respiration exam Q

• Describe the process of glycolysis ? (6 marks )

  first glucose is phosphorylated to hexose bisphosphate this uses 2 ATPs. next hexose bisphosphate is spilt into two triose phosphate molecules which is then converetd into pyruvate. NAD is also converted to NADH in the process
• four molecules of glucose undergo glycolysis. state how many of the following molecules would be produced

  i- triose phosphate

  ii- pyruvate

  iii- ATP

  two triose phosphate molecules

  two pyruvate molecules

  net yield on two ATP molecules
• describe and explain the role of pyruvate in anaerobic respiration in mammals. (4 marks )

  pyruvate helps to regenerate NAD by accepting a hydrogen from NADH which allows glycolysis to continue
• describe how pyruvate is converted into lactate and NAD during anaerobic respiration in animals. (2 marks)

  explain why the production of lactase is beneficial when oxygen availablity is low.

  pyruvate acts as a hydrogen acceptor from NADH forming lactate. this also allows NAD to be regenerated so its available for glycolysis
• Pyruvate is formed when glucose is broken down during respiration.
• When there is sufficient oxygen, pyruvate is fully broken down.
• The products of the reaction are CO2 and ATP.
• If there is a shortage of oxygen in muscle cells during exercise, some pyruvate is converted into lactic acid.
• Lactic acid can dissociate into lactate and H+.
• The dissociation of lactic acid affects enzymes in muscle cells because it lowers pH as it increases H+ which can affect the speed of enzymes as it can change tertiary structure.
• Lactate and pyruvate are energy sources, so if they are produced in the muscle cells, the ATP will be used up quickly.
• substrate level phosphorylation and oxidative phosphorylation are two ways of producing ATP. Contrast these different forms of ATP production (3 marks )

  in substrate level phosphorylation, a phosphate is added to ADP directly, whereas in oxidative phosphorylation it isn't.

  substrate level phosphorylation doesn't involve a proton gradient but oxidative phosphorylation does.

  finally substrate level phosphorylation does not use NADH whereas oxidative phosphorylation does
• the krebs cycle does not require oxygen directly. However, this cycle stops in the absence of oxygen. Using your knowledge of aerobic respiration, explain why the Krebs cycle stops in the absence of oxygen (4 marks )

  as oxygen acts as a final electron acceptor in oxidative phosphorylation, without it, all of the NAD and FAD will end up staying reduced (FADH and NADH) if there is no NAD and FAD available to accept hydrogen in the Krebs Cycle it cannot operate
• what is the chemical equation to represent the production of ATP? (1 mark )

  describe how ATP is synthesised in oxidative phosphorylation.(6 marks )

  1. ADP + Pi = ATP
  2. first electrons pass down an ECT which has lower energy levels. Next the energy released is used to pump protons across the membrane creating a proton gradient between the intermembrane space and the matrix. this allows H+ to flow through ATP synthase and provide energy for ATP synthesis
• A continual source of ATP is required for neurons in the brain to form healthy connections and sustain memory formation.
• Alzheimer's disease is a progressive neurodegenerative disorder in which brain cells die, causing a gradual loss of memory.
• A primary onset of Alzheimer's disease is the loss of cristae in the mitochondria of neurons.
• The loss of mitochondrial cristae impacts ATP production in neurons, impairing memory function in Alzheimer's patients.
• Loss of mitochondrial cristae results in less oxidative phosphorylation, meaning less ATP is produced.
• Less ATP available for the sodium-potassium pump may impact memory function in Alzheimer's patients.