Bio 150 Chapter 5

Chapter 5: The Structure and Function of Large Biological Molecules

Organic Compounds

• Organic compounds are carbon-based molecules.

  • Carbon atom: 6 protons, 6 neutrons.

The Characteristics of Life

• Life requires energy from the environment.

  • Producers extract energy/nutrients from nonliving sources.

  • Consumers get energy/nutrients by eating other organisms.

  • Decomposers obtain nutrients from dead organisms/organic waste.

• Autotrophs vs Heterotrophs

Animal Diets

• Herbivores: Mainly eat plants/algae.

• Carnivores: Mainly eat other animals.

• Omnivores: Eat both plants and animals.

Classes of Large Biological Molecules

• Four classes:

  1. Carbohydrates

  2. Lipids

  3. Proteins

  4. Nucleic Acids

Macromolecules

• Macromolecules are large, complex molecules with unique properties due to atomic arrangement.

• Polymers are long molecules made of similar building blocks called monomers.

  • Polymer types include:

    • Carbohydrate polymer

    • Protein polymer

    • Nucleic acid polymer

Synthesis and Breakdown of Polymers

• Enzymes speed up chemical reactions.

• Dehydration Reaction: Bonds two monomers by losing a water molecule.

• Hydrolysis: Breaks polymers into monomers by adding water.

• Polymers vary among the cells of an organism, between species, and can be built from a small set of monomers.

Carbohydrates

• Serve as fuel and building material.

• Include simple sugars and polysaccharides.

• Monosaccharides are the monomers of carbohydrates (C, H, O composition).

  • Examples include: Glucose (C6H12O6).

Classification of Monosaccharides

• Based on the carbonyl group location:

  • Aldoses: Aldehyde sugars.

  • Ketoses: Ketone sugars.

• Based on the number of carbons:

  • Trioses: 3 carbons

  • Pentoses: 5 carbons

  • Hexoses: 6 carbons

Disaccharides

• Formed via dehydration reaction joining two monosaccharides (glycosidic linkage).

  • Example: Sucrose (Glucose + Fructose).

Polysaccharides

• Function in energy storage and structural roles.

• Structure and function depend on sugar monomers and glycosidic linkages.

• Types of polysaccharides:

  • Starch: Storage for plants (Amylose and Amylopectin).

  • Glycogen: Storage in animals, primarily in liver/muscle cells.

  • Cellulose: Major component of plant cell walls; glycosidic linkages differ from starch.

  • Chitin: Structural polysaccharide in arthropod exoskeletons and fungal cell walls.

Lipids

• Lipids are the one class of large biological molecules that do not form true polymers.

• They are hydrophobic and consist mainly of hydrocarbon regions.

• Major types:

  1. Fats: Composed of glycerol and fatty acids.

  2. Phospholipids: Make up cell membranes, with hydrophobic tails and a hydrophilic head.

  3. Steroids: Characterized by four fused rings (example: cholesterol).

Proteins

• Proteins have varied structures/functions.

• Made from amino acid monomers (20 types).

• Functions:

  • Structural: Provides support (Keratin, Collagen).

  • Enzymatic: Catalyze reactions (Digestive enzymes).

  • Transport: Move substances (Hemoglobin).

  • Motor: Movement (Myosin, Actin).

  • Hormonal/Receptor proteins: Regulate processes.

Protein Structure

• Levels of structure:

  1. Primary: Sequence of amino acids.

  2. Secondary: Coils and folds (α helices, β pleated sheets).

  3. Tertiary: Overall 3D shape.

  4. Quaternary: Assembly of multiple polypeptide chains.

Denaturation

• Loss of structure = loss of function; can result from environmental factors (pH, temperature).

Nucleic Acids

• Store, transmit, and help express hereditary information.

  • DNA: Deoxyribonucleic acid, stores genetic info.

  • RNA: Ribonucleic acid, involved in protein synthesis and gene expression.

• Genes direct polypeptide synthesis via messenger RNA (mRNA).

Structure of Nucleic Acids

• Composed of nucleotides (nitrogenous base + sugar + phosphate group).

  • Base pairing rules: A-T, G-C for DNA; A-U, G-C for RNA.

• DNA forms double helix structure, while RNA is usually single-stranded.