Question 18N.3.SL.TZ0.4
| Date | November 2018 | Marks available | [Maximum mark: 6] | Reference code | 18N.3.SL.TZ0.4 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Calculate, Distinguish, Outline, Suggest | Question number | 4 | Adapted from | N/A |
The energy used by the brain and skeletal muscle of a 70 kg man was measured over the period of one day.
The metabolic rate is the energy used per kilogram of mass per day. Calculate the metabolic rate of the brain.
[1]
1000 ✔
Working not required
Using only the data in the table, distinguish between the use of energy in the brain and in skeletal muscle.
[2]
a. skeletal muscle uses more total energy than the brain ✔
b. the brain uses more energy per kg than skeletal muscle
OR
the brain has higher metabolic rate ✔
Accept numerical answers if comparative terms are used
Suggest one reason for the difference between the brain and skeletal muscle in metabolic rate.
[1]
a. «brain requires more» energy to maintain a proper ionic balance/homeostasis/active transport ✔
b. «brain requires more» energy for synapses/neurotransmitters ✔
c. «brain requires more» energy for thinking and memory ✔
d. skeletal muscle active on demand but brain constantly active ✔
Outline the role of the brain in involuntary control.
[2]
a. does not require conscious thought ✔
b. can respond to emergency situation and «actively» return the body to normal ✔
c. medulla/brain stem controls involuntary activities ✔
d. eg: swallowing/breathing/heart rate ✔
Accept other valid examples