Respiration

Question 1

What is the general equation for respiration?

Answer 1

C₆H₁₂O₆ + 6O₂ = 6CO₂ + 6H₂O + energy

Question 2

What is the general description of respiration?

Answer 2

• Catabolic oxidation of fuels
• Breaks down glucose from carbohydrates, proteins or lipids
• Used in most eukaryotic and prokaryotic organisms
• Releases the huge amount of energy stored in glucose in many gradual steps, each catalysed by an enzyme

Question 3

What are the steps of aerobic respiration?

Answer 3

GIKEA

• Glycolysis: +2ATP, 0CO2, +2NADH
• Occurs in the cytosol
• Glucose is phosphorylated: glucose + 2ATP = 6C sugar diphosphate + 2ADP + 2P_I
• 6C sugar diphosphate = 2 3C sugar phosphate
• Conversion to pyruvate: 2 3C sugar phosphate + 2NAD⁺ + 4ADP = 2 pyruvate + 2NADH + 2H⁺ + 4ATP
• Intermediate reaction: +2CO₂, +2NADH
• Occurs in the mitochondrion matrix
• Pyruvate converted to acetyl-CoA: pyruvate + NAD⁺ + CoA = acetyl-CoA + NADH + H⁺ + CO₂
• Krebs Cycle: +2ATP, +4CO₂, +6NADH, +2FADH₂
• Occurs in the mitochondrion matrix
• Citrate formed: acetyl-CoA + oxaloacetate = citrate + CoA
• Citrate + NAD⁺ = 5C molecule + NADH + H⁺ + CO₂
• 5C molecule + NAD⁺ + ADP = 4C molecule + NADH + H⁺ + CO₂ + ATP
• Oxaloacetate regenerated: 4C molecule + FAD²⁺ + NAD⁺ = oxaloacetate + FADH₂ + NADH + H⁺
• ETC +34ATP
• Electrons from NADH + H⁺ and FADH₂ travel along the ETC
• A proteon motive force forms which pumps H⁺ ions into the intermembrane space
• The H⁺ ions come from the electrons carriers and the dissociation of water: H₂O = OH^- + H⁺
• At the end fo teh ETC the electrons fall to O₂: 1/2O₂ + 2H⁺ + 2e^- = h₂O
• H⁺ ions reenter the matrix through ATP synthase: ADP + P_I = ATP

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Question 4

What are the steps of ethanol fermentation?

Answer 4

• Occurs in yeast when O₂ levels are low
• Glycolysis occurs as normal to produce pyruvate
• 2 pyruvate = 2 2C molecules + 2CO₂
• 2 2C molecules + 2NADH + 2H⁺ = ethanol + 2NAD⁺

Question 5

What are the steps of lactic acid fermentation?

Answer 5

• Occurs in muscle cells when O₂ is low
• Does not produce CO₂
• Glycolysis occurs as normal to produce pyruvate
• 2 pyruvate + 2NADH + 2H⁺ = 2 lactate + 2NAD⁺