Advantages and disadvantages of C4 and C3 carbon fixation

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Advantages and disadvantages of C4 and C3 carbon fixation

5. C4 photosynthesis

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C3, C4, and CAM plants (article) | Khan Academy

Many plants which live in dry conditions have evolved an alternative carbon fixation pathway to enhance the efficiency of rubisco so that they don’t have to keep their stomata open as much, and thus they run less risk of dying due to dehydration. These plants are called C4 plants, because the first product of carbon fixation is a 4-carbon compound (instead of a 3-carbon compound as in C3 or “normal” plants). C4 plants use this 4-carbon compound to effectively “concentrate” CO2 around rubisco, so that rubisco is less likely re react with O2.

C3 Plants: What, Examples and Comparison

PEP carboxylase is located in the mesophyll cells, on the leaf exterior near the stomata. There is no rubisco in the mesophyll cells. CO2 entering the stomata is rapidly fixed by PEP carboxylase into a 4-carbon compound, called malate, by attaching the CO2 to PEP. The malate is then transported deeper into the leaf tissue to the bundle sheath cells, which are both far away from the stomata (and thus far away from oxygen) and contain rubisco. Once inside the bundle sheath cells, malate is decarboxylated to release pyruvate and CO2; the CO2 is then fixed by rubisco as part of the Calvin cycle, just like in C3 plants. Pyruvate then returns to the mesophyll cells, where a phosphate from ATP is used to regenerate PEP. Thus in C4 plants, C4 carbon fixation has a net added cost of 1 ATP for every CO2 delivered to rubisco; however, C4 plants are less likely to die of dehydration compared to C3 plants in dry conditions.

Difference Between C3 and C4 Plants - Clarify Yourself

C4 plants are better adapted than a C3 plant with high daytime temperatures, intense sunlight, drought, or CO2 limitation.


C4 photosynthesis has evolved among land plants a number of times and there are several versions of it. We will learn the NADP-malic enzyme type, which is present in maize, sugarcane, sorghum, and crabgrass, among others.


An alternative to the C4 path would be significant improvement in the carboxylating efficiency of RUBISCO. Some improvement has occurred over time (more ancient photosynthetic lineages have RUBISCO isoforms that are a little less specific fro CO2 than those in plants) but not enough to suppress the adaptive value of the C4 path. has not. It may be that changes in RUBISCO that would abolish oxygenation are not structurally possible.

Types of Photosynthesis: C3, C4 and CAM - …

Hello professor, i think this video, , is very good in explaining the difference among C3,C4 and CAM.

In nature, however, C4 plants are actually more efficient than C3 because they avoid the wasteful process of photorespiration. In air, the following results occur:


The advantage of being C4 is affected by temperature and water availability. At higher temperatures, oxygenation reactions in C3 plants increase but C4 plants still do no oxygenation. This increases the advantage of being C4. C4 plants are also more efficient at photosynthesizing without losing water. Because PEPCase has a low Km for CO2, C4 plants can keep their stomata a little more closed than C3 plants without slowing carboxylation.

The C3 plant had a middle rate of photosynthesis because it isn't as efficient as C4 plants because they perform photo respiration.
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  • Photorespiration and C4 Plants - Biology Pages

    The Cam plant would have the highest rate of respiration at night when compared to C4 plants and C3 plants.

  • C3, C4, and CAM Photosynthesis Flashcards | Quizlet

    The difference between C3, C4, and CAM plants are their process of light and dark reactions

  • 20/04/2008 · C3 and C4 Photosynthesis ..

    C4 and CAM plants are plants that use certain special compounds to gather carbon dioxide (CO 2 ) during photosynthesis

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What Is the Advantage of C4 Photosynthesis? | Sciencing

The C4 path is illustrated in your text in figure 8.11. To summarize, in the mesophyll cells of C4 plants, the carboxylating enzyme PEPCase combines CO2 with phosphoenolpyruvate, yielding oxaloacetate, a 4 carbon compound. This is how C4 photosynthesis gets its name. The first product of carboxylation is a 4 carbon compound. (The first stable product of carboxylation in C3 plants is 3PGA, a 3 carbon compound).

"What Is the Advantage of C4 Photosynthesis?"


RUBISCO and the Calvin cycle are present in the chloroplasts of the bundle sheath cells of C4 plants. CO2 levels in the bundle sheath chloroplasts are roughly 10 times the air level because of the release of CO2 from malate. Also, oxygen is relatively low in bundle sheath chloroplasts because of the absence of PS II. The high ratio of CO2 to oxygen in the bundle sheath cells prevents the oxygenation reaction of RUBISCO and the processing of 2 phosphoglycolate is thus unnecessary. C4 plants exhibit no detectable photorespiration.

Temperature response of photosynthesis in C3, C4, and …

Maize plants and other NADP-malic enzyme C4 plants have a characteristic architecture of their leaves. The photosynthetic cells are divided into 2 types: mesophyll cells and bundle sheath cells. The bundle sheath cells form a ring around the vascular bundles of the leaves. The mesophyll cells are the rest of the photosynthetic cells, more distant from the vascular bundles (See Figure 8.9 in your text for micrographs). Mesophyll and bundle sheath cells differ in their photosynthetic machinery, as described below:

Cam, C3, and C4 Plants and their Rate of Photosynthesis duri


The different Km values of PEPCase and RUBISCO can be seen in the carboxylation rates of C3 and C4 plants when measured over a range of carbon dioxide concentrations.

What are C3 and C4 plants? - Quora

The C3 and C4 refer to how these classes of plants assimilate carbon dioxide into their systems. During the first steps in CO2 assimilation, C3 plants form a pair of three carbon-atom molecules. C4 plants, on the other hand, initially form four carbon-atom molecules. In C3 plants CO2 enters the leaf through the stomata, which are microscopic pores found on the under-surface of leaves and on stems. They occur in the epidermal tissue. The CO2 then diffuses into the mesophyll cells where a bifunctional enzyme called Rubisco fixes carbon dioxide or molecular oxygen, which leads to photosynthesis or photorespiration. The Rubisco catalyzes the CO2 of and forms two Phosphoglycerate (PGA) molecules, which is a three carbon compound. This PGA is converted to sugars and transported to the growing leaves, roots and reproductive structures. This form of photosynthesis is found in all major plant families or in about 300,000 species and make up 95% of all plants. Typical C3 plants include: barley, sunflower, rice, tomatoes, wheat, peanuts, cotton, sugar beet, oats, and most trees and are found in typically cooler and wetter environments. C4 plants on the other hand the CO2 enters through the stomata again, but goes into the mesophyll tissue, where it is fixed by PepCarboxylase to form , which unlike Rubisco does not have the ability to fix oxygen, which contributes to lower photorespiratory carbon losses in C4 plants. This Oxaloacetate is then converted to malate, which is a four carbon molecule and transported to the bundle sheath cells. From this CO2 is released and forms sucrose and starch. These plants have a special mechanism within their leaves by which they are able to increase CO2 concentration several times higher than ambient levels. These plants tend to be found in warmer and water-limited environments. Typical examples include many tropical grasses and agricultural crops such as maize (corn), sugarcane, and sorghum. Characteristically, C4-plants have higher rates of photosynthesis than C3-plants. Photosynthesis in C4 plants does not saturate but increases at high light intensities and can continue at very low CO2 concentrations. Subsequently, these plants have rapid growth rates and higher biomass and economic yields than C3-plants.

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