Question

All enzymes of TCA cycle are located in the mitogl matrix except one which is located in inner membranes in eukaryotes and in cutors'thiti This enzyme is (a) isocitrate dehydrogenase (b) ketoglutarate dehydrogenase (c) succinate dehydrogenase d) lactate dehydroqenase.

Short answer

The enzyme in the TCA cycle located in the inner mitochondrial membrane is (c) succinate dehydrogenase.

Step-by-step solution

Understanding the Location of TCA Cycle Enzymes

Recognize that all the enzymes of the TCA cycle, also known as the Krebs cycle or citric acid cycle, are located within the mitochondrial matrix in eukaryotic cells, except one.

Identifying the Exception

Identify the enzyme that is not located in the mitochondrial matrix but is instead associated with the inner mitochondrial membrane.

Evaluating the Options

Review the list of enzymes provided in the options. Determine which one is known to be involved in the TCA cycle and is located in the inner mitochondrial membrane rather than the matrix.

Associating the Correct Answer

Recall that succinate dehydrogenase is the enzyme in the TCA cycle that is integrated into the inner mitochondrial membrane, functioning as a part of the electron transport chain, thus distinguishing it from the other TCA cycle enzymes.

Key concepts

Krebs cycle

The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins into carbon dioxide.

In addition to ATP production, the cycle also produces precursors for various compounds needed by the cell, making it a central hub in cellular metabolism. The Krebs cycle takes place in the mitochondrial matrix, an enzyme-rich fluid that fills the interior of mitochondria.

During this process, energy stored in acetyl-CoA is transferred to several carriers, including NADH and FADH2, which are later used to produce ATP in the electron transport chain.

Succinate dehydrogenase

Succinate dehydrogenase is unique among the TCA cycle enzymes because it's embedded in the inner mitochondrial membrane.

It serves a dual function: it participates in both the Krebs cycle and the electron transport chain, distinguishing it from other TCA cycle enzymes that are soluble in the mitochondrial matrix.

Interestingly, this enzyme is integral to the production of ATP in two ways—it helps convert succinate to fumarate in the Krebs cycle, and it also acts as complex II in the electron transport chain, contributing to the generation of a proton gradient used to power ATP synthesis.

Mitochondrial matrix

The mitochondrial matrix is highly specialized for the metabolic functions of the mitochondria. It contains a dense solution of enzymes, including those essential for the Krebs cycle and the duplication of mtDNA and mtRNA.

The consistency of the matrix can affect the efficiency at which these enzymes operate, thus influencing the cell's overall energy production.

As mitochondria are the 'powerhouses' of the cell, the health and functionality of the mitochondrial matrix are critical in ensuring that the cell has a steady supply of ATP for all its energy-dependent processes.

Electron transport chain

The electron transport chain (ETC) is the final stage of cellular respiration, where electrons are transferred from electron donors to electron acceptors like oxygen, in redox reactions. This process takes place in the inner mitochondrial membrane.

During these reactions, a series of proteins, including succinate dehydrogenase (complex II), use the energy transferred by electrons to pump protons across the membrane, creating a proton gradient.

The flow of protons back into the mitochondrial matrix through ATP synthase is what generates ATP. Since the functioning of the ETC is essential for ATP production, any interruption can lead to significant drops in cellular energy supply.