How does C 4 photosynthesis differ from C 3 ?

Name: Problem 56, Chapter 10: Plant Systematics
Uploaded: 2020-06-17T03:57:43-08:00
Duration: 28 s
Channel: Sam Limsuwannarot
Description: How does C 4 photosynthesis differ from C 3 ?

Key Concepts

Photorespiration

Photorespiration is a process in C3 plants where the enzyme RuBisCO fixes oxygen instead of CO2, leading to energy losses and reduced photosynthetic efficiency. This process becomes significant under stress conditions and is largely avoided in C4 plants due to their CO2 concentrating mechanism.

Kranz Anatomy

Kranz anatomy refers to the specialized leaf structure found in most C4 plants, characterized by a concentric organization of mesophyll and bundle sheath cells. This arrangement facilitates the spatial separation of initial CO2 fixation and the Calvin cycle, thereby minimizing photorespiration and enhancing overall photosynthetic efficiency.

C3 Photosynthesis

C3 photosynthesis is the most common pathway for carbon fixation in plants, where CO2 is directly incorporated into a three-carbon compound by the enzyme RuBisCO. This pathway is efficient under moderate conditions but can suffer from photorespiration, a process that decreases efficiency when oxygen levels are high or temperatures increase.

C4 Photosynthesis

C4 photosynthesis is an adaptation that enhances the efficiency of carbon fixation under conditions of high light intensity, temperature, and low CO2 availability. In this pathway, CO2 is initially fixed into a four-carbon compound in mesophyll cells and then shuttled to bundle sheath cells where it is released for use in the Calvin cycle, effectively reducing the impact of photorespiration.

Carbon Concentration Mechanism

The carbon concentration mechanism in C4 plants involves the initial fixation of CO2 into a four-carbon compound in the mesophyll cells, which is then transported to bundle sheath cells where CO2 is released for the Calvin cycle. This mechanism effectively raises the concentration of CO2 around RuBisCO, reducing the likelihood of photorespiration and increasing the efficiency of photosynthesis in challenging environmental conditions.

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