Major metabolic pathways

Major metabolic pathways.

The first part of this section concerns the biosynthetic pathways by which lipids, amino acids, and nucleotides are formed. The second concerns the intersection of biochemical pathways at various key junctions and physiological integration.

Regarding the biosynthesis of macromolecular precursors, the detailed, difficult pathways, such as synthesis of purines or the more complicated amino acid syntheses, do not need to be memorized for the MCAT. You do need to give yourself a sense of this material, though, because there are aspects at the basic level that can make it to the exam. Our suggestion is to aim for one step beyond the Bio 101 level but don't sacrifice too much study time. Get a good feel for this material, but don't spend a month memorizing all of those pathways at the expense of studying the immune system.

The second part of this section deals with the key junctions, endocrine control and the metabolic profile of various tissues. This second part definitely is at the core biochemistry you need to master for the MCAT, so you need a somewhat different disposition towards the second part of this section than the first. Mastery of the second part is one of the keys to a superior MCAT. It's that important.

WikiPremed Resources

Learning Goals


Understand how to see a biochemical control system as a modular circuit comprised of signaling components, ranges of signal response behavior, and modes of biochemical feedback.

Be comfortable discussing the regulatory mechanisms that allow the major pathways of energy metabolism (glycolysis, the citric acid cycle, fatty acid and amino acid oxidation, and oxidative phosphorylation) to function together in a concerted way to produce ATP and biosynthetic precursors.

Be able to describe the integration of the major bioenergetic and biosynthetic pathways glycolysis, citric acid cycle, gluconeogenesis and the pentose phosphate pathway.

Have a clear picture of the metabolic conditions leading to ketogenesis and the mechanisms involved in the use of ketone bodies for energy.

Possess a basic familiarity with the mevalonate pathway for the production of isopentenyl pyrophosphate and dimethylallyl pyrophosphate and how it relates to the biosynthesis of terpenoids and steroids.

Understand the various differences in the metabolic patterns of the brain, muscle, adipose tissue, kidney, and liver.

Suggested Assignments

The question server contains a general section covering basic concepts from gluconeogenesis, the pentose phosphate pathway, glyocogen metabolism, fatty acid metabolism, the urea cycle, and metabolic integration. After review complete the crossword puzzle for energy metabolism. Here is the solution to the puzzle.

Read pp. 77-79 in ExamKrackers Biology I. Perform practice items 57-64 on pg. 80.

Review the web resources for integration of metabolism.

Conceptual Vocabulary for Integration of Metabolism