Topic 5 - Energy transfers in and between organisms.

Question 1

What are the two stages of photosynthesis?

Answer 1

The light independent reaction and the light dependent reaction.

Question 2

Give 2 ways how chloroplasts are adapted for photosynthesis?

Answer 2

• Contains grana which provides large surface area for the attachment of chlorophyll, electrons and enzymes.
• Chloroplasts contain DNA allowing them to synthesise proteins needed in light dependent reaction.

Question 3

Where does the light dependent reaction occur?

Answer 3

Thylakoid membranes of the chloroplasts.

Question 4

What is the FIRST step of the light dependent reaction?

Answer 4

The chlorophyll absorbs light, which excites the electron - leading to the photo ionisation of chlorophyll.

Question 5

What is the SECOND step of the light dependent reaction?

Answer 5

• Redox reactions pass electrons down the
  chain from one electron carrier to the next.
• ATP is generated due to the phosphorylation of ADP and inorganic P.
• NADP is converted to reduced NADP.

Question 6

What is the THIRD step of the light dependent reaction?

Answer 6

• Light energy splits water molecules into protons, electrons and oxygen.
• Protons are pumped across the membrane using ATP during the this process (chemiosmosis). This creates a chemical potential gradient.

Question 7

What is the FOURTH step of the light dependent reaction?

Answer 7

Reduced NADP is generated.

Question 8

What is the FINAL step of the light dependent reaction?

Answer 8

ATP is synthesised.

Question 9

What are products of the light dependent reaction that are useful in the light INDEPENDENT reaction?

Answer 9

Reduced NADP and ATP.

Question 10

How is reduced NADP useful in the light INDEPENDENT reaction?

Answer 10

To form simple sugars and provide H+ ions.

Question 11

How is ATP useful in light INDEPENDENT reaction?

Answer 11

The synthesis of ATP provides energy.

Question 12

What is the light INDEPENDENT also referred to as?

Answer 12

The Calvin cycle.

Question 13

Where does the light INDEPENDENT reaction take place?

Answer 13

The stroma of the chloroplasts.

Question 14

What’s the FIRST step of the light INDEPENDENT reaction?

Answer 14

5-carbon RuBP combines with carbon dioxide. This reaction is catalysed by the enzyme rubisco.

Question 15

What’s the SECOND step of the light INDEPENDENT reaction?

Answer 15

The RuBP gets converted into 2 glycerate 3-phosphate (GP).

Question 16

What’s the THIRD step of the light INDEPENDENT reaction?

Answer 16

Reduced NAPD and ATP are used to reducce GP into triose phosphate (TP). During this reduction, NADP is oxidised simultaneously.

Question 17

What’s the FOURTH step of the light independent reaction?