AQA A Level Biology Paper 3 June 2023 question paper 7402/3

Describe how stimulation of a Pacinian corpuscle produces a generator potential.

Scientists investigated the stimulation of a Pacinian corpuscle in the skin of a fingertip. The scientists applied two different pressures to the fingertip and recorded the changes in membrane potential of the Pacinian corpuscle’s sensory neurone.

Figure 1 shows the scientists’ results.

Use Figure 1 to describe what is meant by the all-or-nothing principle.

On Figure 1, from 0.6 ms to 4.0 ms, no new generator potential could be produced. What is this time period called?

A student investigated the effect of different sugars on the rate of respiration in yeast. Yeast normally respires glucose.

Figure 2 shows the method she used for her first experiment.

Other than those stated, suggest two variables the student needed to keep constant in her investigation.

Figure 3 shows the result she obtained for yeast in glucose solution.

Use Figure 2 and Figure 3 to calculate the rate of carbon dioxide production in mm s^–1 for yeast in glucose solution.

Give your answer in standard form and to 2 significant figures.

Show your working.

The student repeated the experiment using yeast in maltose solution. She found the rate of carbon dioxide production was slower than with yeast in glucose solution. Suggest why.

Below are four statements about the structure of prokaryotic cells.

1. No prokaryotic cell has DNA that is associated with proteins.

2. No prokaryotic cell has membrane-bound organelles.

3. All prokaryotic cells have one or more flagella.

4. All prokaryotic cells have smaller ribosomes than eukaryotic cells.

Which statements about the structure of prokaryotic cells are correct?

Tick () one box.

A student investigated the effect of two antibiotics on the growth of the bacterium Micrococcus luteus.

During the investigation, the student:

• transferred 9 cm³ of a liquid culture of M. luteus into each of three bottles

• added the antibiotic chloramphenicol to the first bottle

• added the antibiotic novobiocin to the second bottle

• added no antibiotic to the third bottle.

After 24 hours, he diluted the contents of each bottle by 1 in 100 000 (10^–5). He then transferred 0.25 cm³ samples from the first bottle onto each of 3 separate agar plates. He repeated this with 0.25 cm³ samples from the second bottle and the third bottle, resulting in 9 agar plates in total.

He incubated the plates for 48 hours.

Table 1 shows the number of colonies of bacteria he counted on each plate after 48 hours’ incubation.

Calculate the mean number of bacteria in the undiluted bottle of liquid culture containing novobiocin.

Give your answer in standard form. Show your working.

Starting with a single bacterium, calculate how many generations it would take to produce at least the number of bacteria you have calculated for your answer in Question 03.2

You can assume no bacteria die.

You could use the ln or log button on your calculator to calculate your answer.

M. luteus is not resistant to chloramphenicol.

Suggest two reasons why the bacteria were able to grow in the culture containing chloramphenicol.

Following a body injury, bone marrow stem cells move to the site of damage and undergo cell differentiation.

Figure 5 shows how this differentiation occurs.

Suggest how SCFR is destroyed by a lysosome.

After a heart attack, cardiomyocytes (cardiac muscle cells) die, and become infarcted tissue. Infarcted tissue cannot contract.

Stem cells in bone marrow cannot move to the infarcted tissue and differentiate into cardiomyocytes. Scientists used laboratory rats to investigate if bone marrow stem cell transplants could be used to repair infarcted tissue resulting from a heart attack.

They split the rats into three groups.

• Control group did not get a transplant of bone marrow stem cells.

• c-KIT+ group got a transplant of bone marrow stem cells with a functioning c-KIT gene.

• c-KIT– group got a transplant of bone marrow stem cells with no functioning c-KIT gene.

After 9 days, the scientists measured the mean ventricular blood pressure of each of the three groups.

Figure 6 shows their results.

The differences between the groups were all statistically significant.

Using all of the information, suggest explanations for the results for the Control group and the c-KIT– group shown in Figure 6.

Nine days after transplantation, the c-KIT+ group showed that 68% of infarcted tissue was made up of new cardiomyocytes. The control group had no new cardiomyocytes.

Assuming that mean ventricular blood pressure is directly proportional to the number of cardiomyocytes, calculate the percentage of infarcted tissue that was made up of new cardiomyocytes in the c-KIT– group.

All new cardiomyocytes produced:

• Connexin-43, a channel protein that allows electrical impulses to pass between cardiomyocytes

• GATA-4, a transcriptional factor that stimulates the expression of genes for actin and myosin.

Suggest how production of Connexin-43 and GATA-4 could give the result seen in the c-KIT+ group in Figure 6 (on page 13).

Do not include details of transcription or translation in your answer.

Scientists investigated the effect that the release of heated water into a river from a power station had on the biodiversity of a local fish community over 29 years.

They measured the species richness and the number of fish of each species at the same site in October every year. The scientists used this information to calculate an index of diversity (d) of fish for each year.

Figure 7 and Figure 8 show their results.

The scientists used the following formula to calculate the index of diversity (d) of fish.

where N = total number of fish of all species and n = total number of fish of each species

In some years, the values were N = 624 and Σ n (n –1) = 64 792

Which years had these values?

Use Figure 8 and the formula above to work out your answer.

In 1997, the scientists recorded the highest species richness, but the lowest value of d over the 29 years.

Describe and explain how these results for 1997 were possible.

A journalist studied Figure 7 and Figure 8 (on page 16) and concluded that releasing heated water from a power station has no effect on local fish communities.

Use all the information to suggest reasons why the journalist’s conclusion might not be valid.

Give two types of cell that can stimulate an immune response.

An autoimmune disease causes the immune system to attack healthy body tissues. Scientists investigated the immune responses of healthy mice and mice with autoimmune disease.

The chemical OXA causes an immune response in mice and can make their skin swell. Mice had olive oil applied to their left ear and OXA in olive oil applied to their right ear.

The immune response was recorded in two ways:

• the cellular response by measuring the mean increase in ear thickness 24 hours after exposure to OXA

• the humoral response by measuring the mean concentration of anti-OXA antibody in blood 14 days after exposure to OXA.

Table 2 shows the results of this investigation. The values in the brackets show ± 2 standard deviations. A value of ± 2 standard deviations from the mean includes over 95% of the data.

Suggest and explain one reason why olive oil was applied to the left ear of the mice.

Plot a suitable graph for mean increase in ear thickness for each group of mice in Table 2.

Include the data for ± 2 standard deviations on your graph.

What can you conclude about the effects of autoimmune disease on the cellular response and the humoral response in male and female mice?

Use the data to justify your conclusions.

Some studies have shown that in humans, oestrogen has the opposite effect on two different autoimmune diseases. Oestrogen:

• accelerates the progression of systemic lupus erythematosus (SLE)

• prevents the progression of rheumatoid arthritis (RA).

The scientists investigated the effect of oestrogen on the immune response in healthy mice and mice with autoimmune disease.

Table 3 shows the scientists’ results.

A student studying these data made the following conclusions.

1. In humans, SLE is caused by an overproduction of antibodies.

2. In humans, RA is caused by an overproduction of cytotoxic T cells (T_C cells).

Evaluate the student’s conclusions.

In mice, one type of autoimmune disease is inherited as a dominant allele. Would the Hardy–Weinberg principle hold true for a population of mice, some of which had this autoimmune disease?

Explain your answer.

Write an essay on one of the topics below.

Either

The importance of interactions between organisms and their environment.