energy transfers in and between organisms 3.5

Question 1

what reaction occurs in the thylakoid?

Answer 1

light dependent reaction

Question 2

what reaction occurs in the stroma?

Answer 2

light independent reaction

Question 3

what are the four stages of LDR?

Answer 3

photolysis , photoionisation of chlorophyll, chemiosmosis and production of ATP and reduced NADP

Question 4

what happens in photolysis of water?

Answer 4

• light energy absorbed by chlorophyll splits water into oxygen electrons and H+ ions
• H+ ions picked up by NADP to form reduced NADP and used in LIR
• electrons pass along chain of electron carrier protein
• oxygen is either used for respiration or diffuses out of stomata

Question 5

what happens in photoionisation of chlorophyll?

Answer 5

• light energy absorbed by chlorophyll results in electrons becoming excited and raising an energy level to leave chlorophyll
• therefore chlorophyll ionised by light
• some of the energy released from electrons is used to make ATP and reduced NADP in chemiosmosis

Question 6

what happens in chemiosmosis?

Answer 6

• electrons that gained energy and left the chlorophyll move along a series of proteins embedded within the thylakoid membrane
• as they move along they release energy and some of this energy is used to pump protons across the chloroplast membrane (stroma to thylakoid membrane)
• an electrochemical gradient is created, the protons pass through the enzyme ATP synthase via facilitated diffusion resulting in the production of ATP (phosphorylation of ADP)
• the proton comes back to stroma which then combines with co enzyme NADP to form reduced NADP

Question 7

what enzyme is required in the Calvin cycle (LIR)?

Answer 7

RuBisCo

Question 8

what happens in the LIR?

Answer 8

• CO2 reacts with 5C RuBP to form two molecules of 3C GP this reaction is catalysed by RuBisCo
• GP is reduced to TP using ATP energy and by accepting a H from reduced NADP
• one carbon from TP leaves cycle to be converted to useful organic substances
• rest of TP is regenerated back to RuBP with the use of ATP

Question 9

what are the limiting factors of photosynthesis?

Answer 9

light intensity carbon dioxide and temperature