Problem 79 - Objective Biology for NEET

Question

Kreb's cycle is also known as (a) Glyoxylate cycle (b) EMP pathway (c) Citric acid cycle (d) Glycolate cycle

Step-by-Step Solution

Answer

The correct answer is (c) Citric acid cycle.

Step 1: Analyze the Options

Read the four options carefully: (a) Glyoxylate cycle, (b) EMP pathway, (c) Citric acid cycle, (d) Glycolate cycle. It's important to recall your knowledge about these metabolic pathways.

Step 2: Recall Kreb's Cycle

Kreb's cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a series of chemical reactions used by all aerobic organisms to release stored energy.

Step 3: Match The Options

After recalling the details about Kreb's cycle, match the options with your recalled knowledge. Here, you could notice that Kreb's cycle is described as the citric acid cycle in option c.

Key Concepts

Citric Acid Cycle

The Citric Acid Cycle, often referred to as the Kreb's Cycle, is a key component of cellular respiration. It takes place in the mitochondria of cells and plays a critical role in generating energy. The cycle involves a series of chemical reactions that work together to oxidize acetyl-CoA to carbon dioxide, while storing energy in the form of NADH, FADH2, and GTP (or ATP).
The Citric Acid Cycle not only releases energy but also provides several important intermediates for other pathways. During this cycle:

• Acetyl-CoA combines with oxaloacetate to form citrate.
• Citrate is then transformed through several steps, producing key molecules like NADH and FADH2, which are used in the electron transport chain.
• It ends by regenerating oxaloacetate, making it a cycle.

Understanding this process helps explain how aerobic organisms efficiently extract energy from nutrients.

Metabolic Pathways

Metabolic pathways are series of interconnected chemical reactions occurring within a cell. These pathways are crucial for maintaining life, as they manage the energy and resources of the cell efficiently. There are two main types: catabolic pathways, which break down molecules to release energy, and anabolic pathways, which build up molecules to store energy.
In the context of the Citric Acid Cycle, it is a significant part of catabolic metabolism in aerobic organisms. This cycle connects with and supports other metabolic pathways by providing essential components and energy carriers.
For example:

• NADH and FADH2 produced in the Citric Acid Cycle are utilized in the electron transport chain to generate ATP, the energy currency of the cell.
• Intermediates like α-ketoglutarate and succinyl-CoA are also used in biosynthesis pathways, linking metabolism to cell growth and repair.

Integrating these pathways enables cells to respond flexibly to energy demands and nutrient availability.

Tricarboxylic Acid Cycle

Though it shares a name with the Citric Acid Cycle, the term Tricarboxylic Acid Cycle (TCA Cycle) specifically emphasizes the involvement of molecules containing three carboxyl groups in the process. The TCA Cycle is another nickname for the Citric Acid Cycle, and it is unambiguously important in aerobic energy production.
Within the TCA Cycle:

• Citrate, isocitrate, and α-ketoglutarate are examples of tricarboxylic acids, each playing a pivotal role in the carbon oxidation process.
• This cycle not only results in energy extraction but also in carbon skeleton rearrangement, which is vital for cell metabolism.
• Crucially, the TCA Cycle is central to the anaplerotic reactions, which replenish cycle intermediates ensuring its continuity alongside energy production.

Recognizing these reactions highlights the TCA Cycle's importance beyond energy production, serving as a hub integrating diverse metabolic functions necessary for life.