Question

Select the correct statement(s) regarding mitochondria.
(a) Mitochondria show a great degreee of variability in their shape and size but their number remains constant per cell.
(b) Outer membrane is compose of 80% proteins and 20% lipids.
(c) The enzymes and electron carriers for the formation of ATP are present only in the inner membrane.
(d) These are miniature biochemical factories where proteins and fats are completely reduced.

• A. (a), (b) and (c)
• B. (b), (c) and (d)
• C. (c) and (d) only
• D. (c) only

Answer 1

The correct option is D (c) only

(a) The number of mitochondria per cell is variable depending on the physiological activity of the cells. In terms of shape and size also, a considerable degree of variability is observed. Typically it is sausage-shaped or cylindrical having a diameter of 0.2-1.0µm (average 0.5µm) and length 1.0-4.1µm.

(b) Each mitochondrion is a double membrane-bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments, i.e., the outer compartment and the inner compartment. The inner compartment is called the matrix. The outer membrane forms the continuous limiting boundary of the organelle. The inner membrane forms a number of infoldings called the cristae towards the matrix.

(c) Mitochondria are the sites of aerobic respiration. They produce cellular energy in the form of ATP, hence they are called ‘powerhouses’ of the cell.

(d) The matrix also possesses single circular DNA molecule, a few RNA molecules, ribosomes (70s) and the components required for the synthesis of proteins.

So, the correct option is ' (c) only'.