Question

The figure below shows the structure of a mitochondrion with its four labels (A), (B), (C) and (D). Select the part correctly matched with its function.

I. Part (C): Cristae- possess single circular DNA molecules and ribosomes.
II. Part (A): Matrix- a major site for respiratory enzymes.
III. Part (D): Outer membrane- gives rise to the inner membrane by splitting
IV. Part (B): Inner membrane- forms infoldings called cristae.

Answer 1

Hint: Mitochondria has circular double-stranded DNA which is present in the mitochondrial matrix, while cristae are the inward folding of the inner membrane of mitochondria which contains enzyme-like ATP synthase and a variety of cytochromes.

Complete answer: Mitochondria (Powerhouse of the cell) is the double membranous structure present in almost every eukaryotic cell (except in RBCs). Its outer membrane is the limiting boundary of the mitochondria and it is almost permeable for almost everything while the inner membrane is selectively permeable and forms folding towards the inner side facing the matrix called cristae. This folding of the inner membrane increases the surface area and both the membranes have their own enzymes associated with it. Mitochondria is the organelle besides plastid which is semi-autonomous in nature that means it is having its own genetic material (Circular double-stranded DNA) so it can do some of the function of its own like replication but for the major function, it has to depend on nuclear DNA and hence it is semi-autonomous in nature not completely autonomous.
-Part A is pointing towards crista but the option matrix is written and hence option (II) is incorrect.
-Part C is pointing toward crista correctly but the description is wrong, circular double-stranded DNA is present in the matrix of mitochondria not on cristae.
-Part B is correctly pointing towards the inner membrane which gives rise to crista and this is given in option (IV).
So, option (IV) is the correct answer.

Additional information:
Mitochondria were discovered by Kollicker. Many scientists believe that mitochondria resemble prokaryotic cells as both of them contain circular DNA and 70S ribosomes and both of them divide by binary fission. Mitochondria is the site for aerobic respiration. The first step occurs in the matrix of the mitochondria (Kreb cycle) and the second step occurs in the inner membrane of mitochondria (ETS).

Note: There is a difference in the inheritance patterns of nuclear DNA and mitochondrial DNA. Traits carried by nuclear DNA from both of the parents are inherited to the offspring, But in the case of mitochondrial DNA, maternal inheritance is shown that is those characters are only inherited from their mother.