Photosynthesis

Question 1

2 main stages

Answer 1

light dependent reactions and calvin cycle

Question 2

where do light dependent reactions occur

Answer 2

in thylakoid membranes of chloroplasts

Question 3

what happens during photolysis

Answer 3

water is split into oxygen, protons, and electrons using light energy

Question 4

describe the pathway of electrons in non cyclic photophosphorylation

Answer 4

electrons move from PSII to PSI via the etc, generating ATP and reducing NADP to NADPH

Question 5

how does cyclic photophosphorylation differ from non cyclic

Answer 5

cyclic only involves PSI, recycling electrons to produce ATP but no NADPH or O2

Question 6

where does calvin cycle occur

Answer 6

stroma of chloroplast

Question 7

3 main stages of calvin cycle

Answer 7

carbon fixation - CO2 combines with RuBP to form 2 molecules of GP (glycerate-3-phosphate)
reduction - GP reduced to triose phosphate using ATP and NADPH
regeneration - some TP regenerates RuBP using ATP

Question 8

what is the role of RuBisCO in calvin cycle

Answer 8

catalyses the fixation of CO2 to RuBP

Question 9

how are chloroplasts adapted for photosynthesis

Answer 9

thylakoids with large surface area for light absorption
stroma contains enzymes for calvin cycle
double membrane regulates material exchange

Question 10

3 main limiting factors of photosynthesis

Answer 10

light intensity, carbon dioxide concentration, temperature

Question 11

how does temperature affect photosynthesis

Answer 11

enzymes like RuBisCO operate optimally within a specific temperature range, extreme temperatures reduce efficiency

Question 12

what is the compensation point in photosynthesis

Answer 12

the point where the rate of photosynthesis equals the rate of respiration

Question 13

How are photosynthesis and respiration linked?

Answer 13

Photosynthesis produces glucose and oxygen, which are substrates for respiration. Respiration produces CO₂ and H₂O, substrates for photosynthesis

Question 14

Which processes involve ATP synthesis via chemiosmosis?

Answer 14

photophosphorylation in photosynthesis

Question 15

How can you measure the rate of photosynthesis using pondweed (e.g., Elodea)?

Answer 15

Use a photosynthometer to collect and measure the volume of oxygen produced over time.

Question 16

What factors can you vary in a pondweed experiment to investigate photosynthesis?

Answer 16

Light intensity, carbon dioxide concentration, and wavelength of light.

Question 17

How is the rate of oxygen production calculated in a pondweed experiment?

Answer 17

Record the volume of oxygen gas produced (e.g., using a gas syringe) over a set time.

Question 18

How can hydrogen carbonate indicator be used to investigate photosynthesis?

Answer 18

The indicator changes color based on CO₂ concentration:
High CO₂: Yellow
Low CO₂: Purple
Normal CO₂: Red

Question 19

What does a color change in the hydrogen carbonate indicator show?

Answer 19

Photosynthesis removes CO₂, turning the indicator purple. Respiration increases CO₂, turning it yellow.

Question 20

How can you investigate the effect of light intensity on photosynthesis?

Answer 20

Place pondweed at varying distances from a light source and measure oxygen production. Use a light meter to quantify light intensity.

Question 21

How do you control variables in a limiting factor experiment?

Answer 21

Use a water bath to maintain constant temperature and a fixed CO₂ concentration using sodium hydrogen carbonate.

Question 22

How can chromatography be used to separate photosynthetic pigments?

Answer 22

Extract pigments from leaves, apply to chromatography paper, and use a solvent to separate them based on solubility.

Question 23

How do you calculate the Rf value for pigments in chromatography?

Answer 23

Rf = Distancetraveledbysolvent / Distancetraveledbypigment
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Question 24

What pigments are commonly identified in a chromatography experiment?

Answer 24

Chlorophyll a, chlorophyll b, carotenoids, and xanthophylls.

Question 25

How can the compensation point of a plant be determined?

Answer 25

Place a plant in sealed tubes with hydrogen carbonate indicator under varying light intensities. Measure CO₂ levels to identify when photosynthesis equals respiration.