Biological molecules

As Biology ( 9700)
June 2025
11/ 11/2024
Part 1
Carbohydrates ( mono and disaccharides )

Class work
1. Definition of macromolecule / example
2. Definition of polymer / example
3. Name monomer or each polymer
4. Comparison between mono / di / poly
5. Draw ring structure of alpha / beta glucose and beta fructose
6. Mention the type of bond and monomer of maltose and sucrose
 Biological molecules
Fats
Carbohydrates ( 3 structures alpha glucose , beta glucose , beta fructose )
Proteins ( basic structure of amino acid )
Fatty acids and
Fats / lipids ( 3 fatty acids and glycerol ….recognise )
glycerol -

Macromolecules Giant molecules with large molecular mass

Example carbohydrates , proteins , fats and nucleic acids

Polymer Made up of many repeated subunits which are similar or identical to each other

Polysaccharides Proteins Nucleic acids

DNA / RNA
Amino acids Nucleotide
Monosaccharides
Example glucose
 1. Carbohydrates Macromolecule and polymer
C: H:O
1. Formula
1:2: 1
2. Solubility
3. Reducing or not
11 or more
4. Taste
5. glycosidic bond Disaccharides Polysaccharides
Monosaccharides

n = number of carbon atoms n = number of glucose molecules

2 x C6H12O6 - H2O
Cn H2nOn C12H22O11 ( C6H12O6) n - ( H2O) n
(CH2O)n (C6 H10 O 5)n
Triose ….3C…..C3H6O3
Pentose ….5C ….C5H10O5
Hexose …..6C ….C6H12O6

Water soluble Water soluble but less readily Water insoluble

soluble than monosaccharides

Sweet Sweet Not sweet

Reducing sugars with reducing ends Lactose , maltose …reducing sugars All non reducing sugars with
SUCROSE …non reducing no reducing ends

With no glycosidic bond Have glycosidic bond Have glycosidic bond

Monosaccharides Monomer …1 sugar unit ..glucose / fructose ( both are hexoses )

Glucose C6H12O6
6 Study how to draw the ring structure
CH2OH
H
P1 5
&C H
H H
1 Alpha glucose
4
H
f
C OH OH H
OH 2
OH
3
HO
3
C H
H OH
C OH
4
H 6
CH2OH

C OH
T
H
5

H OH
H
I
OH Beta glucose
G
H C U

H
OH H
OH
H 3 f

Linear straight chain H OH

Fructose
H

&
OH
H
- C OH CH2OH
2

C
I
OH CH2OH
H 3 I
H
Y
HO C H
3

OH H 6;10
U

H C OH

5
H C OH

C OH
C
H
H Study how to draw the ring structure
CH2OH CH2OH 6

H 5
H OH CH2OH OH
H j
I 2
2 j
H H
H OH
OH OH
4
CH2OH
H Y H
OH
3
H H U

OH
3 2 3 2
OH
.
2

OH H
H OH H OH
Alpha glucose Beta glucose
Beta fructose
Disaccharides 2 sugar units attached with a glycosidic bond

B) sucrose ..alpha glucose + beta fructose

A) maltose from condensation reaction between 2 alpha glucose
CH2OH CH2OH
6
CH2OH
6

OH
6

5 CH2OH
H
5
H H H H H
H H j 2
U 2
U 2 H
OH CH2OH
OH H OH OH OH H OH OH It H It
32
OH OH
2 3 2 Y
3

OH
H OH H OH OH OH H
It

Hydrolysis CH2OH I
CH2OH
+H2O Condensation reaction
12
H

Y
-H2O H
OH CH2OH
OH OH
CH2OH OH OH
CH2OH
5 It
OH OH
5 H H
H H H

10OH
H 2 Hydrolysis

·y +H2O Condensation reaction

OH H O 2
H OH -H2O
OH
H OH
H OH
1, 4 glycosidic bond 1, 2 glycosidic bond
CH2OH D it
1. Disaccharide CH2OH

2. Monomer is alpha glucose

3. Linked by 1, 4 glycosidic bond
↑2
OH
OH O OH CH2OH

4. Reducing sugar OH OH H
Check list
1. Definitions of macromolecules and polymers
2. Comparison between mono , di , polysaccharides in terms of
A) formula
B) taste
C) solubility
D) reducing or non
E) glycosidic bond or not
3. Draw ring structure of alpha glucose , beta glucose and beta fructose
4.know that maltose made from 2 alpha glucose bond by 1, 4 alpha glycosidic bond
5.know that sucrose made from alpha glucose and beta fructose bond by 1, 2 glycosidic bond

Maltose Sucrose
Disaccharide Disaccharide
Monomer ..alpha glucose Monomer..alpha glucose , beta fructose
1, 4 glycosidic bond 1, 2 glycosidic bond
Condensation Condensation reaction
Reducing sugar Non reducing sugar
13/11
Part 2
Polysaccharides

Class work
1. how to carry test for reducing sugars
2. name the two polysaccharides of which starch is
made from
3. Compare between the 2 polysaccharides of starch
4. State the advantages of having a highly branched
molecule
5. Describe structure of cellulose
6. How cellulose have a structural function
7. Compare between cellulose and glycogen
Brain storm on what has been taken before With free functional groups /
ketone group
1. Mono saccharides
Alpha glucose ………beta glucose ……..beta fructose
CH2OH CH2OH OH
CH2OH
H H OH
H H H
H H OH
OH OH H
OH H H CH2OH
OH OH
H OH OH
H
OH
H
2. Disaccharides
Maltose ……………………..sucrose

2 alpha glucose Alpha glucose + beta fructose

1, 4 glycosidic bond 1, 2 glycosidic bond
Reducing sugar Non reducing sugar
CH2OH H
CH2OH
cott
CH2OH

# -
Tox2 ht
H

H OH
H2 4

OH H
·

OH OH
OH
3 2 3
2
OH
3

OH Oll
OH H Alpha glucose
H Alpha glucose
Alpha glucose
 1. How to test for reduing sugar :

Heating the sample with Benedict’s reagent

+2 +2
Reducing sugar + Cu Oxidised sugar + Cu
Reduced to

A_ how to carry test for sucrose using Benedict’s ? Paper 2

Sucrose is a non reducing sugar with its free functional group involved in glycosidic bond so no reducing end

1. Heating of sample with dilute HCL …hydrolysis to glycosidic bond ..release free monosaccharides ( glucose
and fructose ) ..with free functional group
2. KOH neutralise acid
3. adding Benedict’s reagantr and heat at 95 C , if brick red color appears , so this inicated the presence of
sucrose

B_ how to carry test for sucrose using Benedict’s ? Paper 1

1. Test with Benedict’s reagent so if gives negative result remaining blue color …so no reducing sugars
Sucro
2. Heat with dilute HCL , neutralise with KOH , then add Benedict’s reagent and heat ,,, if +very
se
only brick red color appears so ,,,,,sucrose is present
 1. Do Benedict;s ( reagent + heat ) ..brick red
• reducing sugar ……are present
• Glucose , fructose ,maltose , lactose , galactose

Reducing sugars
2. HCL , heat , neutralise with KOH , then add benedict’s reagent
No reducing sugars
Positive brick red Colour
Or both
Can either be reducing or non reducing sugar

1 carry Benedict’s test ..to give negative so no reducing sugar

2. Then dilute HCL , heat , add KOH ,,,add Benedict’s,,,,,positive brick red so
non reducing sugar is present ( sucrose ) .
Polysaccharides 11 or more monosaccharides
Starch , cellulose , glycogen

A . Starch Mixture of 2 polysaccharides which are amylose and amylopectin

Amylose Amylopectin

I
Monomer is alpha glucose
Linked by 1, 4 glycosidic bond

No 1, 6 glycosidic bond Has both 1, 4 and 1, 6 glycosidic bond

Unbranched
Branched
Spiral / helical

Less compact More compact

Advantage of having a highly branched molecule :

1. Insoluble so doesn’t affect the osmotic balance / water potential of cells

2. Many terminals ( branched ) ..for easily removal and attachment of glucose
3. QUICKLY hydrolysed by enzymes when energy is needed
4. Compact so store more glucose while occupying less space
5. its a Store of glucose / energy

B. Glycogen Same as amylopectin but more branched

1. Polysaccharide
2. Water insoluble
3. Monomer is alpha glucose
4. 1, 4 and 1, 6 glycosidic bond
5. Non reducing sugars
Break
6. Both starch and glycogen have metabolic function
6;00

Molecules can either have metabolic or structural functions

Structural ……no change in structure
Metabolic …involved in chemical / metabolic reaction
 C. Cellulose

• its polysaccharide
• with monomer beta glucose
• linked by 1, 4 glycosidic bond
• each glucose molecule is found alternating at 180 degree relative to the other
• So form a flat ribbon S
• unbranched ( linear / straight chain ) Microfibrils
... ...

S S
• So molecules lie parallel to each other .
↓

...g
Cellulose have a structural function
-S
• formed from beta glucose monomer
• Linked by 1, 4 glycosidic bond , where each glucose molecule is found alternating at 180 degree relative to the
other
• Forming a flat ribbon
• unbranched ( straight / linear chain ) polymer …allowing cellulose molecules to lie // to each other with many oH
groups projecting in different direction
• Allow the formation of many hydrogen bonds between cellulose molecules to give // chains ..forming microfibrils
• Many microfibrils together held with more hydrogen bonds forming cellulose fibres
• Fibres found at right angles ( criss cross together ) forming cellulose cell wall with high tensile strength and
unstretchable prevent plant cell wall from busting , freely permeable ( gaps ) , insoluble
Cellulose
Strength and support
Prevent the cell from bursting
Helps keep its shape / turgid

Beta glucose
1, 4 glycosidic
Cellulose
Hydrogen bonds
Microfibrils
Hydrogen bonds
Fibres
Cell wall
 Glycogen Cellulose

Polysaccharides
Monomer is glucose
Water insoluble
Both have glycosidic bond

• Monomer is alpha glucose . Monomer is beta glucose

• 1, 4 and 1,6 glycosidic bond • 1, 4 glycosidic bond

• So has two types of bonds • So only one type of bond

• branched • unbranched ( linear / straight )

• metabolic function • structural function

• no hydrogen bonds between glycogen molecules • hydrogen bonds between cellulose molecules
Water molecules O A) water is dipolar with electrons being unequally distributed / shared
between oxygen and hydrogen ( oxygen more electronegative than
i S
↓
hydrogen )
. Oxygen has a slight / small / partially negative charge
.....S While hydrogen has slight / small / partially positive charge .

3 S
B) hydrogen bond is formed between water molecules
↓

· Each oxygen atom forms 2 hydrogen bonds and each hydrogen atom
forms one hydrogen bond

↓
S
C) hydrogen bond is a weak bond

Water is dipolar . With +.GHydrogen atoms and , -SOxygen atom -

CHLON Polar molecules

Charged Ions I
OH / NH / SH / CO
Attracted to opposite charges NaCL of Ot
S -S

..........
Y
OH
S

HH &
+

x D

.
He
S
Tt
·

.
O

of Y
x8
N +
I
o
S
Cl-
Na+
O
O
f
Y .....
+S
&

*
&
-

H S O
B + +
O
-

S
Water dissolve ions where the + hydrogen atom will be attracted to -ve ion and the - Oxygen atom will be attracted to +ve ion f
18/11/2024 6;10
Lipid and types of bonds in protein

Class work

1. . 2 examples of lipids ( triglycerides and phospholipids )

2. Composition of triglycerides and how they join
3. Number of ester bonds in triglycerides
4. Compare between saturated and unsaturated fatty acids
5. Phospholipids composition
6. Comapre between phospholipids and triglycerides
7. Draw structure of amino acid
8. Importance of R group
9. state Types of bonds involved in protein molecule
 Examples
Lipids A) triglycerides ( 1 glycerol + 3 fatty acids )
B) phospholipid ..cell membrane

Triglyceride
Phospholipid
3 fatty acids
2 fatty acids
Glycerol

Glycerol
P
R_OH. + R-COOH ………..R_ C _O_R Glycerol + 2 fatty acids + 1 phosphate group
Ester bond
Molecules
Explain why lipids are water insoluble ? Charges / ions …soluble in water..hydrophilic
Polar ….OH / NH/ SH / CO..soluble in water ..hydrophilic as they
1. Elements C, H, O can form hydrogen bond with water

2. Water insoluble Non polar ..hydrophobic ..water insoluble

3. because they have reduced number of Oxygen to carbon and hydrogen

4. So reducing number of OH
5. So lipids are non polar
6. So can’t form hydrogen bond with water
A) triglycerides They are esters formed from glycerol and fatty acids

Glycerol Study Fatty acids ( saturated or unsaturated ) Recognise

H

H C OH
H. H. H H. H. H H. H. H

C OH HO C C. C. C. C. C. C. C. C. C
H
H. H. H H. H. H H. H. H I

H C OH
Hydrocarbon
H Hydrophobic
Non polar fatty acid tail

estenork
.

H H. H. H H. H. H H. H. H

C OH HO C C. C. C. C. C. C. C. C. C H
H
H. H. H H. H. H H. H. H I H C O
im
C
H C OH H. H. H H. H. H H. H. H Condensation reaction O

H C O "m
C
HO C C. C. C. C. C. C. C. C. C
H C OH O
H. H. H H. H. H H. H. H -3H20 "M
H C O C
H
I

H. H. H H. H. H H. H. H
H
HO C C. C. C. C. C. C. C. C. C
Triglyceride with 3 ester bonds
H. H. H H. H. H H. H. H
I
Two types of fatty acids

Saturated fatty acids Unsaturated fatty acids

1. Has carbon to carbon

1. Has no carbon to double bonds
carbon double bond 2. has kinks
2. Straight 3. doesnt have the
3. With maximum maximum number of
number of hydrogen hydrogen atoms
atoms 4. Liquid at room
4. Solid at room temperature
temperature

da

Hydrophobic hydrocarbon tail

Hydrophobic hydrocarbon tail
Number of hydrogen atoms in tail =
Has kinks
(nC x2 )+1
( nC x2) +1-- number of carbon atoms having double bond
(9C x 2)+1 = 19
19- 2= 17
B) Phospholipids

Hydrophobic hydrocarbon tail

Hates water

1. Hydrophilic phosphate head ( polar )

Hydrophilic
…facing cytosol / tissue fluid
phosphate head
2. Hydrophobic hydrocarbon
( polar )
tails ..facing one another away from
Loves water
water forming hydrophobic core
 Triglycerides Phospholipids

1 glycerol + 3 fatty acids 1 glycerol + 2 fatty acids + phosphate group

3 ester bonds 2 ester bonds

Both have ester bonds

Elements ( C, H, O )
Both have carbon to carbon double bond in their hydrocarbon tails

Hates water Hydrophobic Hydrophilic head

Loves water

Triglycerides are storage of energy

Due to the large number of C- H bonds in hydrocarbon tail ( fatty acid tail )
Larger mass per unit volume

Why triglycerides are higher source of energy over the carbohydrates

Fats have more C-H bonds

Source of more H
For respiration
Proteins Monomer Amino acid

Enzymes
Part of cell membrane H
Some hormones ( insulin and glucagon)
Collagen ..in walls of blood vessels
N. C. C. OH
L-Carbon
H Carboxyl group
R
Antibodies
Keratin in hairs and nails Amine group

Haemoglobin

1. Variable side chain

Different in different amino acids

2. Determine the 3D shape of protein

As well as it determines whether its water soluble
( hydrophilic with polar hydrophilic R group ) or water
insoluble with hydrophobic R group .
 1. Types of bonds involved in a protein molecule https://youtu.be/hok2hyED9go?si=dhAiY3uZiXfixsa7

2 Bonds are formed between

1. Bonds are formed between R groups of amino acids
amino acids in a poly peptide 1. Hydrogen bond between polar R groups
chain without the involvement of 2. Ionic bond between ioniosed R groups
the R groups 3.Disulphide bond between cysteine amino acids
4.Hydrophobic interaction between non polar R groups

1 peptide bond 2 hydrogen bond

Know how to draw
A. Bonds between carboxyl group of B. Between oxygen of a carbonyl
one amino acid and the amine group group of one amino acid and H of Next page
of another amino acids the amine group of another amino
R groups are not involved acid .
H H
H
H i H
H
N C C N C C OH
N. C. C. OH H
N. C. C. OH
Carboxyl
Amine group
-

L-Carbon
H Carboxyl group R
-

R
H
L-Carbon
R -
H
Amine group
Carboxyl group
Amine group R H
H
Condensation
H
N C C N C C OH
Amine group H Carboxyl

R R
8
..... H
H
8
H It It
+ H2O
N. C. C. N. C. C. OH H
N C C N C C OH
-

L-Carbon
-

H L-Carbon

R H
Carboxyl group
Amine group
R Amine group H Carboxyl

R R
....
 Bonds involving R group interaction

2- Bonds are formed

between R groups of amino acids

Hydrophobic
Hydrogen bonds
interaction
Between polar R groups Ionic bonds
Disulfide bond
NH, , SH , OH , CO Interaction
Between ionised R groups Between cysteine
Ionised NH3+ of R group of between 2
Between R groups amino acids
one amino acid and ionised hydrophobic non
with Carboxyl and
carboxylic acid group COO- of polar R groups
amine groups
R group of another amino acid .

#
 1. R group charged ….ionic
2. R group polar …hydrogen
3. R group non polar …hydrophobic interaction
4. R group is containing S ..disulphide

C OH
Carboxyl

COO
-

C -

Carboxylic acid
Carbonyl group
group
20/ 11/ 2024
Part 4
Protein structure
Different types of protein

1. Classwork :
2. describe primary structure
3. Describe secondary structure
4. Describe tertiary structure
5. Describe quaternary structure
6. Name the bonds involved in each protein level
7. Describe the structure of haemoglobin
8. Desctribe structure of collagen
9. compare between globular and fibrous protein
2 protein structure

• Linear sequence of amino acids in a polypeptide chains

A 1. Primary structure
• With a PEPTIDE BOND between amino acids , which is a strong
covalent bond that is last to break by changes in temperature and pH
• No R group interaction
Formed through condensation reaction
Between amine group of one amino acid and carboxyl group of another
amino acid .

B 2. Secondary structure
Involves hydrogen bonds between the oxygen of carbonyl group C=O of one amino acid and the H of the amine
NH group of another amino acid with no R group involvement ( within same polypeptide )

A) beta pleated sheets b) alpha helix

Beta pleated sheets are flat sheets , where the hydrogen bonds Has alpha helix which is held by hydrogen
are formed between the Oxygen of a carbonyl group of one bonds between amine group of one amino
amino acid and H of amine group of another amino on acid and carbonyl group three or four amino
adjacent part of the polypeptide acids apart in same polypeptide .
C Tertiary structure

Over all folding and coiling of a polypeptide chain into a specific 3D shape
Maintained by R group interactions and bonds :

A) hydrogen bond between polar R groups between -NH / and OH / -CO .

B) ionic bond between ionised R groups amines and carboxylic acid groups)
C) disulfide bond between Cysteine amino acids
D) hydrophobic interaction between between non polar R groups .

D Quaternary structure Primary structure

Peptide bond
3D shape of TWO OR MORE polypeptides
held together by R group interaction and
bonds :
Secondary structure
A) hydrogen bond between polar R groups
Hydrogen bond
B) ionic bond between ionised R groups
C) disulfide bond between Cysteine amino
acids Tertiary structure
R groups
D) hydrophobic interaction between between Ionic , hydrogen , disulfide ,

non polar R groups . hydrophobic interaction

Quaternary structure:
R groups
Ionic , hydrogen , disulfide ,
hydrophobic interaction
 Types of proteins 1. Globular
R
2. Fibrous
P
=

P22
A . Globular proteins i -
R
R
-

~R

1. Water soluble protein

2. Amino acids with hydrophilic R groups are facing outside to be able to form hydrogen bonds with water, while
amino acids with hydrophobic R groups are facing inside / pointing inwards .
3. Spherical / ball shaped
4. Have a tertiary structure ( like enzymes , haemoglobin , antibodies , insulin ….) metabolic functions
5. Some have quaternary structure such as haemoglobin and transport proteins.

Example as haemoglobin

1. Globular protein ..spherical , water soluble because it has amino acids

with hydrophilic R groups facing outside to be able to form hydrogen
bonds with water and amino acids with hydrophobic R groups facing
inside / pointing inwards .
2.Have metabolic function
3. Quaternary structure ..made from 4 polypeptides ( 2 alpha and 2 beta
globins ) connected together by hydrogen bonds ,disulfide bond ..
Each polypeptide has a haem group
( prosthetic group i.e not made from amino acids )
 Haem Porphyrin ring

B
Iron ion

Contain iron ion attached to porphyrin ring to bind with oxygen molecules forming oxyhaemoglobin
Hb + 4O2 …….HBO8
4 polypeptides with 4 haem groups attach to 4 oxygen molecules ( 8 oxygen atoms )
B. Fibrous proteins Simpler structure , so more stable to changes in pH and temperature

• long polypeptide strands made of of thousands of amino acids

• Don’t curl up into tertiary structure
• Large number of repeated sequence of amino acids
• Structural function
• water insoluble with hydrophobic R groups facing outside

Compare between globular and fibrous protein

Globular protein Fibrous protein

• Metabolic function • structural function

• Water soluble ( with hydrophilic R • Water insoluble ( with hydrophobic R groups facing
groups facing outside ) outside )
• Irregular sequence of amino acids • Regular sequence of amino acids
• Spherical with tertiary structure • Long strand / chain with no tertiary structure
• Less stable • More stable
• Enzymes , antibodies , haemoglobin • Collagen
 Structure of collagen as an example of fibrous protein
Helical polypeptide = helix
Fibrils Fibres

4
.
i
N _C _C_OH

is
Collagen molecules
Helix are tightly packed /
Small R group lie // to each other
three polypeptides closely with cross links
formed between
associated.
Poly peptide is found in form collagen molecules )

of Helix and not alpha helix

NH of glycine can form which are covalent
bonds
as its not tightly wound hydrogen bond with C=O of Form fibrils
Glycine amino acid repeated adjacent amino acid ( in Staggered ends to
avoid any weak point
at every third position ( small other polypeptide ) along along fibril
R group) Three helices wind together
held by hydrogen bonds +
forming collagen molecule
Describe structure of collagen :
1. Insoluble fibrous protein
2. formed from 3 helical polypeptides / which are found in form of helix
3. Each polypeptide has a glycine amino acid found at every third position pf the polypeptide chain , with
smallest R group ( H ) so the helix are tightly packed / three polypeptides are tightly associated for
highest stability
4. Where the helices are held together by hydrogen bond ( NH of glycine can form hydrogen bond with
C=O of adjacent amino acid ( in another polypeptide ) forming COLLAGEN molecule
5. Collagen molecule lie parallel to each other and linked by cross links ( covalent bonds ) forming fibrils ,
ends of the polypeptides are staggered so no weak points
6. Fibrils together form fibres with high tensile strength
25/ 11/ 2024
Part 5
Water properties
Practice

Class work :
1. Explain the importance of water as solvent
2. Explain why water has high melting and boiling point
3. Explain the importance of water having high surface tension
4. Explain why water has high specific heat capacity
5. Explain the importance of water having high specific heat capacity
6. Explain why water has High latent heat of vaporisation
7. Explain the importance of water having high latent heat of
vaportaisation
8. Explain importance of water having low density at -4C
 1. Solvent
Dipolar + describe
2. High melting and boiling points
3. High surface tension
Hydrogen bonds 4. High specific heat capacity
5. High latent heat of vaporisation
Density below -4C 6. Water density
Collagen

1. Helices are held together by hydrogen bonds forming COLLAGEN

MOLECULE. ( NH of glycine can form hydrogen bond with C=O of
adjacent amino acid ( in another polypeptide )

Water

. Dipolar
2. Each water molecule has a. SOxygen and a.+ SHydrogen atom .
-

3. So can form hydrogen bond with each other where …hydrogen of one
water molecule forms a hydrogen bond with-Oxygen of another water
molecule , SOxygen forms two hydrogen bonds with 2 different water
-

molecules .

Between two cellulose molecules

While referring /describing any structure

involving hydrogen bond ..add details of hydrogen
bond ( formed between H of the OH and O of the
OH group )
Proteins in secondary structure Il

Secondary structure
nig
It
2C

Involves hydrogen bonds between the

H R

oxygen of carbonyl group C=O of "

H

one amino acid and the H of the TN - C 2C

amine NH group of another amino H R
acid with no R group involvement ........

#n 2C

I is

Tertiary structure

A) hydrogen bond between polar R groups between -NH / and OH / -CO .

Hydrogen bonds are formed between polar R groups

( between R groups with polar hydrogen atom and R
group with amine or carboxyl groups )

-SS 6S
H ………..NH / CO/ OH
 Properties of Water molecule
S

A) solvent
I
·
*
S
1. Dipolar , unequal distribution of electrons
2. each water molecule has a slightly / partially / small negative oxygen atom and slightlly / partially / small
postively charged hydrogen
3. Dissolve ions where slightly negative oxygen atom attract +vely charged ions ( cation ) and slightly positive
hydrogen atom attract -ve charged ion ( anion ) and dissolve / form hydrogen bonds with polar molecules
( OH / NH / SH / CO) -
S
-
S

B) high melting and boiling point -

: i
..... P

-
P

1. Dipolar …unequal distribution of electrons

2. Each water molecule has a slightly / partially/ small negative oxygen atom and a slightly / small /
partially positively charged hydrogen.
3. So can form hydrogen bond with each other …
4. It takes a lot of energy to break down all hydrogen bonds holding the molecules together .
C) high surface tension Cohesion Adhesion
------

A) tension of surface of water by attraction forces between water molecules ( cohesion ) ..allow
animals to move / stand on water surface .
B) cohesion ..force by which water molecules stick together by hydrogen bonds
C) adhesion …force of attraction between water molecules and other different miolecules Break
5;47

High specific heat capacity : Amount of heat needed to change the temperature

For water 4200 joules to raise the temperature of 1 kg of water by 1 C

Due to presence of large number hydrogen bonds between water molecules.
1. Provides constant body temperature, optimum temperature for maximum enzymatic activity .
2. Stabilise temp. Of water in lakes and oceans as temperature of environment changes ,….stabilise
environment of aquatic life

High latent heat of vaporisation Latent heat : Amount of heat needed to change the state

Heat energy needed to break down the hydrogen bonds between the water molecules to change the state from
liquid to gas ,,,latent heat of vaprorisation

High latent heat of vaporisation …..due to high specific heat capacity …..due to the presence of many
hydrogen bonds …..so water needs large amount of heat energy to break down the hydrogen bonds
 1. Plays a role in decreasing body temperature ( by evaporation of sweat using excess latent heat ) with
reducing risk of dehydration
2. Plays role in cooling down the plant through transpiration without risk of losing to much water

Water density

Low water density

If temperature falls below -4C ..water will freeze ..form ice …so float on water surface ….formimg a layer
of insulation to the water under ice ..prevent aquatic animals from freezing .