Photosynthesis as an Energy Transfer Process (CIE A Level Biology)

Fig. 1 shows an electron microscope image of a chloroplast.

Fig. 1

Identify structures A-C in Fig. 1.

Fig. 1 is an electron microscope image.

Explain why an electron microscope rather than a light microscope is needed to view the internal structures of chloroplasts.

The large, pale coloured structures inside the chloroplast in Fig. 1 are starch granules.

Explain why starch granules are present inside chloroplasts.

The part of the chloroplast labelled B in Figure 1 contains various photosynthetic pigments.

State the role of photosynthetic pigments in photosynthesis.

Explain the advantage of the presence of various photosynthetic pigments.

Fig. 1 shows the absorption spectra for three different photosynthetic pigments.

Fig. 1

Compare the absorption spectra of chlorophyll b and carotenoids shown in Fig.1.

With reference to Fig. 1:

Suggest the colour of carotenoid pigments.

[1]

Explain your answer to part i).

[1]

It is also possible to represent action spectra on a graph like that shown in Fig. 1.

State how the information represented by an action spectrum is different to that represented by an absorption spectrum.

Sketch a suggested action spectrum onto the graph shown in Fig.1.

A researcher wanted to investigate the wavelengths of light that hit the ground in a woodland area. They measured the wavelengths of direct sunlight and of sunlight that had passed through the tree canopy. Fig. 2 shows their results.

Fig. 2

Only a small number of plant species are found on the ground below the trees in woodland areas.

Use Fig. 1 and 2 to suggest why.

The pigments in a chloroplast can be separated and identified using a technique called thin layer chromatography. After extracting pigments from a spinach leaf, a student carried out thin layer chromatography.

Some of the student's results can be seen in Fig.1.

Fig. 1

Use the equation provided to calculate the R_f values for pigments X and Y in Fig.1.

Describe the arrangement of the pigments described in part a) inside a chloroplast.

Outline the following processes connected to the pigment arrangements described in part b):

Photoactivation

[2]

Photolysis

[2]

In addition to the processes outlined in part c) the light dependent reactions of photosynthesis also involve the processes of oxidation and reduction.

Explain where oxidation and reduction occur during the light dependent reactions.

Fig. 1 shows some of the events of the light independent reactions.

Fig. 1

Name the process shown in Fig.1.

[1]

Give two reasons for your answer to part i).

[2]

The element cadmium, sometimes present in polluted soils, is toxic to plants even at low concentrations. Research has shown that cadmium can bind to photosystem II, impacting the process marked A in Fig 1.

Name the process marked A in Fig.1 that could be impacted by cadmium.

[1]

With reference to your answer to part i), outline the impact that cadmium would have on photosynthesis.

Describe the process taking place at the position marked B in Fig.1.

[3]

Fig.1 shows a representation of the light independent stages of photosynthesis.

Fig. 1

From Fig.1, identify:

[1]

Compound O.

[1]

The enzyme that catalyses the reaction between compounds M and O.

With reference to Fig.1 explain how the products of the light dependent reactions are used in the light independent reactions.

Compound P is a product of the light independent reactions.

Give three other molecules that could be formed from compound P inside plant cells.

[3]

Name the type of reaction that would convert compound P into a polymer.

Explain one reason why compound P is converted into other molecules such as those given in part c) i) rather than being stored as a 6C molecule in the cells.

Fig. 1 is a transmission electron micrograph of a chloroplast.

Fig. 1

Many compounds and structures involved in photosynthesis are located in a chloroplast.

Using the labels A, B or C, complete Table 1 to show the location of four of these compounds or structures.

You may use each of the letters A, B and C once, more than once, or not at all.

Table 1

[3]

Elodea canadensis is an aquatic plant that lives submerged in freshwater.

Equal‐sized plants of E. canadensis were exposed to different wavelengths of light for the same period of time. As each plant photosynthesised, the number of bubbles of oxygen leaving the plant was counted.

For each wavelength, the rate of oxygen production was calculated.

The results are shown in Fig. 2.

Fig. 2

Describe and explain the results shown in Fig. 2

Chlorophyll b, carotene and xanthophyll are known as accessory pigments. Describe the role of the accessory pigments in photosynthesis.

Fig.1 is an outline diagram of the Calvin cycle.

Fig. 1

(i)

With reference to Fig.1:

• Name the stage of the Calvin cycle occurring at A
• Name the enzyme involved in the stage of the Calvin cycle occurring at A
• Name two examples of substance C
• Name the biochemical process that produces reduced NADP and ATP.

(ii)

With reference to Fig.1, outline what is occurring at stage B of the Calvin cycle.

Explain why there is a tight ring of mesophyll cells around the bundle sheath cells in the leaves of a C4 plant.

Corals grow in shallow sea water. Corals consist of colonies of small animals called polyps. These polyps have photosynthetic protoctists called algae within their cells, which is advantageous both to the coral polyps and to the algae.

The algae that live within the cells of coral polyps can also live independently as free-living algae.

The algae that live within the cells of coral polyps have five different chloroplast pigments.

Table 1 shows the light wavelengths at which each algal chloroplast pigment shows its two largest peaks of light absorption.

Table 1

Corals can be kept in glass tanks that are usually lit by lamps radiating mainly violet and blue light, with wavelengths in the range of 400 nm to 490 nm.

With reference to Table 1, suggest why lamps radiating mainly violet and blue light are expected to increase the growth of coral polyps more than lamps radiating light of all wavelengths.

Photosynthesis in the algae living within the cells of coral polyps is the same as photosynthesis in plant cells.

Outline the process of cyclic photophosphorylation.

Paper chromatography can be used to separate photosynthetic pigments obtained from chloroplasts.

Fig. 1 shows the chromatography strip with distinct pigment bands.

Fig. 1

The teacher explains that the four bands represent four pigments: chlorophyll a, chlorophyll b, xanthophylls and carotenes (but not necessarily in that order). The teacher asks a student to suggest which bands most likely represent the two chlorophyll pigments. The student suggests bands 3 and 4.

Explain why this is the correct choice.

Describe how someone could accurately identify the pigments in the chromatogram shown in part (a).

Fig. 2 shows the chromatograms.

Fig. 2

Palmaria also contain a red pigment known as phycoerythrin. The pigment appears red because it absorbs blue light and reflects red light. The pigment phycoerythrin is absent from the chromatogram above.

Suggest why this might be.

Light of shorter wavelengths penetrates water to greater depths than light of longer wavelengths.

Using information here and from part (c), suggest why red algae such as Palmaria can live at greater depths than many other aquatic algae.

In a woodland the concentration of carbon dioxide gas in the air changes during a 24-hour period. It can also vary depending on the height above the ground at which a gas measurement is taken.

Explain the variation in carbon dioxide concentration in a woodland over time and at different heights. Assume that there is no air movement caused by wind throughout the 24-hour period.

A team of researchers investigated the effect of changing the carbon dioxide concentration on the levels of glycerate-3-phosphate (GP) and ribulose bisphosphate (RuBP) in photosynthesising cells.

Table 1 shows the results obtained when the carbon dioxide concentration was reduced.

Table 1

Explain the decrease in the level of GP at the lower carbon dioxide concentration.

The researchers carried out a similar experiment but increased the carbon dioxide concentration from 1% to 2%. The relative levels of GP and RuBP remained the same both before and after the experiment.

Suggest three reasons why.

Some primitive species of bacteria that live on the ocean floor do not have access to light for photosynthesis. Instead, they use the process of chemosynthesis to make food (glucose) using the energy stored in chemicals such as methane, hydrogen sulfide (H₂S) and carbon dioxide.

A simplified chemical equation of one of these reactions is shown below:

6CO₂  + 12H₂S → C₆H₁₂O₆ + 6H₂O + 12S

Use your knowledge of photosynthesis to suggest what the hydrogen sulfide is used for in chemosynthesis in these bacteria.