Cellular Metabolism and Respiration Quiz

Cellular Metabolism

• Metabolism is the total cellular chemical changes. It has two parts:
  • Anabolism: Building up processes
  • Catabolism: Breaking down processes
• Calorie: Measures the energy contained in food.
• ATP (Adenosine Triphosphate): The energy source for cells.

Cellular Respiration

• Organic molecules from food are broken down into simpler components.
• ATP is produced from further breakdown of these organic molecules.
• Glucose is the primary energy source.
• Cellular respiration occurs in 3 steps:
  • Glycolysis
  • Pyruvate Oxidation
  • Krebs Cycle (Citric Acid Cycle)
  • Electron Transport Chain (ETC)
• The overall reaction for cellular respiration is: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

Glycolysis

• The first step in glucose breakdown.
• A beginning point for both aerobic and anaerobic processes.
• Glucose is broken down into smaller molecules.
• Final outcome: 2 pyruvate molecules, 2 ATP molecules (anaerobic), and 2 NADH molecules.

The Krebs/Citric Acid Cycle

• Starts with pyruvic acid from glycolysis.
• Pyruvic acid is oxidized into acetyl-CoA.
• Acetyl-CoA enters the Krebs cycle in the mitochondria.
• Final outcome: 6 CO₂, 8 NADH (2 from pyruvate oxidation), 2 FADH₂, and 2 ATP (total 2 pyruvate molecules = 1 glucose molecule).

Electron Transport Chain (ETC)

• A series of reduction/oxidation reactions.
• Requires oxygen (O₂).
• Uses electron carriers.
• Number of ATP molecules depends on electron carriers.
• Water is a waste product.
• Oxygen is the terminal electron acceptor.

Summary of ATP Production

• Estimates of ATP production can range from 30-38 per glucose molecule during cellular respiration.

Anaerobic Respiration

• Occurs when oxygen is absent.
• Produces less ATP than aerobic respiration.
• Fermentation: Occurs in yeast cells, producing CO₂, ethanol, and ATP.
• Anaerobic muscle metabolism: Occurs in muscles when oxygen supply is limited.

Fermentation

• Yeast breaks down glucose anaerobically.
• Pyruvic acid is still produced by glycolysis.
• Pyruvate is broken down to carbon dioxide and acetaldehyde.
• Final products: 2 ATP, CO₂, and ethanol

Anaerobic Muscle Metabolism

• Pyruvate is converted to lactate (lactic acid) when oxygen is low.
• Lactate is a waste product that can contribute to muscle soreness
• 2 ATP are produced per glucose molecule

Lactate and Gluconeogenesis

• Lactate can be converted back into glucose in the liver (gluconeogenesis).
• This process is important for replenishing glucose levels in the blood.

Other Energy Sources

• Carbohydrates: Broken down into simple sugars (glucose) which can be stored in the liver or converted to fat
• Fats (Lipids): Digested into fatty acids and glycerol; glycerol enters at PGA stage of glycolysis, fatty acids enter the Krebs Cycle.
• Proteins: Digested into amino acids; enter Krebs cycle at various stages.

Ketogenesis

• Occurs when cells lack a carbohydrate source.
• Acetyl CoA builds up from fat or amino acid breakdown.
• The liver converts Acetyl-CoA into ketone bodies.
• Ketone bodies may be used as fuel by some cells, but prolonged ketosis is harmful.
• Ketoacidosis: Very harmful condition, prolonged ketosis.

Test your knowledge on cellular metabolism and respiration! This quiz covers key concepts such as anabolism, catabolism, ATP production, and the various steps involved in cellular respiration including glycolysis and the Krebs cycle. Perfect for students studying biology or life sciences.