Question

How many moles of ATP is required to regenerate one mole of RuBP? (a) 1 (b) 2 (c) 3 (d) 4

Short answer

(c) 3

Step-by-step solution

Identify the biochemical process

Identify the process that involves the regeneration of RuBP. It is the Calvin cycle in photosynthesis.

Understand the role of ATP in the Calvin cycle

Understand that ATP (adenosine triphosphate) provides the energy required for the biochemical reactions in this cycle.

Recall the number of ATP used in the regeneration of one mole of RuBP

Recall that 3 moles of ATP are used to regenerate one mole of RuBP.

Key concepts

ATP

Adenosine triphosphate (ATP) is often called the "energy currency" of the cell. It plays a crucial role in various cellular processes because it stores and provides energy where it's needed, acting like a rechargeable battery.

ATP consists of an adenosine molecule bonded to three phosphate groups. When a cell needs energy, it breaks away one of the phosphates, transforming ATP into ADP (adenosine diphosphate), releasing energy in the process. This energy release powers many biochemical reactions within the cell, including those in the Calvin cycle.

In the context of photosynthesis, ATP provides the necessary energy to drive the reactions that convert carbon dioxide and water into glucose. It is especially critical during the regeneration of ribulose bisphosphate (RuBP) in the Calvin cycle, where three moles of ATP are consumed for every mole of RuBP regenerated.

RuBP

Ribulose bisphosphate (RuBP) is a five-carbon sugar that plays a vital role in the Calvin cycle of photosynthesis.

RuBP is the molecule that reacts with carbon dioxide, catalyzed by the enzyme ribulose bisphosphate carboxylase/oxygenase (RuBisCO), to produce two molecules of 3-phosphoglycerate, which are further transformed into glucose.

Since it is part of a cyclic process, RuBP must be regenerated to continue capturing carbon dioxide and sustaining glucose production. This regeneration process depends on ATP, using three moles of it for each mole of RuBP produced. Understanding RuBP’s role highlights its importance as a carbon dioxide acceptor and a key component in the continual process of the Calvin cycle.

Photosynthesis

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. This process essentially powers plant growth and provides oxygen, which is vital for life on Earth.

Photosynthesis takes place primarily in plant leaves within specialized organelles called chloroplasts. It can be divided into two main stages:

• Light-dependent reactions: Capture sunlight and use it to make ATP and NADPH.
• Calvin cycle (light-independent reactions): Use ATP and NADPH produced in the first stage to convert carbon dioxide into glucose.

The Calvin cycle, where RuBP plays a central role, occurs in the stroma of the chloroplasts. It is crucial because this cycle incorporates atmospheric carbon dioxide into organic molecules, a fundamental step in producing the sugars that fuel plant and animal life.

Biochemical Reactions

Biochemical reactions are the chemical processes that occur within living organisms. They are the foundation of life, supporting growth, reproduction, and maintaining cellular structures and functions.

In photosynthesis, several intricate biochemical reactions occur, particularly in the Calvin cycle. These reactions work together to transform carbon dioxide and water into glucose, a usable form of energy for plants.

The Calvin cycle consists of three main phases:

• Carbon fixation: Atmospheric CO₂ is captured by RuBP to form 3-phosphoglycerate.
• Reduction phase: ATP and NADPH are utilized to convert 3-phosphoglycerate into glyceraldehyde-3-phosphate.
• Regeneration of RuBP: ATP is used to regenerate RuBP from glyceraldehyde-3-phosphate, maintaining the cycle.

This intricate series of reactions demonstrates how energy input in the form of ATP is critical to maintain the cycle and enable photosynthesis to produce the building blocks of life.