Cellular Respiration, ATP, and Enzyme Function

Energy and ATP

• Energy is defined as the ability to do work.
• Food contains chemical energy stored within its molecular bonds.
• When these bonds break, energy is released for the cell to use.
• ATP (Adenosine Triphosphate) is the primary energy-carrying molecule used by cells.
• Energy is specifically stored within the phosphate bonds of the ATP molecule.

Enzymes: Biological Catalysts

• Enzymes are biological catalysts that speed up chemical reactions within cells.
• They function by lowering the activation energy required for a reaction to occur.
• Each enzyme is highly specific and works with only one particular substrate (often described by the lock and key model).
• Exposure to the wrong temperature or pH level causes an enzyme to denature, meaning its shape changes and it stops working.

Water and Hydrolysis

• Water is essential to break large organic molecules down into smaller, manageable ones.
• Adhesion occurs when water sticks to other substances, which assists in biological transport.

Hydrolysis

• This process uses water to function.
• It breaks chemical bonds and releases energy.
• It transforms large molecules into small molecules.
• Example: The process of digestion.

Anaerobic Respiration: Fermentation

When no oxygen is present, cells undergo fermentation.

• Anaerobic: This process occurs without the presence of oxygen.
• Location: It takes place within the cytoplasm of the cell.
• Purpose: It allows glycolysis to continue producing ATP in the absence of oxygen.

Types of Fermentation

• Alcoholic Fermentation:
  • Produces alcohol and Carbon Dioxide (CO₂).
  • Used by yeast and causes bread to rise.
• Lactic Acid Fermentation:
  • Produces lactic acid.
  • No CO₂ is released during this process.
  • Occurs in animal muscle cells during intense exercise.

Key Memory Sentence

"Glycolysis starts it, Krebs makes CO₂, ETC makes most ATP — oxygen grabs electrons."

Dehydration Synthesis

• This process releases water as a byproduct.
• It forms chemical bonds and stores energy.
• It transforms small molecules into large molecules.

Note: If bonds break and energy is released, the process is hydrolysis.

Cecum and Animal Diets

• The cecum is a pouch in the large intestine specifically designed to digest plant material (cellulose).

Cellular Respiration

Definition: The process by which cells break down food to release energy and store it in the form of ATP.

Chemical Equation:
Glucose + Oxygen → Carbon Dioxide + Water + ATP
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

The Role of the Mitochondria

• The mitochondria is the organelle where most cellular respiration occurs.
• It converts the chemical energy found in food into usable ATP.
• Both the Krebs Cycle and the Electron Transport Chain (ETC) occur here.

The Three Stages of Cellular Respiration

1. Glycolysis

• Location: Cytoplasm.
• Oxygen required? No (Anaerobic).
• Inputs: 1 Glucose molecule, 2 ATP, ADP molecules, and NAD⁺.
• Outputs: 2 Pyruvic Acid molecules, 4 ATP, and NADH.
• Net Gain: 2 ATP.
• Advantages: It is a very fast process and does not require oxygen.

2. The Krebs Cycle

• Location: Mitochondria.
• Input: Pyruvic Acid.
• Products: Carbon Dioxide (CO₂), ATP, and electron carriers (NADH, FADH₂).
• CO₂ is considered a waste product and is expelled when you exhale.
• During each turn of the cycle, ADP is converted into ATP.

3. The Electron Transport Chain (ETC)

• Location: Mitochondria.
• Inputs: High-energy electrons, Oxygen, and H⁺ ions.
• Oxygen: Acts as the final electron acceptor.
• Energy is used to pump H⁺ ions across the membrane.
• ATP Synthase: This enzyme uses the flow of H⁺ ions to generate ATP.
• Efficiency: The most ATP is produced during this stage.
• Outputs: ATP and Water (H₂O).