ch. 2

Lactates and Carbohydrates

  • Lactose is not broken down; involves dehydration synthesis and hydrolysis.
  • Polysaccharides serve as storage units for monosaccharides in plants (starch) and animals (glycogen).
  • Glycogen is stored in muscle and liver cells; liver releases glycogen when glucagon is present.
  • Cellulose is structural in plant cell walls; serves as dietary fiber in humans.

Functions of Carbohydrates

  • Primary function: energy (quick energy from glucose).
  • Structural carbohydrates (e.g., cellulose) also present.
  • Carbohydrates are involved in cell recognition on plasma membranes.

Lipids

  • Lipids are hydrophobic; major categories include fats (triglycerides) and steroids.
  • Triglycerides consist of three fatty acids attached to glycerol.
  • Saturated fats are fully hydrogenated (single bonds), unsaturated fats contain double bonds.

Fats and Health

  • Unsaturated fats are generally healthier, raise HDL levels.
  • Triglycerides are key for long-term energy storage and insulation.

Phospholipids

  • Phospholipids are amphipathic: hydrophobic and hydrophilic regions; crucial for cell membranes.

Steroids

  • Characterized by four hydrocarbon rings; include cholesterol, estrogen, and testosterone.
  • Cholesterol is essential for cell membrane structure.

Eicosanoids

  • Function as signaling molecules within the immune system; include prostaglandins.

Proteins

  • Proteins perform most cellular functions; diverse functions include support, transport, enzymes, and antibodies.
  • Comprised of 20 amino acids; peptide bonds form between amino acids.
  • Proteins fold into primary, secondary, tertiary, and quaternary structures.

Protein Denaturation

  • Heating or pH changes can denature proteins, altering their function.

Enzymes

  • Enzymes catalyze biochemical reactions, bind substrates at active sites.

Nucleic Acids

  • DNA (double helix) and RNA (single strand), involved in genetic coding.
  • Structural unit is nucleotide (sugar, phosphate, nitrogenous base).
  • DNA bases: adenine, thymine, cytosine, guanine; RNA bases: adenine, uracil, cytosine, guanine.

ATP

  • ATP (adenosine triphosphate) is the energy currency of the cell, produced via aerobic and anaerobic respiration.