Difference Between C3, C4 and CAM pathway

The key difference between C3, C4 and CAM pathway is the synthesis of different products during the grasping of carbon dioxide for photosynthesis from the sunlight and then conversion of it to glucose.

When photosynthetic plants yield 3-carbon acid or 3-phosphoglyceric acid(PGA)  as their first product during the carbon dioxide fixation, it is known as C3 pathway. When photosynthetic plants before entering the C3 pathway produce oxaloacetic acid or 4-carbon compound as its primary product is known as Hatch and Slack  or C4 pathway.

The pathway is CAM (crassulacean acid metabolism) when plants grasp the solar energy during the day and use the energy at night time to assimilate or fix carbon dioxide.

Top Differences in NEET Biology:

C3 Pathway

  • These temperate or cool-season plants flourish at an optimum temperature of 65-75℉, soil temperature 40-45℉
  • Less efficient at higher temperatures
  • Primary product is 3-phosphoglyceric acid or 3-carbon acid
  • It takes place in three steps – carboxylation, reduction and regeneration

C4 Pathway

  • Plants in the tropical region are observed following this pathway
  • Two-step process where Oxaloacetic acid is a 4-carbon compound that is produced
  • Takes place in bundle sheath and mesophyll cells found in the chloroplast
  • These can either be annual or perennial and ideal temperature for their growth is 90-95℉
  • Examples are Indiana grass, big bluestem, Bermudagrass,

CAM Plants

  • In this type of photosynthesis, entities absorb energy during daytime from sunlight using this energy at the night aby gathering carbon dioxide
  • This adaptation is observed during the time of drought, allowing gaseous exchange during the night when the temperature of the air is cooler along with loss of water vapour
  • Examples are plants such as euphorbias and Cactus.
  • Irregular water supply has caused bromeliads and orchids to adapt to this pathway

Difference Between C3, C4 and CAM pathway

Listed below are some significant differences

What it means
This pathway is observed in C3 plants wherein the primary product from sunlight post carbon-grasping is 3-phosphoglyceric acid to produce energy Sunlight is converted into oxaloacetic acid by some plants prior to C3 cycle which is further converted into energy. The plants are known as C4 plants. It is the C4 pathway Plants store solar energy post which they convert into energy in the night, such plants are CAM plants and the pathway is referred to as CAM pathway
Cells included
Mesophyll cells Bundle sheath cells, Mesophyll cells Mesophyll cells in C3 and C4, both
Observed in
All plants carrying out photosynthesis Tropical plants Semi-dry climatic conditions
Plant types that use this cycle
Hydrophytic, Mesophytic, Xerophytic plants Mesophytic plants Xerophytic plants
Photorespiration process
Observed in higher rates Not seen as much Observed in the noon time
First-stable product produced
3-phosphoglycerate Oxaloacetate Daytime – 3-phosphoglycerate

Night time – Oxaloacetate

Number of molecules of NADPH and ATP required to produce glucose
NADPH – 12

ATP – 18

NADPH – 12

ATP – 30

NADPH – 12

ATP – 39

The ideal photosynthetic temperature 
15-25 degree celsius 30-40 degree celsius Greater than 40-degree celsius
Calvin cycle functional
Not accompanied with any other cycle Accompanied along with C4 pathway C4 pathway and C3
Beans, Spinach, Sunflower, Rice, Cotton Maize, Sorghum, Sugarcane Orchids, Cacti, euphorbias
Carboxylating enzyme
In C3, RuBP carboxylase PEP carboxylase – mesophyll

RuBP carboxylase – bundle sheath

RuBP carboxylase – day time

PEP carboxylase –  night time

Ratio – Co2:ATP: NADPH2
The ratio is 1:3:2 The ratio is 1:5:2 The ratio is 1:6:5:2
Kranz Anatomy
Not present Present Not present
Initial CO2 receptor
Ribulose-1, 5-biphosphate Phosphoenolpyruvate Phosphoenolpyruvate
Carbon dioxide compensation point (In PPM)
Thirty to seventy six to ten In dark: 0-5

These were some of the differences between the pathways. Learn more about related concepts at BYJU’S.

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