Photosynthesis

Question 1

Light-dependent reaction produces….

Answer 1

NADPH, oxygen, ATP, H+

Question 2

Light-independent reaction produces…

Answer 2

trisphosphate sugar, NADP, ADP

Question 3

Calvin cycle

Answer 3

Light-independent reaction that converts carbon dioxide to triosephosphate
Cycles 6 times to make up one sugar

Question 4

Steps in Calvin cycle (in order):

Answer 4

1. Carboxylation
2. Reduction
3. Regeneration

Question 5

In carboxylation, carbon dioxide is…

Answer 5

fixed through using rubisco (enzyme) and ribulose bisphosphate

Question 6

The end product of carboxylation is an….

Answer 6

unstable 6C compound which immediately breaks into to two 3C compound (phosphoglycerate)

Question 7

Glycerate-3-phosphate (phosphoglycerate) combines with (…) to make (…)

Answer 7

ATP and NADP, triose phosphate

Question 8

Ribulose 1,5, bisphosphate can be remade through…

Answer 8

using ATP on the 5C of glycerate-3-phosphate to make 3 ribulose bisphosphate

Question 9

Calvin cycle uses (…) ATP for the first time, (…) NADPH and (…) ATP for the last time in one cycle

Answer 9

6,6,3

Question 10

Rubisco properties

Answer 10

Catalyses CO2 fixation
Available in the stroma
Can oxygenase

Question 11

Rubisco’s fatal flaw is….

Answer 11

Oxygenation, fixing oxygen to become 2-phosphoglycolate

Question 12

Photorespiration

Answer 12

When rubisco oxygenates, toxin is produced and needs to be detoxified

Question 13

Photorespiration is bad because…

Answer 13

it produces toxins that needs to be detoxified (through peroxisome, mitochondria and chloroplast) hence expending more ATP and result more CO2

Question 14

C2 Cycle is also called as…

Answer 14

oxidative photosynthetic carbon cycle, since photorespiration is abundant process

Question 15

C2 vs C3

Answer 15

C2 - photorespiration, used for plants in extremely hot and dry environments, 2C
C3 - common 3C carbon fixation cycle. Calvin cycle

Question 16

C4 photosynthesis have…

Answer 16

PEP (Phosphoenolpyruvate) carboxylase
Spatial segregation

Question 17

What does PEP carboxylase do?

Answer 17

It only fixes carbon dioxide/bicarbonate so it combines CO2 to PEP (3C) to make a 4C compound (malate) then transfers it to low CO2 concentration (near chloroplast) area where malate decarboxylates. PEP carboxylase have a higher affinity to carbon dioxide than rubisco. Malate is then recycled back.

Question 18

How does the segregation help concentrate the CO2 in one area?

Answer 18

The spatial segregation helps divide the concentration of CO2 between the two spaces. The top space is mesophyll cell and the bottom is bundle sheath cell, where Calvin cycle occurs. Mesophyll cell collects the CO2 using the PEP carboxylase.

Question 19

How does C4 come about?

Answer 19

Due to the influx of photorespiration, photosynthesis and photorespiration are competing with each other

Question 20

CAM (Crassulacean acid metabolism)

Answer 20

Have temporal segregation as stomata opens at night time to reduce water loss. Malate is stored in the vacuole and decarboxylated during the day