Photosynthesis

Question 1

Definition of wavelength

Answer 1

The distance from peak to peak and is measured in nanomaters.

Question 2

Definition of primary pigment

Answer 2

Chlorophyll A, found in reaction centre, absorbs light energy and excites 2 electrons.

Question 3

Definition of accessory pigments

Answer 3

Absorbs different wavelength of light, passes energy down to primary pigment / reaction centre.

Question 4

Describe thylakoids in chloroplasts.

Answer 4

They contain photosynthetic pigment. Chlorphyll found on its membrane which traps light energy.

Question 5

Describe grana in chloroplasts

Answer 5

Stack of thylakoids, where the light dependent reaction occurs.

Question 6

Describe stroma in chloroplasts

Answer 6

Fluid-filled chlorphyll matrix where the light independent reaction reaction occurs.

Question 7

Explain what an absorption spectrum graph represents.

Answer 7

The wavelength of light energy that is absorbed by the different pigments.

Question 8

Explain what an action spectrum graph represents.

Answer 8

The relative effectiveness of different wavelengths on photosynthesis.

Question 9

Definition of oxidation

Answer 9

Loss of electrons and/or hydrogens.

Question 10

Definition of reduction

Answer 10

Gain of electrons and/or hydrogens.

Question 11

Definition of an electron carrier

Answer 11

A protein molecule that transfers electrons in the ETC.

Question 12

Definition of photolysis

Answer 12

Splitting water into protons, electrons and oxygen, using light energy.

Question 13

Definition of photophosphorylation

Answer 13

Addition of a phosphate molecule, using light energy.

Question 14

Definition of photoionisation

Answer 14

Molecules absorb light energy exciting electrons to leave the molecules.

Question 15

Describe the light dependent reaction (7 points)

Answer 15

1. Chlorophyll absorbs light energy.
2. Excites electrons out of chlorophyll / photosystem.
3. Electrons move along the electron trnapsort chain releasing energy.
4. Energy is used to join ADP and Pi to from ATP by chemiosmosis.
5. Photolysis of water produces protons, electrons and oxygen.
6. NADP reduced by electrons/hydrogen.
7. Oxygen is released as waste gas. ATP and red NADP go to light independent reaction.

Question 16

Describe the light dependent reaction (7 points)

Answer 16

1. Chlorophyll absorbs light energy.
2. Excites electrons out of chlorophyll / photosystem.
3. Electrons move along the electron trnapsort chain releasing energy.
4. Energy is used to join ADP and Pi to from ATP by chemiosmosis.
5. Photolysis of water produces protons, electrons and oxygen.
6. NADP reduced by electrons/hydrogen.
7. Oxygen is released as waste gas. ATP and red NADP go to light independent reaction.

Question 17

Describe chemiosmosis (5 points)

Answer 17

1. Energy is released as electrons pass along the ETC in the thylakoid membrane.
2. Energy is used to pump protons from the photolysis of water from the stroma into the intermembranal space.
3. Proton graident is established.
4. Protons flood from intermembranal space to stroma down concentration gradient.
5. Causes ATP synthase to smash ADP and Pi to form ATP.

Question 18

Describe the light independent reaction (6 points)

Answer 18

1. Carbon dioxide combines with ribulose bisphosphate (RuBP).
2. Produces an unstable 6C which breaks into twoglycerate phosphate molecules.
3. Glycerate phosphate reduced to triose phosphate.
4. Using reduced NADP and energy from ATP produced in light dependent stage.
5. Triose phosphate converted to glucose.
6. Or regenerated into ribulose bisphosphate (RuBP).

Question 19

Write out the pathway taken by carbon dioxide from the atmosphere into the chloroplast (6 points)

Answer 19

1. Diffuse through the stomata.
2. Diffuse through the spongy mesophyll.
3. Dissolves in water around palisade cells.
4. Diffuses through palisade membrane.
5. Diffuses through palisade cytoplasm.
6. Diffuses through chloroplast envelope into the stroma.

Question 20

Definition of a limiting factor

Answer 20

The factors that presents in the lowest amount (and therefore the one that limits the rate of the overall reaction).

Question 21

Which stage of photosynthesis is the most affected by temperature?

Answer 21

Light independent as it is enzyme-controlled.

Question 22

Describe and explain the effect of temperature on the rate on photosynthesis.

Answer 22

Increase in kinetic energy, increased collisions between active site of RuBisCO and CO2. More enzyme-substrate complexes, more enzyme product complexes form, so more GP formed.
Increase in kinetic energy break hydrogen bonds in tertiary structure and changes shape of active site of RuBisCO. Active site is no longer complementary to CO2. Less enzyme substarte complexes, less enzyme product complexes.

Question 23

Which stage of photosynthesis is affected by concentration of CO2?

Answer 23

Light independent as CO2 is the substrate for the reaction.

Question 24

Explain how carbon dioxide affects the rate of photosynthesis.

Answer 24

Increasing the concentration means more substrate available. More collisions. More enzyme substrate complexes and enzyme-product complexes. More GP produced.

Question 25

Which stage of photosynthesis will be most affected by light intensity?

Answer 25

Light dependent.

Question 26

Describe and explain the effect of light intensity on the rate of photosynthesis.

Answer 26

As light intensity increases, rate of photosynthesis also increases. Directly proportional.
As light intensity increases, the rate of photosynthesis plateaus. Another limiting factor is limiting the rate, e.g. temperature, carbon dioxide concentration.