Problem 149 - Objective Biology for NEET

Question

Assertion: ATP is energy currency of cell. Reason: ATP is formed in catabolic pathway.

Step-by-Step Solution

Answer

The assertion and reason are correct. ATP is the energy currency of the cell as it transfers energy within the cell, and its formation is a result of energy release through catabolic pathways.

Step 1: Understanding ATP (Adenosine Triphosphate)

ATP is often referred to as the 'energy currency' of the cell because it acts as a medium for transferring energy from energy-releasing reactions to energy-requiring reactions within the cell.

Step 2: Understanding Catabolic Pathways

Catabolic pathways are a series of chemical reactions that break down complex molecules into simpler ones, releasing energy in the process. This energy is often stored in the form of ATP.

Step 3: Relating ATP and Catabolic Pathways

Catabolic pathways are crucial to ATP formation. Nutrients break down through catabolic reactions, producing energy which is then stored as ATP. ATP forms when a phosphate group is added to ADP (adenosine diphosphate) in a process known as phosphorylation. This ATP can then move energy to other cellular processes that require energy, making ATP the 'energy currency' of the cell.

Key Concepts

Energy Transfer

Energy is crucial for all cellular activities. ATP, or Adenosine Triphosphate, plays a key role in this process by functioning as an energy transfer molecule in cells. When cells perform activities that require energy, such as muscle contractions or active transport across membranes, they rely on ATP to provide the necessary power.

• ATP consists of three phosphate groups, and the bond holding the third phosphate is known as a high-energy bond.
• When this bond is broken, energy is released to fuel various cellular reactions that require power.
• This reaction converts ATP into ADP (Adenosine Diphosphate) and an inorganic phosphate, releasing the stored energy.

This basic principle underlies how energy is moved and used throughout a cell. Think of it as the universal currency to pay for the cell’s energy expenses. This mechanism allows ATP to effectively transfer energy from reactions that release energy, like catabolism, to processes needing energy input.

Catabolic Pathways

Catabolic pathways are an essential part of metabolism in living organisms. These pathways involve the breakdown of complex molecules into simpler ones, releasing energy during the process. The energy from catabolic reactions is crucial because it often gets stored in the form of ATP.

• Examples of catabolic pathways include glycolysis, the citric acid cycle, and the breakdown of fatty acids.
• During these processes, molecules like glucose and fatty acids are systematically broken down, and energy is harvested.

The released energy is captured by molecules like ATP through processes such as phosphorylation. This energy capture is vital because it ensures cells have a reservoir of readily available energy to support their needs.

Phosphorylation

Phosphorylation is a crucial chemical process that involves the addition of a phosphate group to an organic molecule. This is a key step in the synthesis of ATP from ADP in the cell, often referred to as oxidative phosphorylation when it occurs in the mitochondria.

• Phosphorylation in cellular respiration is what allows ADP to "pick-up" a phosphate group, forming ATP, thus storing energy for the cell.
• It occurs in various biochemical pathways, including oxidative phosphorylation in aerobic respiration and substrate-level phosphorylation in glycolysis.

This process is essential for maintaining cellular energy balance, enabling cells to store and release energy efficiently. Without it, cells would not be able to form ATP, making phosphorylation a cornerstone of energy metabolism. Think of it as adding a charge to a battery, making it ready to power up various cellular functions when needed.