Oxygen

Question 1

Species B is more active than species A. Use Figure 5 to explain how the hemoglobin of species B allows a greater level of activity. Species B has a lower affinity. [3]

Answer 1

haemoglobin unloads oxygen more readily;
more oxygen to cells;
for greater respiration;

Question 2

What can you conclude from Figure 7 about the processes involved in the uptake of calcium ions by these plant cells? Use evidence from Figure 7 to support your answer. with oxygen curve plateaus; with no oxygen straight line from 0.1 to 0.3. [6]

Answer 2

Between 0 and 0.1 calcium (ions) cannot enter by facilitated diffusion;
Between 0.1 and 0.3 calcium (ions) enter by facilitated diffusion;
know this since they enter without oxygen;
Between 0 and 0.1 calcium (ions) enter by active transport;
Movement is against the concentration gradient;
As calcium (ions) only enter in presence of oxygen/oxygen is required for active transport;

Question 3

Suggest one way in which the scientist could have ensured the solutions she used for curve X contained no oxygen. [1]

Answer 3

she could have boiled and cooled water or put a layer of oil on top of the solution;

Question 4

What is the role of oxygen in the electron transport chain, and why is it so essential?

Answer 4

Oxygen acts as the final electron acceptor in the electron transfer chain, resulting in the formation of H2O. This is essential because without it, the electron transfer chain cannot function resulting in a lack of oxidative phosphorylation in the inner membrane of the mitochondria. Further more, the lack of functioning electron transport chain means that NADH and FADH2 cannot be oxidized, creating a lack of NAD+ and FAD, which are coenzymes for reactions in the Link reaction and the Krebs cycle.
Consequently, during anaerobic respiration only glycolysis can occur. This reduces the ATP production of aerobic respiration from 38, to the ATP of anaerobic respiration of 12, as well as producing waste products such as lactate which must be removed.

Question 5

Explain the advantage for larger animals of having a specialised system that
facilitates oxygen uptake.

Answer 5

1. Large(r) organisms have a small(er) surface
   area:volume (ratio);
2. Overcomes long diffusion pathway

Answer 6

1. Water has low(er) oxygen partial
   pressure/concentration (than air);
2. So (system on outside) gives large surface area
   (in contact with water)
   OR
   So (system on outside) reduces diffusion
   distance (between water and blood);
3. Water is dense(r) (than air);
4. (So) water supports the systems/gills;

Answer 7

1. In fish, blood leaving (V) has more oxygen than
   water leaving (E);
2. (But) in humans, blood leaving (V) has less
   oxygen than air leaving (E);
3. Difference in oxygen (concentration) between
   artery and vein is greater in fish than in humans;
4. (So) fish remove a greater proportion from the
   oxygen they take in;