecule, it must have the ability to replicate itself. Proteins lack the ability to serve as templates for replication, as they do not have a straightforward mechanism to encode and transfer genetic information, unlike nucleic acids such as RNA, which can both store information and catalyze reactions.

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Related Practice

Textbook Question

The structural level of a protein least affected by a disruption in hydrogen bonding is the

a. Primary level.

b. Secondary level.

c. Tertiary level.

d. Quaternary level.

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Textbook Question

If a cell were to use only 10 of the 20 possible amino acids, how much effect would you expect this to have on protein diversity? Calculate and compare the number of different sequences that can be generated by randomly assembling either 10 or 20 amino acids into peptides that are five residues long.

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Textbook Question

Explain how molecular chaperones facilitate protein folding in many different polypeptides, each with their own specific shape.

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Textbook Question

Different proteins are composed of different sequences of ________.

a. Sugars

b. Lipids

c. Fats

d. Amino acids

e. Carbohydrates

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Textbook Question

Predict the effect on protein function if each polypeptide adopted only a single, inflexible shape based on its primary structure.

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Textbook Question

Proteins may function as ________.

a. Genetic material

b. Cholesterol molecules

c. Fat reserves

d. Enzymes

e. All of the above

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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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