Chapter 2 - Photosynthesis.

Question 1

Name a cell where chloroplast would be found?

Answer 1

Palisade Mesophyll cells.

Question 2

What are the 2 stages in photosynthesis?

Answer 2

• Light dependent stage (Non-/Cyclic Photophosphorylation).

- Light-Independent Stage (Calvin cycle).

Question 3

What is photophosphorylation?

Answer 3

An endergonic reaction bonding a phosphate ion to a molecule of ADP using energy from light, making ATP.

Question 4

What is the process that splits water and what are the end products?

Answer 4

Photolysis - Produces H+ protons, e- electrons and O2 waste gas.

Question 5

How are chloroplasts transducers?

Answer 5

They turn energy in the photons of light into chemical energy, made available through ATP and incorporated into molecules such as glucose.

Question 6

What is the difference between an Absorption Spectrum and an Action Spectrum?

Answer 6

Absorption spectrum - A graph showing how much light is absorbed at different wavelengths.
Action Spectrum - A graph showing the rate of photosynthesis at different wavelengths.

Question 7

What are the 4 Photosynthetic Pigments that can be found in chloroplasts?

Answer 7

Chlorophyll a.
Chlorophyll b.
Carotenoids (B-Carotene).
Xanthophylls.

Question 8

What is an Antenna Complex?

Answer 8

An array of protein and pigment molecules in the thylakoid membranes of the grana that transfer energy from light of a range of wavelengths to Chlorophyll a, at the reaction entre.

Question 9

What does a close correlation between the action spectrum and the absorption spectrum suggest?

Answer 9

Suggests the pigments responsible for absorbing the light are used in photosynthesis.

Question 10

What are the 2 Photosystems that can be found?

Answer 10

• Photosystem I (P700).

- Photosystem II (P680).

Question 11

What happens in the reaction centre?

Answer 11

Electrons are excited.

Question 12

Why is chlorophyll a referred to as the primary pigment?

Answer 12

Because it passes energy to the subsequent reactions of photosynthesis.

Question 13

What are the products of the Light-dependent stage that are required for the Light-independent stage?

Answer 13

• Reduced NADP (NADPH2).

- ATP.

Question 14

What is the Z scheme?

Answer 14

The pathways taken by electrons in non-cyclic photophosphorylation.

Question 15

What are the 2 passages that electrons can take?

Answer 15

Cyclic Photophosphorylation.

Non-Cyclic Photophosphorylation.

Question 16

Where does Photolysis occur?

Answer 16

In the thylakoid spaces.

Question 17

How is ATP made is photophosphorylation?

Answer 17

The protons from the photolysis of water accumulate in the thylakoid space, forming an electrochemical gradient. The electrons pump more protons into this space to maintain the gradient. Chemiosmosis occurs and once the protons are in the stroma, they reduce NADP.

Question 18

What is the acceptor molecule in the Calvin cycle that joins with CO2 and what enzyme catalyses this reaction?

Answer 18

Ribulose Bisphosphate, catalysed by RUBISCO.

Question 19

What happens to the unstable 6C compound that is formed when RuBP joins with CO2?

Answer 19

The 6C compound immediately splits into 2 molecules of Glycerate-3-Phosphate.

Question 20

How is GP reduced to Triose Phosphate?

Answer 20

It is reduced by adding H2 from reduced NADPH2. This requires energy obtained from ATP.

Question 21

How many turns of the Calvin cycle are needed to make 1 molecule of glucose?

Answer 21

12. For every 6 turns of the Calvin cycle only 1 molecule of Triose phosphate and 2 molecules of TP are need to make 1 molecule of glucose.

Question 22

What needs to happen to triose phosphate to reform Ribulose Bisphosphate?

Answer 22

It goes through a series of reactions using the energy from ATP made in the Light-dependent reactions.

Question 23

What factors create a suitable environment which ensures plants can be efficient at photosynthesis?

Answer 23

• The reactants CO2 and water.
• Light at enough intensity and of suitable wavelengths.
• A suitable temperature.

Question 24

What is the light compensation point?

Answer 24

It’s the light intensity at which a plant has no net gas exchange as the volume of gases used and produced in respiration and photosynthesis are equal.

Question 25

Why do plants need Nitrogen?

Answer 25

The amino groups are used in making amino acids and its a key component of chlorophyll.

Question 26

Why do plants need Magnesium?

Answer 26

It also forms part of the chlorophyll molecule. They’re also important enzyme activators.