Photosynthesis

Where does the LDR occur?

Thylakoid membrane

Where does the LIR occur?

Stroma

What are the 3 stages and product of the Light Dependent reaction?

• Photolysis

• Photoionisation of chlorophyll

• Chemiosmosis

• Products: ATP and NADPH

Give the equation of photolysis and why it occurs

• Chlorophyll in the thylakoid membrane absorbs light energy

• 2H₂O → 4H⁺ + O₂ + 4e^-

What happens to the hydrogen ions from photolysis?

Reduces NADP to form NADPH 

What happens to the oxygen from photolysis?

• Used for respiration

• Diffuses out of stomata

What happens to the electrons from photolysis?

• Replaces chlorophyll’s lost electrons

• Used in ETC in chemiosmosis

What 3 things is the energy in excited electrons from photoionisation used for? 

• Photolysis

• Producing NADPH

• Phosphorylation

What is phosphorylation

Adding Pi to ADP to make ATP using light energy

What gradient is made in chemiosmosis?

Electrochemical gradient

What products from the LDR are used in the LIR?

ATP and NADPH

How many carbons does RuBP/Ribulose Bisphosphate have?

5

What is enzyme Rubisco used to catalyse the reaction between and what does this form

• Carbon dioxide and RuBP/Ribulose Bisphosphate

• Highly unstable 6 carbon molecule → 2 G3P molecules

What are the G3P molecules reduced with?

• Energy from hydrolysis of ATP

• H from reducing agent NADPH

What are the G3P molecules reduced to?

2 triose phosphate molecules (3 carbons)

What happens each cycle when one carbon leaves the triose phosphates?

• Carbon molecules form glucose after 6 cycles

• Remaining 5 carbons regenerate RuBP with energy from hydrolysis of ATP

3 limiting factors of photosynthesis?

• Light intensity

• CO₂ Concentration

• Temperature