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

8. Respiration

Review of Aerobic Cellular Respiration

General Biology

8. Respiration

Review of Aerobic Cellular Respiration

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1:46 minutes

Problem 9

Textbook Question

Which of the three stages of cellular respiration is considered the most ancient? Explain your answer.

Verified step by step guidance

Identify the three stages of cellular respiration: Glycolysis, the Krebs cycle (also known as the Citric Acid Cycle), and the Electron Transport Chain (ETC).

Understand that glycolysis is the process by which glucose is broken down into pyruvate, releasing energy and producing ATP and NADH. This process occurs in the cytoplasm of the cell.

Recognize that the Krebs cycle and the Electron Transport Chain are more complex processes that occur in the mitochondria, involving a series of reactions that further break down products from glycolysis to produce ATP.

Consider the evolutionary perspective: Glycolysis is thought to be the most ancient form of energy production because it is found in nearly all organisms, from the simplest bacteria to complex multicellular organisms, indicating its presence before the development of mitochondria.

Conclude that glycolysis is considered the most ancient stage of cellular respiration due to its ubiquity and simplicity, suggesting that it was the earliest form of ATP production in primitive cells.

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Key Concepts

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

Cellular Respiration

Cellular respiration is the metabolic process by which cells convert nutrients into energy, primarily in the form of ATP. It involves three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation. This process is essential for all living organisms as it provides the energy required for various cellular functions.

Glycolysis

Glycolysis is the first stage of cellular respiration, occurring in the cytoplasm, where glucose is broken down into pyruvate, producing a small amount of ATP and NADH. This process does not require oxygen, making it an anaerobic pathway. Glycolysis is considered one of the most ancient metabolic pathways, as it is found in nearly all organisms, indicating its evolutionary significance.

Evolution of Metabolic Pathways

The evolution of metabolic pathways refers to the development and adaptation of biochemical processes over time. Glycolysis is thought to be one of the earliest forms of energy production, predating the more complex aerobic processes. Understanding the evolutionary context of these pathways helps explain why glycolysis is still utilized by modern organisms, highlighting its fundamental role in energy metabolism.

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Related Practice

Textbook Question

Most of the CO₂ from cellular respiration is released during

a. Stage 1: Glycolysis

b. Stage 2: Pyruvate oxidation

c. Stage 2: The citric acid cycle

d. Stage 3: Oxidative phosphorylation

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Textbook Question

Which of the following is the most immediate source of energy for making most of the ATP in your cells?

a. The transfer of from intermediate substrates to ADP

b. The movement of H⁺ across a membrane down its concentration gradient

c. The splitting of glucose into two molecules of pyruvate

d. Electrons moving through the electron transport chain

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Textbook Question

Most CO₂ from catabolism is released during

a. Glycolysis.

b. The citric acid cycle.

c. Lactate fermentation.

d. Electron transport.

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Textbook Question

Most of the energy in an ATP molecule is released ________.

a. During cellular respiration.

b. When the terminal phosphate group is hydrolyzed.

c. In the form of new nucleotides.

d. When it is transferred to NADH.

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Textbook Question

Early estimates suggested that the oxidation of glucose via aerobic respiration would produce 38 ATP. Based on what you know of the theoretical yields of ATP from cellular respiration, show how this total was determined. Why do biologists now think this amount of ATP per molecule of glucose is not achieved in cells?

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Multiple Choice

Which stage of cellular respiration produces the most ATP?

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Multiple Choice

What is the primary difference between aerobic and anaerobic respiration?

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Multiple Choice

Which of these is required for aerobic cellular respiration?