Question

Atennate name of Krebs' cycle is (a) TCA gycle (b) otric acid cycle (c) both (a) and (b) (c) none of these.

Short answer

The alternate names of Krebs' cycle are both the TCA cycle and the Citric Acid cycle, so the correct answer is (c) both (a) and (b).

Step-by-step solution

Identify the Correct Terminology

The alternate name of Krebs' cycle must be identified from the options given. Krebs' cycle is a key part of cellular respiration where energy is produced inside the mitochondria.

Eliminate Incorrect Options

Option (d) 'none of these' can be eliminated if we know at least one of the other names is correct.

Recognize Common Nicknames for Krebs' Cycle

Krebs' cycle is commonly known by two other names, the Tricarboxylic Acid (TCA) cycle and the Citric Acid cycle.

Choose the Correct Answer

Since both TCA cycle and Citric Acid cycle are correct, the answer is option (c) 'both (a) and (b)'.

Key concepts

Cellular Respiration

Cellular respiration is a fundamental biological process where cells convert nutrients, particularly glucose, into energy and waste products. This process is crucial for the survival of most cells as it provides the adenosine triphosphate (ATP) needed for numerous cellular functions. Cellular respiration occurs in three main stages: glycolysis, the Krebs' cycle, and the electron transport chain. During glycolysis, glucose is broken down into pyruvate in the cytoplasm, generating a small amount of energy. The pyruvate then enters the mitochondria, signaling the start of the Krebs' cycle.

The Krebs' cycle, also known as the Tricarboxylic Acid (TCA) cycle or Citric Acid cycle, is the second stage of cellular respiration. It is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate—derived from carbohydrates, fatty acids, and amino acids—into carbon dioxide. Furthermore, the cycle also produces the reduced forms of cofactors, NADH and FADH₂, which are later used in the electron transport chain to produce a significant amount of energy.

Tricarboxylic Acid (TCA) Cycle

The Tricarboxylic Acid (TCA) cycle, also known as the Krebs' cycle or Citric Acid cycle, is a pivotal metabolic pathway taking place in the matrix of mitochondria. It's not just a circle of reactions generating energy; the TCA cycle also plays a role in the synthesis of precursors for many biomolecules such as amino acids. Moreover, it plays a part in regulating the metabolic functions based on cellular needs.

The Steps of the TCA Cycle:

• Oxidation of acetyl-CoA produces CO₂ and transfers electrons to NAD+, forming NADH.
• Regeneration of the four-carbon molecule oxaloacetate, allowing the cycle to repeat.
• Production of GTP or ATP through substrate-level phosphorylation.
• Reduction of FAD to FADH₂.

These reactions release waste carbon dioxide and capture high-energy electrons in a form usable by the cell to produce ATP.

Citric Acid Cycle

The Citric Acid cycle is another label for the Krebs' cycle or TCA cycle and is named after the first product generated in the cycle, citrate (or citric acid). It begins when the two-carbon acetyl group from acetyl-CoA combines with a four-carbon oxaloacetate molecule to form citrate. This six-carbon molecule undergoes a series of transformations, releasing two molecules of carbon dioxide and regenerating oxaloacetate.

Every turn of the cycle also produces three NADH molecules and one FADH₂ molecule, which are crucial in transferring electrons to the electron transport chain, where the bulk of ATP will be synthesized. This multistep process is carefully controlled by various enzymes to efficiently manage energy production.

Mitochondria Energy Production

Mitochondria are commonly referred to as the powerhouse of the cell, highlighting their key role in energy production. They house the enzymes necessary for the processes like the Krebs' cycle and the electron transport chain, both integral to cellular respiration.

The energy production in mitochondria occurs in the inner membrane, which is highly folded into structures called cristae, increasing the surface area for energy-generating reactions. Here, NADH and FADH₂, created from earlier stages like the Krebs cycle, donate electrons to the electron transport chain. This transfer leads to a process known as oxidative phosphorylation, where the energy released from electrons is used to pump protons across the membrane, creating an electrochemical gradient. ATP synthase, a unique enzyme, utilizes this gradient to synthesize ATP from ADP and inorganic phosphate. The entire orchestrated process is vital for the life of the cell and the organism as a whole.