Exam (elaborations)
A2 RESPIRATION QUESTIONS AND ANSWERS 2024
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Exam of 7 pages for the course Aerobic Respiration at Aerobic Respiration (A2 RESPIRATION)
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A2 RESPIRATIONThe student closed the tap. After thirty minutes the drop of colored liquid had moved
to the left. Explain why the drop of colored liquid moved to the left - answer1. Oxygen
taken up/used (by woodlouse);
2. Carbon dioxide (given out) is absorbed by solution/potassium hydroxide;
3. Decrease/change in pressure;
Reference to vacuum negates last marking point
What measurements should the student have taken to calculate the rate of aerobic
respiration in mm3 of oxygen g-1 h-1? - answer1. Distance (drop moves) and time;
2. Mass of woodlouse;
3. Diameter/radius/bore of tubing/lumen/cross-sectional area;
If answer refers to measuring volume using the syringe allow 2
max -
one mark for measuring volume;
one mark for mass of woodlouse
DNP inhibits respiration by preventing a proton gradient being maintained across
membranes. When DNP was added to isolated mitochondria the following changes
were
observed
• less ATP was produced
• more heat was produced
• the uptake of oxygen remained constant.
Explain how DNP caused these changes - answer1. Less/no proton/H+ movement so
less/no ATP produced;
2. Heat released from electron transport/redox reactions/energy not
used to produce ATP is released as heat;
3. Oxygen used as final electron acceptor/combines with
electrons (and protons)
Give the location of Glycolysis in a liver cell. - answerCytoplasm
Give the location of Krebs cycle in a liver cell. - answerMitochondrion
Apart from respiration, give three uses of ATP in a liver cell - answerSource of energy/of
phosphate;
Active transport;
Phagocytosis / endo- /exocytosis / pinocytosis;
Bile production;
Cell division / mitosis;
, Synthesis of: glycogen;
protein / enzymes;
DNA / RNA;
lipid / cholesterol;
urea
Human skeletal muscle can respire both aerobically and anaerobically. Describe what
happens to pyruvate in anaerobic conditions and explain why anaerobic respiration is
advantageous to human skeletal muscle - answerForms lactate; Use of reduced NAD /
NADH;
Regenerates NAD;
NAD can be re-used to oxidise more respiratory substrate / correct e.g./
allows glycolysis to continue;
Can still release energy/form ATP
when oxygen in short supply/when no oxygen
In which part of the mitochondrion does the Krebs cycle take place? - answermatrix
Name two substances for which there would be net movement into the mitochondrion -
answerpyruvate;
ADP;
P / inorganic phosphate;
reduced NAD;
oxygen
The mitochondria in muscles contain many cristae. Explain the advantage of this -
answerlarger surface area for electron carrier system / oxidative
phosphorylation; provide ATP / energy for contraction
Give one piece of evidence from the diagram which suggests that the conversion of
pyruvate to ethanol involves reduction - answeroxygen removed from pyruvate/ reduced
NAD is oxidised/
donates hydrogen/donates electrons
Explain why converting pyruvate to ethanol is important in allowing the continued
production of ATP in anaerobic respiration - answerallows NAD to be recycled/re-
formed;
so that glycolysis/described/ candidates answer to (i) can proceed/
so that (more) glucose can be
converted to pyruvate/so that process X can continue
Give two ways in which anaerobic respiration of glucose in yeast is similar to anaerobic
respiration of glucose in a muscle cell - answerATP formed/used;
pyruvate formed/reduced;
NAD/reduced NAD;
glycolysis involved/two stage process
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