RuBP Full Form

What is the full form of RuBP?

The full form of RuBP is (Ribulose 1,5-bisphosphate) is a 5-carbon compound that participates in the Calvin cycle, one of the photosynthesis's light-independent processes. It is a colourless anion, a double phosphate ester of the five-carbon sugar Ribulose, which contains ketone molecules. Although RuBP salts can be isolated, their biological function only occurs in solution. In addition to plants, RuBP is present in all life forms, including Archaea, Bacteria, and Eukarya. In this article, learn more about the Calvin-Benson Cycle, interactions with Rubisco, and the role of RuBP in photorespiration.

This Story also Contains

1. What is the full form of RuBP?
2. Calvin Cycle
3. Model of Calvin Cycle
4. Role of RuBP in photosynthesis and the Calvin-Benson Cycle

Calvin Cycle

The stroma of chloroplasts in a plant cell undergoes a sequence of processes known as the Calvin cycle. With the aid of ATP and NADPH, which is created during the photosynthesis dark process, the carbon dioxide that the plant cell has absorbed is converted to glucose. This cycle results in a 3-carbon sugar, which is a relatively stable molecule.

American biochemist Melvin Calvin and his team originally identified the mechanism, which involves the fixation of carbon dioxide and subsequent carbohydrate reduction.

Plant cells generate organic compounds from light reactions like ATP and NADPH. The endergonic reactions are powered by ATP, while the reducing power of NADPH provides the hydrogen and electrons needed to attach them to carbon atoms. The C-H bonds in sugar use the light energy that is absorbed during photosynthesis.

The enzyme ribulose-1, 5-bisphosphate carboxylase, often known as Rubisco, is an important component of the Calvin cycle. In the C3 cycle, it produces three different products: 3-Phosphoglycerate (3-PGA), Glyceraldehyde 3-P (GAP), and Dihydroxyacetone Phosphate (DHAP). All of these products are used in the production of fructose-1,6 bisphosphate and fructose-6 phosphate.

Model of Calvin Cycle

1. Processes

The Calvin cycle consists of three complex processes that happen during the dark reaction phase of photosynthesis. The steps of the Calvin cycle include:

1. Fixation of carbon - The Calvin cycle's first crucial phase, carbon fixation, involves reducing carbon dioxide and attaching it to an organic molecule. The molecule is created by reassembling the bonds of two intermediate glycolysis products, fructose 6-phosphate and glyceraldehyde 3-phosphate, to create the energy-dense 5-C compound ribulose 1, 5-bisphosphate (RuBP) and a 4-C sugar.

As a result of the carbon fixation reaction, two molecules of 3-PGA are created when carbon dioxide attaches to RuBP. This reaction is catalysed by the enzymes ribulose bisphosphate carboxylase/oxygenase. This big 4-subunit enzyme is located in the stroma and functions slowly, breaking down only one RuBP molecule every second. Because CO₂ is converted from an inorganic form into organic molecules, the process is known as carbon fixation.

2. Reduction - After forming two molecules of 3-PGA, they are broken down into a simple sugar called glyceraldehyde-3 phosphate (G3P). In this process, energy is produced from the use of ATP and NADPH, and it is transferred to sugar molecules for long-term storage. Because electrons are transported from 3-PGA to G3P during this process, it is known as reduction.

3. Regeneration - This stage involves the regeneration of RuBP. One of the G3P molecules first exits the Calvin cycle and is then sent to the cytoplasm to help create the products required by the plant body. As a result, there are 3 carbon atoms left in the chloroplast, and it takes three cycles of the Calvin cycle to fix net carbon in order to export one molecule of G3P.

However, 2 molecules of G3Ps are created throughout each rotation, resulting in a total of 6 molecules of the complex. The other G3P molecules are employed to regenerate RuBP while one is exported. The regeneration reactions require three more ATP molecules, which allows the system to fix more CO₂ as a result.

2. Equation of Calvin Cycle

6 NADPH + 9 ATP + 3CO_{2} + + 5 H_{2}O \rightarrow G3P + 2H+ + 6NADP+ + 9ADP + 8Pi

Where, G3P ⇒ Glyceraldehyde-3-Phosphate= G3P

Pi ⇒ Inorganic phosphate

3. Products of Calvin Cycle

The following are the products of the Calvin cycle:

1. Every cycle turn fixes a single carbon molecule.

2. In three cycles, one G3P molecule is produced.

3. One glucose molecule is created when two G3P molecules join.

4. In the reduction phase, 3-PGA is converted to G3P and RuBP is regenerated using 3 ATP and 2 NADPH molecules.

5. One glucose molecule is created from 18 ATP molecules and 12 NADPH molecules.

Role of RuBP in photosynthesis and the Calvin-Benson Cycle

1. RUBP carboxylase, the primary enzyme of the dark reaction, also catalyses another reaction that interferes with the Calvin cycle's activity.

2. RUBP carboxylase has a stronger affinity for oxygen than carbon dioxide when the temperature and oxygen concentration rises.

3. As a result, RUBP (ribulose 1,5 bisphosphate) acts as an oxygenase in the presence of elevated oxygen concentrations and high temperatures, converting RUBP into the 3-carbon product phosphoglyceric acid (PGA) and the 2-carbon molecule phosphoglycolate. Glycolate or glycolic acid is produced quickly from phosphatidyl glycolate. Chloroplasts may experience these reactions.

4. It serves as a significant carbon dioxide acceptor.