WILTIMS #87: Hello again!

Happy New Year! 2013 was a great year for me (yay med school!), especially compared to 2012 (boo cancer!), so here's to 2014 upping the ante!

We hit the ground running (as usual) today and covered most of hemodynamics (the physics of blood circulation) in Physiology and ALL of glycolysis in Biochemistry. It's still amazing that something that took about a week to teach in undergrad was covered in an hour in medical school - and in greater detail.

Perhaps I'm overreacting though. After all, glycolysis consists of only 10 simple steps!

Glucose is phosphorylated by hexokinase to form glucose 6-phosphate (G6P) via the dephosphorylation of adenosine triphosphate (ATP) to adenosine diphosphate (ADP). G6P is then rearranged into fructose 6-phosphate (F6P) by phosphoglucose isomerase. F6P is irreversibly phosphorylated by phosphofructokinase to form fructose 1,6-bisphosphate (F1,6BP) after the consumption of an additional ATP molecule. F1,6BP is then split by aldolase into dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GADP). DHAP and GADP are interconverted by triosephosphate isomerase, allowing for complete conversion to GADP, which is exclusively consumed in the next step.

-Halfway there!-

Everything in the second half is doubled thanks to the two molecules of GADP that we derived from glucose. Inorganic phosphate (P_i) is added to GADP by glyceraldehyde phosphate dehydrogenase which simultaneously reduces NAD⁺ to NADH and produces 1,3-bisphosphoglycerate (1,3BPG). Phosphoglycerate kinase transfers one of 1,3BPG's phosphate groups to ADP, producing ATP and 3-phosphoglycerate (3PG). The remaining phosphate is transferred from the C-3 carbon to C-2 by phosphoglycerate mutase, forming 2-phosphoglycerate (2PG). 2PG is dehydrated to phosphoenolpyruvate (PEP) by enolase. Lastly, pyruvate kinase removes the remaining phosphate, forming another molecule of ATP and our final product, pyruvate.

The net reaction for glycolysis is:
glucose + 2 NAD⁺ + 2 ADP + 2 P_i → 2 pyruvate + 2 NADH + 2 H⁺ + 2 ATP + 2 H₂O

Appologies for taking this opportunity to study at you!

TIL: The body uses ~200 grams of glucose every day. 80% of this is consumed by the brain and blood cells.

Vasodilator medications reduce the pressure in the arterioles (small arteries) of the circulatory system but also result in increased pressure in capillaries and venules (small veins).