Calvin Cycle and Photorespiration

Question 1

Rubisco

Answer 1

RuBP carboxylase/oxygenase

Question 2

RuBP

Answer 2

Ribulose 1, 5 Bisphosphate

Question 3

End product of Calvin Cycle

Answer 3

PGAL

Question 4

Step 1 of Calvin Cycle

Answer 4

CO2 fixed to RuBP by Rubisco

-Makes 6 C sugar that breaks into 2 PGA per RuBP

Question 5

Step 2

Answer 5

Reduction

• PGA reduced to PGAL
• REquires 1 ATP and NADPH per PGA
• ADP and NADP+ go back to light reactions

Question 6

Fate of PGAL

Answer 6

1. Regenerates RuBP

2. Leaves CC and goes to cytoplasm to make glucose

Question 7

How many turns to make 6 PGAL

Answer 7

3

Question 8

2 abilities of Rubisco

Answer 8

1. Fix CO2 to RuBP

2. Fix O2 to RuBP

Question 9

Products of Photorespiration

Answer 9

1 PGA (regenerates RuBP)
1 phosphoplycolate (useless and goes through salvage process)

Question 10

Salvage Process

Answer 10

Costly w/ 7 steps and 3 organelles

• Doesn’t generate ATP
• Uses CO2 and releases O2 (bad in hot/dry conditions)

Question 11

Kranz Anatomy

Answer 11

Stomata found on both epidermises

• Mesophyll not divided into layers
• HUGE bundle sheaths
• C4

Question 12

C4

Answer 12

Kranz Anatomy
Enzyme compartmentalization
-Mesophyll chloroplasts have thylakoids and chlorophyll
-Bundle Sheath chloroplasts have Rubisco and enzymes in stroma

Question 13

Normal C3 reactions

Answer 13

Light reactions and calvin cycle occur in same chloroplast

Question 14

C4 Pathway

Answer 14

Light reactions in mesophyll
PEPco carbon fixation in mesophyll
Calvin cycle in bundle sheath

Question 15

PEPco carbon fixation

Answer 15

• Occurs in cytoplasm of mesophyll cells
• Fixes CO2 to PEP via PEP carboxylase
• Makes 4 C acid–> transferred to bundle sheath
• Causes decarboxylation

Question 16

Purpose of C4

Answer 16

Acts as a carbon pump

• CO2 is gathered from mesophyll and pumped into a few bundle sheaths
• CO2 levels in bundle sheaths stays high
• Photorespiration is reduced

Question 17

Benefits of C4

Answer 17

Efficient photosynthesis in hot and dry conditions

3x as h2o efficient

Question 18

Drawbacks of C4

Answer 18

Cost 2 extra ATP for every turn

6 extra ATP per PGAL

Question 19

CAM

Answer 19

Temporal separation of reactions

• All reactions occur in same cell
• pineapples, cacti

Question 20

CAM at night

Answer 20

Plants open stomata for gas exchange
Starch is converted to PEP
CO2 is fixed by PEP
-Resulting malate is stored in vacuole

Question 21

CAM during the day

Answer 21

Plants close stomata
Malate is transferred out of vacuole and decarboxylated
Pyruvate converted to starch

Question 22

Benefit and Drawback of CAM

Answer 22

5x as water efficient but very slow metabolism and growth rates