Download Chemical components of living organisms

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 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

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