5-A photosynthesis

Question 1

equation for photosynthesis

Answer 1

6CO2 + 6H2O + energy —> C6H12O6 + 6O2

Question 2

light dependent reaction

Answer 2

1. photoionisation - light strikes chlorophyll exciting the electrons
2. excited electrons pass along electron transfer chain
3. provides energy for protons to be pumped into thylakoids space from stroma (creating a high concentration)
4. light strikes water in thylakoid space splitting it (photolysis)
5. oxygen diffuse out of thylakoid hydrogen splits into protons and electrons
6. addition of protons increases the concentration in thylakoid space
7. protons diffuse down a concentration gradient through ATP synthase providing energy to regenerate ATP
8. protons and electrons bond with NADP to form a NADPH

Question 3

LDR 1

Answer 3

Photo ionisation-light strikes the chlorophyll exciting electrons

Question 4

LDR 2

Answer 4

excited electrons pass along electron transfer chain

Question 5

LDR 3

Answer 5

movement of electrons across ETC provides energy for protons to be pumped into thylakoids space from stroma (creating a high concentration)

Question 6

LDR 4

Answer 6

light strikes water in thylakoid space splitting it (photolysis)

Question 7

LDR 5

Answer 7

oxygen diffuse out of thylakoid hydrogen splits into protons and electrons

Question 8

LDR 6

Answer 8

addition of protons from photolysis increases the concentration in thylakoid space

Question 9

LDR 7

Answer 9

protons diffuse down a concentration gradient through ATP synthase providing energy to regenerate ATP

Question 10

LDR 8

Answer 10

protons (now in stroma) and electrons (from movement across ETC) bond with NADP to form a NADPH

Question 11

light independent reaction

Answer 11

1. CO2 combines with RuBP (carboxylation) to form 2x glycerate 3 phosphate (catalysed by rubisco)
2. GP is converted to triose phosphate x2 using energy released from ATP>ADP + Pi and reducing power of NADPH (both from LDR)
3. NADP and ADP and Pi are reused in LDR
4. ATP from LDR regenerates RuBP from TP releasing one carbon molecule
5. 6 LIR cycles form one glucose molecule and 6 RuBP

Question 12

LIR 1

Answer 12

carboxylation catalysed by rubisco - CO2 combines with Ribulose bio phosphate (RuBP) to form 2x glycerate 3 phosphate

Question 13

LIR 2

Answer 13

GP is converted to triose phosphate x2 using energy released from ATP>ADP + Pi and reducing power of NADPH>NADP (both from LDR)

Question 14

LIR 3

Answer 14

NADP and ADP and Pi are reused in LDR

Question 15

LIR 4

Answer 15

ATP from LDR regenerates RuBP from TP releasing one carbon molecule

Question 16

LIR 5

Answer 16

6 LIR cycles from one glucose molecule and 6 RuBP

Question 17

effect of a reduction of carbon dioxide on photosynthesis

Answer 17

GP - decrease because less carboxylation of RuBP
TP - decrease because less GP is made
RuBP - increase because less will bind with CO2 to make GP
LDR- will run out of ADP + Pi and NADP to convert to ATP and NADP

Question 18

effect of reduced light intensity on photosynthesis

Answer 18

GP - increase because less will be converted to TP
TP - less made because less energy to convert GP (less ATP and NADPH will be made in LDR)
RuBP - eventually runs out because it isn’t regenerated from TP
LDR - reduced because photoionsation and photolysis will be reduced

Question 19

effect of temperature increase on photosynthesis

Answer 19

GP - rubisco will denature so RuBP can’t be carboxylated to GP
TP - no GP to be converted to TP
RuBP - increase because rubisco won’t catalyse reaction to make GP
LDR - increase rate of reaction until optimum is exceeded and ATP synthase denatures

Question 20

effect of temperature decrease on photosynthesis

Answer 20

GP - decrease as rubisco is catalysing RuBP to GP slower
TP - less ATP and NADPH from LDR so less is made
RuBP - increases because it is carboxylated slower
LDR - ATP synthase is slower so ATP is produced slower