A2 Respiration test Total marks [40]

The diagram below shows some of the stages in glycolysis: Glucose Hexose phosphate Hexose biphosphate Triose phosphate Pyruvate X Y Z Reduced Z State precisely where this process occurs ………………………………………[1] Identify substance X ……………………………………………..…………………[1] Identify substance Y ………………………………………………………………..[1] Briefly outline the fate of substance ‘reduced Z’ ………………………………… ………………………………………………………………………………….. …… ………………………………………………………………………………………..[2] in the cytoplasm ATP/phosphate group from ATP hydrogen Enters mitochondria; is (re-)oxidised; in the electron transport chain;

Carefully read the following account of aerobic respiration and then fill in the blanks: In the first stages of respiration which occurs in the ……………………………………….. of the cell, glucose is ……………………………….. to pyruvic acid. Glycolysis yields …………………………. and a reduced coenzyme. The pyruvic acid then combines with coenzyme A to form …………………………………….. which enters the Kreb’s cycle which occurs in the …………………………………………. of the ……………………………………………….. During these reactions hydrogen atoms are removed from a series of intermediate compounds by enzymes called …………………………………… . The hydrogen atoms are passed to carriers such as ……………………………………… . In the third stage of aerobic respiration, the carriers are alternately reduced and ……………………. as they gain and lose …………………………. . Energy is released and used to phosphorylate ADP, forming ………………………. . The hydrogen atoms finally combine with……………………….. to form ……………………………. . [13] cytoplasm oxidised ATP acetyl CoA matrix mitochondria dehydrogenases NAD/FAD oxidised electrons ATP oxygen water

Below is a diagram of a mitochondrion Add labels where indicated. [5] matrix cristae b) any point on the inner membrane inner membrane outer membrane intermembrane space Indicate on the diagram the precise site of the electron transport chain [1]

The same amount of ADP was added each time. An experiment was carried out to measure the rate at which a sample of mitochondria used oxygen under different conditions. The mitochondria were placed in a well oxygenated liquid with a water potential equal to the water potential of their contents. At time A, an end-product of glycolysis was added to the liquid. At times B, C and D, ADP was added. The same amount of ADP was added each time. The results of this experiment are shown in the graph below: 0 2 4 6 8 Time (mins) Oxygen concentration in the liquid A B D C

………………………………………………………………………………………………………… [2] a) Explain why the liquid used in the experiment should have the same water potential as the contents of the mitochondria ……………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………… [2] to ensure there is no net movement of water/osmosis that would cause a dilution/concentration of the matrix contents or damage to mitochondria/bursting of organelle

b) (i) State the name of the substance that was added at A ……………………………………………………………… [1] (ii) Name the two stages of the respiratory process that take place in the mitochondria …………………………………………………………… …………………………………………………………. [2] (iii) State the role of oxygen in these respiratory processes ……………………………………………………………… ……………………………………………………..………. [1] pyruvate/pyruvic acid link reaction; Kreb’s cycle; ETC; oxidative phosphorylation to reoxidise the last substance/last cytochrome in the ETC

Oxygen concentration in the liquid c) Explain the result of adding ADP at the following points on the graph; B and C …………………………………………………………………………… ………………………………………………………………………..… [3] oxidative phosphorylation can occur/ADP converted to ATP which requires oxygen to react with hydrogen to form water less occurs at C than B because amount of reduced coenzymes is less/ORA 0 2 4 6 8 Time (mins) Oxygen concentration in the liquid A B D C

Oxygen concentration in the liquid (ii) D .............................................................................................................. ……………………………………………………………………..……… [2] no reaction occurs due to lack of reduced NAD/FAD which means lack of hydrogen ions/electrons for ETC 0 2 4 6 8 Time (mins) Oxygen concentration in the liquid A B D C

because glycolysis occurs that requires additional ADP Yeast cells can respire anaerobically using glucose as a substrate. (i) State the end products formed from the glucose if oxygen is not available to the yeast cells ……………………………………………………………………………………………… ……………………………………………………………………………………………… [2] (ii) Explain why ADP is required in anaerobic conditions [3] ethanol/ethanal carbon dioxide to form ATP because glycolysis occurs that requires additional ADP to give a net gain of 2 ATP molecules