Respiration (OCR A Level Biology)

Honeypot ants belong to several different genera. Some specialised individuals are used as food storage vessels. These individuals have swollen abdomens that store various foods, which can be given to members of the colony when required.

One such individual is shown in Fig. 1.

Fig. 1

An investigation was carried out into the respiratory substrate of three different genera of honeypot ant, by measuring oxygen uptake and carbon dioxide production.

The data are shown in Table 1.

Table 1

Use the data in Table 1 to suggest the likely diet of each genus of honeypot ant.

Justify your answer.

[3]

Chitin is a polysaccharide found in insects. It is used to form the hard outer casing of their bodies.

Fig. 2 shows the chemical structure of chitin.

Using information from Fig. 2, state two similarities and two differences between the structures of chitin and glycogen.

Insects use glucose to generate ATP.

Outline the processes involved in the generation of ATP through chemiosmosis.

A group of students set up a simple respirometer, as shown in Fig. 1, and used it to determine the rate of respiration in germinating mung beans.

• They placed a small muslin bag of soda lime into the syringe and then added five germinating mung beans, which were held in place with the syringe plunger.
• The students measured the movement of the red fluid in the capillary tube.
• After each set of readings the plunger was reset to return the fluid to its original position.

Fig. 1

The results are shown in Table 1.

Table 1

Give one limitation of using this method to investigate respiration rate.

Read the procedure carefully. Identify one variable that had not been controlled in this experiment and suggest an improvement to control that variable.

Describe how you would add the red fluid to the capillary tube at the start of the experiment.

The data shows an anomalous result at 60 seconds.

Explain why the result is considered to be anomalous and describe one correct way of dealing with this type of result.

Using the data the student obtained, calculate the mean rate of respiration for germinating mung beans between 90 and 150 seconds. 

What additional information would be needed to calculate:

The group of students wanted to find out if the rate of respiration of a small invertebrate animal was comparable to that of the mung beans.

Adapt the procedure used to investigate the respiration rate of a small invertebrate, such as a woodlouse or caterpillar, with that of mung beans.

Comment on the results you might expect from this experiment and the conclusions you might draw.

Gluten helps to trap carbon dioxide within bread dough. This enables bread to rise when it is baked.

The carbon dioxide is produced by baker’s yeast, Saccharomyces cerevisiae. This species of yeast is able to convert ethanol to acetyl CoA at low glucose concentrations.

Fig. 2 shows the oxygen consumption and carbon dioxide production of a population of S. cerevisiae grown in batch culture. The population was provided with glucose as their only initial source of carbon.

Fig. 2

(i)

Suggest and explain what conclusions can be drawn from Fig. 2 about the factors that affected the rate and type of respiration carried out by S. cerevisiae in this batch culture.

[3]

(ii)

Describe two practical considerations to ensure the S. cerevisiae population grows successfully when the initial culture is established.

[2]

They carried out the following two dilutions:

• 1 cm³ of the original solution was mixed with 9 cm³ of nutrient solution to make solution 2.
• 1 cm³ of solution 2 was mixed with 9 cm³ of nutrient solution to make solution 3.

The scientists transferred 0.1 cm³ of solution 3 onto an agar plate. 15 separate colonies grew on the plate.

Calculate the number of yeast cells in the original 25 cm³ solution.

Express your answer in standard form to three significant figures. Show your working.

[2]

(iv)

A group of students were designing an experiment to investigate the effect of temperature on the respiration rate of S. cerevisiae.

Their planned method included the following:

• S. cerevisiae yeast suspension will be divided into six equal volumes to form the experimental groups.
• Six temperatures will be tested: 15 °C, 20 °C, 25 °C, 30 °C, 35 °C and 40 °C.
• Beakers of S. cerevisiae will be placed in water baths to control the temperature.
• Respiration rate will be measured by using a pH probe to monitor changes in the pH of the suspensions.
• The experiment will be repeated four times.

Evaluate whether the students’ method is likely to produce valid results.

[3]

(v)

The students used a Student’s t-test to compare the results at 30 °C and 35 °C.

They calculated a t value of 2.200.

The critical value for p = 0.05 is 2.306.

Assuming their final method was valid, what can the students conclude from the result of the t-test?

[1]

Part of the body’s response ‘fight or flight’ is to run away from the threat. Prolonged vigorous exercise puts high demands on the body’s metabolism.

The muscle cells require an adequate supply of oxygen for respiration. If insufficient oxygen is available, the cells must respire anaerobically.

Fig. 2 outlines the process of anaerobic respiration in muscle cells.

Fig. 2

Identify the compounds labelled D and E in Fig. 2.

[2]

(ii)

What is the role of compound D in anaerobic respiration?

[1]

(iii)

Why is it important that compound G is formed during the reaction in which compound D is converted into compound E in anaerobic respiration?

[2]

(iv)

Compound E is toxic and is removed from the muscle cell. It is transported to an organ in the body.

Which organ is compound E transported to and how does it reach this organ?

[1]

Athletic sprinters require large amounts of energy in short periods of time. Many elite sprinters can run 100 metre races in under 10 seconds.

Under normal conditions, exercise requires an increased rate of breathing. It has been observed that some of the best sprinters only take one breath at the start of the race and do not inhale again until the end of the race.

Suggest how these sprinters can expend so much energy without needing to carry out aerobic respiration.