Respiration

• Respiration is the controlled release of energy from organic compounds to form ATP.
• Name 3 processes which organisms need energy for ?

  Active transport

  Movement of the cytoskeleton

  Replication of DNA
• What is the function of inner mitochondrial membrane ?

  Contains electron transport chains and ATP synthase
• Name 4 stages of aerobic respiration ?

  Glycolysis

  Link reaction

  Krebs cycle

  Oxidative phosphorylation
• Where does glycolysis occur ?

  Cytoplasm
• What is the purpose of glycolysis ?

  To convert large glucose molecules into smaller molecules of pyruvate which can be actively transported into the mitochondria
• Coenzymes are organic non-protein cofactors. They contribute to enzyme-catalysed reactions by accepting or donating hydrogen ions or chemical groups
• Describe the process of glycolysis ?

  1. Glucose is phosphorylated using 2 molecules of Pi released from 2 molecules of ATP forming hexose bisphosphate
  2. Hexose bisphosphate is unstable so splits into two molecules of triose phosphate
  3. Each triose phosphate is oxidised and dephosphorylated by removal of hydrogen and Pi to form two molecules of pyruvate and 4 ATP molecules
  4. NAD+ accepts the removed hydrogens forming 2 molecules of reduced NAD
• What is the net gain of ATP during glycolysis ?

  2 ATP molecules
• Where does the link reaction occur ?

  Mitochondrial Matrix
• Describe the process of the link reaction ?

  1. Pyruvate undergoes decarboxylation (removal of carbon dioxide)and oxidation (removal of hydrogen) forming acetate
  2. The hydrogen atoms that are removed from pyruvate are accepted by NAD+ forming reduced NAD.
  3. Acetate combines with coenzyme A to form acetyl coenzyme A.
• There is no waste produced in the Link reaction.
• Where does the krebs cycle occur ?

  Mitochondrial matrix
• Describe the Krebs cycle ?

  1. Acetyl CoA combines with a 4c molecule to form a 6c molecule.
  2. Coenzyme A is released in this reaction
  3. The 6c molecule returns to a 4C molecule via a series of oxidation and decarboxylation reactions.
  4. The regeneration of 4c molecule allows the Krebs cycle to begin again.
• What is produced from the Krebs cycle for 1 glucose molecule ?


  2 molecules ATP

  2 molecules of FADH2

  6 Molecules of NADH

  4 molecules of CO2
• Name 2 coenzymes involved in respiration ?

  NAD and FAD
• In the start of Krebs cycle where does the acetyl CoA come from ?

  The link reaction
• Why is ATP produced in the Krebs cycle ?

  As a result of substrate level phosphorylation (a phosphate group is transferred directly from a donor molecule to ADP)
• Where does the Coenzyme A go after being released in the Krebs cycle ?

  Rejoins the link reaction
• Name 4 differences between NAD and FAD ?

  1. NAD takes parts in all stages of cellular respiration but FAD is only used during the Krebs cycle.
  2. NAD accepts 1 hydrogen but FAD accepts 2
  3. NAD is oxidised at the start of electron transport chain while FAD is oxidised further along
  4. NAD results in synthase of 2.5 ATP molecules while FAD results in synthase of 1.5.
• where does oxidative phosphorylation occur ?

  cristae
• chemiosmosis = the process of ATP production driven by the movement of hydrogen ions across a membrane as a result of electrons moving down an electron transport chain.
• Describe the process of oxidative phosphorylation ?

  1. NADH and FADH2 are oxidised, releasing hydrogen atoms which split into protons and electrons.

  2. Electrons pass along a chain of electrons transfer carriers, losing energy at each carrier.

  3. Released energy is used to actively transport protons into the inter-membrane space creating an electrochemical gradient.

  4. Protons diffuse back into the matrix through ATP synthase channels driving the synthesis of ATP

  5. At the end of electron transport chain oxygen combines with electrons and protons forming water.
• How many molecules of ATP does 1 NADH make in oxidative phosphorylation ?


  2.5
• How many molecules of ATP does 1 FADH2 make in oxidative phosphorylation ?

  1.5
• How many molecules of ATP are made in oxidative phosphorylation ?

  28 molecules per one glucose
• How many molecules of ATP are made from all the NADH in oxidative phosphorylation ?

  25 molecules from 10 NADH molecules
• How many molecules of ATP are made from all the FADH2 in oxidative phosphorylation ?

  3 from 2 FADH2 molecules
• How many molecules of ATP are made in aerobic respiration ?

  32 ( 4 from substrate level phosphorylation ) (28 from oxidative phosphorylation )
• Explain why a mitochondrion in a muscle cell has more cristae than mitochondrion in less metabolically active cells?

  Cristae are folds of the inner mitochondrial membrane which increase SA, the greater the surface area for electron transport chains which results in production of more ATP. ATP is needed in larger amounts in muslces cells for muscle contraction.
• Explain why glycolysis is said to involve oxidation ?

  Each triose phosphate is oxidised by the removal of hydrogen to form two molecules of pyruvate. NAD+ accepts the hydrogens forming teo molecules of NADH
• Explain why glycolysis is said to involve phosphorylation ?

  Glucose is phosphorylated using two molecules of Pi released from ATP forming hexose bisphosphate.
• Where does alcoholic fermentation occur ?

  Plant and fungi cells
• Where does lactate fermentation occur ?

  animal cells
• What is the benefit of anaerobic respiration to organisms?

  The production of lactate/ethanol regenerates oxidised NAD+, allowing the glycolysis to continue even when oxygen is in short supply.
• what are the consequences on respiration when oxygen is in short supply ?

  No final electron acceptor in electron transport chain

  No more ATP is produced from oxidative phosphorylation

  NAD and FAD are not oxidised by electron carrier

  Krebs cycle stops as no oxidised NAD and FAD available for dehydrogenation.
• Describe the steps os alcoholic fermentation ?

  1. Pyruvate is decarboxylated to form ethanal, producing CO2
  2. Ethanal is reduced by enzyme, alcohol dehydrogenase, forming ethanol
  3. Ethanal accept the hydrogens from NADH.
• What are the products of alcoholic fermentation ?

  2 x oxidised NAD

  CO2

  Ethanol
• Describe the process of lactate fermentation ?

  1. Pyruvate is reduced by enzyme, lactate dehydrogenase, forming lactate.
  2. Pyruvate accepts hydrogen ions from NADH.
• What are the products of lactate fermentation ?

  Lactate

  2 x oxidised NAD