Oxidative phosphorylation

Respiration allows cells to carry out processes such as DNA replication.

Outline why cellular respiration is necessary in cells that are carrying out DNA replication.

Chemiosmosis is a mechanism that is thought to occur in both respiration and photosynthesis.

Evidence for chemiosmosis during photosynthesis can be demonstrated by:

• isolating chloroplasts from plant cells

• placing the chloroplasts in an acidic solution, in the dark

• shining light onto the chloroplasts in the solution

• measuring the final pH of the solution.

Explain what is likely to happen to the pH of the solution when light is shone on the chloroplasts.

André Jagendorf provided evidence for chemiosmosis in an experiment carried out in the 1960s.

In his experiment, Jagendorf:

• broke open chloroplasts to expose thylakoids, in the dark

• placed the thylakoids into a solution buffered at pH 4 (solution 1)

• after a short time period, transferred some of these thylakoids to a new solution buffered at pH 4 that contained ADP and P_i (solution 2)

• transferred other thylakoids from solution 1 to a new solution buffered at pH 8 that contained

ATP production was measured in solution 2 and solution 3.

Explain what you would expect to observe in solution 2 and solution 3 after the transfer of the thylakoids.

Vitamins are molecules that are consumed in the diet of animals and have essential roles in the body.

Thin layer chromatography (TLC) was used to separate a mixture of vitamins from a vitamin supplement tablet.

Most vitamins are colourless.

Suggest one method for visualising the vitamins in TLC.

The results of the TLC are shown in the chromatogram in Fig. 2.1.

Use Fig. 2.1 to calculate the R_f value of vitamin B₂.

Vitamin B₉ is needed for the synthesis of molecule D, shown in Fig. 2.2.

Fig. 2.2

Molecule D is a component in the structure of DNA.

A deficiency of vitamin B₉ in the diet can cause interphase to stop in some cells.

Use Fig. 2.2 to explain why a deficiency of vitamin B₉ can cause interphase to stop.

Vitamin B₂ is used by the body to make FAD. Vitamin B₃ is used by the body to make NAD.

A mitochondrion is shown in Fig. 2.3.

Label Fig. 2.3 to show the locations where FAD gains H atoms and where FAD releases H atoms during respiration.

• Use the letter E to show where FAD gains H atoms.

• Use the letter F to show where FAD releases H atoms.

The table lists features that are correct for FAD, NAD, both or neither.

Complete the table by adding a tick (✓) to a box where the feature is correct and a cross (✗) where the feature is incorrect. You should add either a tick or a cross to every box in the table.

ATP is produced in respiration. Some of these molecules of ATP are used to release energy for processes in respiration. For example, ATP is used in the early stages of glycolysis.

Suggest one other way in which ATP contributes to the process of respiration.

Vitamin C affects the activity of enzymes in different ways.

Vitamin C acts as a coenzyme for several enzymes in the synthesis of collagen.

Outline the role of coenzymes in biological reactions.

A scientist investigates the effect of vitamin C on the activity of the enzyme adenylyl cyclase.

Adenylyl cyclase catalyses the conversion of ATP to cAMP.

The scientist measures the activity of adenylyl cyclase without vitamin C and with 1 mmol dm^–3 of vitamin C.

The scientist’s results are shown in Fig. 2.4.

Explain what can be concluded from the results in Fig. 2.4 about the effect of vitamin C on the activity of adenylyl cyclase.

The image below is a photomicrograph of a mitochondrion.

State the type of microscope used to produce this image.

Identify the structures labelled M and N in the photomicrograph.

Describe two ways in which the structure of mitochondrial membranes is related to the function of a mitochondrion.

The endosymbiosis theory suggests that mitochondria may have evolved from bacteria that were taken inside other cells.

These cells then evolved into eukaryotes.

Give two structural features of mitochondria that support this theory.

Explain why early eukaryotes were able to grow more quickly than cells that did not possess mitochondria.

Which of the following, A to D, is a similarity in the way ATP is made in respiration and photosynthesis?

A both involve NAD

B both involve substrate level phosphorylation

C both involve photons

D both involve proton gradients

Your answer

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. 19.1.

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 19.1.

Use the data in Table 19.1 to suggest the likely diet of each genus of honeypot ant.

Justify your answer.

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

Fig. 19.2 shows the chemical structure of chitin.

Using information from Fig. 19.2, 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.