Respiration

• Why is respiration important in living organisms such as humans?

  Allows for the release of energy from nutrients such as carbohydrates, fats and proteins in the form of ATP. ATP can be used by cells.
• In glycolysis, when glucose reacts with 2 ATP’s, what is the product?

  Hexose bisphosphate( a 6 carbon sugar with a phosphate at each end). This forms due to each ATP transferring a phosphate to glucose!
• What happens to the hexose bisphosphate after being formed in the first step of glycolysis?

  It splits into 2 molecules of TP.
• how is the intermediate, triose bisphosphate, formed from TP?

  The two molecules of TP, each react with an inorganic phosphate( from the cytoplasm) to form triose bisphosphate
• How is pyruvate formed in glycolysis from the intermediate, triose bisphosphate?

  The two phosphate groups on each molecule of triose bisphosphate react with 2 molecules of ADP to form 2 molecules of ATP. After this has happened you are left with pyruvate( 3 carbon sugar with no phosphate groups).
• What is the net product of ATP, reduced NAD and pyruvate formed from one glucose?

  ATP:2(2 ATP’S are initially used but 4 ATP‘s are produced so 4-2)

  Reduced NAD:2( this is produced at the end of glycolysis)

  pyruvate: 2( one pyruvate from each molecule of TP)
• How much energy does glycolysis release and why?

  Very little energy released because a lot of the energy is still stored within pyruvate.
• What happens to the pyruvate produced in glycolysis?


  Its actively transported into the matrix of mitochondria to be used in the link reaction
• What is the link reaction and where does it occur?

  The link reaction involves pyruvate reacting with coenezyme A to form acetyl Coenzyme A and carbon dioxide. This reaction occurs in the matrix
• What is going on in the link reaction?

  Decarboxylation of pyruvate, which releases carbon dioxide. Also NAD is being reduced to form NADH.
• Where is the reduced NAD produced in glycolysis, the link reaction and the Krebs cycle going to be used?

  In oxidative phosphorylation (along with reduced FAD) which is the final stage in aerobic respiration.
• Does oxidative phosphorylation require oxygen, and if so, why?

  Yes because oxygen acts as the final electron acceptor. Without oxygen, reduced NAD and reduced FAD can’t be oxidised .
• What can be used to measure the rate of respiration in anaerobically respiring yeast?


  Redox indicators such as methylene blue/DCPIP. The rate of colour change corresponds to the rate at which dehydrogenase catalyses the conversion of NAD to reduced NAD and therefore the rate of anaerobic respiration.When methylene blue/DCPIP change from blue to colourless, this means they have been reduced instead of NAD.
• Briefly describe a method where the effect of temperature on the rate of anaerobic respiration in yeast can be measured.

  Yeast suspension is added to a test tube containing a set volume and concentration of glucose solution aswell as a set volume of DCPIP.The test tube is placed in a temperature controlled water bath. A timer should record the time it takes for the colour change of the redox indicator to occur. Then repeat these steps at different temperatures.
• At high temperatures, is the rate of anaerobic respiration in yeast greater?

  Yes, because DCPIP accepts electrons/hydrogen quickly so the time for the colour change to occur will be less.
• The effect of different respiratory substrates on the rate of anaerobic respiration in yeast can also be measured by keeping everything else such as temperature and amount of substrate constant but using different substrates such as lipids and proteins.
• what has an effect on the rate of anaerobic respiration in yeast?

  Substrate concentration, respiratory substrate used and high temperature
• What can be used to measure the rate of aerobic respiration?

  A respirometer. It can measure the oxygen consumed by an organism.
• Out of lipids, proteins and carbohydrates, which has the highest energy value?

  Lipids as they contain a lot of hydrogen atoms. When they are broken down, they release a lot of hydrogen atoms that can be accepted by NAD AND FAD. Reduced FAD and reduced NAD is used in oxidative phosphorylation to produce lots of ATP
• How do you calculate the respiratory quotient?

  Ratio of CO2 produced in respiration to the oxygen consumed.
• If a respiratory substrate has a RQ of 1, what does that tell you?

  That the substrate is a carbohydrate
• If a respiratory substrate has a RQ of 0.7, what does that tell you about the substrate?

  That the substrate is a lipid
• If the respiratory substrate has a RQ of 0.9, what does that tell you?

  The substrate is a protein!