Question

In which of the following part of mitochondria \(\mathrm{se}\) dehydrogenase enzyme is located? (a) Perimitochondrial space (b) Outer membrane (c) Matrix (d) Inner membrane

Short answer

Succinate dehydrogenase enzyme is located in the inner membrane of the mitochondria.

Step-by-step solution

Understanding the Question

The question asks us to identify the specific part of the mitochondria where the enzyme succinate dehydrogenase is located. Succinate dehydrogenase is an enzyme involved in the citric acid cycle and the electron transport chain.

Identifying the Location of Succinate Dehydrogenase

Succinate dehydrogenase is known to be an integral component of Complex II in the electron transport chain of mitochondria. Complex II is embedded within the inner mitochondrial membrane.

Choosing the Correct Option

Since succinate dehydrogenase is part of Complex II which is located in the inner mitochondrial membrane, the correct answer is option (d) Inner membrane.

Key concepts

Electron Transport Chain

The electron transport chain (ETC) is a series of protein complexes and small molecules that transfer electrons from electron donors to electron acceptors via redox reactions. This process generates energy in the form of a proton gradient that is ultimately used to produce ATP, the main energy currency of the cell. The ETC is located in the inner mitochondrial membrane, which provides the necessary environment for the chain's function.

Succinate dehydrogenase, the enzyme mentioned in the exercise, is also known as Complex II in the ETC. It catalyzes the oxidation of succinate to fumarate, simultaneously reducing flavin adenine dinucleotide (FAD) to FADH2. Electrons from FADH2 are transferred to coenzyme Q (ubiquinone), which then carries them through the remainder of the ETC for energy production.

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle or tricarboxylic acid (TCA) cycle, is a crucial metabolic pathway that takes place in the matrix of mitochondria. It's here that acetyl-CoA, derived from carbohydrates, fats, and proteins, is oxidized to produce carbon dioxide, ATP, and reduced coenzymes NADH and FADH2.

The role of succinate dehydrogenase in the citric acid cycle is to facilitate one step of this elaborate process. Beyond its intramitochondrial location, it's important to note how this enzyme interfaces with the ETC by generating FADH2, which then donates electrons for ATP synthesis. Therefore, understanding succinate dehydrogenase's role provides insight into its pivotal location at the crossroads of cellular respiration.

Inner Mitochondrial Membrane

Within the mitochondrion, the inner mitochondrial membrane plays a defining role. Unlike the outer membrane, it is selectively permeable and is the site where the electron transport chain and ATP synthesis occur. Its highly folded structure, with folds known as cristae, increases the surface area, thus enhancing the mitochondria's ability to produce ATP.

Complex II, which includes succinate dehydrogenase, is embedded in this membrane, emphasizing its strategic location for cellular energy production. This membrane's properties are vital for maintaining the mitochondrial membrane potential, which is essential for the ETC's proton gradient and subsequent ATP generation.