The researcher performed a follow-up experiment to measure the rate of oxygen consumption by muscle and brain cells. Predict the
effect of the MT - ND5 mutation on the rate of oxygen consumption in muscle and brain cells. Justify your prediction. The researcher had hypothesized that the addition of the vitamin that is similar in structure to NADH would increase the activity of the mutated NADH dehydrogenase enzyme in individuals with the disorder. Explain how the vitamin most likely increased the activity of the enzyme.
Mitochondria are plentiful in mammalian cells, with their proportions varying across different tissues, from less than 1% in white blood cells to as high as 35% in heart muscle cells. It is essential to understand that mitochondria are not static structures but instead form a dynamic network that frequently undergoes processes of fission and fusion. In skeletal muscle, they exist as part of a reticular membrane network. The two subpopulations, subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria, occupy different subcellular regions and exhibit slight differences in their biochemical and functional characteristics tied to their anatomical context. The SS mitochondria are positioned just beneath the sarcolemma, while IMF mitochondria are found closely associated with myofibrils. Their distinct properties likely play a role in their adaptability. SS mitochondria make up about 10-15% of the total mitochondrial volume and are believed to be more adaptable than their IMF counterparts, despite the latter displaying higher levels of protein synthesis, enzyme activity, and respiration (1).
The rate at which muscle and brain cells consume oxygen is expected to decline. The MT-ND5 mutation leads to a buildup of lactic acid resulting from glycolysis not progressing to the Krebs cycle; rather, it ends up in fermentation. Consequently, since the Krebs cycle is not being utilized, oxygen consumption ceases.
