Respiration

• What is the first stage of respiration?

  Glycolosis.
• Where does glycolysis occur?

  Cytoplasm.
• What is the aim of glycolysis (simple)?

  Trapping glucose in the cell by phosphorylating the molecule and then spitting it in two.
• What is produced by glycolysis?

  2 pyruvate, 2 NADH (reduced NAD), net gain of 2 ATP.
• What is the first stage of glycolysis?

  phosphorylation
• What happens during phosphorylation?

  Glucose (6C) is phosphorylated by 2 ATP to form phosphorylated glucose (6C) and 2 ADP.
• What is the second stage of glycolysis?

  Lysis.
• What happens during lysis.

  The phosphorylated glucose (6C) splits into two molecules of triose phosphate (3C).
• What is the third stage of glycolysis?

  Oxidation.
• What happens during oxidation in glycolysis?

  Hydrogen is removed from each molecule of triose phosphate and transferred to coenzyme NAD to form 2 reduced NAD (NADH).
• What is the fourth stage of glycolysis?

  Dephosphorylation.
• What happens during Dephosphorylation in glycolysis?

  Phosphates are transferred from the intermediate molecules to form 4 ATP. 4Pi + 4ADP = 4ATP.
• What is the last stage of glycolysis?

  2 Pyruvate being produced that will be used in the next stage of respiration.
• What is the second stage of respiration?

  link reaction.
• How does Pyruvate enter the link reaction?

  When oxygen is Pyruvate moves across the double membrane of the mitochondria via active transport to then take part in the link reaction in the matrix.
• Where does the link reaction occur?

  mitochondrial matrix.
• Describe the two steps in the link reaction.

  2 pyruvate (3C) are oxidised by 2NAD to produce 2 acetate (C2), 2CO2, and 2 reduced NAD (NADH).The 2 acetate then combines with coenzyme A (CoA) to form 2 acetyl coenzyme A.
• What is produced by the link reaction?

  2 acetyl coenzyme (COA)

  
  

  CO2

  
  

  2 reduced NAD
• What is the overall equation for the link reaction?

  2 pyruvate + 2NAD + CoA = 2 acetyl CoA + 2CO2 + 2 reduced NAD.
• What is the third stage of respiration?

  Krebs cycle.
• What is the Krebs cycle?

  A series of enzyme controlled reactions.
• Describe the Krebs cycle.

  Acetyl coenzyme A (2C) enters the cycle from the link reaction. This is accepted by oxaloacetate (4C) to form citrate (C6) and releases coenzyme A. Citrate is then converted back to oxaloacetate through a series of redox reactions.
• What is produced from the Krebs cycle?

  4 CO2, 2 ATP, 6 NADH, 2 FADH2
• Why does the Krebs cycle need two cycles per glucose molecule at the beginning of respiration?

  Because the glucose is split into two pyruvate which is converted to two acetyl CoA, and each acetyl CoA requires one cycle of Krebs.
• What is the fourth stage of respiration?

  oxidative phosphorylation.
• Where does oxidative phosphorylation occur?

  inner mitochondrial membrane.
• What is produced by oxidative phosphorylation?

  ATP and water.
• Describe the process of oxidative phosphorylation?

  Electrons from reduced NAD and FAD produced by the Krebs cycle are donated to the electron transporter chain and the hydrogen ions (protons) are released into the mitochondrial matrix. As the electrons move across the ETC they release small amounts of energy which is used to transport the hydrogen ions through the inner membrane into the inter membrane space. This creates a hydrogen ion (proton) concentration gradient where they are more concentrated in the inter membrane space. Further along the membrane, hydrogen ions (protons) move down the gradient back into the matrix through facilitated diffusion through ATP synthase. This provides energy for ATP synthesis. At the end of the chain oxygen combines with the remaining protons and electrons to form water molecules.
• What is the theoretical yield of ATP in aerobic respiration?

  38 ATP
• Why is the theoretical yield of ATP in aerobic respiration not always met?

  Pyruvate and reduced NAD are polar so needs to be actively transported requiring ATPSome hydrogen ions leak through the inner mitochondrial membrane back into the matrix reducing the amount of ATP produced.
• What does NAD + 2H =?

  NAD + 2H = NADH + H+
• What does FAD + 2H =?

  FAD + 2H = FADH2
• When are the following coenzymes used? NADP NAD FAD

  NADP - photosynthesis NAD - respiration FAD - Krebs
• How many molecules of ATP are produced per reduced NAD?

  Three
• How many molecules of ATP are produced from one molecule of FADH2

  Two
• Why can't usual respiration occur in anaerobic conditions?

  Oxygen cannot be used as the terminal electron acceptor meaning oxidative phosphorylation cannot occur, and the whole pathway therefore cannot occur.
• Which step of respiration still occurs in anaerobic conditions?

  Glycolysis.
• Where does anaerobic respiration take place?

  In the cytoplasm.
• How do mammals anaerobically respire?

  Lactate fermentation.
• Describe the process of lactate fermentation (anaerobic respiration in mammals).

  2 pyruvate is reduced to lactate by the enzyme lactate dehydrogenase, accepting the hydrogen from reduced NAD to form NAD. Lactate can be further metabolised either through oxidation back to pyruvate then added to the link reaction to continue with aerobic respiration. However this requires extra oxygen (referred to as oxygen debt).