ch.11

Question 1

Organisms Undergoing ATP Synthesis without Oxygen

Answer 1

Examples: Many bacteria, yeast, and muscle cells in animals can synthesize ATP in the absence of oxygen through anaerobic respiration or fermentation

Question 2

Summary of Anaerobic Respiration

Answer 2

Definition: Anaerobic respiration is a process where cells generate ATP without oxygen by using an electron transport chain (ETC) with a different final electron acceptor.
Difference from Aerobic Respiration: Uses molecules other than oxygen (e.g., nitrate, sulfate) as final electron acceptors.
ETC: Yes, anaerobic respiration has an ETC, but with alternative electron acceptors.
Final Electron Acceptors: Commonly nitrate (NO₃⁻) or sulfate (SO₄²⁻), depending on the organism.

Question 3

Summary of Fermentation

Answer 3

Definition: Fermentation is an anaerobic process that allows ATP production through glycolysis and regenerates NAD⁺ without using an ETC.
Goal: Regenerate NAD⁺ to allow continuous ATP production via glycolysis.
Types of Fermentation:
Alcohol Fermentation: Produces ethanol and CO₂.
Lactic Acid Fermentation: Produces lactic acid.
ATP Yield: 2 ATP per glucose molecule.
Oxygen Requirement: Does not require oxygen.

Question 4

Alcohol and Lactic Acid Fermentation

Answer 4

Alcohol Fermentation:
Process: Pyruvate is converted to ethanol and CO₂.
Organisms: Yeasts and some bacteria.
Lactic Acid Fermentation:
Process: Pyruvate is reduced to lactic acid.
Organisms: Certain bacteria and muscle cells in animals.

Question 5

Efficiency Ranking of ATP Production

Answer 5

1. Aerobic Respiration: Most efficient (~30-32 ATP per glucose), fully oxidizing glucose.
2. Anaerobic Respiration: Less efficient due to alternative electron acceptors, yields fewer ATP.
3. Fermentation: Least efficient, producing only 2 ATP per glucose molecule, as it only uses glycolysis.

Question 6

Alternative Organic Molecules in Cellular Respiration

Answer 6

1. Carbohydrates (first choice for energy).
2. Fats (second, broken down into glycerol and fatty acids).
3. Proteins (used last, broken into amino acids).

Question 7

Entry Points of Monosaccharides

Answer 7

Monosaccharides other than glucose (from disaccharides and polysaccharides) enter cellular respiration at glycolysis, after being converted into intermediates like glucose-6-phosphate.

Question 8

Breakdown of Fats

Answer 8

Process:
Lipases: Enzymes that break fats into glycerol and fatty acids.
Beta-Oxidation: Fatty acids are broken down in mitochondria (and peroxisomes) to produce acetyl-CoA.
Entry Points:
Glycerol: Enters glycolysis as an intermediate.
Acetyl-CoA: Enters the citric acid cycle.

Question 9

Breakdown of Proteins

Answer 9

Process:
Proteases/Peptidases: Break down proteins into amino acids.
Deamination: Removes amino groups from amino acids, converting them into intermediates.
Entry Points:
Deaminated Amino Acids: Enter glycolysis, pyruvate processing, or the citric acid cycle, depending on the specific amino acid.
Amino Group Removal: Excess amino groups are converted to urea in the liver and excreted by the kidneys in vertebrates.

Question 10

Use of Cellular Respiration Intermediates in Biosynthesis

Answer 10

Examples of Anabolic Pathways:
Glucose: Provides building blocks for glycogen and starch.
Pyruvate: Used to synthesize amino acids.
Glycolysis Intermediates: Can form nucleotides and amino acids.
Acetyl-CoA: Used to build fatty acids and cholesterol.
Citric Acid Cycle Intermediates: Serve as precursors for amino acids, heme groups, and other biomolecules.