a nucleotide with central role in energy metabolism in cells
b type of respiratory enzyme that catalyses removal of hydrogen atoms from a substrate, for example in the Krebs cycle
c the ratio of volume of carbon dioxide produced divided by the volume of oxygen consumed
Respiratory quotient/RQ (value)
2 Describe the difference between:
a anaerobic respiration in mammals and in yeast
Mammals produce lactate/lactic acid but yeast produces CO2 and ethanol. In mammals anaerobic respiration is reversible but it is irreversible in yeast.
2 Describe the difference between: b lipids and proteins as respiratory substrates
Lipids have more energy than proteins Lipid 39 kJ g−1 and protein 17 kJ g−1/lipid more than twice as much energy Lipids digested to glycerol and fatty acids and protein digested to amino acids Fatty acid hydrocarbon chain acetyl sections enter link reaction but amino acids deaminated to keto acids which enter Krebs cycle
2 Describe the difference between: c oxidative and substrate level phosphorylation.
Oxidative takes place at, cristae/inner mitochondrial membrane, but substrate level takes place in, cytoplasm/matrix Oxidative requires, electron transport/oxygen as final electron acceptor Substrate level involves ATP synthesis coupled to a, glycolysis/Krebs cycle, reaction
ii Suggest the type of reaction that removes a phosphate group from an ATP molecule.
a State the stage or stages of aerobic respiration during which:
i carbon dioxide is produced
Link reaction and Krebs cycle
a State the stage or stages of aerobic respiration during which: ii oxygen is used.
At each temperature respirometer C, which contained only glass beads, was a control. Respirometer B, at each temperature, also contained some glass beads.
i Suggest why, at each temperature, respirometer B contained some glass beads.
To make the volume of, contents/‘peas’ , the same (in the respirometers) Idea that because the volume of peas in A is greater than the volume of peas in B OR The peas in A, are bigger/take up more space OR The peas in A have absorbed water OR The peas in B, are smaller/take up less space As without the beads there would be more, air/gas/oxygen, in B than in A
b i Certain parasites live in the blood of mammals.
Suggest why, even though blood carries oxygen, these parasites are adapted to respire anaerobically.
Two from: Idea that parasites have little access to oxygen (inaccessible because) little oxygen dissolved in plasma/oxygen not very soluble (in plasma) (inaccessible because) idea that oxygen is, combined with haemoglobin/contained in red blood cells Idea that haemoglobin has greater affinity for oxygen than parasite (pigment) has
ii The anaerobic respiration pathway in animal cells can be reversed, but the anaerobic respiration pathway in yeast cells cannot be reversed.
Explain why, using your knowledge of the differences between the two pathways.
Four from: In animals A1 pyruvate is, converted/reduced, to, lactate/lactic acid A2 can be reversed as no, atoms lost/other product formed A3 lactate dehydrogenase available to reverse the reaction In yeast Y1 pyruvate converted to ethanol (in two steps) AND carbon dioxide/CO2 Y2 cannot be reversed as, carbon dioxide is/atoms are, lost Y3 (de)carboxylase enzyme cannot reverse the reaction