Difference Between C3 C4 And Cam Pathway

Photosynthesis is the prime pathway that occurs in plants and is responsible for food production. Playing a crucial role in deriving the world, the process occurs through three pathways, with all of them suitable for different conditions. The C3 pathway is the most common photosynthesis. The C4 pathway takes place in 3% of vascular plants, and the CAM pathway is seen in semi-arid plants.

Table of Contents

Photosynthesis
C3 Photosynthesis
C4 Photosynthesis
CAM Photosynthesis
Difference Between C3, C4 and CAM Pathway
Practice Problems
Frequently Asked Questions

Photosynthesis

Photosynthesis is the process that occurs in the presence of sunlight, carbon dioxide and water to produce carbohydrate, which is the source of energy. It is an enzymatic pathway that occurs in the chloroplasts of the plant cells.

C3 Photosynthesis

Here photosynthesis occurs via Calvin or C3 cycle. The carbon dioxide is fixed into a three-carbon compound, 3-phosphoglycerate. This compound is responsible for the name C3 cycle and it forms from the unstable intermediate of six carbon compounds. The reaction is catalysed by ribulose 1,5-phosphate.

C4 Photosynthesis

It is generally found in tropic plants where plants need to conserve water during day time. The stomata of the plant cells remain closed, thus preserving the water and inhibiting the gas exchange. The lack of gas exchange subsequently leads to carbon dioxide deficiency in the plant, decreasing the possibility of photosynthesis. However, the negative effect accompanies the phenomenon, which is referred to as photorespiration. To combat the same, plants have adapted to perform C4 photosynthesis. They use an alternative enzyme, phosphoenolpyruvate carboxylase, that eliminates the possibility of photorespiration due to lesser sensitivity to oxygen.

CAM Photosynthesis

It is specifically and mostly found in plants resident in semi-arid conditions. Here the plants prevent evapotranspiration by keeping their stomata closed. But, they store water in them, which serves as one reactant. The other reactant, carbon dioxide, is gained during the night and fixed for usage in the morning when NADPH and ATP are available.

Difference Between C3, C4 and CAM Pathway

Factors	C3	C4	CAM
Name	Calvin cycle	Hatch and Slack Pathway	Crassulacean Acid Metabolism
Location	Mesophyll cells	Bundle sheath and mesophyll cells	Mesophyll cells
Occurrence in plants	Plants in all regions	Tropical regions and 3% of vascular plants	Semi-dry regions
Nature of plants	Xerophytic, mesophytic and hydrophytic	Mesophytic	Xerophytic
Required NADPH	12	12	12
Required ATP	18	30	39
First Product	3-phosphoglyceric acid	Oxaloacetic acid	Day- 3-phosphoglyceric acid Night- Oxaloacetic acid
Carbon fixing enzymes	RuBP carboxylase	Bundle sheath - RuBP carboxylase Mesophyll - PEP carboxylase	Day - PEP carboxylase Night - RuBP carboxylase
Carbon dioxide receptor	Ribulose 1,5 bisphosphate or RuBP	Phosphoenol pyruvate or PEP	Phosphoenol pyruvate or PEP
Additional cycles	No	C4/Hatch and Slack Cycle	C3 and C4/Hatch and Slack Cycle
Optimum temperature	15-25 degree	30-40 degree	More than 40 degree
Optimum time	Daylight	Both day and night	Both day and night
Photosprespuration	Occurs	Reduced due to separation of cells for fixation and C3 cycle	Reduced due to different times of fixation and C3 cycle
Example	Barley, Wheat, Soybeans	Sorghum, Millet, Maize	Cacti, Crassula, Sagittaria

Practice Problems

Q1. Kranz anatomy is present in which type of photosynthetic pathway?

A. C3
B. C4
C. CAM
D. All the plants

Ans. B. C4 pathway

Kranz anatomy refers to the structure of the leaf in C4 plants where two types of cells, mesophyll and bundle sheath cells, are present.

Q2. Crabgrass plants undergo which type of photosynthesis?

A. C3
B. C4
C. CAM
D. All the plants

Ans. B. C4

Crabgrass, corn and sugarcane are examples of plants carrying out C4 photosynthesis.

Q3. What is the full form of RubisCo?

A. Ribulose bis carboxylase
B. Ribose bisphosphate carboxylase oxygenase
C. Ribulose bisphosphate carboxylase oxygenase
D. Ribulose bicarbonate carboxylase oxygenase

Ans. C. Ribulose bisphosphate carboxylase oxygenase

Ribulose bisphosphate carboxylase oxygenase, or RubisCo, is an important enzyme for photosynthesis.

Frequently Asked Questions

Q1. What are the similarities between C3, C4 and CAM pathways?
Ans. All these pathways occur in plants, are responsible for photosynthesis and require light reactions and the Calvin cycle to manufacture their food.

Q2. How does the photosynthetic pathway help scientists and common people?
Ans. Understanding the photosynthetic pathway helps open the door to adapt and hence easily grow the plants in deteriorating environmental conditions. Alarming increases in carbon dioxide levels and heat, these pathways are crucial to enhance crop production.

Q3. Which law is associated with photosynthesis?
Ans. Sheldon’s law of tolerance indicates the limiting factor or lowest available component necessary for photosynthesis derives its rate.