Photosynthesis

Question 1

What are some key adaptations of the leaf that maximises photosynthesis?

Answer 1

> The large surface area that absorbs as much sunlight as possible
Thin as most light is absorbed in.
A transparent cuticle and epidermis that let light through
Numerous stomata for gaseous exchange

Question 2

What is the structure of chloroplasts and the role of chloroplasts in photosynthesis ?

Answer 2

> Surrounded by a double membrane
grana: stacks of up to 100 disc-like substructures called
thylakoid -> where the light-independent stage of photosynthesis takes place
The stroma-fluid-filled matrix is the light-independent stage of photosynthesis

Question 3

What is oxidation?

Answer 3

Oxidation - gains oxygen or loses hydrogen in the process

Question 4

What is reduction?

Answer 4

substances lose oxygen or gain hydrogen

Question 5

What are the 7 steps on the light-dependant reaction?

Answer 5

1. Photons of light hit the chlorophyll molecules in photosystem 2 causing electrons to become excited - called photoionisation and electrons leave chlorophyll

2.Photolysis is the splitting of water using light, producing hydrogen protons - which reduces NADP - NADPH), oxygen and electrons (used in electron transport chain)

3.Electrons are now passed along several electron carriers in a series of oxidation-reduction reactions. These electron carriers form a transfer chain that is located in the membranes of the thylakoids

4.Each new carrier is at a slightly lower energy level than the previous one in the chain, so electrons lose energy at each stage

5. Some energy is used to pump protons from the stroma using protein carried in the thylakoid membrane using proton pumps.

6.An electrochemical gradient is created. The protons pass through the enzyme ATP synthase which results in the production of ATP

7.The protons combine with the co-enzyme NADP to become NADPH. Because the protons move from high to low concentration this is known as chemiosmosis

Question 6

Where does the light-dependent reaction occur?

Answer 6

Thylakoid

Question 7

Where does the light-independent reaction takes place?

Answer 7

(stroma - temp sensitive)

Question 8

What occurs in the calvin cycle?

Answer 8

> Carbon dioxide reacts with RUBP{catalysed by Rubisco) (5C) - 2 molecules of GP
GP is reduced to TP using energy from ATP and by accepting a H from NADPH
Some of the carbon from TP leaves the cycle each turn be converted into useful organic substances (hexose sugar)
The rest of the molecules are used to regenerate RuBP using ATP