13.3 Photosynthesis

Question 1

What does ATP stand for?

Answer 1

Adenosine Triphosphate

Question 2

What makes up ATP?

Answer 2

A ribose sugar
3 phosphate groups
Nitrogenous base (adenine)

Question 3

Name the 2 uses of ATP

Answer 3

Provides energy for active transport/muscle contraction/protein synthesis
Phosphorylation

Question 4

What its phosphorylation?

Answer 4

When a phosphate molecule binds to an enzyme to lower the activation energy and increase the reactivity by altering the tertiary structure

Question 5

How is ATP formed?

Answer 5

via ADP and phosphate group (Pi)

Question 6

Why is ATP easily broken?

Answer 6

The bond between the second and third phosphate group is easily broken and releases small amounts of energy

Question 7

Why is ATP useful?

Answer 7

• Releases small amounts of energy
• Easily reformed
• Single step process
• Immediate release of energy
• Phosphorylates to make enzyme more reactive

Question 8

Contrast the structure of ATP and DNA

Answer 8

DNA has a deoxyribose sugar whereas ATP has a ribose sugar
DNA has 1 phosphate molecule whereas ATP has 3
ATP always has adenine as its base whereas DNA either has cytosine, thymine, guanine or adenine

Question 9

What does NADP stand for?

Answer 9

Nicotinamide Adenine Dinucleotide Phosphate

Question 10

What does NADP act as?

Answer 10

Hydrogen acceptor

Question 11

What is NADPH?

Answer 11

Reducing agent

Question 12

What happens when NADPH loses a hydrogen?

Answer 12

Becomes oxidised to NADP

Question 13

What is NADP?

Answer 13

Coenzyme
- molecule that binds to support the function of an enzyme

Question 14

Name all the components of a chloroplast

Answer 14

Granum
Thylakoid
Thylakoid membrain
Stroma
Free DNA
70s ribosomes
Starch grains
Inner and outer membrane

Question 15

What is the word equation for photosynthesis?

Answer 15

Carbon dioxide + water –> Glucose + oxygen

Question 16

What is the number equation for photosynthesis?

Answer 16

6CO2 + 6H2O –> C6H12O6 + 6O2

Question 17

What are the two stages of photosynthesis?

Answer 17

Light dependent reaction
Light independent reaction

Question 18

Photoionisation definition

Answer 18

When light energy excites energy levels of electrons in chlorophyll

Question 19

Photolysis definition

Answer 19

The splitting up of water with light to produce 2 protons, 2 electrons and 1/2 oxygen

Question 20

Phosphorylation definition

Question 21

Where does LDR take place?

Answer 21

In the thylakoid membrane

Question 22

what does the LDR result in?

Answer 22

Production of ATP and NADPH

Question 23

Describe the light dependent reaction

Answer 23

1. Chlorophyll absorbs light energy via photoionisation
2. Excites electrons to a higher energy level, the chlorophyll is oxidised
3. The electrons travel down an electron transport chains, releasing energy
4. Energy is released by the electrons used to form the proton gradient
5. H+ ions diffuse through ATP synthase (photophosphorylation)
6. This provides energy too join ADP and Pi, to form ATP
7. Photolysis of the water produces 2 protons, 2 electrons and 1/2 oxygen molecules
8. NADP reduced by electrons and protons

Question 24

Photolysis equation

Answer 24

2H2O –> 2H+ + 2e- + 1/2O2

Question 25

What are the two essential things needed for the LDR?

Answer 25

NADPH ATP

Question 26

Chemiosmotic theory definition

Answer 26

The movement of ions (protons) across a membrane down an electrochemical gradient (usually established through redox reactions and activation of proton pumps)

Question 27

What does weed killer do?

Answer 27

Stop electrons being released from the chlorophyll Less ATP No reduced NADP can be formed

Question 28

What does the use of fluorescence do?

Answer 28

Electron transport chain not available for excited electron Electron cannot leave chlorophyll and lose energy via the electron transport chain This releases energy as light or heat

Question 29

In plants, ATP is produced in the LDR, suggest why this is not the plants only source of ATP?

Answer 29

Plants doing photosynthesise in the dark Not all parts of the plant photosynthesise (roots) Plants require more ATP than is produced in the LDR ATP is used in active transport

Question 30

Describe the effect of introducing a herbicide on the electron transport chain

Answer 30

Reduced transport of protons across thylakoid membrane Reduced chemiosmotic gradient Reduced ATP produced Reduced NADP produced Slower LDR

Question 31

What are the three stages of the light independent reaction?

Answer 31

Carbon fixation Reduction Regeneration

Question 32

Describe the light independent reaction

Answer 32

Carbon dioxide combines with RuBP with the enzyme ribisco to form 2 GP molecules. hey are reduced to two ribose phosphate molecules with the energ from ATP and reduced NADP. Some triose phosphate molecules are converted into amino acids, or starch or cellulose. Most triose phosphate molecules are regenerated into RuBP via the phosphate from AP

Question 33

How is the Calvin cycle controlled?

Answer 33

Enzymes

Question 34

Describe fixation in the Calvin cycle

Answer 34

RuBP acts as a carbon dioxide acceptor and is catalysed by the enzyme rubisco. he CO2 reacts with the RuBP to form two molecules of GP.

Question 35

Describe reduction in the Calvin cycle

Answer 35

The two GP molecules are reduced to 2 triose phosphate molecules, this required NADP and the energy from ATP. Some of the triose phosphate molecules are converted into useful organic compounds - carbohydrates,amino acids and triglycerides

Question 36

Describe the regeneration stage of the Calvin cycle

Answer 36

Most triose phosphate molecules are used to regenerate RuBP using phosphate from ATP

Question 37

How is the chloroplast adapted to maximising the rate of photosynthesis in the stroma?

Answer 37

The chloroplast has its own DNA to transcribe and translate its own proteins needed in the light independent reaction It also has a large surface area to allow as much light as possible to be absorbed, this increases the rate of the light dependent reaction and therefore photosynthesis.

Question 38

What are the three factors affecting the rate of photosynthesis?

Answer 38

- Temperature - Carbon dioxide concentration - Light intensity and wavelength