Energy Nutrition: Metabolism of Carbohydrates and Fats

This will likely be a very short post as most of the content has already been covered in posts for BIOC3004. (Note: CHO = carbohydrate)

Describe the molecules from which we derive energy

The molecules from which we derive energy are proteins, carbohydrates and fats. Most of our energy is derived from carbohydrates, a smaller percentage is derived from fats, and only a very small amount is derived from proteins. If you want to know even more about these molecules, I've written about them in excruciating detail for CHEM1004.

Outline hepatic processing and interconversion of fats and CHOs

The liver can carry out a lot of processes, but we'll only focus on a few of these processes here. Processes involving carbohydrates include glycogenesis, glycogenolysis, gluconeogenesis and conversion of monosaccharides into other monosaccharides (e.g. converting fructose into glucose). (If you don't know what those terms mean, see here.) Interestingly enough, glucose 6-phosphatase, the last enzyme in glycogenolysis, is only present in the liver. That means that the liver can break down glycogen into glucose that can leave the cell and be transported elsewhere around the body, whereas other tissues (such as muscle) can only get as far as glucose-6-phosphate, which cannot leave the cell.

Liver processes involving fats include beta-oxidation (the liver is the primary site of beta-oxidation), synthesis of fats and cholesterol, conversion of excess acetyl CoA to ketone bodies, storage, formation of lipoproteins (e.g. VLDL) and conversion of cholesterol into bile salts. The liver is truly one very busy organ!

Outline the mechanisms by which we derive energy from fats and CHOs

We derive energy from fats via beta-oxidation, and from carbohydrates via glycolysis. Both beta-oxidation and glycolysis result in acetyl CoA, which can enter the TCA cycle and then oxidative phosphorylation.

Outline the processes of glycolysis, the TCA cycle, & oxidative phosphorylation

Glycolysis: Glycolysis and the Pentose Phosphate Pathway
The TCA cycle: The TCA Cycle
Oxidative phosphorylation: Electron Transport Chain and Oxidative Phosphorylation

Outline the processes of lipolysis & β–oxidation

Beta-Oxidation

Describe the roles of energy carrying intermediates in energy metabolism

The energy carrying intermediates in energy metabolism are NADH, FADH₂ and ATP, which I've written about in pretty much all of the posts linked to above. (They're also discussed here.)