Chapter 4: Cellular Respiration

Question 1

Cellular Respiration

Overall balanced chemical equation

Answer 1

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP + Heat)

This means glucose (C₆H₁₂O₆) and oxygen (O₂) are used to produce carbon dioxide (CO₂), water (H₂O), and energy in the form of ATP.

Question 2

Key Players + ATP Yield

Glycolysis

Answer 2

1. Key Players:
   
   • Glucose: Starting molecule (6-carbon sugar).
   • Pyruvate: End product (two 3-carbon molecules).
   • NAD⁺: Electron carrier that becomes NADH.
   • ATP: Provides energy for the process.
2. ATP Yield:
   
   • Uses 2 ATP during the process.
   • Produces 4 ATP.
   • Net gain: 2 ATP per glucose molecule.

Question 3

Pyruvate Oxidation

Answer 3

1. Key Players:
   
   • Pyruvate: 3-carbon molecule produced from glycolysis.
   • NAD⁺: Electron carrier that gets reduced to NADH.
   • Coenzyme A (CoA): Combines with the acetyl group to form acetyl CoA.
   • Pyruvate Decarboxylase: Enzyme that catalyzes the decarboxylation reaction.
2. ATP Yield:
   
   • NADH Produced: 2 NADH (1 per pyruvate molecule).

Location: Mitochondrial matrix

Question 4

ATP yield + key players

Citric Acid Cycle (Krebs Cycle)

Answer 4

TOTAL: 36-38 ATP

Key Players:
- NADH: Energy carrier (reduced form of NAD⁺).
- Acetyl-CoA: Combines with oxaloacetate at the start of the Krebs cycle.
- ATP: Final product and energy source, created through phosphorylation.
- Protein Complexes: Help establish the ETC through oxidation reactions.

Question 5

ETC & Chemiosmosis – Process and Energy Production

Answer 5

Electron Transport Chain (ETC):
- The ETC happens in the inner membrane of the mitochondria.
- NADH and FADH₂ give electrons to the chain, which pass through proteins, releasing energy.
- This energy is used to pump H⁺ ions into the space between the mitochondria’s membranes, creating a proton gradient.
- Oxygen accepts the electrons at the end of the chain, forming water.

Chemiosmosis:
- The build-up of H⁺ ions creates a gradient (more H⁺ outside than inside the mitochondria).
- This gradient causes H⁺ to want to flow back into the mitochondria.
- As H⁺ flows through ATP synthase, ATP is made.

Energy Production:
- Chemiosmosis powers the production of ATP by using the flow of H⁺ through ATP synthase.
- This process makes 32-34 ATP molecules from the energy carried by NADH and FADH₂.

Question 6

Importance of Oxygen in Cellular Respiration

Answer 6

• Oxygen: Oxygen is the final electron acceptor in the electron transport chain (ETC). It combines with hydrogen to form water. Oxygen’s strong pull (electronegativity) helps drive the ETC and establish the proton gradient needed for ATP production. The creation of water is essential since water plays a vital role in all body functions.

Question 7

Importance of Water in Cellular Respiration

Answer 7

• At the end of the ETC, oxygen combines with electrons and protons to make water. This prevents electrons from building up and keeps the process running smoothly.
• Water also dissolves important molecules like glucose and enzymes, helping the reactions in cellular respiration happen.
• By forming water, the cell avoids making harmful substances called reactive oxygen species (ROS).
• Without water, the ETC would stop working, and the cell wouldn’t be able to make the energy it needs to survive.

Question 8

Importance of Food in Cellular Respiration

Answer 8

• Food: Food provides glucose, which is broken down to start glycolysis. Without glucose from food, the cycle of cellular respiration wouldn’t begin, as glycolysis is the first step in the process.