ETIABO: Photosynthesis - Light-independent Reaction

Question 1

Where does the LIR occur?

Answer 1

Stroma

Question 2

What are the two stages of photosynthesis?

Answer 2

• Light dependent reaction
• Light independent reaction

Question 3

What are the two products needed for the light-independent reaction to occur?

Answer 3

• ATP
• 2x Reduced NADP (aka NADPH)

Question 4

What is the Calvin cycle another name for?

Answer 4

Light-independent reaction

Question 5

Where does the LIR occur in a chloroplast?

Answer 5

Stroma

Question 6

What are the three main substances involved in the LIR?

Answer 6

• Ribulose biphosphate (RuBP)
• Glycerate 3 phosphate (GP)
• Triose phosphate (TP)

Question 7

What enzyme catalyses the conversion of RuBP into GP?

Answer 7

Rubisco

Question 8

When carbon dioxide enters the stroma it reacts with ______ to form __ _____ molecules, catalysed by rubisco.

Answer 8

Ribulose biphosphate (RuBP)
2 Glycerate 3 phosphate (GP)

Question 9

How many carbons does RuBP have?

Answer 9

5

Question 10

How many carbons does 1 GP molecule have?

Answer 10

3

Question 11

Carbon dioxide reacts with RuBP in the stroma to form what?

Answer 11

Two GP molecules.

Question 12

How does GP become TP?

Answer 12

• Two molecules of NADPH gives a proton each to a GP molecule. This forms two NADP molecules and two GP molecules.
• ATP is used

Question 13

What is the difference between GP and TP?

Answer 13

GP has a negatively charged oxygen molecule
TP has a hydrogen molecule

This is why NADPH is needed- NADPH gives the proton (H) to GP, so GP is reduced and can form TP.

Question 14

ATP is needed for the reduction reaction of GP being converted into TP. Where does this ATP come from?

Answer 14

Product of the LDR.

Question 15

How does ATP provide energy for processes?

Answer 15

Hydolyses into ADP + Pi

Question 16

What molecules are produced from the LIR that are needed for the LDR?

Answer 16

• ADP
• Pi
• NADP

Question 17

Most triose phosphate goes on to produce ______, little of it goes on to produce _______ ________.

Answer 17

Ribulose biphosphate (RuBP)
Organic subtances

Question 18

A little bit of the triose phosphate made goes on to produce organic substances. What three organic substances are made?

Answer 18

• Glucose
• Amino acids
• Glycerol

Question 19

Glucose is one of the 3 organic substances made by triose phosphate. Why is glucose produced?

Answer 19

Used in respiration

Question 20

Amino acids are one of the 3 organic substances made by triose phosphate. Why are amino acids produced?

Answer 20

Used to create proteins

Question 21

Glycerol is one of the 3 organic substances made by triose phosphate. Why is glycerol produced?

Answer 21

Used to form triglycerides- good energy storage and water source

Question 22

Most of the triose phosphate molecules formed are used to make ribulose biphosphate. This requires energy in the form of _____.

Answer 22

ATP

Question 23

What are the three main limiting factors for photosynthesis?

Answer 23

Light
Carbon dioxide
Temperature

Question 24

What are the end products produced by the LIR?

Answer 24

• ADP
• Pi
• NADP
• Ribulose biphosphate
• Organic subtances: glucose, amino acids, glycerol

Question 25

What impact does increased light intensity have on the rate of photosynthesis? Why?

Answer 25

Increases the rate of photosynthesis overall. - Light is needed for photoionisation and photolysis. More light means these processes can happen at a greater rate. - These processes produce ATP and NADPH, allowing for the LIR to happen at a greater rate. - Will increase the rate of photosynthesis until a limiting factor occurs.

Question 26

Why is carbon dioxide needed?

Answer 26

Used in the conversion of RuBP into GP

Question 27

What impact does increased carbon dioxide concentration have on the rate of photosynthesis? Why?

Answer 27

Increases the rate of photosynthesis overall. - Carbon dioxide is needed in the light-dependent reaction to convert RuBP into GP. - Will increase the rate of photosynthesis until a limiting factor occurs.

Question 28

What impact does increased temperature have on the rate of photosynthesis? Why?

Answer 28

Increases the rate of photosynthesis up to optimum temperature, decreases rate of photosynthesis when temp is too high. - Higher temperatures provides more kinetic energy to molecules, allowing enzyme rubisco to catalyse at a greater rate. - Too high temperatures will mean enzyme rubisco is denatured, decreasing the rate of reactions in the LIR. - Too high temperatures will also negatively impact the thylakoid membrane e.g damage chlorophyll-containing proteins in the membrane, preventing the normal functioning of the ETC, decreasing the rate of reactioons in the LDR.