Carbon and Biological Molecules

Introduction

• Carbon is the sixth element with 6 protons and 6 electrons.
• It has 4 valence electrons, allowing it to form 4 covalent bonds.
• Carbon compounds are stable and diverse, forming single, double bonds, chains, and rings.

Macromolecules

• Polymers: Large molecules made of monomers.
• Main Classes: Polysaccharides, polypeptides, lipids, and nucleic acids.

Condensation Reactions

• Links monomers into polymers, releasing water (H2O).
• Requires energy supplied by ATP.

Hydrolysis Reactions

• Breaks polymers into monomers using water.

Carbohydrates

Monosaccharides

• Basic unit of carbohydrates.
• Example: Glucose (C6H12O6), a quick energy source.
• Properties: Soluble in water, oxidizes for energy.

Disaccharides and Polysaccharides

• Disaccharides: Two sugar molecules.
• Polysaccharides: Long chains, e.g., starch, glycogen, cellulose.
  • Starch: Only in plants, contains alpha glucose.
  • Glycogen: In animals, similar to starch but more branched.
  • Cellulose: Made of beta glucose, strong structure for plant cell walls.

Glucose Structure

• Comes in alpha and beta forms.
• Structural differences influence polysaccharide properties.

Glycoproteins

• Carbohydrates attached to proteins on cell membranes.
• Important in cell recognition and immune response (e.g., blood types).

Lipids

General Properties

• Composed of carbon, hydrogen, and oxygen.
• Hydrophobic, not soluble in water.
• Includes fats, oils, waxes, and steroids.

Fatty Acids

• Building blocks of lipids.
• Can be saturated (single bonds) or unsaturated (double bonds).

Triglycerides and Phospholipids

• Triglycerides: Three fatty acids linked to glycerol.
  • Used for long-term energy storage.
• Phospholipids: Similar to triglycerides, but one fatty acid is replaced by a phosphate group.
  • Form cell membranes.

Saturation and Isomers

• Saturated: Straight chains, packed tightly, higher melting points (solids like butter).
• Unsaturated: Bent chains, lower melting points (liquids like oil).
• Cis vs. Trans: Refers to hydrogen orientation around double bonds.

Steroids

• Unique structure with four carbon rings.
• Hydrophobic, can pass through lipid bilayers.

Conclusion

• Understanding the chemistry of carbon and its ability to form diverse compounds is essential for studying biological molecules and their functions in living organisms.