ch.10

Question 1

aerobic cellular respiration

Answer 1

Uses oxygen and an electron transport chain (ETC) to produce ATP.

Question 2

Anaerobic Cellular Respiration

Answer 2

Uses an ETC but does not require oxygen; instead, uses other molecules (e.g., nitrate) as the final electron acceptor.

Question 3

Fermentation

Answer 3

Does not use oxygen or an ETC; instead, it relies on glycolysis and regenerates NAD⁺ by transferring electrons to organic molecules.

Question 4

ATP Generation and Efficiency in Metabolic Processes

Answer 4

ATP Production:
Aerobic Respiration: Produces ~30-32 ATP per glucose (most efficient).
Anaerobic Respiration: Produces fewer ATP than aerobic respiration.
Fermentation: Generates 2 ATP per glucose from glycolysis.

Question 5

Types of Fermentation

Answer 5

Lactic Acid Fermentation
Alcohol fermentation

Question 6

Alternative Reactants for ATP Generation

Answer 6

Not Restricted to Glucose: Fats, proteins, and other carbohydrates can also be broken down to enter glycolysis or the citric acid cycle, generating ATP.

Question 7

Redox Reactions and Their Coupling

Answer 7

Definition: Redox reactions involve the transfer of electrons between molecules.
Coupling: These reactions are coupled because one molecule loses electrons (oxidized) while another gains electrons (reduced).

Question 8

Reduction

Answer 8

A molecule gains electrons or hydrogen atoms

Question 9

Oxidation

Answer 9

A molecule loses electrons or hydrogen atom

Question 10

Agents and Roles

Answer 10

Reducing Agent: Donates electrons (becomes oxidized).
Oxidizing Agent: Accepts electrons (becomes reduced).
Electron Donor: Molecule that loses electrons.
Electron Acceptor: Molecule that gains electrons.

Question 11

Identifying Oxidized and Reduced Molecules

Answer 11

Method: Track electron sharing in bonds and hydrogen addition:
Oxidized Molecules: Lose hydrogen or share fewer electrons with other atoms.
Reduced Molecules: Gain hydrogen or have more electron sharing.

Question 12

Dehydrogenase Enzymes

Answer 12

Function: Catalyze the removal of hydrogen atoms from molecules.
Coenzyme: Typically NAD⁺, which accepts electrons and becomes NADH.

Question 13

Components and Structure of NAD⁺

Answer 13

Nicotinamide Adenine Dinucleotide (NAD⁺):
Components: Nicotinamide, ribose, adenine, and phosphate groups.
Structure: Contains an adenine nucleotide linked to a nicotinamide nucleotide; acts as an electron carrier.

Question 14

NAD⁺ vs. NADH

Answer 14

NAD⁺/NADH: NAD⁺ is the oxidized form, NADH is the reduced form carrying electrons and H⁺.

Question 15

FAD vs. FADH₂

Answer 15

FAD/FADH₂: FAD is the oxidized form, FADH₂ is the reduced form carrying electrons and H⁺.

Question 16

Key Energy Carriers in Metabolism

Answer 16

Three Important Carriers:
ATP: Provides immediate energy for cellular processes.
NADH: Delivers electrons to the ETC for oxidative phosphorylation.
FADH₂: Similar to NADH, donates electrons to the ETC but yields less ATP.

Question 17

Energy of Phosphorylated Molecules

Answer 17

Effect of Phosphorylation: Increases a molecule’s energy, making it more reactive.
ATP’s Role: ATP holds an intermediate energy position, allowing it to donate phosphate groups efficiently in energy transfer and signaling.

Question 18

Mitochondrial Structure

Answer 18

Components:
Outer Membrane: Encloses the organelle.
Inner Membrane: Contains cristae, where the ETC is located.
Intermembrane Space: Accumulates H⁺ during electron transport.
Matrix: Site of the citric acid cycle.
Function: Oxidative phosphorylation occurs along the inner membrane, creating an electrochemical gradient.

Question 19

Oxidative Phosphorylation Process

Answer 19

Steps:
Electron Carriers: NADH and FADH₂ donate electrons to the ETC.
ETC: Electrons pass through protein complexes, creating an electrochemical gradient.
ATP Synthase: Uses the H⁺ gradient to produce ATP from ADP

Question 20

Importance of ETC in Aerobic Respiration

Answer 20

Need for ETC: Prevents rapid release of energy by gradually transferring electrons.
Consequence Without ETC: Direct electron transfer to oxygen would release energy as heat, damaging cells.

Question 21

Four Steps of Cellular Respiration

Answer 21

Glycolysis: Occurs in cytoplasm; splits glucose into pyruvate.
Pyruvate Processing: Occurs in the mitochondria; converts pyruvate to acetyl-CoA.
Citric Acid Cycle: Occurs in the matrix; produces electron carriers.
Oxidative Phosphorylation: Occurs along the inner membrane; produces most ATP.

Question 22

Glycolysis Summary

Answer 22

Phases:
Energy Investment: Consumes 2 ATP.
Energy Payoff: Produces 4 ATP (net gain of 2 ATP).
Products per Glucose:
2 pyruvate, 2 NADH, and 2 ATP.

Question 23

Pyruvate Processing Summary

Answer 23

Products per Pyruvate:
1 acetyl-CoA, 1 NADH, 1 CO₂ (2 acetyl-CoA, 2 NADH, and 2 CO₂ per glucose).

Question 24

Citric Acid Cycle Summary

Answer 24

Entry Molecule: Acetyl-CoA combines with oxaloacetate to form citrate.
Products per Cycle:
1 ATP, 3 NADH, 1 FADH₂, and 2 CO₂ (per acetyl-CoA).

Question 25

Regulation of Glucose Oxidation

Answer 25

Importance: Ensures energy production matches demand. Regulation: Controlled by enzyme inhibition, substrate availability, and feedback mechanisms (e.g., ATP inhibits glycolysis).

Question 26

Monitoring Energy Levels

Answer 26

Ratios for Energy Status: ATP/ADP Ratio: High ratio inhibits energy production. NADH/NAD⁺ Ratio: High ratio inhibits citric acid cycle.

Question 27

Phosphofructokinase Regulation

Answer 27

Characteristics: Key enzyme in glycolysis. Sensitive to ATP levels. Control point for glucose oxidation. Regulation by ATP: High ATP levels inhibit phosphofructokinase (allosteric inhibition).

Question 28

Components of Oxidative Phosphorylation

Answer 28

ETC: Generates proton gradient in the inner membrane. ATP Synthase: Uses proton gradient to produce ATP.

Question 29

Why It’s Called Oxidative Phosphorylation

Answer 29

Explanation: Involves oxidation (electron transfer) and phosphorylation (ATP synthesis).

Question 30

ETC Components

Answer 30

Proteins: Complex I: NADH dehydrogenase. Complex II: Succinate dehydrogenase. Complex III: Cytochrome b-c₁ complex. Complex IV: Cytochrome c oxidase. Lipid: Ubiquinone (coenzyme Q) transports electrons between complexes.

Question 31

Terminal Electron Acceptor

Answer 31

Definition: Final molecule that accepts electrons at the end of the ETC. Aerobic: Oxygen. Anaerobic: Often nitrate or sulfate ions.

Question 32

Importance of Stepwise Electron Transfer

Answer 32

Purpose: Prevents a sudden release of energy, allowing for controlled proton pumping and gradient formation.

Question 33

Electron Entry Points in ETC

Answer 33

NADH: Donates electrons at Complex I. FADH₂: Donates electrons at Complex II (contributes less to the proton gradient).

Question 34

Proton Pumping Complexes

Answer 34

Complexes: I, III, IV pump H⁺ ions, creating a gradient in the intermembrane space.

Question 35

ATP Synthase Structure

Answer 35

Components: Rotor: Turns as H⁺ flows through. Stator: Anchors the structure and allows ATP synthesis.

Question 36

Coupling of ETC and ATP Synthase

Answer 36

Mechanism: Proton gradient created by ETC drives ATP production in ATP synthase. Blocking Effect: Blocking either disrupts ATP production and electron flow

Question 37

ATP Yield from 1 Glucose in Aerobic Respiration

Answer 37

Total: ~30-32 ATP. Substrate-Level Phosphorylation: ~4 ATP. Oxidative Phosphorylation: ~26-28 ATP.

Question 38

Estimating ATP Production

Answer 38

Factors: NADH/FADH₂ contribution, proton leak, and variation in cell efficiency affect estimates.

Question 39

ATP Yield per NADH and FADH₂

Answer 39

Estimates: NADH yields ~2.5 ATP; FADH₂ yields ~1.5 ATP.

Question 40

Efficiency of Cellular Respiration

Answer 40

Formula: Efficiency ≈ (ΔG ATP synthesis / ΔG glucose oxidation) × 100. Not 100%: Energy lost as heat.

Question 41

Aerobic Cellular Respiration Equation

Answer 41

Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~30-32 ATP. Type: Exergonic, as energy is released

Question 42

Lactic Acid Fermentation steps

Answer 42

1. Glycolysis: Glucose is broken down into two molecules of pyruvate, producing 2 ATP and 2 NADH. 2. Pyruvate Reduction: Each pyruvate molecule is reduced to lactic acid (lactate) by accepting electrons from NADH, regenerating NAD⁺. 3. Regeneration of NAD⁺: NAD⁺ is recycled back into glycolysis, allowing the cell to continue generating ATP.

Question 43

Alcohol Fermentation steps

Answer 43

1. Glycolysis: Glucose is broken down into two molecules of pyruvate, producing 2 ATP and 2 NADH. 2. Decarboxylation of Pyruvate: Each pyruvate loses a carbon dioxide (CO₂) molecule, forming acetaldehyde. 3. Reduction of Acetaldehyde: Acetaldehyde is reduced by NADH to ethanol, regenerating NAD⁺. 4. NAD⁺ Recycling: The NAD⁺ returns to glycolysis, enabling continued ATP production.

Question 44

Lactic Acid Fermentation Organisms:

Answer 44

Common in animal muscle cells under low oxygen conditions, as well as in certain bacteria (e.g., Lactobacillus in yogurt production).

Question 45

Lactic Acid Fermentation Overall Reaction:

Answer 45

Glucose+2ADP+2Pi→2Lactic Acid+2ATP+2H2O

Question 46

Lactic Acid Fermentation Significance

Answer 46

In Muscle Cells: Provides rapid ATP when oxygen is scarce, though it causes lactic acid buildup, leading to muscle fatigue. In Industry: Utilized in food production, such as in making yogurt and sourdough, where lactic acid contributes to flavor and preservation.

Question 47

Alcohol Fermentation Organisms:

Answer 47

Occurs in yeasts and some bacteria. It is commonly used in the production of alcoholic beverages and bread.

Question 48

Alcohol Fermentation Overall Reaction

Answer 48

Glucose+2ADP+2Pi →2Ethanol+2CO2 +2ATP+2H2O

Question 49

Alcohol Fermentation Significance

Answer 49

In Beverage Production: Yeast fermentation produces ethanol for alcoholic drinks. In Bread Making: CO₂ production causes dough to rise, while ethanol evaporates during baking.

Question 50

ATP yield for fermentations

Answer 50

2 ATP