Biology: Molecules of Life

Study Notes

Understanding of water, carbohydrates, lipids, proteins, and nucleic acids is crucial in biology.

Composed of one oxygen atom and two hydrogen atoms.
Hydrogen atoms are covalently bonded to oxygen through shared electrons.
Oxygen is more electronegative, creating a polar molecule with partial positive (H) and negative (O) charges.
Water's properties:
- Universal solvent due to its polarity.
- Low viscosity and high specific heat capacity.
- High latent heat of vaporization and surface tension.
- Maximum density at 4°C.

Classes include monosaccharides, disaccharides, and polysaccharides.
Disaccharides are characterized by being water-soluble, sweet-tasting, and crystalline. Common examples are maltose, sucrose, and lactose.
Formation and breakdown of maltose involve condensation and hydrolysis reactions.
Polysaccharides are polymers made of many monosaccharides; they are typically large, not sweet, and insoluble in water.
Key polysaccharides:
- Starch: Energy storage in plants; composed of amylose (linear) and amylopectin (branched).
- Glycogen: Major carbohydrate storage in animals; similar to amylopectin but larger and more branched.
- Cellulose: Structural component in plant cell walls.

Made up of 20 amino acids classified based on their side chain properties (polar, nonpolar, acidic, basic).
Structure is determined by the sequence of amino acids:
- Primary Structure: Sequence of amino acids encoded by DNA.
- Secondary Structure: Coiling (α-helix) and folding (β-pleated sheet) held by hydrogen bonds.
- Tertiary Structure: Three-dimensional shape stabilized by interactions among R groups, including hydrogen bonds, ionic bonds, and disulfide bridges.
- Quaternary Structure: Multiple polypeptide chains forming a functional macromolecule.
Factors affecting protein structure:
- Temperature: Higher temperature can disrupt hydrogen bonds and ionic bonds, leading to denaturation.
- pH: Extreme pH levels can alter charges on functional groups, breaking bonds and leading to denaturation.

DNA and RNA differences:
- DNA: Typically double-stranded, stable, with deoxyribose sugar and bases A, T, C, G.
- RNA: Typically single-stranded, less stable, with ribose sugar and bases A, U, C, G, including three types: mRNA, rRNA, and tRNA.
DNA is manufactured in the nucleus and carries genetic information, while RNA plays various roles in protein synthesis and gene expression.