W.B.C.S. Main 2018 Question Answer – Zoology – Mitochondria – Ultrastructure.

WBCS মেইনস ২০১৮ প্রশ্ন উত্তর  – প্রাণীবিদ্যা – মাইটোকন্ড্রিয়া – আল্ট্রা স্ট্রাকচার।

In 1953, Palade and Sjostrand independently described the ultrastructure of mitochondria. Mitochondria are bounded by an envelope consisting of two concentric membranes, the outer and inner membranes. The space between the two membranes is called inter-membrane space.Continue Reading W.B.C.S. Main 2018 Question Answer – Zoology – Mitochondria – Ultrastructure.

Outer Membrane

The outer mitochondrial membrane has high permeability to molecules such as sugars, salts, coenzymes and nucleotides etc. It has many similarities with the ER but differs from it in some respects, e.g., mono-amine-oxidase is present in the mitochondrial outer membrane but not in ER.

On the other hand, the enzyme glucose-6-phosphatase is absent from the mitochondrial outer membrane but is present in ER. The mitochondrial outer membrane contains a number of enzymes and proteins

The inter-membrane space is divided into two regions

(1) Peripheral space and

(2) Intracristal space .

Large flattened cristae are connected to the inner membrane by small tubes called peduculi cristae which are few nanometers in diameter. The inter-membrane space has several enzymes of which “adenylate kinase” is the chief one (Table 2.6). This enzyme transfers one phosphate group from ATP to AMP to produce two molecules of ADP.

Inner Membrane

The inner mitochondrial membrane invaginates inside the matrix; the invaginations are called cristae. This membrane has a high ratio of protein to lipid. “Knobs” or “spheres” of 8-9 nm diameter are spaced 10 nm apart on the cristae membranes. These knobs contain F₁proteins and ATPase responsible for phosphorylation. They are joined to the cristae by 3 nm long stalks called “F₀“. The F₀-F₁ ATPase complex” is called ATP synthase. The inner membrane contains large number of proteins which are involved in electron transfer (respiratory chain) and oxidative phosphorylation . The respiratory chain is located within the inner membrane, and consists of pyridine nucleotides, within the inner membrane, and consists of pyridine nucleotides, flavoproteins, cytochromes, iron-sulphur proteins and quinones.

Besides its role in electron transfer, and phosphorylation, the inner membrane is also the site for certain other enzymatic pathways, such as, steroid (hormone) metabolism.

The interior of mitochondrion is called matrix . It has granular appearance in electron micrographs. Some large granules ranging from 30 nm to several hundred nanometers in diameter are also present in the matrix. The matrix contains enzymes and factors for Krebs cycle, pyruvate dehydrogenase and the enzymes involved in β-oxidation of fatty acids.

However, succinate dehydrogenase is present in the inner membrane instead of matrix; this enzyme catalyses the direct transfer of electrons from succinate to the electron transfer chain.

The enzyme pyruvate dehydrogenase converts pyruvate to acetyl-Coenzyme A (acetyl-CoA) which enters the Krebs cycle. Besides above, matrix also contains DNA, RNA, ribosomes and proteins involved in protein and nucleic acid syntheses.

Our own publications are available at our webstore (click here).

For Guidance of WBCS (Exe.) Etc. Preliminary , Main Exam and Interview, Study Mat, Mock Test, Guided by WBCS Gr A Officers , Online and Classroom, Call 9674493673, or mail us at – mailus@wbcsmadeeasy.in
Visit our you tube channel WBCSMadeEasy™ You tube Channel
Please subscribe here to get all future updates on this post/page/category/website