bio ch5

1. The Structure and Function of Large Biological Molecules

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.

Functions: Serve as fuel and building materials.
Types of Carbohydrates:
- Monosaccharides: Simplest carbohydrates; e.g., Glucose (C6H12O6).
- Polysaccharides: Macromolecules formed from many 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.

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.

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).

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.

Composed of two fatty acids and a phosphate group attached to glycerol.
Form bilayer structures in cell membranes, with hydrophilic heads and hydrophobic tails.

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.

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).

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

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).

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.

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.