Reactions of Organic Phosphorus Compounds
Bioenergetics and Cellular Respiration
|Although the MCAT is not going to nail you on precise mechanistic details from glycolysis or the citric acid cycle, you really do need to have a comfort with the material if you are presented with it on a passage. There are several reasons for including a step by step discussion of glycolysis in these Interdisciplinary Discussions. Follow along the representation of the reactions which is almost certainly in your Biology textbook. Just keep in mind that one of these purposes is NOT to panic you or cause you to spend your whole week memorizing every detail. Glycolysis can occur on the test certainly. For example, it would be well within the purview of the MCAT to expect you to know that the first step of glycolysis transforms glucose into a higher energy form by phosphorylation. However, the MCAT would not expect you to name the enzyme as 'hexokinase'.|
Kinases are enzymes catalyzing the transfer of a phosphoryl group from ATP to an acceptor. Hexokinase catalyzes the transformation of glucose to glucose 6-phosphate, the first ATP utilization in glycolysis.
What does a kinase do? A kinase enables the transfer of a phorphoryl group from ATP to an acceptor. The ability to identify the purpose of a kinase has been tested on the MCAT in the past.
In general, the activity of a kinase involves coordination between phosphate oxygens in ATP and Mg2+ (or Mn2+) in the kinase. By shielding the negative charges of ATP, this activates the phosphoryl group for attack by a nucleophile such as the sugar hydroxyl of glucose.