Photosynthesis

Question 1

How does Light Dependent Reaction occur?

Answer 1

Photoionisation of reaction centre photosynthetic pigments due to the absorption of light energy supplies excited electrons

These are replaces by photolysis of water

Excited electrons travel down an electron transport chain and transfer some of their energy to create a proton gradient across the thylakoid membrane

The energy in the proton gradient is used to produce ATP

Excited electrons and hydrogen ions are used to reduce NADP

Question 2

What is an Autotroph and what are the examples of it?

Answer 2

Carry out photosynthesis and use simple inorganic molecules to synthesise complex organic molecules such as glucose.

Examples: plants and algae

Question 3

What are Heterotrophs and what are some examples of it?

Answer 3

Organisms which obtain molecules by digesting and absorbing complex organic molecules - organic molecules used for growth and respiration

Examples: animals and fungi

Question 4

Where does light dependent stage occur?

Answer 4

Thylakoid

Question 5

What’s the equation for photosynthesis?

Answer 5

6CO2 + 6H20 ——> C6H12O6 + 6O2

Question 6

What are photosynthetic pigments? Some examples of it?

Answer 6

Chemicals that absorb light energy, found in the thylakoid membrane of chloroplasts, absorbs light of a particular range or wavelengths of light energy

Examples: Chlorophyll A, Chlorophyll B, Carotene and Xanthophyll

Question 7

What are accessory pigments?

Answer 7

They surround the primary pigment and absorb light energy and pass the energy from one to another and then onto the primary pigment

Example: Carotenoids

Question 8

What are primary pigments?

Answer 8

Reaction centres where electrons are excited to higher energy levels during the light dependent reaction

Example: Chlorophyll A

Question 9

What is photolysis of water?

Answer 9

Because electrons have been lost from chloroplast due to photoionisation, these electrons are replaced by water. Water molecules are slit using light energy to produce protons, electrons and hydrogen ions. Protons are used in chemiosmosis.

Question 10

What are coenzymes?

Answer 10

Molecule that aids the function of an enzyme. Works by transferring a chemical group from one molecule to another. Example is NADP

Question 11

Non-cyclic photosphorylation?

Answer 11

PSII and PSI are linked through a series of protein electron carriers on the thylakoid membrane forming electron transport chain. Electrons move from PSII to PSI, as they do so energy is lost as each electron becomes reduced and oxidises as it moves. This energy is used to add phosphate to ADP to form ATP and reduce the co-enzyme NADP to reduced NADP

Question 12

What does non-cyclic photophosphorylation produce?

Answer 12

ATP, NADP, O2

Question 13

What is Chemiosmosis?

Answer 13

As electrons flow down the electron transport chain from PSII to PSI, some energy is used to actively transport H+ ions into the thylakoid space which produces a proton gradient. Protons move down the concentration gradient into the stroma through ATP synthase. Energy from the movement is used to form ATP

Question 14

What is cyclic phosphorylation?

Answer 14

Does not involve PSII. Electrons in PSI pass through in a circle to produce ATP not reduced NADP. Electrons are passed back to PSI via electron carriers

Question 15

What is the energy resulting from LDR used for?

Answer 15

1. ) Making ATP from ADP and inorganic phosphate
2. ) Reduced NADP from Oxidised NADP
3. ) Photolysis - into protons, electrons and oxygen