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: Cx(H2O)y. Types of carbohydrates: ~ Monosaccharides ~ Disaccharides ~ Polysaccharides

Monosaccharide Sweet & soluble. General formula: Cn(H2O)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 b

y 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 g

alactose by lactase. Lacking lactase in the body lactose

intolerance

Polysaccharides Complex sugar Compounds of a large number of mon

osaccharides units Insoluble Converted into monosaccharides upo

n 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 testNon-reducing sugar: Acid hydrolysis Enzyme actionStarch 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 + nitrog

en +/- 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 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 + Or

ganic base The three components are combined

by condensation reaction

Types of nucleotides Mononucleotides: only one nucleotid

e unit, e.g. ATP Dinucleotides: 2 nucleotides e.g. NAD Polynucleotides: repeated condensati

on 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 RNADNA

Single strand Base: A, T, C & G Sugar: Deoxyribose Size: long & large Stability: alkali-stabl

e Function: carry gene

tic information Occurrence: in nucle

us

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