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Characteristics of C3 plants

1. C3 plants originate from cold temperate countries.
2. C3 plants are unable to adapt to high temperatures.
3. A temperature of 10-25 degrees Celsius is easy for them to survive.
4. Leaves of C3 plants do not have cranial anatomy.
5. They do not have a layer of mesophyll cells surrounding the leaf bundle sheath.
6. Calvin-Basham cycle occurs in the mesophyll cells of C3 plants.
7. Their CO2 emission rate is low.
8. C3 plants have lower rates of photosynthesis.
9. Their respiration and photorespiration occur more.
10. Their chloroplasts are structurally similar.
11. Their photosynthesis is best when atmospheric CO2 concentration is 50-150 ppm.
12. Stomata of C3 plants are open during the day and closed at night.
13. Most reactions in C3 plants are unidirectional.
14. They tend to waste water more and may not be adapted to dry areas.
15. Ribulose bisphosphate carboxylase enzyme activity is substantial in mesophyll cells of C3 plants.
16. Bundlesheath chloroplasts and mesephyll chloroplasts contain starch granules.
17. Rubisco enzyme activity occurs in both bundlesheath and mesophyll cells.
18. Carbon oxidation by C3 plants is inhibited when the atmosphere contains more than 20% O2.

C3 Plants definition

Plants that produce three-carbon 3-phosphogluceric acid as the first stable compound during carbon assimilation in photosynthesis are called C3 plants.

Importance of Calvin-Basham or C3 cycle

1. In this cycle RuBP combines with CO2 to produce PGA. PGA is formed from PGAld.
2. Complex sugars are produced from PGAld through a series of reactions.
3. CO2 is absorbed in the Calvin cycle. As a result, the amount of CO2 in the environment remains normal.
4. RuBP is regenerated through the Calvin cycle and maintains a photoneutral state.
5. Various compounds produced in the Calvin cycle participate in plant metabolism.
6. Xylulose produced in the Calvin cycle helps form plant cell walls.
7. Glucose produced in the Calvin cycle forms cellulose and cellulose through polymer formation.

Where does C3 cycle occur?

The C3 cycle occurs in algae, bryophyta, pteridophyta and gymnosperms. The C3 cycle occurs in most dicots and some monocots. C3 cycle occurs in plants like rice, wheat, barley/sorghum, mango, yam, jackfruit, litchi, banana, jute, algae, bryophyta, pteridophyta, gymnosperms etc.

Rubisco enzyme importance

The acronym for ribulose bisphosphate carboxylase or oxygenase enzyme is rubisco enzyme. Rubisco enzyme is the most important enzyme in the world. These enzymes create chemical bonds between the natural world and living organisms. Hence it is called a bridge or bonding enzyme. 50% or more of the total protein in leaves is rubisco enzyme. The amount of rubisco enzyme in the world is about 40 million tons. With the help of this enzyme, 100 billion tons of CO2 are converted into carbohydrates every year on earth.

C3 cycle steps, steps of C3 cycle

1. Carboxylation
(i) Ribulose 1, 5 bisphosphate reacts with atmospheric CO2 to produce 6-carbon (C6) keto acids under the action of rubisco enzyme. Keto acid is rapidly broken down to 3-phosphoglyceric acid. (RuBisCO is the most important enzyme in the world)
2. Phosphorylation
(ii) 3-phosphoglyceric acid is converted to 1,3-bisphosphoglyceric acid with the help of the enzyme phosphoglycerokinase. At this time, ATP takes part in the reaction and produces ADP.
3. Reduction
(iii) Phosphoglyceraldehyde dehydrogenase enzyme produces 3-phosphoglyceraldehyde and dihydroxyacetone phosphate from 1,3 bisphosphoglyceric acid. At this time, NADPH+H+ takes part in the reaction to form NADP.
4. Carbohydrate production
(iv) Fructose 1, 6 bisphosphate is produced from 3-phosphoglyceraldehyde by the action of aldolase enzyme.
(v) Fructose 1, 6 bisphosphate is converted to fructose 6-phosphate in the presence of phosphofructokinase enzyme. During this reaction, ADP takes part and produces ATP.
(vi) Glucose 6-phosphate is produced from fructose 6-phosphate under the action of phosphoglucoisomerase enzyme.
(vii) Glucose is produced from glucose 6-phosphate under the action of hexokinase enzyme. At this time, ADP takes part in the reaction to form ATP.
5. Regeneration of RuBP
(viii) 3-phosphoglyceraldehyde reacts with fructose 1,6 bisphosphate to produce ribulose 5 phosphate.
(ix) Ribulose 1, 5-bisphosphate is produced from ribulose 5-phosphate. Ribulose 1, 5 bisphosphate re-enters the Calvin-Basham cycle and keeps the cycle going.

Calvin cycle steps, steps of Calvin cycle

Essential components of Calvin-Basham or C3 cycle

1. ATP: ATP produced by cyclic and acyclic photophosphorylation provides the energy required for the Calvin cycle.
2. NADPH+H+ : The acyclic photophosphorylation process produces NADPH+H+ which acts as a catalyst in the cycle.
3. CO2 : Atmospheric CO2 plays a special role in the production of sugars in this cycle.
4. RuBP: RuBP combines with CO2 to initiate the Calvin cycle.

Characteristics of Calvin or C3 cycle

1. The CO2 consumer in the Calvin cycle is 1,5-ribulose bisphosphate.
2. The first stable compound produced in this cycle is 3-phosphoglyceric acid with three carbons.
3. This cycle occurs at higher concentrations of CO2 (50-150 ppm).
4. The cycle occurs at low temperatures (10-250C).
5. The cycle occurs only in mesophyll chloroplasts. ie occurs in the stroma of chloroplasts.
6. This happens in low light.
7. It mainly occurs in cold climate plants.
8. The process occurs in C3 and C4 plants.
9. The CO2 fixing enzyme in this cycle is Rubisco.
10. Photorespiration occurs in plants during this cycle.
11. The rate of photosynthesis of plants in this cycle is low.

Calvin-Bessham or C3 cycle-definition

Professor M. Calvin of the University of California in the United States, along with his two colleagues Bessham and Benson Benson, described the process of carbon assimilation in the light neutral stage of photosynthesis, called the Calvin-Besham cycle. The first stable compound produced in this cycle is the three-carbon 3-phosphoglyceric acid and is called the C3 cycle. They discovered this cycle in Chlorella and Scenedesmas algae in 1947 using radioactive carbon (14C) (Tracer method). They won the Nobel Prize in Medicine and Physiology in 1961 for their discovery.