, O
C ,H
BIOLOGICA
L
MOLECULE
Carbohydrates
Proteins
Lipids S Ex
pi i
Nucleic acids
SPECIFICATION
(c) Biological molecules
Students should:
🞆 Identify the chemical elements present in carbohydrates, proteins and lipids
(fats and oils)
🞆 Describe the structure of carbohydrates, proteins and lipids as large molecules
made up from smaller basic units: starch and glycogen from simple sugars,
protein from amino acids, and lipid from fatty acids and glycerol
🞆 practical: investigate food samples for the presence of glucose, starch, protein
and fat
The most common molecules in living things;
⚫ Water BUT water is NOT a biological molecule.
⚫ Carbohydrates
⚫ Proteins
⚫ Lipids Biological molecules
⚫ Nucleic acids
Elements that make up biological molecules:
C, H, O, N, S
🞆Carbohydrates contain 3 elements; C, H, O
🞆Lipids contain 3 elements; C, H, O
🞆Proteins contain 4 or 5 elements; C, H, O, N, S
🞆Nucleic acid consists of
• All biological molecules are huge. So, we call them
Macromolecules.
• They are made of small molecules (same type or
different types) joining together. So, we call them
Polymers.
A polymer is a
large molecule
made up of a long
chain of repeating
subunits called
monomers
PMG Biology
• Protein • Starch
• Cellulose
• Glycogen
Amino acid glucose
Basic unit/
monomer
Glycerol +
nucleotide
fatty acid
• Lipids • Nucleic
acid
Carbohydrates
STRUCTURE OF CARBOHYDRATES
🞆Simplest carbohydrates comprise a single molecule and are
called monosaccharides.
Trioses Pentoses Hexoses
(3-carbons) (5-carbons) (6-carbons)
🞆A disaccharide is formed when two monosaccharides join
together by a covalent bond.
🞆Polysaccharides are polymers composed of a large number
of monosaccharides.
Mono= one
Carbohydrates Di= two
Poly= many
Monosaccharides Disaccharides Polysaccharides
Glucose Maltose Starch
Fructose Sucrose Glycogen
Galactose Lactose Cellulose
FUNCTIONS OF CARBOHYDRATES
2. Form the cell wall of
Plants: Cellulose
A2B Car Rental
Fungi: Chitin
Bacteria: Peptidoglycan
Exp
ii
1. Glucose is the
primary fuel in cells Glycogen in the
liver and muscles
of animals
3. Storage of
readily available
energy
Starch in plants
GLUCOSE Glucose
is a
Monosaccharide
&
Glucose is the primary energy Chemical formula
source of organisms. C6H12O6
Structure of glucose
YES, all three
polysaccharides you Starch
learn are made of Glycogen
Researchgate.net
glucose molecules Cellulose
joining together by
covalent bonds.
Food rich in carbohydrates
Protein
STRUCTURE OF PROTEIN
Basic unit is
Amino acid
teaching.ncl.ac.u
k
20 different amino acids
exist naturally in organisms
Polypeptide chain
🞆Amino acids join together by
peptide bonds and form
Peptide bonds polypeptide chains.
🞆Polypeptide chain can fold to
form a 3-D structure to
become a functional protein.
Working protein
FUNCTIONS OF PROTEIN
Innerzyme
3. Provide immunity by
1. Digestion of food by 2. Transport of oxygen by
ANTIBODIES &
ENZYMES HAEMOGLOBIN
ENZYMES
4. Form structures. E.g. hair
5. Energy store for developing embryo.
(keratin), muscles (actin)
FUNCTIONS OF PROTEIN
Role Examples Functions
Break down nutrients in
Digestive enzyme Amylase, lipase, pepsin food into small pieces that
can be readily absorbed
Carry oxygen through out
Transport Hemoglobin
the body in blood
Build different structures,
Structure Actin, keratin
like muscles, hair
Coordinate the activity of
Hormone signaling Insulin, glucagon
different body systems
Protect the body from
Defense Antibodies
foreign pathogens
Provide food for the early
Legume storage proteins,
Storage development of the embryo
egg white (albumin)
or the seedling
Food rich in protein
Lipid
s
LIPIDS (FAT AND OIL)
Fat Oil
heart.org betterhealth.vic.gov.au
• solid at room temperature • liquid at room temperature
• from animal sources • from plant sources
STRUCTURE OF LIPIDS: We can draw a simple
lipid molecule as shown
below.
Lipids are made of two parts:
1. Glycerol back bone
2. One or more hydrocarbon
chains called fatty acids
Unlike carbohydrates,
lipids have much less
oxygen
OpenStax Biology.
FUNCTIONS OF LIPIDS
1. Fat depots
under the skin
and around
organs act as
a long-term
store of
energy
https://www.nature.com/articles/emm20165
2. Cushion vital organs from
mechanical damage (e.g. brain,
kidneys, heart, liver)
FUNCTIONS OF LIPIDS
Fat layer under the
skin acts as thermal
insulation
Form the cell
membrane of
cells.
Wikimedia Commons
Food rich in lipids
Tests to identify
biological molecules
(Food tests)
TEST FOR GLUCOSE
Benedict’s test
1. Add a few drops of Benedict’s solution to the 5ml of the sample solution.
2. Heat the mixture in a water bath.
3. The colour of the solution changes to ORANGE/ BRICK RED if glucose is
present.
sciencephoto.com
BIology Revision Site - Weebly
Safety measures:
1. Use goggles & gloves Benedict’s
solution Glucose
2. Use a water bath
TEST FOR STARCH Iodine test
1. Add one or two drops of Iodine solution (yellow) to the sample (solution or a solid).
2. Iodine turns to BLUE BLACK colour in the presence of starch.
https://fineartamerica.com
Safety measures:
1. Use goggles & gloves
TEST FOR PROTEIN Biuret test
Method 1:
1. Add 1ml of Biuret reagent into 1ml
of aqueous food sample.
2. Mix well.
Method 2:
1. Add 1ml of dilute KOH/NaOH into
1ml of aqueous food sample.
2. Mix well.
3. Add 1% of CuSO4 http://birdingpark.blogspot.com
Observation:
The colour of the solution changes to Safety measures:
1. Use goggles & gloves
PURPLE if protein is present
TEST FOR LIPIDS
Ethanol emulsion test
1. Add a few drops of the liquid food sample to a dry test tube.
2. Add 2cm3 of ethanol and shake it vigorously.
3. Add the mixture into a test tube containing ¾ of distilled water.
By Noureen khaliq
Observation:
A white cloudy emulsion is
formed if lipids are present.
Safety measures:
1. Use goggles & gloves
TACtivities
FOOD TESTS SUMMARY
Colour of
Food sample Reagent Method Initial colour
positive result
Add Benedict’s
reagent to the Brick red
Glucose Benedict’s Blue
food and boil in precipitate
By Noureen khaliq
a water bath.
Add iodine
Starch Iodine reagent to the Yellow-brown Blue-black
food.
Biuret (a
mixture of Add Biuret
Protein potassium reagent to the Blue Lilac/purple
hydroxide and food.
copper sulfate).
Add ethanol to
the food to
Fat & oil Ethanol Colourless White emulsion
dissolve the fat
then add water.
Thank you
By Noureen Khaliq
