Cellular Respiration

Location: Occurs in the cytoplasm of the cell.
Process Overview:
- The main goal is to convert glucose into pyruvate.
- An initial investment of 2 ATP molecules as activation energy leads to the production of 4 ATP, resulting in a net gain of 2 ATP molecules.
Chemical Equation:
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$ext{Glucose} + 2 ext{ADP} + 4 ext{ADP} + 2 ext{NAD} <br /> ightarrow 2 ext{Triose Phosphate} + 4 ext{ATP} + 2 ext{Reduced NAD} + 2 ext{Pyruvate}$
Key Inputs and Outputs:
- Input: 1 glucose, 2 ATP, 2 ADP, 2 NAD
- Output: 2 pyruvate, 2 NADH, 4 ATP (net 2 ATP)

Location: Occurs in the mitochondrial matrix.
Process Overview:
- The main goal is to convert pyruvate into acetyl CoA through an oxidative process.
Chemical Reaction:
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$ext{Pyruvate} + ext{CoA-SH} <br /> ightarrow ext{Acetyl CoA} + ext{CO}_2 + ext{NAD} <br /> ightarrow ext{NADH}$
Conversion Parameters:
- 1 NADH is produced, and 1 CO2 molecule is released.

Location: Occurs in the mitochondrial matrix.
Process Overview:
- The main goal is to convert acetyl CoA into oxaloacetate while facilitating a series of reactions that result in energy production.
- The Krebs Cycle must occur twice per glucose molecule due to the production of two acetyl CoA from glycolysis.
Outputs:
  - Produces:
    - 6 NADH
    - 2 FADH2
    - 2 ATP
    - 4 CO2 molecules.
Input/Output Summary:
- Input: 2 Acetyl CoA
- Output: 6 NADH, 2 FADH2, 2 ATP, 4 CO2
Key Enzymatic Steps and Associated Compounds:
  1. Acetyl CoA + Oxaloacetate → Citrate (Citrate Synthase)
  2. Citrate ↔ Isocitrate (Aconitase)
  3. Isocitrate → α-Ketoglutarate (Isocitrate Dehydrogenase), releasing CO2 and generating NADH
  4. α-Ketoglutarate → Succinyl CoA (α-Ketoglutarate Dehydrogenase), releasing CO2 and generating NADH
  5. Succinyl CoA → Succinate (Succinyl CoA Synthetase), generating GTP from GDP
  6. Succinate → Fumarate (Succinate Dehydrogenase), generating FADH2
  7. Fumarate → Malate (Fumarase)
  8. Malate → Oxaloacetate (Malate Dehydrogenase), generating NADH

Location: Occurs in the cristae folds of the mitochondria.
Process Overview:
- The Electron Transport Chain generates the most ATP compared to other processes in cellular respiration (approximately 34 ATPs).
- Electron transfer through protein pumps establishes a chemiosmotic gradient, ultimately facilitating ATP production through oxidative phosphorylation.
Mechanism:
- Electrons from NADH and FADH2 are transported through complexes I-IV, creating a proton gradient across the inner mitochondrial membrane.
- Protons (H+) are pumped into the intermembrane space, creating a chemiosmotic potential.
**Summary of Reaction: **
-
$2 ext{H}^+ + ext{O}_2 + ext{ADP} + P <br /> ightarrow ext{ATP} + ext{H}_2O$

Definition: The process of breaking down organic molecules (carbohydrates, lipids, proteins) to release stored potential energy.
Types of Respiration:
  - Aerobic Respiration: Requires oxygen.
    - Utilizes mitochondria for ATP production.
  - Anaerobic Respiration: Occurs without oxygen.
    - Includes processes like lactic acid fermentation and alcoholic fermentation.
Glycolysis
  - Definition: Literally means "splitting sugar".
  - Glycolysis is a metabolic pathway composed of 10 chemical reactions catalyzed by enzymes.
  - Process Location: Cytoplasm of all cells (both prokaryotic and eukaryotic).
Glycolysis Overview:
  - Initial Reaction: Begins with a 6-carbon glucose molecule which undergoes phosphorylation requiring 2 ATP (
    - Endergonic process).
  - Final Reaction:
    - 4 ATP are produced via substrate-level phosphorylation, yielding a net total of 2 ATP after the 2 ATP investment.
Overall Products of Glycolysis:
  - 2 Pyruvate (each having 3 carbons)
  - 2 Reduced electron carriers (NADH)
  - 2 ATP molecules
Condition Depending Outcomes:
- Under anaerobic conditions, pyruvate remains in the cytoplasm and serves as a substrate in fermentation.
- Under aerobic conditions, pyruvate is further oxidized in the mitochondria.