Why do we call Photorespiration a wasteful process?
Thus, photorespiration is a wasteful process because it prevents plants from using their ATP and NADPH to synthesize carbohydrates. RuBISCO, the enzyme which fixes carbon dioxide during the Calvin cycle, is also responsible for oxygen fixation during photorespiration.
Photorespiration is a wasteful pathway that occurs when the Calvin cycle enzyme rubisco acts on oxygen rather than carbon dioxide. Crassulacean acid metabolism (CAM) plants minimize photorespiration and save water by separating these steps in time, between night and day.
- This type of photosynthesis is known as Crassulacean Acid Metabolism because of the storage of carbon dioxide at night as an acid. As biologists continue to study photosynthesis in plants, they are learning that more plants than just cacti use CAM.
- Chloroplast, peroxisome and mitochondria are three cellular organelles involved in photorespiration.
- During this reaction, carbon dioxide and water are converted into glucose and oxygen. The reaction requires light energy, which is absorbed by a green substance called chlorophyll. Photosynthesis takes place in leaf cells.
One hypothesis is that photorespiration had a role in early evolution, when there was more carbon dioxide in the air. Another explanation is that plants use photorespiration to slow down photosynthesis under certain stressful conditions, like intense light, so that the photosynthetic apparatus doesn't get damaged.
- The key chemical step in which carbon dioxide is 'fixed' (in other words, condensed with an existing organic molecule) is called a carboxylation reaction. It is catalyzed by the enzyme ribulose 1,5-bisphosphate carboxylase, commonly known as Rubisco, in the 'Calvin cycle' of carbon fixation.
- Glutamic acid is found naturally in tomatoes, grapes, cheese, mushrooms and other foods. MSG is used in the food industry as a flavor enhancer with an umami taste that intensifies the meaty, savory flavor of food, as naturally occurring glutamate does in foods such as stews and meat soups.
- 4. Uses of alcohol
- Used as an ingredient in alcoholic beverages E.g. wine and beer.
- Used to produce methylated spirit (meth) Methylated spirit is ethanol mixed with small amounts of methanol, which is poisonous, making it unfit for consumption.
- Used as a fuel. Ethanol burns cleanly to form carbon dioxide and water.
Glyceraldehyde 3-phosphate or G3P is the product of the Calvin cycle. It is a 3-carbon sugar that is the starting point for the synthesis of other carbohydrates. Some of this G3P is used to regenerate the RuBP to continue the cycle, but some is available for molecular synthesis and is used to make fructose diphosphate.
- Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is the metabolite that occurs as an intermediate in several central pathways of all organisms.
- In the most general sense, the primary function of the Calvin cycle is to make organic products plants need, using the products from the Light Reactions of photosynthesis (ATP and NADPH), These products include glucose, the sugar made using carbon dioxide and water, and also protein (using nitrogen fixed from the soil)
- Glyceraldehyde 3-phosphate or G3P is the product of the Calvin cycle. It is a 3-carbon sugar that is the starting point for the synthesis of other carbohydrates. Some of this G3P is used to regenerate the RuBP to continue the cycle, but some is available for molecular synthesis and is used to make fructose diphosphate.
Updated: 4th December 2019