Biomolecules

Biomolecules: Molecules of Life

  • Biomolecules are essential organic compounds that are present in living organisms.

Average Composition of Biomolecules in Cells

  • Major types of biomolecules include:

    • Carbohydrates

    • Proteins

    • Lipids

    • Nucleic acids

  • All these molecules are organic in nature.

Carbohydrates

  • Composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio.

  • General empirical formula: CnH2nOn.

Functions of Carbohydrates

  • Energy Source: Serves as a fuel during cellular respiration;

    • Energy stored in chemical bonds is released during metabolism.

  • Energy Storage:

    • Plants store energy as starch (amylose).

    • Animals store energy as glycogen in muscles and liver.

  • Structural Material:

    • Plants use cellulose for cell wall construction.

    • Arthropods and fungi use chitin.

Classes of Carbohydrates

  1. Monosaccharides (Simple Sugars):

  • Basic building blocks of carbohydrates.

  • Examples: glucose, fructose, galactose, ribose.

  1. Disaccharides:

  • Formed by joining two monosaccharides via dehydration synthesis (covalent bond).

  • Examples: sucrose, maltose, lactose.

  1. Polysaccharides:

  • Long chains of monosaccharides linked by dehydration synthesis.

  • Examples: amylose, glycogen, cellulose, chitin.

Monosaccharides

  • Can be linear or cyclic structures;

  • Classified by the number of carbon atoms:

    • Pentoses: 5 carbons (e.g., ribose)

    • Hexoses: 6 carbons (e.g., glucose)

  • Exist as isomers with distinct properties; e.g., glucose and fructose are both C6H12O6 but differ in structure.

Disaccharide Formation

  • Formed through dehydration synthesis:

    • Maltose: formed from glucose + glucose.

    • Sucrose: formed from glucose + fructose.

Polysaccharide Structure and Function

  • Long chains derived from multiple monosaccharides;

  • Function depends on monosaccharide isomer and linkages.

  • Example: Cellulose is made only of glucose.

Lipids

  • Nonpolar organic molecules, greasy or oily with one or more fatty acid tails.

    • Includes fats, oils, and waxes.

Functions of Lipids

  • Energy Storage: Fats and oils provide a major energy source.

  • Waterproofing: Waxes provide surface protection.

  • Insulation: Fat layers (e.g., blubber).

  • Cushioning: Fat layers cushion organs.

  • Regulating Metabolic Processes: Includes steroids.

  • Building Cell Membranes: Phospholipids form cell membranes.

Structure of Fats

  • Triglycerides: Comprise glycerol and three fatty acid tails.

  • Formed by dehydration synthesis between glycerol and fatty acids.

Saturated and Unsaturated Fats

  • Saturated Fats: No double bonds in fatty acid tail, more tightly packed, usually solid.

  • Unsaturated Fats: One or more double bonds, usually liquid at room temperature.

Phospholipids

  • Main component of cell membranes;

  • Contain hydrophilic phosphate head and two nonpolar fatty acid tails.

Proteins

  • Comprised of one or more amino acids;

  • Structure determines function, folded into specific shapes.

Amino Acids

  • Small organic compounds with amino group, carboxyl group, and R group.

  • Examples: Alanine, Proline, Glycine, Trypsin.

Functions of Proteins

  • Building structural components (collagen, keratin).

  • Regulating metabolic processes (insulin).

  • Enzymatic activity (catalyzing biochemical reactions).

  • Membrane transport (carrier proteins).

  • Immune functions (antibodies).

Peptide Bonds

  • Link amino acids into chains; formed between amine and carboxyl groups.

  • Chains of amino acids are called polypeptides.

Stages of Protein Structure

  1. Primary Structure: Linear sequence of amino acids.

  2. Secondary Structure: Coiling or folding stabilized by hydrogen bonds.

  3. Tertiary Structure: Three-dimensional structure formed by further folding.

  4. Quaternary Structure: Assembly of multiple polypeptide chains.

Viruses and Bacteria

  • Viruses: Parasites with DNA or RNA encased in a protein coat;

    • Can invade host cells and replicate causing diseases.

  • Bacteria: Prokaryotic cells without a nucleus,

    • Can be classified as either Eubacteria or Archaebacteria.

Bacterial Types

  • Cyanobacteria: Photosynthetic, can thrive in extreme environments.

  • Structural types: Rod, sphere, spiral-shaped bacteria.

Bacterial Movement

  • Flagella: Tail structures for propulsion;

  • Cilia: Surface projections for movement.

Energy Sources in Bacteria

  • Autotrophs: Make their own energy using solar or chemical energy;

  • Heterotrophs: Consume others for energy (e.g., E. coli).

Cell Cycle

  • Mitosis: Ordinary cell division ensuring equal chromosome distribution;

    • Four stages: Prophase, Metaphase, Anaphase, Telophase.

  • Meiosis: Special division reducing chromosome number for gamete formation.

  • Two phases: Meiosis I and II, ensuring genetic diversity in offspring.