Biological Molecules: Structure, Function, and Diversity

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Ch. 3: Biological Molecules

Introduction to Biological Molecules

Biological molecules are essential for life, forming the backbone of cellular structure and function. They are primarily carbon-based, with hydrogen, oxygen, nitrogen, phosphorus, and sulfur as common elements.

Hydrocarbons: Molecules consisting of only carbon and hydrogen. Example: Methane (CH4).
Carbon's versatility: Carbon can form four covalent bonds, allowing for a vast diversity of molecular structures.
Organic molecules: Defined by the presence of carbon atoms, often arranged in chains or rings.

Handwritten notes on biological molecules, carbon structure, and hydrocarbon examples

Carbon Skeletons and Functional Groups

The arrangement of carbon atoms (carbon skeletons) determines the shape and function of organic molecules. Functional groups are specific clusters of atoms that confer unique properties.

Carbon skeletons: Can be linear, branched, or cyclic.
Functional groups: Common groups include hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), phosphate (-PO4), methyl (-CH3), and sulfhydryl (-SH).
Polarity: Functional groups influence molecular polarity and reactivity.

Notes on carbon skeletons, functional groups, and their properties

Properties and Roles of Functional Groups

Functional groups are critical for molecular interactions and biological activity.

Hydroxyl group: Polar, found in sugars.
Carboxyl group: Acidic, found in amino acids and fatty acids.
Amino group: Basic, found in amino acids.
Phosphate group: Polar, found in nucleotides.
Methyl group: Nonpolar, affects gene expression.
Sulfhydryl group: Found in proteins, forms disulfide bonds.

Notes on functional groups, their properties, and examples

Macromolecules and Polymers

Monomers and Polymers

Macromolecules are large molecules composed of repeating subunits called monomers. Polymers are formed by linking monomers through dehydration synthesis (removal of water).

Dehydration synthesis: Joins monomers, releasing water.
Hydrolysis: Breaks polymers into monomers by adding water.
Examples: Polysaccharides (carbohydrates), proteins, nucleic acids.

Notes and diagrams on monomers, polymers, dehydration synthesis, and hydrolysis Notes and diagrams on hydrolysis and classes of biological molecules

Classes of Biological Molecules

There are four main classes of biological macromolecules:

Carbohydrates: Energy storage, structure, cell recognition.
Lipids: Energy storage, membranes, signaling.
Proteins: Catalysis, structure, transport, defense.
Nucleic acids: Information storage and transfer.

Carbohydrates

Monosaccharides and Polysaccharides

Carbohydrates are composed of monosaccharides (simple sugars) and polysaccharides (complex carbohydrates).

Monosaccharides: Glucose, fructose, galactose. Generic formula: .
Polysaccharides: Starch, glycogen, cellulose. Formed by linking monosaccharides.
Functions: Energy storage (starch, glycogen), structural support (cellulose).

Notes and diagrams on monosaccharides, polysaccharides, and carbohydrate structure

Proteins

Structure and Function of Proteins

Proteins are polymers of amino acids, performing diverse functions such as catalysis, defense, and structure.

Amino acid structure: Central carbon, amino group, carboxyl group, R group (side chain).
Peptide bonds: Link amino acids to form polypeptides.
Levels of protein structure: Primary (sequence), secondary (alpha helix, beta sheet), tertiary (3D folding), quaternary (multiple polypeptides).

Notes and diagrams on amino acid structure and protein function Notes and diagrams on protein structure, R groups, and polypeptide formation

Denaturation

Denaturation is the process by which a protein loses its shape and function due to environmental changes.

Causes: High temperature, pH changes, high salt concentration.
Effect: Loss of biological activity.

Nucleic Acids

Structure and Function of Nucleic Acids

Nucleic acids (DNA and RNA) store and transmit genetic information.

Monomers: Nucleotides, composed of a sugar, phosphate group, and nitrogenous base.
DNA: Double helix, deoxyribose sugar, bases A, T, C, G.
RNA: Single-stranded, ribose sugar, bases A, U, C, G.

Notes and diagrams on nucleic acid structure and nucleotide components Notes and diagrams on DNA vs. RNA, nucleotide structure, and Chargaff's rule

Chargaff's Rule

Chargaff's rule states that in DNA, the amount of adenine equals thymine, and the amount of cytosine equals guanine.

Formula:
Application: Used to determine base composition in DNA samples.

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