13.10 End of Chapter Questions
Question 1 – 3
1. What are the products of the light dependent reactions of photosynthesis? [1]
A. ATP, RuBP and reduced NAD
B. ATP, oxygen and reduced NADP
C. GP, oxygen and reduced NAD
D. GP, reduced NADP and RuBP
B;
2. Where in the chloroplast are the products of photophosphorylation used? [1]
A. envelope
B. granum
C. stroma
D. thylakoid
C;
3. In separate experiments, an actively photosynthesising plant was supplied with one of two labelled reactants: [1]
- water containing the 18O isotope of oxygen
- carbon dioxide containing the 17O isotope of oxygen.
In which products of photosynthesis would these isotopes be found?
| 18O | 17O | |
| A | oxygen produced by chloroplast grana | carbohydrate produced by the chloroplast stroma |
| B | oxygen produced by the chloroplast stroma | carbohydrate produced by chloroplast grana |
| C | carbohydrate produced by chloroplast grana | oxygen produced by the chloroplast stroma |
| D | carbohydrate produced by the chloroplast stroma | oxygen produced by chloroplast grana |
A;
Question 4
a Explain how the inner membrane system of a chloroplast makes it well adapted for photosynthesis. [5]
allows chlorophyll and other pigments to be arranged into photosystems;
provides large surface area for pigments;
increases efficiency of light harvesting;
allows electron carriers to be arranged appropriately;
provides structure for proton gradient for chemiosmosis;
anchors ATP synthase;
b Copy the table below and insert ticks or crosses to show which structural features are shared by a plant chloroplast and a typical prokaryotic cell. [6]
✓= structural feature shared; ✗ = structural feature not shared.
| Structural feature: | Structural feature shared by chloroplast and typical prokaryotic cell: |
| circular DNA | |
| DNA combined with structural protein to form chromosomes | |
| ribosomes about 18 nm in diameter | |
| complex arrangement of internal membranes | |
| peptidoglycan wall | |
| size ranges overlap |
| Structural feature: | Shared by chloroplast and typical prokaryotic cell: |
| circular DNA | ✔ |
| DNA combined with structural protein to form chromosomes | ✘ |
| ribosomes about 18 nm in diameter | ✔ |
| complex arrangement of internal membranes | ✘ |
| peptidoglycan wall | ✘ |
| size ranges overlap | ✔ |
Question 5
a When isolated chloroplasts are placed in buff er solution with a blue dye such as DCPIP or methylene blue and illuminated, the blue colour disappears. Explain this observation. [4]
photolysis of water occurs in light;
H+ released;
accepted by DCPIP / methylene blue;
colourless when reduced;
shows ‘reducing power’ of chloroplasts;
b Name the compound, normally present in photosynthesis, that is replaced by the blue dye in this investigation. [1]
NADP
Question 6
Distinguish between:
a. cyclic and non-cyclic photophosphorylation [2]
cyclic photophosphorylation:
electron emitted by chlorophyll of photosystem I returns to chlorophyll by a series of carriers;
non-cyclic photophosphorylation:
electron emitted by chlorophyll of photosystem II does not return to that chlorophyll (but is absorbed by photosystem I and electron emitted by photosystem I is absorbed by NADP);
b. photophosphorylation and oxidative phosphorylation [2]
photophosphorylation:
synthesis of ATP using light energy in photosynthesis in a chloroplast;
oxidative phosphorylation:
synthesis of ATP using energy released from the electron transport chain in aerobic respiration in a mitochondrion;
c. the roles of NAD and NADP in a plant. [2]
NAD:
hydrogen carrier in respiration;
NADP:
hydrogen carrier in photosynthesis;
Question 7
Draw a simple flow diagram of the Calvin cycle to show the relative positions in the cycle of the following molecules: [4]
CO2 (1C)
GP/PGA (3C)
triose phosphate (3C)
RuBP (5C)
Show the point in the cycle at which the enzyme rubisco is active. [1]
Question 8
a. Explain what is meant by a limiting factor. [1]
limiting factor: one factor, of many affecting a process, that is nearest its lowest value and hence is rate-limiting;
b. List four factors that may be rate-limiting in photosynthesis. [4]
light intensity;
light wavelength;
concentration of carbon dioxide;
temperature;
c. At low light intensities, increasing the temperature has little eff ect on the rate of photosynthesis.
At high light intensities, increasing the temperature increases the rate of photosynthesis.
Explain these observations. [5]
shows that there are two sets of reactions in photosynthesis;
a light dependent photochemical stage;
a light independent temperature-dependent stage;
photochemical reactions are not affected by temperature;
at low light intensities, light intensity is the rate-limiting factor;
at high light intensities and low temperatures, temperature is the rate limiting factor;
Question 9
a. Copy and complete the table to show the diff erences between mesophyll and bundle sheath cells in C4 plants. Insert a tick (✓) when an item is present in the cell and a cross (✗) when it is not. [7]
| Item: | Mesophyll cell: | Bundle sheath cell: |
| PEP carboxylase | ||
| rubisco | ||
| RuBP | ||
| enzymes of Calvin cycle | ||
| high concentration of oxygen | ||
| light dependent reactions | ||
| contact with air spaces |
| Item | Mesophyll cell | Bundle sheath cell |
| PEP carboxylase | ✔ | ✘ |
| rubisco | ✘ | ✔ |
| RuBP | ✘ | ✔ |
| enzymes of Calvin cycle | ✘ | ✔ |
| high concentration of oxygen | ✔ | ✘ |
| light-dependent reactions | ✔ | ✘ |
| contact with air spaces | ✔ | ✘ |
b. Explain what is meant by photorespiration. [2]
Photorespiration:
rubisco catalyses the combination of RuBP and oxygen;
the result is an overall intake of oxygen and loss of carbon dioxide;
Question 10
a. Distinguish between an absorption spectrum and an action spectrum. [4]
absorption spectrum:
a graph of the absorbance;
of different wavelengths of light by a compound;
action spectrum:
a graph of the rate of a process;
e.g. photosynthesis at different wavelengths of light;
b. Pondweed was exposed to each of three diff erent wavelengths of light for the same length of time..
For each wavelength, the number of bubbles produced from the cut ends of the pondweed were counted and
are shown in the table.
| Wavelength of light / nm | Mean number of bubbles produced in unit time |
| 450 | 22 |
| 550 | 3 |
| 650 | 18 |
Explain these results. [4]
number of bubbles shows rate of photosynthesis;
rate similar at 450 nm (blue) and 650 nm (red);
these are wavelengths that are absorbed by chlorophyll;
rate, much lower / refer to figures, at 550 nm (green);
very little absorbed by any pigment;
