Chemical components of living organisms

Learning objectives To identify the basic chemical components of living organisms. To define roles of carbohydrates, proteins and lipids in terms of energy storage and structural components. To describe formation of carbohydrate, proteins and lipid from basic units. To identify deoxyribonucleic acid (DNA) and ribonucleic acid(RNA) with their bases. To differentiate between DNA and RNA.

The basic chemical components of living organisms Carbohydrate Proteins Lipids Nucleic acids Water Mineral salts

Carbohydrate Carbon + Hydrogen + Oxygen General formula: C x (H 2 O) y. Types of carbohydrates: ~ Monosaccharides ~ Disaccharides ~ Polysaccharides

Monosaccharide Sweet & soluble. General formula: C n (H 2 O) n. Glucose, fructose & galactose

Glucose Found in all living cells Chief end-product of carbohydrate digestion in gut

Fructose Found in fruits and in honey.

Galactose & ribose Galactose ~ Found in milk Ribose ~ Constituent of ribonucleic acid(RNA) and deoxyribonucleic acid (DNA)

Disaccharide 2 monosaccharides joining together by glycosidic bond undergoing a condensation reaction. Disaccharide can be split into its constituent monosaccharides by hydrolysis. Sweet, soluble and crystalline Maltose, sucrose, lactose

Maltose Glucose + Glucose  Maltose Glucose + Glucose + ……  starch It is hydrolysed back to 2 glucose molecules by maltase.

Sucrose Glucose + fructose  sucrose It is also called cane-sugar. It is hydrolysed back to glucose and fructose by invertase.

Lactose Glucose + galactose  lactose It is hydrolysed back to glucose and galactose by lactase. Lacking lactase in the body  lactose intolerance

Polysaccharides Complex sugar Compounds of a large number of monosaccharides units Insoluble Converted into monosaccharides upon hydrolysis As food and energy store

Polysaccharide Starch ~ major food reserve stored in plants but absent in animal. Glycogen ~ animal starch, stored in liver & muscles. Cellulose ~ constitute of plant cell wall, insoluble in water & dissolves in concentrated sulphuric acids.

Function of carbohydrates As respiratory substrate As storage material As structure material

Tests for carbohydrates Reducing sugar: Benedict ’ s test Clinistix paper test Non-reducing sugar: Acid hydrolysis Enzyme action Starch Iodine test

Lipids Carbon + Hydrogen + Oxygen Insoluble in water but dissolve in organic solvents. Fat: semi-solid at room temperature Oils: liquid at room temperature Types of lipids: triglycerides, phospholipids

Function of lipids Food reserve Structural materials Insulation Water-proof layer Transport medium Metabolic regulators Energy source Protection Others

Tests for lipids Grease spot test Sudan III test

Proteins Polymer of amino acids Insoluble in water Carbon + Hydrogen + Oxygen + nitrogen +/- sulphur & phosphorus Basic units: amino acid

Proteins Amino acid + Amino acid  Dipeptide Dipeptide + Dipeptide  Polypeptide The reaction “  ” is condensation. 4 types of bonding: disulphide bond, ionic bond, hydrogen bond & hydrophobic interaction.

Structure of proteins Primary structure Secondary structure Tertiary structure Quaternary structure

Denaturation ~ loss of specific three dimensional conformation of a protein molecule; ~ but the amino acids sequence remains unaffected; ~ loss of biological activities

Factors causing denaturation Heat or radiation Extreme pH Inorganic chemicals Organic chemicals Mechanical force Strong hydrogen bond former

Renaturation the protein resume its natural configuration; the protein regains its normal activity

Types of proteins Fibrous protein ~ regular repetitive sequences of amino acid; ~ parallel chain; ~ insoluble in water ~ e.g. collagen of tendons & ligaments Globular protein ~ irregular sequences of amino acid; ~ spherical & globular shapes chains; ~ e.g. enzymes, antibodies & hormones.

Functions of proteins Structural materials Biocatalyst Metabolic regulators Transportation Protection Muscle contraction Storage Toxins Respiratory substrate

Tests for proteins Biuret test Albustix paper test

Nuleotides Phosphoric acid + Pentose sugar + Organic base The three components are combined by condensation reaction

Types of nucleotides Mononucleotides: only one nucleotide unit, e.g. ATP Dinucleotides: 2 nucleotides e.g. NAD Polynucleotides: repeated condensation of nucleotides e.g. RNA & DNA

RNA Ribonucleic acid Single – stranded polymer of nucleotide Organic bases: A, G, C AND U

DNA Deoxyribonucleic acid Double-strand polymer, form double helix Organ bases: A, G, C and T

DNA vs RNA DNA Single strand Base: A, T, C & G Sugar: Deoxyribose Size: long & large Stability: alkali-stable Function: carry genetic information Occurrence: in nucleus RNA Single strand Base: A, U, C & G Sugar: ribose Size: short & small Stability: stable Function: protein synthesis, carry genetic information from DNA Occurrence: throughout cell

Water Comprise 65-95% of living cells. High specific heat. Strong hydrogen bond. Universal solvent. High tensile strength and high viscosity. High surface tension

Importance of water to life Component of protoplasm. Universal solvent. Participating in metabolic process. Cell turgidity. Surface film. Temperature stability. Translocation medium.

Mineral salt Calcium Chlorine Phosphate Fluorine Iodine Iron