Question

Mitochondrial enzymes for oxidative metabolism are
A) On or within the surface of cristae
B) Located on the outer membrane
C) Floating freely on intermembrane
D) In the mitochondrial lysosomes

Answer 1

The energy released from the breakdown of nutrients is used by the mitochondrial enzymes to synthesize ATP or Adenosine triphosphate which is used by cells to get energy for the reactions. This process takes the help of molecular oxygen received from the blood to complete the oxidation of fat, proteins and sugar to carbon dioxide and water.

Complete answer:
There are basically two divisions of mitochondrial membranes. The outer membrane is like a wall surrounding the inner membrane. The outer membrane can be characterized as a porous layer large enough to allow the movement of ions and the molecules here are as large as small as a small protein. Hence the enzymes are definitely not found here.
The intermembrane is the tiny portion between the inner and outer membrane. This area is so tiny that there is no such probability of availability of any kind of enzyme here.
Lysosomes and mitochondria are different cell organelles with their respective functions. The contact between these two organelles is the inter-organelle metabolites. So, there is no chance of the existence of mitochondrial enzymes in lysosomes.
The cristae are the finger-like projections found in the folds of the inner membrane of mitochondria. The oxidative enzymes are found mainly on the surface of the cristae which may be absorbed within at some point as well. So, we can say that mitochondrial enzymes for oxidative metabolism are on or within the surface of cristae.

Hence the correct answer is option ‘D’.

Note: It should be noted that the enzymes are found within the surface of the inner membrane. This is the region where cristae are located. In singular, it is called Crista. This name is derived from Latin which means ‘crest’ or ‘plume’.