Photosynthesis and Light Independent Reaction

Question 1

What is the light independent reaction also known as?

Answer 1

The Calvin Cycle

Question 2

What does the light independent reaction take place?

Answer 2

In the stroma of the chloroplasts.

Question 3

What are the 6 steps of the light independent reaction?

Answer 3

1. Carbon dioxide combines with ribulose bisphosphate/RuBP;
2. Produces two glycerate (3-)phosphate/GP;
3. GP reduced to triose phosphate/TP;
4. Using reduced NADP;
5. Using energy from ATP;
6. Triose phosphate converted to glucose.

Question 4

What are the products of the light independent reaction and what are they used for?

Answer 4

ATP and reduced NADP and they’re used to reduce carbon dioxide.

Question 5

What is a hexose sugar?

Answer 5

A hexose sugar is a monosaccharide that has six carbon atoms.
Is it made by joining two molecules of triose phosphate together.

Question 6

How many times does the Calvin cycle have to turn to make one hexose sugar?

Answer 6

6 times.

Question 7

What is the name of the 5-carbon compound that combines with carbon dioxide to form an unstable 6 carbon compound in the first reaction of the Calvin cycle?

Answer 7

Ribulose biphosphate/ RuBP

Question 8

The 6 carbon compound produced only exists fleetingly before it breaks down into two molecules of a 3-carbon compound. What is the name of this 3 carbon compound?

Answer 8

Glycerate 3-phosphate/GP

Question 9

Is the formation of two molecules of triose phosphate an oxidation or reduction reaction?

Answer 9

Reduction

Question 10

Describe the role of ATP in the Calvin cycle.

Answer 10

ATP is needed for the reduction of glycerate 3-phosphate/GP to triose phosphate/TP.
It’s also needed for the regeneration of ribulose biphosphate/RuBP from triose phosphate/TP.

Question 11

To make one hexose sugar how many molecules of ATP are needed?

Answer 11

18

Question 12

Describe how the products of the Calvin cycle are used to make large carbohydrates?

Answer 12

Two triose phosphate molecules are joined together to produce a hexose sugar.
Large carbohydrates are then made by joining the hexose sugars together.

Question 13

Describe how the products of the Calvin cycle are used to make lipids?

Answer 13

Lipids are made from glycerol and fatty acids.

Glycerol is synthesised from triose phosphate, while fatty acids are made from glycerate 3-phosphate.

Question 14

Describe how the products of the Calvin cycle are used to make proteins?

Answer 14

Some amino acids are made from glycerate 3-phosphate, which are joined together to make proteins.

Question 15

Describe the role of electron transport chains in the light-dependent reactions of photosynthesis.

Answer 15

1 electron transport chain accepts excited electrons;
2 from chlorophyll / photosystem;
3 electrons lose energy along chain;
4 ATP produced;
5 from ADP and Pi;
6 reduced NADP formed;
7 when electrons (from transport chain) and H combine with NADP;
8 H from photolysis;

Question 16

Explain how ATP and reduced NADP are used in the light-independent reaction of photosynthesis

Answer 16

GP converted to triose phosphate (reduction)
Reduced NADP provides reducing power
ATP supplies energy for this reaction
phosphate from ATP
for production of RuBP