The Calvin Cycle

Question 1

Calvin cycle involves

Answer 1

11 enzyme catalyst reactions that use NADPH to reduce CO2 to glucose through 3 turns. Endergonic

Question 2

Calvin cycle reaction

Answer 2

1 CO2—1C6H12O6

Question 3

After 3 turns

Answer 3

A G3P molecule is produced. 2 of these are needed to make one glucose

Question 4

3 phases

Answer 4

They each happen during every turn. Fixation, reduction, and regeneration

Question 5

Fixation

Answer 5

A carbon from CO2 is fixed to ribulose 1,5 biphosphate (RuBP) to produce 2 3 carbon 3 phosphoglycerate

Question 6

Reduction

Answer 6

3-Phosphate glyceride gets a p from ATP becoming ADP producing 1, 3 Biphosphate glyceride. Sodium electrons from NADPH reduces them to G3P

Question 7

Regeneration

Answer 7

A multistep process where 5 carbons rearrange to from RuBP

Question 8

In 3 turns

Answer 8

3 CO2 + 3 RuBP— 6 3phosphoglyerides using 6 ATP.

Question 9

Next step in 3 turns

Answer 9

6NADPH + 1, 3 phosphoglycerate— 6G3P molecules. Using ATP 5 G3P are turned into 3 RuBP

Question 10

Overall

Answer 10

One extra G3P is produced and 9 ATP and 6 NADPH were used

Question 11

Monosaccharides next steps

Answer 11

Becomes a disaccharide like sucrose or a polysaccharide like starch or cellulose , or consume G3P and change

Question 12

Things G3P can become

Answer 12

Amino acids, fatty acids, lipids in the cytoplasm or cytosol

Question 13

Sucrose

Answer 13

Glucose linked to fructose. Most common product to circulate from cell to cell. Stores organic molecules

Question 14

RuBP

Answer 14

Most common protein on earth making up 50% of plant protein. Catalyzes the fixation of CO2.

Question 15

Rubisco

Answer 15

A very slow enzyme

Question 16

Rubisco shape

Answer 16

Cube with 8 small and 8 large sub units

Question 17

Large subunits

Answer 17

Active site with defined bonding sites for CO2 and RuBP

Question 18

Small subunit

Answer 18

Regulatory by not a catalyst

Question 19

Rubisco synthesis

Answer 19

Uses genes from 2 different genomes. Large subunit encoded in the chloroplast and the small encoded in the cytosol, and then imported to the chloroplast for unification

Question 20

Why is rubisco slow?

Answer 20

It is not only an enzyme for CO2, but also photo respiration

Question 21

Photorespiration

Answer 21

Oxygen bonds with rubisco and a 2 carbon compound from the cytoplasm is made into CO2 using ATP

Question 22

Rubisco evolution

Answer 22

Long time ago because many bacteria and archaea have them

Question 23

Why does rubisco accept oxygen

Answer 23

In its evolutionary phase there was little oxygen present therefore it was not a problem the enzyme needs to fix

Question 24

Oxygen and rubisco

Answer 24

A competitive inhibitor in a process called oxygenase

Question 25

Oxygenase

Answer 25

Results in 1, phosphoglycerate and 1, 2 carbon phosphoglycolate. No carbon gain

Question 26

Phosphoglycolate

Answer 26

Cant be processed by cells. When it is broken down by cells toxic glycolate is produced and takes carbon with it as it is expelled

Question 27

Rubisco in the lab

Answer 27

In equal parts has a higher affinity for CO2, but in the real world there is much more oxygen that CO2 in the air.

Question 28

Rubisco reaction rates

Answer 28

1/4 is oxidation, 3/4 is carboxylation

Question 29

Carbon-concentrating mechanisms

Answer 29

In algae because water doesn’t have enough CO2

Question 30

Carbon-concentrating mechanisms function

Answer 30

It pumps inorganic carbon in keeping the concentration in the cell high

Question 31

Bicarbonate

Answer 31

Most used carbon in water plants. Pumped into the cytosol to become CO2 by an ATP dependent transported on the plasma membrane. CO2 then diffuses to the rubisco site to keep the concentration high

Question 32

2 problems of land plants

Answer 32

Photorespiration and water loss. They are connected

Question 33

Stomata

Answer 33

Holes in the plant leaves to allow for gas exchange. The diffusion determines the direction of CO2 in or )2 and H2O out

Question 34

Stomata regulation

Answer 34

Done by the plants when they need, and nothing more

Question 35

Why is oxidation worse in heat

Answer 35

All gas concentration decreases in heat but CO2 more rapidly. Therefore there is more oxygen bonding to the rubisco

Question 36

C4 cycle

Answer 36

A second carbon fixation pathway to reduce photorespiration

Question 37

C4 cycle process

Answer 37

CO2 and 3 carbon PEP — oxaloacetate– malate– transportation to the Calvin cycle– oxidation– pyruvate and CO2— PEP

Question 38

Oxaloacetate

Answer 38

First product of C4. A 4 carbon chain

Question 39

C3 vs C4

Answer 39

Distinguishes plants with or without the C4 cycle

Question 40

Key distinction C3 and C4

Answer 40

Carboxylation reaction. C4 uses PEP carboxylase which is faster and can’t accept oxygen

Question 41

C4 location

Answer 41

The mesophyll cells (the ones near the surface of the plant

Question 42

Malate movement

Answer 42

Into the bundle sheath cells (not exposed to oxygen) where the calvin cycle makes them pyruvate and CO2

Question 43

Why don’t all plants use C4

Answer 43

Every cycle uses 1 more ATP, it is good in the heat because there is lots of light and ATP with low CO2. But in colder climates it is worse

Question 44

Why is C4 better for dry climates

Answer 44

In C3 the stroma had to stay open longer losing water

Question 45

CAM plants

Answer 45

Crassulaceae acid metabolism. Plants switch between C3 and C4 reaction

Question 46

CAM at night

Answer 46

Stomata’s open to release oxygen and bring in CO2, C4 works to make malate, and pyruvate is turned back into malate

Question 47

In the day CAM

Answer 47

Stamata’s close, malate diffuses and is oxdized to pyruvate molecules, the Calvin cycle occurs

Question 48

Plants

Answer 48

Photosynthesis in ones with chloroplast, cellular respiration happens in them all.

Question 49

Photosynthesis vs cellular respiration

Answer 49

Opposite products vs reactants, both involve an ETC and G3P