Biology

Summary of the overall chemical reactions of cellular respiration from a glucose molecule:

Glycolysis (in the cytoplasm):

• One glucose molecule (C₆H₁₂O₆) is split into two pyruvate molecules (C₃H₄O₃).
• This reaction generates 2 ATP molecules and 2 NADH molecules.

Pyruvate Oxidation (in the mitochondria):

• Each pyruvate molecule is converted into acetyl-CoA (C₂H₃O-CoA).
• One CO₂ is released per pyruvate, and one NADH molecule is produced.

Krebs Cycle (Citric Acid Cycle):

• Acetyl-CoA enters the cycle, producing per turn: 2 CO₂, 3 NADH, 1 FADH₂, and 1 GTP (or ATP).
• For one glucose molecule, the cycle occurs twice, yielding a total of 4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP.

Electron Transport Chain (in the mitochondrial membrane):

• NADH and FADH₂ from earlier stages donate their electrons to the electron transport chain.
• This generates a proton (H⁺) gradient across the mitochondrial membrane, enabling ATP synthase to produce about 34 ATP.
• At the end, oxygen (O₂) accepts electrons and combines with protons to form water (H₂O).

Total Yield: For one glucose molecule, cellular respiration produces up to 38 ATP molecules (though this number can vary slightly), 6 CO₂ molecules, and 6 water molecules.

Here is a translation of the summary of the chemical reactions involved in the two types of fermentation: lactic fermentation and alcoholic fermentation.

1. Lactic Fermentation:

Lactic fermentation occurs in the absence of oxygen (anaerobic conditions) in cells, such as muscle cells in animals or in certain bacteria. It allows for the regeneration of NAD⁺ to continue glycolysis and produce a small amount of energy (ATP).

Chemical Reactions:

Glycolysis:

• One glucose molecule (C₆H₁₂O₆) is converted into 2 pyruvate molecules (C₃H₄O₃).
• Produces: 2 ATP and 2 NADH.

Reduction of Pyruvate to Lactate:

• The 2 pyruvate molecules are reduced by the 2 NADH molecules into 2 lactate molecules (C₃H₅O₃).
• Produces: 2 lactate molecules and regeneration of 2 NAD⁺.

Summary of Lactic Fermentation:

• 1 glucose → 2 lactates + 2 ATP (from glycolysis).
• This reaction allows cells to produce energy in the absence of oxygen, but it is less efficient than cellular respiration.

2. Alcoholic Fermentation:

Alcoholic fermentation occurs in yeast and certain bacteria. It is also an anaerobic pathway that produces alcohol (ethanol) and carbon dioxide (CO₂), while regenerating NAD⁺ to sustain glycolysis.

Chemical Reactions:

Glycolysis:

• One glucose molecule (C₆H₁₂O₆) is converted into 2 pyruvate molecules (C₃H₄O₃).
• Produces: 2 ATP and 2 NADH.

Decarboxylation of Pyruvate to Acetaldehyde:

• Each pyruvate molecule loses a CO₂ molecule to form 2 acetaldehyde molecules (C₂H₄O).
• Produces: 2 CO₂ molecules.

Reduction of Acetaldehyde to Ethanol:

• The 2 acetaldehyde molecules are reduced by the 2 NADH molecules to form 2 ethanol molecules (C₂H₆O).
• Produces: 2 ethanol molecules and regeneration of 2 NAD⁺.

Summary of Alcoholic Fermentation:

• 1 glucose → 2 ethanols + 2 CO₂ + 2 ATP (from glycolysis).

Overall Summary:

• Lactic fermentation converts glucose into lactate, regenerating NAD⁺ for glycolysis, and produces 2 ATP.
• Alcoholic fermentation produces ethanol and carbon dioxide from glucose while regenerating NAD⁺, with 2 ATP also produced.

Both processes enable energy production in the absence of oxygen but are far less efficient than aerobic respiration