The three major pathways of glucose catabolism are glycolysis, the citric acid cycle, and oxidative phosphorylation.

Growth hormone, testosterone, and estrogen are anabolic hormones. Adrenaline, cortisol, and glucagon are catabolic hormones. Glucose metabolism fluctuates with an individual’s circadian rhythms which regulate anabolism and catabolism. Adrenaline, cortisol, and glucagon are catabolic hormones.

Glycolysis is a universal catabolic pathway that converts glucose into pyruvate through a sequence of ten enzyme-catalyzed reactions, and generates the high-energy molecules ATP (adenosine triphosphate) and NADH (reduced nicotinamide adenine dinucleotide).

Glycolysis occurs in the cytoplasm and it generates some NADH from NAD+. The NAD+ is an obligatory substrate for the reaction of glyceraldehyde-3-phosphate to 1,3-diphosphoglycerate. If NAD+ is not regenerated, glycolysis will halt.

If glycolysis is interrupted, these cells lose their ability to maintain their sodium-potassium pumps, and eventually, they die. The last step in glycolysis will not occur if pyruvate kinase, the enzyme that catalyzes the formation of pyruvate, is not available in sufficient quantities.

Nearly all living organisms carry out glycolysis as part of their metabolism. The process does not use oxygen and is therefore anaerobic. Glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells.

No H+ would move through ATP synthase and ATP would not be made. What is a poison that can stop glycolysis?

Why do all cells need an energy source, and what would happen if glycolysis were blocked in a red blood cell? All cells must consume energy to carry out basic functions, such as pumping ions across membranes. A red blood cell would lose its membrane potential if glycolysis were blocked, and it would eventually die.

In the absence of ADP, the ATP synthase stops functioning and when it stops, so too does movement of protons back into the mitochondrion. With this information, it is possible to understand the link between energy usage and metabolism. The root of this, as noted, is respiratory control.

In glycolysis, glucose is converted into pyruvate; in gluconeogenesis, pyruvate is converted into glucose.

Even though we don’t get much glucose from fat, a meal that’s high in fat can affect how fast our bodies digest carbohydrate. Because fat slows down the digestion of carbohydrate, it also slows down the rise in blood sugar levels. This sometimes can cause a high blood sugar level several hours after eating.

Pyruvate can be converted into carbohydrates via gluconeogenesis, to fatty acids or energy through acetyl-CoA, to the amino acid alanine, and to ethanol.

Glucagon and epinephrine trigger the breakdown of glycogen. Muscular activity or its anticipation leads to the release of epinephrine (adrenaline), a catecholamine derived from tyrosine, from the adrenal medulla. Epinephrine markedly stimulates glycogen breakdown in muscle and, to a lesser extent, in the liver.

Glycogen degradation consists of three steps: (1) the release of glucose 1-phosphate from glycogen, (2) the remodeling of the glycogen substrate to permit further degradation, and (3) the conversion of glucose 1-phosphate into glucose 6-phosphate for further metabolism.