End of Topic Tests Flashcards
Young mammals receive antibodies in their mother’s milk.
This is an example of which type of immunity. [1 mark]
Natural passive immunity
Explain how it is possible for ACh to have an effect on cells in the skin of a squid. [2 marks]
- ACh is secreted by glands in the centre of the body and will bind to receptors on the cell surface membrane of skin cells after being transported in the blood
- this allows for a change to occur inside the skin cells
An antibiotic called A22 irreversibly binds to Protein B. Despite its antibiotic properties, A22 is not used in humans.
Suggest why scientists have advised that A22 should not be used in humans. [1 mark]
It would irreversibly bind to sites on actin needed for myosin or other chemicals, which may prevent the movement of muscles
A student setting up an experiment to investigate the effect of light on cress plant seedlings accidentally shone the bright light onto one side of the face of another student. He noticed that the student immediately responded by raising her hand to shield her eye from the light.
The response of the cress seedlings to light shining from one direction was slower, but after 24 hours the cress seedlings had grown towards the light.
Describe the mechanisms that produced the responses to light in the cress seedlings and in the human. [6 marks]
cress seedlings -
- a slower, hormonal response
- a results of phototropism where auxin is found in great concentrations on the side of the stem with the least light
- this causes the tip of the shoot to bend towards the light, maximising absorbance
human -
- a fast, neuronal response
- receptors in the eye detected the increase of bright light in the visual field
- electrical impulse travels down the sensory neurone to the motor neurone (via an intermediate neurone) in the spinal cord
- this reflex arc allows the muscles in the arm (effectors) to move the students hand to shield their eyes
The coleoptiles in groups 4, 5 and 6 were then exposed to light from one direction, as shown in Fig 3.2, and left to grow for two days.
Identify three variables that would need to be controlled in this experiment to produce valid results. [3 marks]
- the temperature surrounding the plants
- the species of the plant used
- the volume and concentrations of the solutions applied to the seedlings and coleoptiles
Groups 1 and 4 were controls in this experiment.
Explain why these controls were necessary. [1 mark]
To act as a comparison when looking at the results to see the impact of solutions J and K against what would happen if the seedling were left alone.
After death, the concentration of ATP in muscle cells decreases. During this time, the muscles become rigid in a process called rigor mortis.
Suggest why a lack of ATP leads to muscle rigidity. [2 marks]
- ATP cannot allow for the breaking of the actin-myosin cross-bridge or the hydrolysis of ATP into ADP
- so actin and myosin fibrils cannot be separated and the muscle cannot relax
Plants produce callose in response to pathogenic infection, injury and changes in environmental temperature. Scientists wanted to investigate the effect of temperature on callose production.
Outline a valid plan that could be used to investigate the effect of temperature on callose production in plants.
You should include a suggestion for how callose production could be observed.
- use a suitable range of temperatures
- use a suitable sample size (50 plants)
- use the same species of plant throughout
- maintain the light intensity and duration
- take a tissue sample
- use a stain to make for easier viewing (e.g. aniline blue)
- observe under a microscope to compare the callose production
Banana plants first undwerwent artificial selection thousands of years ago.
Some scientists claim that banana crops will be extinct within a few years.
Use the information about to justify the scientist’s claim. [3 marks]
- artificial selection will reduce the sexual reproduction (due to decrease in pollen and seeds)
- so less genetic variation within the organism and its population
- so the gene pool is decreased and the banana plant becomes more susceptible to disease and less likely to cope with environmental change
Outline the properties of water which make it an ideal habitat for amphibians. [2 marks]
- has a high density (so the frogs are able to float)
- it is a good solvent
