Chapter 1 Biological Molecules
,Chapter 1 Biological Molecules
Testing For Reducing Sugars
● all monosaccharides and some disaccharides, e.g. maltose are
1.1 Introduction To Biological Molecules reducing sugars
● Benedict’s reagent is an alkaline solution of copper(II) sulfate
Bonding And The Formation Of Molecules
(CuSO4)
● covalent bonding
1. Add Benedict’s solution into the tested food sample.
● ionic bonding
2. Heat the mixture gently in a boiling H2O bath.
● hydrogen (H) bonding
● + result: solution turns from blue to brick red
Polymerisation And The Formation Of Macromolecules
● monomers link together to form polymers by polymerisation
1.3 Carbohydrates – Disaccharides And
Condensation And Hydrolysis Reactions Polysaccharides
Disaccharides
condensation reactions hydrolysis reactions
● glucose + glucose → maltose
● glucose + fructose → sucrose
Condensation reaction – Hydrolysis reaction –
● glucose + galactose → lactose
Joining of two molecules Breaking a chemical bond
together with the formation between two molecules Disaccharide – Molecules formed by the condensation of two
of a chemical bond involving involving the use of a water monosaccharides.
the elimination of a molecule molecule. ● monosaccharides bond together by glycosidic bond during
of water. condensation reactions
● e.g. amino acids → a ● maltose, sucrose and lactose have a formula of C12H22O11
polypeptide,
monosaccharide C6H12O6
→ polysaccharide starch Test For Non-reducing Sugars
● other disaccharides, e.g. sucrose and all polysaccharides are
non-reducing sugars
● non-reducing sugar must be hydrolysed into its
monosaccharide components to be tested
1. Carry out Benedict’s test with the tested food sample and
observe if the mixture stays blue.
2. Boil the mixture with acid and then neutralise with alkali.
● addition of acid hydrolyses any glycosidic bonds present in any
carbohydrate molecules
Metabolism
3. Heat the mixture with Benedict’s solution gently in a boiling
Metabolism – All the chemical processes that take place in living
H2O bath.
organisms.
● + result: solution turns from blue to brick red
Polysaccharides
Polysaccharide – Molecules formed by the condensation of
1.2 Carbohydrates – Monosaccharides many monosaccharides.
Life Based On Carbon ● polysaccharides are very large molecules
○ make it insoluble and suitable for storage
● C atoms are ready to form bonds with other C atoms
Test For Starch
○ allows a sequence of C of various lengths to be built up
● test is carried out at room temp.
■ a backbone is formed
1. Add iodine solution to the tested food sample.
● + result: solution turns from yellow to blue-black
The Making Of Large Molecules
Monomers – The smaller units from which larger molecules are
made.
● e.g. monosaccharides, amino acids and nucleotides 1.4 Starch, Glycogen And Cellulose
Polymers – Molecules made from a large number of monomers Starch
joined together. Starch – A polysaccharide made of alpha glucose monomers that
● basic monomer unit in carbohydrates is sugar is used as the main storage of energy in plants.
○ monosaccharide: a single monomer of carbohydrate
○ disaccharide: a pair of combined monosaccharides starch
○ polysaccharides: large numbers of combined
monomers ● α-glucose
monosaccharides
Monosaccharides
bond between ● 1-4 glycosidic bonds in amylose
Monosaccharide – The individual sugar monomers
monomers
from which larger carbohydrates are made.
● general formula (CH2O)n, e.g. glucose, galactose
and fructose
● C6H12O6 is the main substrate for respiration and
has two isomers (α-glucose and β-glucose)
, ● 1-4 and 1-6 glycosidic bonds in function ● major carbohydrate storage product
amylopectin of animals
● insoluble
○ no osmotic effect
■ does not draw H2O into the
cells by osmosis
● coiled
○ makes molecule compact
■ a lot of glucose can be stored
location ● found in starch grains inside plant
in a small space
cells
properties to ● branched form has many ends
functions ○ enzymes can act on
● made of 2 polymers simultaneously
○ amylose: an unbranched helix ○ have a higher metabolic rate and
structure chain respiratory rate than plants
○ amylopectin: a branched ■ more active
molecule
● never found in plant cells
● forms an important component of
function food Cellulose
● is the major energy source in most Cellulose – A polysaccharide made of β-glucose monomers that is
diets
used as a structural polysaccharide which provides strength to
plant cell walls.
● insoluble
○ no osmotic effect cellulose
■ does not draw H2O into the
cells by osmosis
monomers ● β-glucose
● large molecule
○ does not leave the cell
○ contains large no. of glucose bond between ● 1-4 glycosidic bonds
units monomers
● coiled
properties to ○ makes molecule compact
function ■ a lot of glucose can be stored
in a small space
● forms α-glucose when hydrolysed
○ provides glucose readily used in
respiration location ● found in cell wall of plant cells
● branched form has many ends
○ enzymes can act on ● long, straight chains running parallel
simultaneously to one another
■ glucose monomers are structure ○ allows H bonds to form
released rapidly cross-linkages between adjacent
● never found in animal cells chains
● provides rigidity to the plant cell
Glycogen
○ provides the maximum SA for
Glycogen – A highly branched polysaccharide made of alpha photosynthesis
glucose monomers that is used as the main storage of energy in ● prevents cell from bursting as H2O
humans and animals. function enters it by osmosis
○ is done by exerting an inward
glycogen pressure that stops any further
influx of H2O
monomers ● α-glucose
● made up of β-glucose
bond between ● 1-4 and 1-6 glycosidic bonds ○ forms long, straight and
monomers unbranched chains
■ provides support and rigidity
properties to ● parallel chains crossed linked by H
function bonds
○ adds collective strength
● grouped molecules
○ form microfibrils to provide more
location ● found in muscles and liver cells in strength
animals
structure ● has shorter chains than starch
● more highly branched than starch
1.5 Lipids
● main groups of lipids are triglycerides and phospholipids
, ● a phospholipid is made up of 2 parts
Roles Of Lipids ○ hydrophilic head (phosphate) interacts with H2O but not
● phospholipids contribute to the flexibility of membranes and with fat
the transfer of lipid-soluble substances across them ○ hydrophobic tail (two fatty acids) orients itself away from
● source of energy H2O but mixes readily with fat
○ provide more than twice the energy as the same mass of ● molecules that have two ends behaving differently are said to
carbohydrate when oxidised be polar
○ release valuable H2O when oxidised ○ polar molecules position themselves when placed in H2O
● waterproofing ○ hydrophilic heads are as close to the H2O as possible
○ insoluble in H2O ○ hydrophobic tails are as far away from H2O as possible
○ plants and insects have waxy, lipid cuticles that conserve The Related Properties To Functions Of Phospholipids
H2O ● polar molecules that have a
○ mammals produce an oily secretion from the sebaceous hydrophilic head and a hydrophobic
glands in the skin tail of two fatty acids
● insulation ○ hydrophobic barrier is formed
○ fats are slow conductors of heat between the inside and outside
○ help retain body heat of a cell
○ act as electrical insulators in the myelin sheath around ○ form a bilayer within cell-surface membranes in an
nerve cells aqueous membrane
● protection ● hydrophilic phosphate heads of phospholipid molecules
○ often stored around delicate organs, e.g. kidney ○ help to hold hydrophilic PO43- heads at the surface of
the cell-surface membrane
Triglycerides ● phospholipid structure
Triglyceride – A type of lipid formed by ○ allows them to form glycolipids by combining with
the condensation of one molecule of carbohydrates within the cell-surface membrane
glycerol and three molecules of fatty ○ important in cell recognition
acid.
● an ester bond forms when a Test For Lipids
hydroxyl (OH) group on glycerol 1. Add ethanol then add H2O and shake.
bonds with the carboxyl (COOH) ● + result: cloudy-white emulsion
group of the fatty acid ○ light passing through the emulsion is refracted as it
● fatty acid is described as saturated passes from oil droplets to H2O droplets
if the hydrocarbon chain has no
C=C bond
● fatty acid is described as 1.6 Proteins
mono-unsaturated if there is a
single C=C bond
Structure Of An Amino Acid
● fatty acid is described as polyunsaturated if more than one Amino acid – The monomers containing an amino group (NH2), a
C=C bond is present carboxyl group (COOH), a H atom and a variable R group that
The Related Properties To Functions Of Triglycerides make up protein.
● long hydrocarbon chains contain many C-H bonds with ● basic monomer units which combine
little O to make up polypeptide that can be
○ C-H bonds break when oxidised during cellular combined to form proteins
respiration
○ release an excellent source of energy used to produce The Formation Of A Peptide Bond
ATP ● amino acid monomers combine
● low mass to energy ratio together by a peptide bond to
○ much energy can be stored in a small vol. form a dipeptide in
○ good storage molecules condensation reaction
○ reduces the mass animals have to carry as they move ● a hydroxyl (OH) is lost from the COOH and a H atom is lost
around from the NH2 group of another amino acid
● large, non-polar molecules
○ allows their storage to not affect osmosis in cells or the The Primary Structure Of Proteins – Polypeptides
H2O potential of them Primary structure – The individual sequence
○ insoluble in H2O of amino acids bonded by covalent peptide
● high ratio of H to O atoms bonds in a polypeptide.
○ release H2O when oxidised ● the sequence of amino acids in a
○ important source of H2O polypeptide chain is determined by DNA
○ important for determining the final
Phospholipids 3D shape of a protein molecule
Phospholipid – A type of lipid formed by the condensation of one ● determines its ultimate shape and function
molecule of glycerol, two molecules of fatty acid and a phosphate ○ change in an amino acid in the primary sequence can lead
group. to a change in the shape of the protein
,Chapter 1 Biological Molecules
Testing For Reducing Sugars
● all monosaccharides and some disaccharides, e.g. maltose are
1.1 Introduction To Biological Molecules reducing sugars
● Benedict’s reagent is an alkaline solution of copper(II) sulfate
Bonding And The Formation Of Molecules
(CuSO4)
● covalent bonding
1. Add Benedict’s solution into the tested food sample.
● ionic bonding
2. Heat the mixture gently in a boiling H2O bath.
● hydrogen (H) bonding
● + result: solution turns from blue to brick red
Polymerisation And The Formation Of Macromolecules
● monomers link together to form polymers by polymerisation
1.3 Carbohydrates – Disaccharides And
Condensation And Hydrolysis Reactions Polysaccharides
Disaccharides
condensation reactions hydrolysis reactions
● glucose + glucose → maltose
● glucose + fructose → sucrose
Condensation reaction – Hydrolysis reaction –
● glucose + galactose → lactose
Joining of two molecules Breaking a chemical bond
together with the formation between two molecules Disaccharide – Molecules formed by the condensation of two
of a chemical bond involving involving the use of a water monosaccharides.
the elimination of a molecule molecule. ● monosaccharides bond together by glycosidic bond during
of water. condensation reactions
● e.g. amino acids → a ● maltose, sucrose and lactose have a formula of C12H22O11
polypeptide,
monosaccharide C6H12O6
→ polysaccharide starch Test For Non-reducing Sugars
● other disaccharides, e.g. sucrose and all polysaccharides are
non-reducing sugars
● non-reducing sugar must be hydrolysed into its
monosaccharide components to be tested
1. Carry out Benedict’s test with the tested food sample and
observe if the mixture stays blue.
2. Boil the mixture with acid and then neutralise with alkali.
● addition of acid hydrolyses any glycosidic bonds present in any
carbohydrate molecules
Metabolism
3. Heat the mixture with Benedict’s solution gently in a boiling
Metabolism – All the chemical processes that take place in living
H2O bath.
organisms.
● + result: solution turns from blue to brick red
Polysaccharides
Polysaccharide – Molecules formed by the condensation of
1.2 Carbohydrates – Monosaccharides many monosaccharides.
Life Based On Carbon ● polysaccharides are very large molecules
○ make it insoluble and suitable for storage
● C atoms are ready to form bonds with other C atoms
Test For Starch
○ allows a sequence of C of various lengths to be built up
● test is carried out at room temp.
■ a backbone is formed
1. Add iodine solution to the tested food sample.
● + result: solution turns from yellow to blue-black
The Making Of Large Molecules
Monomers – The smaller units from which larger molecules are
made.
● e.g. monosaccharides, amino acids and nucleotides 1.4 Starch, Glycogen And Cellulose
Polymers – Molecules made from a large number of monomers Starch
joined together. Starch – A polysaccharide made of alpha glucose monomers that
● basic monomer unit in carbohydrates is sugar is used as the main storage of energy in plants.
○ monosaccharide: a single monomer of carbohydrate
○ disaccharide: a pair of combined monosaccharides starch
○ polysaccharides: large numbers of combined
monomers ● α-glucose
monosaccharides
Monosaccharides
bond between ● 1-4 glycosidic bonds in amylose
Monosaccharide – The individual sugar monomers
monomers
from which larger carbohydrates are made.
● general formula (CH2O)n, e.g. glucose, galactose
and fructose
● C6H12O6 is the main substrate for respiration and
has two isomers (α-glucose and β-glucose)
, ● 1-4 and 1-6 glycosidic bonds in function ● major carbohydrate storage product
amylopectin of animals
● insoluble
○ no osmotic effect
■ does not draw H2O into the
cells by osmosis
● coiled
○ makes molecule compact
■ a lot of glucose can be stored
location ● found in starch grains inside plant
in a small space
cells
properties to ● branched form has many ends
functions ○ enzymes can act on
● made of 2 polymers simultaneously
○ amylose: an unbranched helix ○ have a higher metabolic rate and
structure chain respiratory rate than plants
○ amylopectin: a branched ■ more active
molecule
● never found in plant cells
● forms an important component of
function food Cellulose
● is the major energy source in most Cellulose – A polysaccharide made of β-glucose monomers that is
diets
used as a structural polysaccharide which provides strength to
plant cell walls.
● insoluble
○ no osmotic effect cellulose
■ does not draw H2O into the
cells by osmosis
monomers ● β-glucose
● large molecule
○ does not leave the cell
○ contains large no. of glucose bond between ● 1-4 glycosidic bonds
units monomers
● coiled
properties to ○ makes molecule compact
function ■ a lot of glucose can be stored
in a small space
● forms α-glucose when hydrolysed
○ provides glucose readily used in
respiration location ● found in cell wall of plant cells
● branched form has many ends
○ enzymes can act on ● long, straight chains running parallel
simultaneously to one another
■ glucose monomers are structure ○ allows H bonds to form
released rapidly cross-linkages between adjacent
● never found in animal cells chains
● provides rigidity to the plant cell
Glycogen
○ provides the maximum SA for
Glycogen – A highly branched polysaccharide made of alpha photosynthesis
glucose monomers that is used as the main storage of energy in ● prevents cell from bursting as H2O
humans and animals. function enters it by osmosis
○ is done by exerting an inward
glycogen pressure that stops any further
influx of H2O
monomers ● α-glucose
● made up of β-glucose
bond between ● 1-4 and 1-6 glycosidic bonds ○ forms long, straight and
monomers unbranched chains
■ provides support and rigidity
properties to ● parallel chains crossed linked by H
function bonds
○ adds collective strength
● grouped molecules
○ form microfibrils to provide more
location ● found in muscles and liver cells in strength
animals
structure ● has shorter chains than starch
● more highly branched than starch
1.5 Lipids
● main groups of lipids are triglycerides and phospholipids
, ● a phospholipid is made up of 2 parts
Roles Of Lipids ○ hydrophilic head (phosphate) interacts with H2O but not
● phospholipids contribute to the flexibility of membranes and with fat
the transfer of lipid-soluble substances across them ○ hydrophobic tail (two fatty acids) orients itself away from
● source of energy H2O but mixes readily with fat
○ provide more than twice the energy as the same mass of ● molecules that have two ends behaving differently are said to
carbohydrate when oxidised be polar
○ release valuable H2O when oxidised ○ polar molecules position themselves when placed in H2O
● waterproofing ○ hydrophilic heads are as close to the H2O as possible
○ insoluble in H2O ○ hydrophobic tails are as far away from H2O as possible
○ plants and insects have waxy, lipid cuticles that conserve The Related Properties To Functions Of Phospholipids
H2O ● polar molecules that have a
○ mammals produce an oily secretion from the sebaceous hydrophilic head and a hydrophobic
glands in the skin tail of two fatty acids
● insulation ○ hydrophobic barrier is formed
○ fats are slow conductors of heat between the inside and outside
○ help retain body heat of a cell
○ act as electrical insulators in the myelin sheath around ○ form a bilayer within cell-surface membranes in an
nerve cells aqueous membrane
● protection ● hydrophilic phosphate heads of phospholipid molecules
○ often stored around delicate organs, e.g. kidney ○ help to hold hydrophilic PO43- heads at the surface of
the cell-surface membrane
Triglycerides ● phospholipid structure
Triglyceride – A type of lipid formed by ○ allows them to form glycolipids by combining with
the condensation of one molecule of carbohydrates within the cell-surface membrane
glycerol and three molecules of fatty ○ important in cell recognition
acid.
● an ester bond forms when a Test For Lipids
hydroxyl (OH) group on glycerol 1. Add ethanol then add H2O and shake.
bonds with the carboxyl (COOH) ● + result: cloudy-white emulsion
group of the fatty acid ○ light passing through the emulsion is refracted as it
● fatty acid is described as saturated passes from oil droplets to H2O droplets
if the hydrocarbon chain has no
C=C bond
● fatty acid is described as 1.6 Proteins
mono-unsaturated if there is a
single C=C bond
Structure Of An Amino Acid
● fatty acid is described as polyunsaturated if more than one Amino acid – The monomers containing an amino group (NH2), a
C=C bond is present carboxyl group (COOH), a H atom and a variable R group that
The Related Properties To Functions Of Triglycerides make up protein.
● long hydrocarbon chains contain many C-H bonds with ● basic monomer units which combine
little O to make up polypeptide that can be
○ C-H bonds break when oxidised during cellular combined to form proteins
respiration
○ release an excellent source of energy used to produce The Formation Of A Peptide Bond
ATP ● amino acid monomers combine
● low mass to energy ratio together by a peptide bond to
○ much energy can be stored in a small vol. form a dipeptide in
○ good storage molecules condensation reaction
○ reduces the mass animals have to carry as they move ● a hydroxyl (OH) is lost from the COOH and a H atom is lost
around from the NH2 group of another amino acid
● large, non-polar molecules
○ allows their storage to not affect osmosis in cells or the The Primary Structure Of Proteins – Polypeptides
H2O potential of them Primary structure – The individual sequence
○ insoluble in H2O of amino acids bonded by covalent peptide
● high ratio of H to O atoms bonds in a polypeptide.
○ release H2O when oxidised ● the sequence of amino acids in a
○ important source of H2O polypeptide chain is determined by DNA
○ important for determining the final
Phospholipids 3D shape of a protein molecule
Phospholipid – A type of lipid formed by the condensation of one ● determines its ultimate shape and function
molecule of glycerol, two molecules of fatty acid and a phosphate ○ change in an amino acid in the primary sequence can lead
group. to a change in the shape of the protein
