Aerobic respiration

This is a transmission electron micrograph of a chloroplast.

Identify the components labelled A and B and describe how they are adapted for their function.

Identify one similarity and one difference between the structures of chloroplasts and the structures of mitochondria.

A student used thin layer chromatography (TLC) to separate the photosynthetic pigments in a chloroplast extract.

This is the result of the TLC.

Origin Solvent

Calculate the R_f for the most soluble pigment.

Give your answer to 2 significant figures.

The student noticed that the spots were very faint and thought that there might be other pigments present in the mixture that were too faint to be seen.

Describe how the student could increase the intensity of the spots using the same chloroplast extract.

Describe how the student could use the same equipment but increase the accuracy of the calculated R_f value.

The student was not able to identify any of the pigments using R_f values from a data book.

Suggest an explanation for this.

Describe how the student could use TLC to identify the pigments present in the mixture without calculating R_f values.

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.

NAD, FAD and Coenzyme A (CoA) are molecules that are involved in cellular respiration.

Which of the following statements about these molecules is/are correct?

1 NAD and FAD are examples of coenzymes. 2 NAD is reduced by accepting hydrogen atoms. 3 CoA delivers the three carbon atoms of pyruvate to the Krebs cycle in the form of an acetyl group.

A 1, 2 and 3 are correct

B only 1 and 2 are correct

C only 2 and 3 are correct

D only 1 is correct

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.

ATP can be produced in various ways. Each stage of respiration contributes to the production of ATP.

Describe the production of ATP by substrate-level phosphorylation in different stages of respiration with reference to the number of ATP molecules produced.

Glucose and other carbohydrates are present in respiring cells. The concentrations of carbohydrate molecules vary between tissues.

A student conducted tests on three tissues, A, B and C. Table 2 shows the results of these

Two of the tissues were known to be phloem tissue and liver tissue.

Use the evidence in Table 2 to identify which tissue, A, B or C, is phloem and which tissue is liver. Explain your answer.

Tissue........ must be phloem because........

Tissue........ must be liver because........

Using the information in Fig. 2, calculate the percentage of carbon atoms in the fatty acid that are able to enter the Krebs cycle.

The percentage of carbon atoms that a reaction makes available for use in the Krebs cycle can be described as the efficiency of the reaction.

Calculate the efficiency of the link reaction. Using your answer to part (i), state whether the link reaction is more, less or equally efficient when compared to the reactions described in Fig. 2.

Show your working.

Link reaction is........ efficient

Fig. 2 shows the role of coenzyme A in beta oxidation.

Suggest a role for coenzymes other than coenzyme A in beta oxidation.