| Date | May 2016 | Marks available | 3 | Reference code | 16M.3.SL.tz0.12 |
| Level | Standard Level | Paper | Paper 3 | Time zone | time zone 0 |
| Command term | Explain | Question number | 12 | Adapted from | N/A |
Question
List two enzymes responsible for the digestion of protein in the human body.
1.
2.
Using an example, explain how the components of a negative feedback mechanism help maintain homeostasis.
Markscheme
Pepsin✔
trypsin✔
trypsinogen / chymotrypsinogen / carboxypeptidase✔
receptor / input to control centre / nerve impulses / chemical signals✔
eg changes in salt concentration are detected by receptors.
control centre / sets range of values/evaluates input / generates output command ‹nerve or chemical› / to effector✔
eg message is received at the hypothalamus that the salt concentration has changed.
effector / receives output from control centre / produces response✔
eg pituitary gland adjusts the output of ADH.
the result of the response is constantly being monitored by receptors and if the desired state is attained the control centre will stop sending the command✔
Award [1 max] for definition of homeostasis.
Accept flow diagram.
Examiners report
surprisingly poorly answered by many candidates.
many candidates did not appear to understand the question and did not respond to ‘using an example’ appropriately.
