1. For a plant to be able to photosynthesise, it first needs to absorb light. Name the photosynthetic pigment that absorbs light.
Answer
Chlorophyll.
2. Photosynthesis is split into two separate stages, the light dependent and the light independent. Name the part of the chloroplast where each of these stages take place.
Answer
Light dependent: Thylakoid membrane.
3. Name the enzyme that catalyses the carboxylation of ribulose bisphosphate in the light-independent stage of photosynthesis.
Answer
Rubisco.
4. Name the environmental factors that can affect the rate of photosynthesis.
Answer
Light intensity, wavelength of light, carbon dioxide concentration, temperature and availability of water.
5. How can farmers use their understanding of limiting factors to increase yield ?
Answer
They can ensure that all factors are not limiting the rate of photosynthesis for that particular plant, therefore increasing yield, to ensure that the rate of photosynthesis is considerably higher than the rate of respiration.
6. A student obtained a suspension of chloroplasts from fresh spinach leaves using cell fractionation. Describe how.
Answer
The sample is homogenised (blended). The solution in which the spinach leaves are homogenised is kept cold, has the same water potential, and contains a buffer. The homogenate is then filtered to remove debris. The filtrate is spun at a low speed to remove nuclei. The supernatant is respun at a higher speed for longer to allow the chloroplasts to settle at the bottom.
7. The figure below shows some of the structures within the thylakoid membrane. The arrows indicate the movement of a particular ion. Name this ion.
Answer
Hydrogen ion (H+).
8. Give the letter in the figure above that represents the stroma.
Answer
Letter C because H+ move into the thylakoid lumen during the electron transport chain. They then diffuse out (by facilitated diffusion) through ATP synthase.
9. Explain the role of structure B in the figure above.
Answer
The role of structure B is ATP synthase. H+ ions diffuse out of the thylakoid and into the stroma through this enzyme. As a result, ADP is phosphorylated. ATP synthase catalyzes this phosphorylation.
10. A student carried out an experiment to investigate the pigments present in spinach leaves. She used paper chromatography to separate the pigments. When she set up the chromatogram, she used a pencil to draw the origin line. The figure below shows the results and the Rf values for four different pigments. In setting up the chromatogram, explain why the student marked the origin on the paper using pencil, placed a concentrated spot of pigment on the origin line and ensured the level of the solvent was below the origin line.
Answer
The pencil would not dissolve in the solvent (so it can be seen). She placed a concentrated spot of pigment on the origin line so that enough pigment would be visible once separated. She ensured that the level of the solvent was below the origin line so the pigments could rise up the paper rather than dissolve in the solvent.
11. Identify the pigments at positions X and Y.
Answer
X = xanthophyll (Evidence of 5.6 cm/9.5 cm)
Y = chlorophyll a (Evidence of 2.4 cm/9.5 cm)