Question 18M.3.SL.TZ2.4
| Date | May 2018 | Marks available | [Maximum mark: 7] | Reference code | 18M.3.SL.TZ2.4 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Describe, Explain, Identify, Outline | Question number | 4 | Adapted from | N/A |
Outline the function of one named photoreceptor in the mammalian eye.
[2]
a. name: rod
OR
cone
b. function: rod detects wide range of wavelengths/monochrome/low light intensity/dim light
OR
detects coloured light / colour «photoreceptor»
The graph shows the energy consumption of photoreceptors in three different species of fly (Drosophila melanogaster, Drosophila virilis and Sarcophaga carnaria) at the mean of the highest transmission rate for each species at rest and while sending a nerve signal (signalling).
Explain how neurons at rest still consume energy.
[2]
a. maintenance metabolism/respiration of the neuron
b. use of Na-K/sodium potassium pump to maintain resting potential
c. cell repair «consumes energy»
Identify the species with photoreceptors that have the fastest signalling transmission rate.
[1]
S. carnaria / Sarcophaga carnaria
Describe the relationship between energy consumption and transmission rate.
[2]
a. energy consumption increases from rest to signalling «in all three species»
b. faster transmission consumes more energy
OR
positive correlation
c. doubling of transmission rate requires more than double the increase in energy consumption
OR
exponential increase
OR
the higher the energy consumption at rest, the higher the energy consumption at signalling