Chemistry · Ch 10 — Biomolecules
Summary
Summary
- Carbohydrates: Polyhydroxy aldehydes or ketones. Classified as monosaccharides (e.g., glucose ), oligosaccharides (e.g., sucrose), and polysaccharides (e.g., starch, cellulose). Glucose exists as and anomers due to cyclization.
- Glucose structure: Open-chain (aldose) and cyclic (pyranose) forms. The group reacts to form a hemiacetal; the at C-5 determines or configuration.
- Reducing vs. non-reducing sugars: Sugars with a free aldehyde or ketone group (e.g., glucose, fructose) reduce Tollens’ or Fehling’s reagent. Sucrose is non-reducing because its glycosidic linkage involves both anomeric carbons.
- Polysaccharides: Starch (amylose + amylopectin, -glycosidic bonds) and cellulose (-glycosidic bonds, linear, indigestible by humans). Glycogen is animal starch.
- Proteins: Polymers of -amino acids linked by peptide bonds (). Each amino acid has a general structure .
- Amino acid classification: Essential (must be obtained from diet) vs. non-essential. By relative numbers of and groups: acidic, basic or neutral.
- Protein structure levels: Primary (sequence), secondary (-helix, -pleated sheet via H-bonds), tertiary (3D folding via disulfide bonds, hydrophobic interactions), quaternary (subunit assembly, e.g., haemoglobin).
- Denaturation: A change of pH or temperature disturbs the H-bonds that hold a native protein's folded shape — the secondary and tertiary structures are destroyed (primary stays intact) and biological activity is lost (e.g., coagulation of egg white on boiling).
- Enzymes: Biological catalysts, mostly proteins. Active site binds substrate; lock-and-key vs. induced-fit models. Factors: pH, temperature, inhibitors.
- Vitamins: Organic compounds required in small amounts. Fat-soluble (A, D, E, K) and water-soluble (B-complex, C). Deficiency causes specific diseases (e.g., scurvy for vitamin C). …