5.1 Photosynthesis

Question 1

What is photosynthesis?

Answer 1

The production of useful energy from light energy in a plant

Question 2

What is the equation for Photosynthesis?

Answer 2

6CO2 + 6H2O + sunlight energy = C6H12O6 + 6O2

Question 3

What are chlorophyll?

Answer 3

Pigments found in the chloroplasts in a plant. They absorb light and have different wavelengths. For example, chlorophyll a and chlorophyll b have affinities for red and blue lights.

Question 4

Why is chlorophyll green?

Answer 4

They are green because we see the light which is reflected. They have a minimal affinity for green light because the sun emits a lot of green light. The inability to process this acts as a “sunscreen” to prevent over production in the plant.

Question 5

What is photoionization?

Answer 5

Ionisation by light of a chlorophyll to release two e- into the electron transfer chain.

Question 6

What is chemiosmosis?

Answer 6

The movement of ions across a semi-permeable membrane down an electrochemical gradient to produce energy

Question 7

What is photolysis?

Answer 7

The splitting of water using light energy, specifically photons.

Question 8

What are the adaptions of a leaf which allows successful photosynethisis.

Answer 8

Air spaces, waxy cuticle. xylem, thin upper epidermis, stomata, palisade layer.

Question 9

What is oxidation?

Answer 9

The loss of electrons.

Question 10

What is reduction?

Answer 10

The gain of electrons.

Question 11

What is the Light Dependent Reaction?

Electron ONLY

Answer 11

Chlorophyll absorbs light energy
Two electrons are released and move to high energy levels.
Electrons are taken up by electron carriers and are transferred down the electron transfer chain, releasing energy as they move.
The energy which is released is used to make ATP

Question 12

What is the Light Dependent Reaction?

Water ONLY

Answer 12

The electrons which are lost from the chlorophyll are replaced by electrons released during the photolysis of water, where oxygen is released as a bi product.

The water split into O2, H+ and e-

The electrons are used to replenish the chlorophyll
The H+ is used to reduce the NADP co enzyme carrier.

Question 13

What is the Calvin Cycle?

Answer 13

The sequence of reactions that form the Light Independent Reaction.

Question 14

Calvin Cycle:

Ribulose Bisphosphate + Rubisco +CO2

Answer 14

2 Glycerate 3 Phosphate
G3P
3 Carbons

Question 15

Calvin Cycle:

2 Glycerate 3 Phosphate REDUCED

Answer 15

to 2 Triose Phosphate
3 Carbons
This is sometimes used to make other sugars, amino acids and lipids.

Question 16

Calvin Cycle:

2 Triose Phosphate - 1Carbon

Answer 16

Ribulose Bisphosphate
RuBP
5 Carbons

Question 17

Where does the LIR occur?

Answer 17

In the stroma of the chloroplats

Question 18

Where does LDR occur?

Answer 18

The membrane of the Thylakoids.

Question 19

What is happening to NADPH when G3P is being reduced in the Calvin Cycle?

Answer 19

NADPH from the LIR is a reducing agent as it is oxidised and forms NADP. This returns and replenishes LIR.

Question 20

What is happening to ATP when G3P is being reduced in the Calvin Cycle?

Answer 20

ATP from the LIR is an oxidising agent as it is reduced and forms ADP. This returns and replenishes the LIR

Question 21

What are the limiting factors of Photosynthesis?

Answer 21

[CO2]
T’
Light Intensity

Question 22

How does CO2 affect the rate of photosynthesis?

Answer 22

Without CO2 RuBP cannot be converted into G3P

Question 23

How does temperature affect the rate of photosynthesis?

Answer 23

Rubisco wont work at low T’ as theres not enough Ea
Rubisco is an enzyme and will denature if T’ is too high and break down.
Approx. rate doubles for every 10’ increase

Question 24

How does light affect the rate of photosynthesis?

Answer 24

Light is needed in the LDR
The graph Rate/Light will plateau as other factors stop the rate
The more photons of the light; the more chlorophyll are ionised.

Question 25

What is Photo-Phosphorylation?

Answer 25

In the process of photosynthesis, the phosphorylation of ADP to form ATP using the energy of sunlight is called photophosphorylation

Question 26

What Mnumonic helps you remember the Calvin Cycle?

Answer 26

Remember             RuBP
Remember             Rubisco
Crazy                     CO2
Girls                        G3P
Always                   ATP-> ADP
(K)Now                   NAD-> NADH
This                       2 TP
Cycle                     C