bio ch5

1. The Structure and Function of Large Biological Molecules

• Overview of biological molecules

2. Macromolecules

• Definition: Large polymers built from monomers

• Polymers: Long molecules made of similar building blocks called monomers

  • Examples: Carbohydrates, proteins, nucleic acids

• Synthesis and Breakdown of Polymers:

  • Synthesis: Dehydration reaction occurs when two monomers bond, resulting in loss of water.

  • Breakdown: Hydrolysis reaction disassembles polymers back into monomers.

  • Enzymes: Specialized macromolecules that speed up these reactions.

3. Carbohydrates

• Functions: Serve as fuel and building materials.

• Types of Carbohydrates:

  • Monosaccharides: Simplest carbohydrates; e.g., Glucose (C6H12O6).

  • Polysaccharides: Macromolecules formed from many monosaccharides.

4. Sugars (Monosaccharides)

• Molecular formulas: Typically multiples of CH2O.

• Classification:

  • Based on carbonyl group location: Aldose (end carbonyl) or Ketose (internal carbonyl).

  • Number of carbons in skeleton.

• Structure: Often form rings in aqueous solutions; serve as major fuel for cells.

  • Disaccharides: Formed when two monosaccharides are joined through dehydration, creating glycosidic linkages.

5. Polysaccharides

• Roles: Storage and structural functions.

• Storage Polysaccharides:

  • Starch: Storage in plants (amylose is simplest form).

  • Glycogen: Storage in animals (primarily in liver and muscle cells).

• Structural Polysaccharides:

  • Cellulose: Major component of plant cell walls; differs in glycosidic linkages compared to starch.

  • Chitin: Found in arthropod exoskeletons and fungal cell walls.

6. Lipids

• Overview: Diverse group of hydrophobic molecules; not true polymers.

• Characteristics: Mix poorly with water; mostly hydrocarbon regions.

• Types of Lipids:

  • Fats (triglycerides): Composed of glycerol and fatty acids.

  • Phospholipids: Form the structural basis of cell membranes (bilayers).

  • Steroids: Composed of four fused carbon rings (e.g., cholesterol).

7. Fats

• Structure: Consist of glycerol and three fatty acids linked by ester linkages.

• Types of Fatty Acids:

  • Saturated: No double bonds, solid at room temperature (mostly animal fats).

  • Unsaturated: One or more double bonds, liquid at room temperature (plant and fish fats).

• Health Impact:

  • Diet rich in saturated fats may lead to cardiovascular disease.

  • Hydrogenation: Converts unsaturated fats to saturated, may create trans fats contributing to disease.

  • Main function is energy storage.

8. Phospholipids

• Composed of two fatty acids and a phosphate group attached to glycerol.

• Form bilayer structures in cell membranes, with hydrophilic heads and hydrophobic tails.

9. Proteins

• Importance: Comprise over 50% of the dry mass of cells; perform various functions including catalysis and structural support.

• Enzymes: Specialized proteins that speed up chemical reactions.

• Structure: Composed of amino acids (20 types), linked by peptide bonds into polypeptides.

10. Protein Structure

• Levels of Structure:

  • Primary: Unique amino acid sequence.

  • Secondary: Coils and folds (alpha helices and beta sheets).

  • Tertiary: Overall shape from interactions of R groups.

  • Quaternary: Assembly of multiple polypeptides (e.g., hemoglobin).

11. Sickle-Cell Disease

• Caused by a single amino acid substitution in hemoglobin, altering structure and function.

12. Nucleic Acids

• Types: DNA and RNA, involved in storing and transmitting genetic information.

• Structure: Nucleotides (base, sugar, phosphate) linked by phosphodiester bonds.

• Function: DNA directs synthesis of mRNA, controlling protein synthesis (gene expression).

13. DNA Structure

• Composed of two polynucleotide strands forming a double helix with specific base pairing (A-T, G-C).

• RNA is single-stranded; thymine is replaced with uracil.

14. Genomics and Proteomics

• Genomics: Study of whole genomes; accelerated by advancements in sequencing technology.

• Proteomics: Study of protein structures and functions.

• Molecular evolution: DNA and protein sequences can trace evolutionary relationships.