Fundamental Biomolecules and Their Functions in General Biology

Biomolecules: Structure and Classification

Main Structural Forms of Biomolecules

Biomolecules are essential organic compounds found in living organisms. Their structure determines their function and classification.

• Lipids: Exist mainly as ring (e.g., steroids) and chain (e.g., fatty acids, triglycerides) forms.

• Proteins: Composed of amino acids linked by peptide bonds; primary structure is a linear chain, which folds into secondary, tertiary, and quaternary structures.

• Amino Acids: The building blocks of proteins; each has a central carbon, amino group, carboxyl group, and variable R group.

• Monosaccharides: Simple sugars (e.g., glucose, fructose) with a backbone of carbon atoms and functional groups such as carbonyl and hydroxyl.

Example: Glucose is a monosaccharide with a six-carbon backbone and multiple hydroxyl groups.

Monomers and Polymers

Monomers are the basic units that join to form polymers through dehydration synthesis.

• Nucleotides: Monomers of nucleic acids (DNA and RNA).

• Amino Acids: Monomers of proteins.

• Monosaccharides: Monomers of carbohydrates.

• Fatty Acids: Components of many lipids.

Biomolecule Functions

Primary Functions of Major Biomolecules

Each class of biomolecule has distinct roles in cellular structure and metabolism.

• Proteins: Catalysis (enzymes), structural support, transport, signaling.

• Lipids: Long-term energy storage, insulation, membrane structure.

• Nucleic Acids: Store and transfer genetic information (DNA, RNA).

• Carbohydrates: Short-term energy storage, structural support (e.g., cellulose in plants).

• Hormones: Chemical messengers; can be proteins (e.g., insulin) or lipids (e.g., steroids).

• Minerals: Inorganic elements essential for various cellular processes.

• Enzymes: Biological catalysts, usually proteins, that speed up chemical reactions.

• Vitamins: Organic molecules required in small amounts for metabolic processes.

Example: Glycogen is a carbohydrate used for short-term energy storage in animals.

Chemical Bonds and Reactions

Types of Chemical Bonds

Bonds are crucial for the structure and function of biomolecules.

• Phosphodiester Bonds: Link nucleotides in nucleic acids (DNA/RNA).

• Ester Bonds: Found in lipids, connecting fatty acids to glycerol.

• Hydrogen Bonds: Stabilize secondary structures in proteins and base pairing in DNA.

• Ionic Bonds: Form between charged groups, important in protein folding.

Example: DNA backbone is formed by phosphodiester bonds between nucleotides.

Key Chemical Reactions

Biomolecules are synthesized and broken down by specific reactions.

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

• Oxidation: Loss of electrons, often involved in energy metabolism.

• Osmosis: Movement of water across membranes.

Membrane Structure and Properties

Phospholipid Bilayer

Cell membranes are primarily composed of phospholipids arranged in a bilayer.

• Hydrophilic Heads: Face outward toward aqueous environments.

• Hydrophobic Tails: Face inward, away from water, forming the core of the membrane.

Example: The plasma membrane's selective permeability is due to its phospholipid bilayer.

Hydrophobic vs. Hydrophilic Effects

These effects influence molecule solubility and membrane formation.

• Hydrophobic Effect: Nonpolar molecules aggregate to avoid water.

• Hydrophilic Effect: Polar molecules interact favorably with water.

Example: Lipids are generally insoluble in water due to their nonpolar hydrocarbon tails.

Classification and Comparison Tables

Comparison of Saturated and Unsaturated Fatty Acids

Type	Bond Structure	Physical State
Saturated Fatty Acids	No double bonds (all single C-C bonds)	Solid at room temperature (rigid)
Unsaturated Fatty Acids	One or more double bonds (C=C)	Liquid at room temperature (fluid)

Major Classes of Biomolecules

Biomolecule	Monomer	Main Function
Protein	Amino Acid	Structure, catalysis, transport
Carbohydrate	Monosaccharide	Energy, structure
Lipid	Fatty Acid & Glycerol	Energy storage, membranes
Nucleic Acid	Nucleotide	Genetic information

Nucleic Acids: DNA and RNA

Structure and Function

Nucleic acids are polymers of nucleotides and serve as information carriers in cells.

• DNA: Double-stranded helix, stores genetic information.

• RNA: Usually single-stranded, involved in protein synthesis and gene regulation.

Example: DNA's double-stranded structure provides stability, while RNA's single-stranded form allows flexibility in function.

Phosphodiester Bonds in Nucleic Acids

Phosphodiester bonds connect the 3' carbon of one nucleotide to the 5' carbon of the next.

• Equation:

$\text{Nucleotide}_n + \text{Nucleotide}_{n+1} \xrightarrow{\text{Dehydration Synthesis}} \text{Nucleotide}_n\text{-Phosphodiester-}\text{Nucleotide}_{n+1}$

Functional Groups in Biomolecules

Common Functional Groups

Functional groups determine the chemical reactivity of biomolecules.

• Carboxyl Group (-COOH): Acts as an acid, donates protons.

• Amino Group (-NH2): Acts as a base, accepts protons.

• Hydroxyl Group (-OH): Increases solubility in water.

• Phosphate Group (-PO4): Involved in energy transfer and nucleic acid structure.

Example: The carboxyl group in amino acids allows peptide bond formation.

Additional info:

• Some context and definitions were expanded for clarity and completeness.

• Tables were inferred and constructed based on standard biology knowledge.