Biomolecules

Each class plays a unique role in cellular structure, metabolism, and information storage.

Carbon: The Foundation of Biomolecules

Properties of Carbon

• Carbon is the most abundant element in living systems (excluding water).

• Organic molecules are defined as molecules containing both carbon and hydrogen.

• Hydrocarbons are molecules made up of only carbon and hydrogen atoms.

• Carbon atoms can form four covalent bonds, allowing for a variety of molecular shapes (linear, branched, ring).

Example: Organic molecules include carbohydrates, proteins, nucleic acids, and lipids.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They are commonly found attached to the carbon backbone of organic molecules.

• Hydroxyl (-OH)

• Carbonyl (C=O)

• Carboxyl (-COOH)

• Amino (-NH2)

• Sulfhydryl (-SH)

• Phosphate (-PO4)

• Methyl (-CH3)

These groups influence the physical and chemical properties of biomolecules.

Monomers and Polymers

Concept of Monomers and Polymers

• Monomers are small, repeating units that serve as the building blocks of polymers.

• Polymers are long chains of monomers linked together by covalent bonds.

• Carbohydrates, proteins, and nucleic acids are polymers; lipids are not true polymers.

Polymerization Reactions

• Dehydration Synthesis: Joins monomers by removing a water molecule, forming a covalent bond.

• Hydrolysis: Breaks covalent bonds between monomers by adding a water molecule.

Equation:

Carbohydrates

Structure and Classification

• Carbohydrates are carbon-based molecules hydrated with many hydroxyl (-OH) groups.

• General formula:

• Three main classes:

  • Monosaccharides: Single sugar units (e.g., glucose)

  • Oligosaccharides: Short chains of monosaccharides

  • Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose, glycogen)

Formation and Breakdown

• Monosaccharides are linked by glycosidic bonds via dehydration synthesis to form polysaccharides.

• Hydrolysis breaks glycosidic bonds, releasing monosaccharides.

Functions of Carbohydrates

• Structural Support: Cellulose in plants, chitin in fungi and arthropods.

• Energy Storage: Starch in plants, glycogen in animals.

Proteins

Structure and Function

• Proteins are polymers of amino acids linked by peptide bonds.

• Amino acids have a central carbon, amino group, carboxyl group, hydrogen atom, and variable R group.

• Proteins perform structural, enzymatic, transport, and regulatory functions.

Levels of Protein Structure

• Primary: Sequence of amino acids

• Secondary: Alpha helices and beta sheets (hydrogen bonding)

• Tertiary: 3D folding due to side chain interactions

• Quaternary: Multiple polypeptide chains

Denaturation and Chaperones

• Denaturation: Loss of protein structure due to environmental changes (e.g., temperature, pH).

• Chaperone proteins assist in proper folding and refolding of proteins.

Nucleic Acids

Structure and Function

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

• Monomers: Nucleotides (composed of a phosphate group, pentose sugar, and nitrogenous base).

• DNA contains deoxyribose; RNA contains ribose.

Nitrogenous Bases

• Pyrimidines: Cytosine, Thymine (DNA), Uracil (RNA)

• Purines: Adenine, Guanine

Formation of Nucleic Acids

• Nucleotides are joined by phosphodiester bonds via dehydration synthesis.

• DNA strands are antiparallel and held together by hydrogen bonds between complementary bases (A-T, G-C).

Lipids

Structure and Types

• Lipids are hydrophobic molecules, not true polymers.

• Main types: Fats (triglycerides), Phospholipids, Steroids, Waxes.

Fatty Acids

• Saturated fatty acids: No double bonds, straight chains, solid at room temperature.

• Unsaturated fatty acids: One or more double bonds, kinked chains, liquid at room temperature.

Triglycerides and Phospholipids

• Triglycerides: Three fatty acids linked to glycerol via ester bonds.

• Phospholipids: Two fatty acids and a phosphate group attached to glycerol; major component of cell membranes.

Steroids and Waxes

• Steroids: Four fused carbon rings (e.g., cholesterol).

• Waxes: Long-chain fatty acids linked to alcohols; protective coatings.

Summary Table: Major Biomolecules

Additional info: This guide expands on the provided notes with definitions, examples, and summary tables for clarity and completeness.