| Date | November 2021 | Marks available | 4 | Reference code | 21N.2.SL.tz0.3 |
| Level | Standard Level | Paper | Paper 2 | Time zone | time zone 0 |
| Command term | Explain | Question number | 3 | Adapted from | N/A |
Question
The diagram represents the ultrastructure of a generalized animal cell.
Annotate structures A, B and C in the diagram.
Explain cardiovascular drift and the relevance of hydration during a 50 km walk.
Markscheme
during prolonged exercise there is an increase in body temperature / blood flow is diverted to the skin;
cooling/sweating causes fluid loss/decreases in blood plasma;
this results in increased blood viscosity/decreased in stroke volume;
to maintain homeostasis/cardiac output (Q) there is a «gradual» increase in HR
OR
reduction in venous return/ stroke volume causes the heart rate to increase to maintain cardiac output;
during prolonged exercise an athlete can ingest drinks/stay hydrated to maintain blood volume/Q <to avoid/reduce cardiovascular drift>;
Award [3 max] for cardiovascular drift.
Examiners report
Candidates were less certain of how to annotate an animal cell. They usually correctly named the mitochondria but not the other 2 organelles.
Candidates did very well at showing their understanding of cardiovascular drift. They commonly missed the fact that the loss of water from the body due to sweating is connected to the loss of plasma and then that it is necessary to hydrate to replace this lost fluid.
