Mitochondria structure or functions

 Mitochondria

Mitochondria (Sing-mitochondrion) 

Mitochondria were first observed in striated flight muscles of insects as a granular structure by Kolliker (1880). The term mitochondria used by Benda (1897) is also called the powerhouse of the cell.

Mitochondria structure or functions

By Google:

An organelle is found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. It has a double membrane, the inner part being folded inwards to form layers (cristae).

By Author:

Mitochondria is a membrane-bound cell organelle that is present in all types of eukaryotic cells. Its function is to generate a large amount of energy for the cell in the form of adenosine triphosphate (ATP). It is most popularly known as the powerhouse of the cell. It has a large quantity of metabolic activity to work. The number of mitochondria per cell is variable depending on the physiological activity of the cell. It is found in a variety of cells.

Mitochondria diagram

Shape & Size/ Structure of Mitochondria

Saucer and typically round to oval are two common shapes of mitochondria. The size of mitochondria is 1 to 4.1m x 0.2 to 1um.

Number: The number of mitochondria per cell is variable depending on the physiological activity of the cell.

Structure of mitochondria

 Mitochondria is double double-membraned cell organelle. The diameter of each membrane is 60-75A" and separated by 80-100A broad space that is called perimitochondrial space (Outer chamber) Both the membranes have their own specific enzyme

• Inner membrane is folded to form cristae (palade 1952) that increase surface area. The outer surface of the inner membrane is called C-face whereas the inner surface is called M-face.

The inner membrane and cristae bear an electron transport chain and tennis racket-like particles called Oxysomes or Elementary particles, F-F, particles or ETP (Electron transport particles) or ATPase particles. The latter is 10-10 in number These are considered functional units of mitochondria and they are the sites of oxidative phosphorylation. The Head part of oxysomes contains ATPase (ATP synthase) enzymes for oxidative phosphorylation.

The mitochondrial matrix is found in the inner chamber. The former contains double-stranded naked, circular, Su long prokaryotic DNA (mt-DNA That is rich in G-C ratio), 70S ribosomes (55S ribosomes in mitochondria of mammals), RNA (5-7%) hence mitochondria are considered as semi-autonomous cell organelles. 70% of the total enzymes of cells are found in mitochondria.

The single, circular mt DNA molecule is 1% of the total DNA of the cell and was discovered by Nass and Nass (1963).

Energy production by mitochondria

The outer mitochondria's membrane is freely permeable to small molecules and it contains special channels capable of transporting large molecules. In contrast, the inner membrane is some less permeable than comparatively outer ones, allowing only very small molecules to cross into the gel-like matrix that makes up the organelle’s central mass. 

Origin: 

They have originated from the symbiosis of a prokaryotic organism (aerobic bacteria) with a host cell that was anaerobic and derived its energy only from glycolysis (Endosymbiotic hypothesis)

Functions of mitochondria

(1)It is the site of aerobic respiration. Most of the ATP is produced by mitochondria during respiration this ATP is required for performing various metabolic activities. Thus mitochondria are called the powerhouse of the cell. Enzymes of the Krebs cycle, fatty acids synthesis, and amino acids synthesis are found in the matrix. The gene for male sterility in maize plants is found in the  DNA. Thus it helps in cytoplasmic inheritance

 Mitochondria help in Vitellogenesis in oocytes protein is required for hemoglobin, mitochondria resonate with the concept cytochrome and myoglobin are synthesized in (t) Enzymes like succinic dehydrogenase, ATPase, and cytochrome oxidase are found in the inner membrane of mitochondria

(2) Mitochondria are rich in Manganese (Mn).

(3) In bacteria the Mesosomes have aerobic respiration hence these are called Chondriald Tous Mesosomes and Mitochondria are analogous organelles.

The mitochondria divide by fusion.

(4) Production of energy is the most important function in producing ATP for the cells.

(5) Production of ATP. Perhaps the most well-known role of mitochondria is the production of ATP, the energy currency of cells.

(6) Calcium Homeostasis.

(7) Regulation of Innate Immunity.

(8) Programmed Cell Death.

(9) Stem Cell Regulation.

(10) Heat production for the cells.

MCQs on Mitochondria structure or functions

Q. What is the primary function of mitochondria in a cell?

a) Synthesis of proteins

b) Storage of genetic information

c) Production of energy

d) Regulation of cell division

Answer: c) Production of energy

Q. Which part of the mitochondria is responsible for increasing the surface area?

a) Outer membrane

b) Inner membrane

c) Cristae

d) Matrix

Answer: c) Cristae

Q. What is the shape of mitochondria?

a) Spherical

b) Cylindrical

c) Saucer-like

d) Tubular

Answer: c) Saucer-like

Q. What is the composition of mitochondrial DNA (mtDNA)?

a) Single-stranded RNA

b) Double-stranded DNA

c) Circular DNA

d) Linear DNA

Answer: c) Circular DNA

Q. What is the popular term used to describe mitochondria?

a) Cell powerhouse

b) Energy generator

c) Genetic reservoir

d) Protein factory

Answer: a) Cell powerhouse