Question

Describe the structure of mitochondria for 8 marks

Answer 1

Mitochondria are rod shaped structure found in both animal and plant cells. It is a double membrane bound organelle. It has the outer membrane and the inner membrane. The membranes are made up of phospholipids and proteins.
The components of mitochondria are as follows:
Outer membrane
It is smooth and is composed of equal amounts of phospholipids and proteins.
It has a large number of special proteins known as the porins.
The porins are integral membrane proteins and they allow the movement of molecules that are of 5000 daltons or less in weight to pass through it.
The outer membrane is freely permeable to nutrient molecules,ions, energy molecules like the ATP and ADP molecules.
Inner membrane
The inner membrane of mitochondria is more complex in structure.
It is folded into a number of folds many times and is known as the cristae.
This folding help to increase the surface ares inside the organelle.
The cristae and the proteins of the inner membrane aids in the production of ATP molecules.
Various chemical reactions takes place in the inner membrane of the mitochondria.
Unlike the outer membrane, the inner membrane is strictly permeable, it is permeable only to oxygen, ATP and it also helps in regulating transfer of metabolites across the membrane.
Intermembrane space
It is the space between the outer and inner membrane of the mitochondria, it has the same composition as that of the cell's cytoplasm.
There is a difference in the protein content in the intermembrane space.
Matrix
The matrix of the mitochondria is a complex mixture of proteins and enzymes. These enzymes are important for the synthesis of ATP molecules, mitochondrial ribosomes, tRNAs and mitochondrial DNA.

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