Chemistry of Lipids and Digestion

Lipid Metabolism

• Lipase breaks down lipid ester bonds.
• Gastric acid and pepsin break down fatty acids.
• Bile acids emulsify lipids.

Cholesterol

• Cholesterol is not derived from cyclopentanoperhydrophenanthrene.
• Cholesterol can be esterified by long-chained carboxylic acid.
• Cholesterol occurs in the human body in free and esterified forms.
• Cholesterol is a part of cell membranes.
• Cholesterol gives rise to bile acids.
• Cholesterol is a precursor for sex hormones and bile pigments.

Bile Acids

• Bile acids are formed in the liver from cholesterol.
• Bile acids are important for the absorption and breakdown of triglycerides.
• Bile acids have shorter side chains than cholesterol.

Sterols

• Phytol belongs to triterpenes.
• Ergosterol is found in yeast.
• By UV irradiation of ergosterol, vitamin D2 (ergocalciferol) is produced.

Proteins

• Proteins have structural, kinetic, transport, regulatory, and defensive functions.
• Proteins consist of amino acids having one-COOH group and one-NH2 group in the molecule.
• Essential amino acids must be supplied in the diet.
• Non-essential amino acids are formed by transamination of oxo acids in the human body.

Amino Acids

• Tyrosine is a hydroxy derivative of phenylalanine.
• Aspartic acid and glutamic acid are acidic amino acids.
• Lysine, proline, histidine are basic amino acids.

Enzymes

• Isomerases catalyze isomers' rearrangement.
• Lyases catalyze nonhydrolytic cleavage of C-C bonds.
• Ligases catalyze synthesis of two substrates in the presence of ATP.

Coenzymes and Nucleic Acids

• NAD and FAD are oxidoreductase coenzymes that contain pyridine.
• Nucleic acids are responsible for the organization and reproduction of living matter.
• DNA and RNA differ in their pentose content, with DNA containing deoxyribose and RNA containing ribose.