Biological molecules

As Biology ( 9700)
2022-2023
11/ 7/ 2023
Part 1
Carbohydrates
 Biological molecules

Macromolecules Giant molecules with large molecular mass

Lipids
Carbohydrates , proteins , and fats Therefore
not a polymer
is

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

- Nucleic acid
Polysaccharides
Proteins

Nucleotides
Monosaccharide
Amino acids
( ex glucose )
Carbohydrates C; H : O
1: 2: 1

Monosaccharides Disaccharides Polysaccharides

(CH2O)n

3 Carbon atoms = n
Triose ….3 ….C3H6O3 2 x C6H12O6- H2O
(C6H12O6)n - (H2O)n
Pentose …5….C5H10O5 C12H22O11
Hexose …..6….C6H12O6 n= number of glucose molecules
(C6H10O5)n

Water soluble Water soluble but less readily Water insoluble

That's why
turned soluble than monosaccharides
is
glucose
to sucrose in
of
transport
Sweet sucrose Sweet Not sweet

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

With no glycosidic bond Have glycosidic bond Have glycosidic bond

Monosaccharides 6 2- glucose
CH2OH
Glucose
H
5
H

1
C 4
H
up
1 -down
OH
-
OH
3 2

OH OH
H C
2

↑ down
OH
>
down H
-

HO C H
3

B glucose
6
CH2OH

H
4
C OH 5
H
H
OH
- up
4 1.

H C OH OH
5
H
OH
p
3 I H

6
CH2OH down H
OH ~ down
Fructose
B- Fructose

L
CH2OH 6
CH2OH OH
2
C 5 2

CH2OH
HO
3
C
A H OH
2 3
V
C OH
It
OH
5C OH

6
CH2OH

6 6

CH2OH CH2OH
5 5 OH 6
CH2OH OH

OH 4 2
5
OH
4
OH
OH 3 2 OH 3 2
OH CH2OH
I
3
OH OH 4

Alpha glucose Beta glucose OH

Beta fructose
Disaccharides 2 sugar units attached with a glycosidic bond

A) maltose ..from condensation reaction of 2 alpha glucose B) sucrose ..alpha glucose + beta fructose
CH2OH CH2OH OH
6 5 2
CH2OH
6
CH2OH I
5
U
OH CH2OH
H 5 OH OH W 3
OH
5 H 3 2
I
I 4
4
OH OH OH
OH OH OH
OH
3 2

OH
3 2

Alpha glucose CH2OH

Alpha glucose OH OH CH2OH
5
2 5
Condensation reaction I

OH CH2O
Hydrolysis U
OH
-H2O OH I
T &
Require heat
High +H2O OH
OH
temperatures 3 2
3 U
6
6
CH2OH CH2OH
OH OH
A H 5
5 Condensation reaction
I 4
I
CH2OH -H2O
OH
4
OH O 3 2 OH CH2OH
OH
3 2 5

1k
OH
2 5
OH
4
OH
OH CH2OH
2

1, 4 glycosidic bond ↑
OH
3 U

OH
OH
1. Disaccharide 1. Disaccharide

2. Monomer ….alpha glucose 2.Monomer ( alpha glucose and beta fructose )

3. 1,2 glycosidic bond
3. 1, 4 glycosidic bond
4, non reducing sugar with no reducing end, where both
4. Reducing sugar
functional groups are involved in the glycosidic bond
 CH2OH
Reducing sugar
5
CH2OH OH
with a reducing
I 5 2 C
CH2OH end
4

OH
OH
4 3

OH With free
2
OH
3

OH
OH functional
Beta fructose
Alpha glucose groups /
ketone group

CH2OH CH2OH

clos
CH2OH
5

Lo-215'
5 5
/
↳Kod
I
4
OH
4
OH
OH 3
OH
3 2 ·
OH
3
2
OH
3

OH
OH
Alpha glucose
Alpha glucose of
Alpha glucose

Maltose 1, 4 glycosidic bond Sucrose 1, 2 glycosidic bond

Testing for reducing sugar

Benedict’s reagent
2 H
Reducing sugar + Cu
+

-
Oxidised sugar + Cu
Reduced to

Paper 2 questions: do benedict

Always -
before
Sucrose …a non reducing sugar ↑
1. Heating with dilute HCL …..hydrolysis to glycosidic bond …..release free monosaccharides
( glucose and fructose ) …with free functional group

2. KOH neutrailse acid

3. Add benedict’s reagent …..heating at 95C ….if brick red color appears ..indicates the presence of
sucrose

-
Steps to follow for paper 1 :
1. Test with Benedict’s……-ve remain blue ….no reducing sugars
2. HCL …heat ….KOH …..benedict;s …..heat …..+ve brick red ppt ….sucrose
present

1. Benedict’s +ve
2. HCL ..+ve
Polysaccharides 11 or more monosaccharides

Starch, glycogen , cellulose

A. Starch Mixture of 2 poly saccharides ( monomer is alpha glucose )

Amylose
Amylopectin

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

Advantages of having a-highly branched molecule :

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

1. Many terminals ( branched ) …for easily removal and attachment of glucose
3. QUICKLY hydrolysed by enzymes when energy is needed
4. Compact so occupy less space

B . Glycogen Same as amylopectin but with more branches

Polysaccharide
Monomer is alpha glucose
1, 4 and 1, 6 glycosidic bond
1, 6 glycosidic bond form branches
Water insoluble
Non reducing sugar
Both starch and glycogen have metabolic function

Molecules can either have metabolic or structural functions

Structural ……no change in structure
Metabolic …involved in chemical / metabolic reaction
12/7/2023
Part 2
Cellulose
Lipids
Practice
1. Maltose …..2 alpha glucose …….1, 4 glycosidic bond
2. Sucrose …..alpha glucose + beta fructose ………1, 2 glycosidic bond
3. Starch
A_) amylose ……alpha glucose ………..1, 4 glycosidic bond , non branched
B_) amylopectin ….alpha glucose …..1, 4 and 1,6 glycosidic bond , branched
4. Glycogen
Similar to amylopectin and more branched
5. Cellulose
C. Cellulose
• its a polysaccharide
• With monomer beta glucose
• Linked by 1, 4 beta glycosidic bond
• Each glucose molecule must be rotated at 180 degree relative to the other
• So forming a flat ribbon
• Unbranched ( linear / straight chains ) Microfibril
• So molecules lie // to each other Parallel
>
-

Cellulose having a structural function

1. Formed from beta glucose monomer

2. Linked by 1, 4 glycosidic bond where each glucose molecule is rotated at 180 degree to the other
Forming a flat ribbon .
3. Unbranched ( straight / linear ) polymer …allowing cellulose molecules to lie // to each other with
many OH groups projecting in different directions .
4. Allowing the formation of hydrogen bonds between cellulose molecules to give // chains …forming
microfibrils.
5. Many microfibrils together with more hydrogen bonds forming cellulose fibres .
6. Fibres found at right angle ( criss cross together ) forming cellulose cell wall with high tensile strength
and unstretchable prevent plant cell wall from bursting + freely permeable ( gaps ) + insoluble
 ⑥

②
② : : : :

: : : :
-

Beta glucose ….cellulose …..many cellulose form microfibrils

Many microfibrils form fibres
 Glycogen Cellulose

Polysaccharides
Insoluble
Glycosidic bond

Monomer is alpha glucose Monomer is beta glucose

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

Two types of bonds Only one type of bond

Metabolic function Structural function

Branched
Unbranched ( linear / straight )

No hydrogen bonds between glycogen molecules There are hydrogen bond between cellulose molecules
Water molecules A) water is dipolar with electrons being unequally distributed / shared
S
between oxygen and hydrogen ( oxygen more electronegative than
X

x I - X
S hydrogen )
0 .......
H Oxygen has a slight / small / partially negative charge
-
While hydrogen has slight / small / partially positive charge .
S I
..
X

0
S
X

H
B) hydrogen bond is formed between water molecules
S I -
Each oxygen atom forms 2 hydrogen bonds and each hydrogen atom
X

forms one hydrogen bond

- S -
S

+8 +8
8 3
C) hydrogen bond is a weak bond
+ +

- S

+6

8
+

Water is dipolar . With +.SHydrogen atoms and , -8 Oxygen atom

Charged Ions Polar molecules

NaCL OH / NH / SH
Attracted to opposite charges
chint out
I -
6 S
+

ot
ot
...........
8 /
H 0
+

S
x 3
-

*p
*
5
+,
-

I 6
* Xy
xg
e
I or
+
O
I s
- I -

Cl- -I
Na+
0
/ .....
C
0
I

↳
·x8HH 6
+
I
x
.
O

* -
5 -I
0

Water dissolve ions where the + hydrogen atom will be attracted to -ve ion and the -SOxygen atom will be attracted to +ve ion
 Triglycerides …..fats. ( 1 glycerol + 3 fatty acids )
Lipids

Phospholipids …..cell membrane

C, H, O ….water insoluble
Reduced proportion of oxygen to carbon and hydrogen
So reducing the number of OH
So lipids are non polar
So can’t form hydrogen bonds with water

Triglycerides Phospholipids

P
Glycerol + 3 fatty acids
( alcohol )
Glycerol + 2 fatty acids + 1
R-OH + R-COOH………R-C-O-R + H2O phosphate group
Ester bond
A . Triglycerides

They are esters formed from B) fatty acids ( saturated , unsaturated )

A) glycerol

C
C. C. C. C. C. C. C. C. C. C
C H

Hydrocarbon tail
C

Triglyceride with 3 ester bonds

A) glycerol
8

C C. C. C. C. C. C. C. C. C. C

H
C - - nu

Condensation reaction
C P
C. C. C. C. C. C. C. C. C. C
-3H20
C - Mu
=

H 0

C
11

C - C-M
C. C. C. C. C. C. C. C. C. C

H
 Saturated fatty acid UnSaturated fatty acid

1. Has carbon to
1, no carbon to carbon carbon double
double bond bond
2. Straight 2. Has kinks
3. With maximum 3. Doesn’t have a
number of hydrogen maximum number
atoms of hydrogen atoms
4. Solid at room 4. Liquid at room
temperature temperature

⑰_
Carboxyl group

Hydrophobic hydrocarbon tail

Hydrophobic hydrocarbon tail
Straight
Has kinks
Calculating the number ( nC x 2) + 1
( nC x2) +1 - number of carbon atoms
of hydrogen atoms ( 9Cx 2) +1= 19 hydrogen atoms
having double bond
19 - 2= 17 hydrogen atoms
B. Phospholipids Hydrophilic phosphate head ( polar )

Hydrophobic hydrocarbon tail

Hydrophobic hydrocarbon tail

Hydrophilic
phosphate head
( polar )

Hydrophilic phosphate head ( polar )…….facing cytosol / tissue fluid

Hydrophobic hydrocarbon tail …..facing one another away from 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 Loves water Hydrophilic head

17/7/2023
Part 3
Proteins
Proteins OH , NH , SH ……polar
If not present …..non polar Polar R

Enzymes group
Non polar R group
Part of cell membrane
Some hormones ( insulin and glucagon)
Collagen ..in walls of blood vessels
Antibodies
Keratin in hairs and nails
Haemoglobin

1. Variable side chain

Monomer
Different in different amino acids
Amino acid

2. Determine the 3D shape of protein

H
H as well as it determines whether is water
N. C. C. OH soluble hydrophilic ( with hydrophilic R
H L

Amine group Carboxyl group group ) or water insoluble ( with hydrophobic

R
R group ) .
3D
R

K.
"t

k.k
 Types of bonds
COOH …carboxyl grp I olt
CO..carbonyl Q
1. Bonds with no R 2. Bonds with R
C

groups not involved groups involved

1. Hydrogen bonds between polar R groups
2. Ionic bond between ionised R group
3. Disulfide bond
Hydrogen bond 4. Hydrophobic interaction.
Peptide bond
B. Between carbonyl group of one
A. Bonds between carboxyl group of
amino acid and the amine group of
one amino acid and the amine group
another amino acid .
of another amino acids 11 H
9
R groups are not involved H I -

-
NC.C
- C - C
H A /
H ↳
H
N. C. C. OH H ! R
H N. C. C. OH
H ⑰
I
...

I H
H
9 H

C_c
I

Condensation reaction
-°
N -
C -
2
A
-H2O ↳ ! R
H .........
H H
N. C. C. N. C. C. OH H -°
I 9 D
N C 2 c C H
I
-

Peptide bond
- -

R H
Covalent
N. bond C.
C. OH
↳ ! R
Strong bond
 Bonds involving R group interaction

Hydrogen bonds Hydrophobic

Ionic bonds Disulfide bond
interaction
Between polar R groups Between ionised R groups Between cystine
NH, , SH , OH Interaction
Ionised NH3+ of R group of amino acids
between 2
one amino acid and ionised
hydrophobic R
carboxylic acid group COO- of
groups
R group of another amino acid .

C=O ,……carbonyl

④
C-OH………carboxyl
-

COO-…….carboxylic acid group

-

-I
 Protein structure

A Primary structure
Linear sequence of amino acids in a polypeptide chain
With PEPTIDE BOND between amino acids ….which is a strong
covalent bond that is last to be broken by temperature ( thermostable )
H O

and pH . N. - C. C. N.
-

-*C. C. - OH

No R group interaction
X

RR
Peptide bond
Formed through condensation reaction
Covalent bond
Between amine group of one amino acid and the carboxyl group COOH Strong bond

of another amino acid

B 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

Beta pleated sheets Alpha helix

Poly peptide chains are held in a flat sheet / parallel sheets Poly peptide chain is coiled into a spiral shape
( helix) , with peptide bond forming back bone
and R groups are projecting in all directions
C Tertiary structure

Over all folding and coiling of a polypeptide chain into a specific 3D shape
Maintained by R group interaction 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 .

Primary

D Quaternary structure Peptide

3D shape of TWO OR MORE polypeptides held

Secondary
together by R group interaction and bonds :
Hydrogen
A) hydrogen bond between polar R groups
B) ionic bond between ionised R groups
Tertiary
C) disulfide bond between Cysteine amino acids
R gps
D) hydrophobic interaction between between non
Ionic , hydrogen ,
polar R groups .
hydrophobic, disulfide

Quaternary
https://youtu.be/hok2hyED9go R groups
Same
 Primary …………..peptide
Secondary ………hydrogen
Tertiary ……..R groups ( hydrogen , ionic , disulfide , hydrophobic )
Quaternary …..R groups ( hydrogen , ionic , disulfide , hydrophobic )

1. Peptide bond ,…between carboxyl group of one amino acid and amine group of another
amino acid ..condensation reaction
2. Hydrogen …….between O of carbonyl group of one amino acid and H of amine group
of another amino acid
3. R groups
Hydrogen between polar R groups
Ionic bond between ionised R groups such as NH3+ and COO-
Disulfide bond between cysteine amino acids
Hydrophobic interaction between non polar hydrophobic R groups
18/7/2023
Part 4
Types of proteins
Water properties
Types of proteins
-R
Spherical/ ball shaped
-
A. Globular proteins
- -R
1. Water soluble proteins -
2. Amino acids with hydrophilic R groups facing outside to be
2 /

able to form hydrogen bond with water , while the amino R

a
acids with hydrophobic R groups are facing inside / -
pointing inwards . I
in
3. Have tertiary structure ( like enzymes , haemoglobin ,
antibodies , insulin ,….) metabolic function
4. Some have quaternary structure such 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. Quaternary structure ..made from 4 polypeptides ( 2 alpha

and 2 beta globins ) connected together by disulfide bond

3. Each polypeptide has a haem group

Fibrous protein Simpler structure , so more stable to changes in pH and temperature

Long polypeptide strands made from thousands of amino acids

Dont curl so no tertiary structure
Larger number of repeated sequence of amino acids
Structural function
Water insoluble with hydrophobic R groups facing outside

Globular protein Fibrous protein

Metabolic function Structural function

Water soluble ( with hydrophilic R Water insoluble ( with hydrophobic R groups

groups facing outside ) facing 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

 Collagen molecule as an example of fibrous protein
Group of fibrils
Fibres will form fibres
Helical polypeptide = helix Collagen = triple helices Fibrils
giving high

Finding
Collagen molecules lie //
Poly peptide is found in tensile strength .
to each other with cross
form of Helix and not Three helices wind together
links formed between
alpha helix as its not tightly held by hydrogen bonds +
collagen molecules )
wound forming collagne molecule
which are covalent bonds
Glycine amino acid
Form fibrils
repeated at every third
Staggered ends to avoid
position ( small R group)
any weak point along
along fibril

helix tightly packed / three

polypeptides closely associated.
NH of gly can form hydrogen

1. Insoluble fibrous protein bond with C=O of adjacent

amino acid (in other polypeptide).
2. Formed from 3 helical polypeptides / where each is found in form of helix
3. Each polypeptide has glycine amino acid repeated at every third position of the polypeptide
with smallest R group ( H) so the three helices can be held together tightly ( allow tight
coiling ) for highest stability
4. Helices are held together by hydrogen bond forming COLLAGEN MOLECULE
5. Collagen molecules lie // to each other and linked with 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 .
Contain iron attached to porphyrin ring to bind with oxygen molecules forming oxyhaemoglobin
Haem
Hb + 4O2 …….HBO8
4 polypeptides with 4 haem groups attach to 4 oxygen molecules ( 8 oxygen atoms )
Porphyrin
ring
Iron

V
19/7/2023
Part 5
Water properties
 N S
-

Water molecule
8
-
-

x 8+8
8
x5
*
-
I

I
C
A) solvent

1. Dipolar ….unequal distribution of electrons

2. Each water molecule has a slightly / partially / small negative oxygen atom and a slightly /
small / partially charged hydrogen atom
3. Dissolve ions where slightly negative oxygen atom attract +ve charged ion ( cation ) and the slightly
positive hydrogen atom attract -ve charged ion ( anion ) and dissolve / form hydrogen bonds with
polar molecules ( OH/ NH/ SH / CO)
-
S

S
-
S

B) high melting and boiling point

x

x 8

x8 ...
6
* .... ↑

-
S

S
x

8
x

1.Dipolar
2.Each water molecule has a. -
8 Oxygen and a. 8 Hydrogen atom
+

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 .
 Adhesion Cohesion
-
C) high surface tension

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

-
S

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

For water 4200 joules to raise the temperature of 1 kg of water by 1 C x8 -

.... ↑

Due to presence of large number bonds between water molecules.

S
-

S
x

x8
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
From liquid to gas
High latent heat of vaporisation Latent heat : Amount of heat needed to change the state

Heat heat energy needed to break down the hydrogen boinds between water molecules to change state from
liquid to gas …..high latent heat of vaporisation

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
Plays a role in decreasing body Plays role in cooling down the plant
temperature ( by evaporation of sweat through transpiration without risk of
using excess latent heat ) with losing to much water
reducing risk of dehydration

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 .
 Properties of water

'
Dipolar nature ..unequal distribution of High surface tension High specific heat capacity
charge A) tension of surface of water by attraction For water 4200 joules to raise the

Where water molecule has a slightly forces between water molecules temperature of 1 kg of water by 1 C
( cohesion ) ..allow animals to move / stand on Due to presence of large number bonds
negative oxygen atom and a slightly water surface . between water molecules.

positive hydrogen atom B) cohesion ..force by which water molecules

stick together by hydrogen bonds
C) adhesion …force of attraction between
water molecules and other different miolecules
1. Provides constant body
temperature, optimum
Solvent High melting and boiling point
temperature for maximum
So can form hydrogen enzymatic activity .
form hydrogen
2. Stabilise temp. Of water in
bind with each other …
bond with polar lakes and oceans as
. It takes a lot of energy to
molecules ( OH / temperature of environment
break down all hydrogen changes ,….stabilise
NH / SH)
bonds holding the environment of aquatic life
So help transport
molecules together .
solutes

Dissolve ions where slightly negative

oxygen atom attract +ve charged ion
( cation ) and the slightly positive
hydrogen atom attract -ve charged ion
( anion ) and dissolve /
 Properties of water

High latent heat of vaporisation Water density

Low water density

From liquid to gas O
If temperature falls below 4C ..water will
-

High latent heat of vaporisation …..due to high specific freeze ..form ice …so float on water surface
heat capacity …..due to the presence of many ….formimg a layer of insulation to the water
hydrogen bonds …..so water needs large amount of under ice ..orevent aquatic animals from
heat energy to break down the hydrogen bonds freezing

Latent heat : Amount of heat needed to change the state

Plays a role in decreasing body

temperature ( by evaporation of sweat
using excess latent heat ) with
reducing risk of dehydration

Plays role in cooling down the plant

through transpiration without risk of
losing to much water
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. 8 Hydrogen atom .
- +

3. So can form hydrogen bond with each other where …hydrogen of one
water molecule forms a hydrogen bond with 6Oxygen of another water
-

molecule , 3Oxygen 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 )
Break
6;06
Proteins in secondary structure H I
H
n c. C C
Secondary structure
- -

i
↳ ! R
Involves hydrogen bonds between the
...

oxygen of carbonyl group C=O of H

H
I 9
one amino acid and the H of the -N -
C -
C C - C
A
amine NH group of another amino ↳ ! R
acid with no R group involvement .........
H 8
H I 11

N - C.C C - C
H
↳ ! R

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 )

8.3
- 6-8
H ………..NH / CO/ OH
And movement of vesicles
Biology 9700 AS Paper 2 Biological molecules

1 May/ June 2010 Syllabus- 9700 Paper 21

1 (a) Fig. 1.1 shows the breakdown of a molecule of sucrose.

r
ab
HOCH 2 O

HOH,OH
(i)
lG
Name the bond indicated byT .
a-glucose
Fig.1.1
fructose
iha
. .. .... .. ... ..... ..... ······ ..... .... .... .. ···· ·· ..... ... ... .... ...... .. ........ ..... ..... .... ....... ... ....... .. .... .. .... ... [1]

(ii) State the name given to this type of reaction in which water is involved .

. ... ... ..... ..... ..... ..... ..... ...... ... .. ... .. ...... .... . ..... .. ... .. .... ..... ..... ....... .. .. ... .. ... .. ..... .. .... ... .. .... [1]

(iii) State two roles of water within plant cells other than taking part in breakdown
.N

reactions.

1 . ........... ... ..... .... ..... ...... ....... .. .... .............. ..... .. .. ..... ... ......... ....... .. .... ........ ..... .... ..... .. .. .

2 . ............................ ............................................................. ........... ........ ......... ...... (2)

(b) Enzymes are globular proteins.

Dr

State what is meant by the term globular.

Spherical
Water soluble
With hydrophilic R groups facing outside and
...hydrophobic R.....groups
... ..... .. ......... ... ..... .... facing
.. .... ... .... .. ... ........ .......inside
..... .. ... ... ............... ... .... .... .. ...... ..... .... ... ... (2)

Has tertiary structure

Dr. Nihal Gabr

59
Biology 9700 AS Paper 2 Biological molecules

2 May/ June 2010 Syllabus- 9700 Paper 22

r
ab
lG
iha
.N

Linear sequence of amino acids bonded by peptide bond forming

a polypeptide chain
Dr

Dr. Nihal Gabr

60
Biology 9700 AS Paper 2 Biological molecules

(ii) The molecular structure of the first two amino acids of lysozyme, lysine and valine,
is shown below.

Use the space to show how these amino acids become linked in a condensation
reaction .

Epaw. numpolar.

r
Condensation

ab
cit
lysine valine

H
(c) 9
N. C. C 4x
H
-

H2O
-

/
H
H
CH24
Nitz
lG [3]
iha
(b) Proteins, such as the enzyme lysozyme, have a secondary structure and a tertiary
structure.

(i) Describe the secondary and tertiary structure of an enzymatic protein, such as
lysozyme.

Involves alpha helix and beta pleated sheets

secondary .. ................ ..... .. .......... .. .... .... .... .... .. ........ .. .... .. ..... .. .... .. .... ...... .. .... .. .......... .
.N

Involving hydrogen bonds between O of carbonyl

group of one amino acid and hydrogen of amine
group of another amino acid
cabul tertiary ..... .. ....... ......... ..... .. ..... ........... ...... .. ....................................... ............ .. .......... .
Dr

Over all folding and coiling of a polypeptide chain

Into a specific 3D shape maintained by R group interaction
·jott
C As hydrogen bond between polar molecules
Ionic bond between ionised R groups ( such as NH3+ and COO-)
Disulfide between cysteine amino acids
Forming a specific shape of active site
............. .. ....... .. .... ......... ....... .. ........................... ... .................................................. [5]

Dr. Nihal Gabr

61
 Biology 9700 AS Paper 2 Biological molecules

To have specific shape of active site

Linked to
nucleic

r
acid &
protein

ab
synthesis

lG
iha
.N
Dr

Dr. Nihal Gabr

62
Biology 9700 AS Paper 2 Biological molecules

3 May/ June 2010 Syllabus- 9700 Paper 23

3 The amino acid sequence of the protein hormone insulin is shown in Fig. 3.1.
polypeptide polypeptide
chain B chain A

2 2

3 3

4 4

r
5 5

6 6 s

ab
s-- s 7

8 8

9 9

10 10

lG 11

12

13

14
11

12

13

14
s
iha
15 15

16 16

17 17

18 18

19 19
s~
.N

20 s 20

21 21

22

23

24
Dr

25

26

27

28

29

30
Fig. 3.1

Dr. Nihal Gabr

63
Biology 9700 AS Paper 2 Biological molecules

Primary
Quaternary

Disulfide

r
ab
lG
iha
I
O
i - Niz
C
.N

<He + H20 Hydrolysis94 -

CHI
I
H
I
CHC
H

A
·

S
- - _oH+
N *-
-Restuchen
Dr

it it

Dr. Nihal Gabr

64
Biology 9700 AS Paper 2 Biological molecules

D4 Nov 2010
_ 1- -
Syllabus- 9700
- - - - - - -
Paper 21
- - -

5 (a) Cellulose is a polysaccharide.

Fig. 5.1 shows three sub-units from a molecule of cellulose.

r
ab
Fig. 5.1

Name the sub-unit molecule of cellulose .

(i)

(ii)
lG
.... .............. ............. ...Beta
...........glucose
............. .............. ............. .............. ............. .............. [1]

Name the bonds that attach the sub-unit molecules together within cellulose .

.... .............. ............. ....Glycosidic

.......... ...........bond
.. .............. ............. .............. ............. .............. [1]
iha
(b) Cellulose has high mechanical strength which makes it suitable for the cell walls of
plants.

Explain how cellulose has such a high mechanical strength making it suitable for the
cell walls of plants .
.N

Molecules of cellulose lie // to each other

Allowing formation of hydrogen bonds between them
Forming microfibrils that are held together by more hydrogen bonds
To form cellulose fibres
Dr

...................................................................................................................................... [2]

Dr. Nihal Gabr

65
Biology 9700 AS Paper 2 Biological molecules

5 May/ June 2011 Syllabus- 9700 Paper 21

r
ab
lG
6

5
Cellulose
iha
I
H

32

16
6 6
.N

I 5
I U I
W

L 2
3 3

N
Amylopectin
Saturated
6 6
Dr

is Is

W I I
&
2 2
1 ↳

I Amylose 13c x2 +
15C x 2+ 1= 31 1=27

Dr. Nihal Gabr

66
Biology 9700 AS Paper 2 Biological molecules

r
L

ab
K
H
K/ M

lG
-
H/ M
J
iha
.N
Dr

Dr. Nihal Gabr

67
 Biology 9700 AS Paper 2 Biological molecules

6 Nov 2011 Syllabus- 9700 Paper 21

r
ab
lG
iha
Linear sequence of amino acids
Bonded together by peptide bond
.N

Have alpha helices

Involving hydrogen bond between O of Carbonyl group of one
amino acid and H of NH group of another amino acid
Dr

Over all folding and coiling of each polypeptide chain

Held by interactions and bonding between R groups

Consist of four polypeptides ( 2 alpha and 2 beta globins )

Held by R group interactions
And have 4 haem groups
Dr. Nihal Gabr
68
Biology 9700 AS Paper 2 Biological molecules

r
ab
8 May/ June 2012 Syllabus- 9700 Paper 23

lG
iha
.N
Dr

Dr. Nihal Gabr

71
Biology 9700 AS Paper 2 Biological molecules

9 May/ June 2013 Syllabus- 9700 Paper 22

Glycosidic bond

r
ab
lG
iha
.N
Dr

Dr. Nihal Gabr

72
Biology 9700 AS Paper 2 Biological molecules

2 3
5
L b I 6 C

3 2 5

1, 1 L

Trehalose

r
ab
I Es
U I U I

e
I

Alpha glucose
lG I 2

Maltose
iha
Cellbiose
.N
Dr

Sucrose

Dr. Nihal Gabr

73
Biology 9700 AS Paper 2 Biological molecules
10 Nov 2013 Syllabus- 9700 Paper 23

Made from beta glucose , each glucose molecule founded

rotated at 180 to the other
Held by 1, 4 glycosidic bond forming a flat ribbon

r
Forming cellulose molecules which lie // to each other ,
unbranched with projecting OH groups

ab
Many hydrogen bonds between cellulose molecules forming
microfibrils

lG
Which are held together with more hydrogen bonds forming
fibres with high tensile strength
And criss cross to form gaps , so cell wall freely permeable
iha
11 May/ June 2014 Syllabus- 9700 Paper 21
.N

Condensation
Dr

CH20H Clolt H20

+

H H A
OH
No- Is
out
it

It OH H
Ult
Glycosidic
Dr. Nihal Gabr
74
 Biology 9700 AS Paper 2 Biological molecules

Alpha glucose Beta glucose

r
Branched Unbranched

ab
Energy storage Cell wall / structural

12 June 2014
lG
Syllabus- 9700
function

Paper 23
iha
13Cx 2= 26 + 1= 27
Has more hydrogen
Saturated
No carbon to carbon
double bond
.N

Has less hydrogen

Has one carbon to
12x2+1 -2= 23H carbon double bond
Dr

Alpha

Dr. Nihal Gabr

75
Biology 9700 AS Paper 2 Biological molecules

D
A

r
Amylose /amylopectin / glycogen

ab
lG
Part 1 is saturated
And has no double bond
iha
.N
Dr

Dr. Nihal Gabr

76
Biology 9700 AS Paper 2 Biological molecules

13 Oct/Nov 2014 Syllabus- 9700 Paper 21

r
ab
lG
iha
14
.N

Oct/Nov 2014 Syllabus- 9700 Paper 22

Dr

Blood passes through the heart twice in one complete circuit

Closed …..blood moving in blood vessels

Dr. Nihal Gabr

77
Biology 9700 AS Paper 2 Biological molecules

r
ab
lG
iha
Its a globular protein , which spherical in shape having a specific 3D
Direct shape
Water soluble
.N

Has amino acids with hydrophilic R groups facing outside , and

hydrophobic R groups facing inside .
They have 4 poly peptides which are 2 alpha globin and beta globins
Dr

( so has quaternary structure ) .

Each poly peptide has a haem group
Heam group has iron and porphyrin ring
Where each haemoglobin binds to 4 oxygen molecules

Dr. Nihal Gabr

78
 Biology 9700 AS Paper 2 Biological molecules

15 May/ June 2015 Syllabus- 9700 Paper 21

Charged

r
Non polar / non charges

ab
Has a phosphate
Has no phosphate group
group

lG en
Straight Kink

her
olt e
iha
.N

Number of fatty acids 2

Dr

3
Number of double bonds 0 1
Number of saturated fatty acids 3 1
Presence of double bond X r

Number of ester bonds 3 2

Dr. Nihal Gabr
79
Biology 9700 AS Paper 2 Biological molecules

r
ab
lG
Golgi / secretor vesicle
iha
Linked to
cell
.N

structure
( Golgi
Vesicles budding off from Golgi body
apparatus
function) Move through cytoplasm to cell surface membrane
Vesicles fuse with cell surface membrane
Release its content which are enzymes by exocytosis
Dr

Using ATP

Dr. Nihal Gabr

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Biology 9700 AS Paper 2 Biological molecules

r
Polar / dipolar

ab
-

Hydrogen bonds

lG
iha
16 Oct/Nov 2015 Syllabus- 9700 Paper 23
.N

Glycogen / amylopectin
Dr

Branched
1, 6 glycosidic bond

Dr. Nihal Gabr

81
Biology 9700 AS Paper 2 Biological molecules

1, 6 glycosidic bond

Direct More compact to occupy less space

Many terminals for easy attachment and removal of glucose
molecules .

r
Can be quickly hydrolyzed when glucose is required

ab
lG
Cellulose unbranched
Monomer is beta glucose
Has only 1, 4 beta glycosidic bond with no 1, 6 glycosidic bond
Form hydrogen bonds with other cellulose molecules .
iha
17 May/ June 2016 Syllabus- 9700 PaperSecondary
21

3- structure
A) helix
.N

B) beta pleated
C) random coils
Dr

Collagen has 3 polypeptides

Glycine is found at every third position
Helix / helical

Dr. Nihal Gabr

82
Biology 9700 AS Paper 2 Biological molecules

18 May/ June 2016 Syllabus- 9700 Paper 22

CH2OH

**

r
ab
H

lG Glycosidic bond
iha
Enzyme has a specific shape of active site required to
form bonds needed in branching ( 1, 6 glycosidic bond )
.N

Linked
to cell
structure
Dr

Nucleolus

Mitochondrion

Golgi body / RER

Dr. Nihal Gabr

83
Biology 9700 AS Paper 2 Biological molecules

19 Oct/Nov 2016 Syllabus- 9700 Paper 21

r
ab
lG
iha
.N

Peptide and disulfide bond

Dr

Linear sequence amino of acids joined together by a

peptide bond

Dr. Nihal Gabr

84
Biology 9700 AS Paper 2 Biological molecules

Breaking down of bond by addition of water

Murein / peptidoglycan

r
ab
Linked
to
Enzymes

lG
iha
.N
Dr

Dr. Nihal Gabr

85
Biology 9700 AS Paper 2 Biological molecules

20 Oct/Nov 2016 Syllabus- 9700 Paper 22

2-

r
ab
Condensation

lG + H2O
iha
Condensation reaction that involves removal of water molecule
Bond is formed between the C of carboxyl group of one amino
acid and N of amine group of another amino acid.
.N
Dr

Dr. Nihal Gabr

86
Biology 9700 AS Paper 2 Synthase …build up Biological molecules

21 Oct/Nov 2016 Syllabus- 9700 Paper 22

Fructose is a monosaccharide vs sucrose is disaccharide

r
Fructose is a reducing sugar with reducing end

ab
Fructose has no glycosidic bond vs sucrose has 1, 2 glycosidic
bond

22 May/June 2017
lG
Syllabus- 9700 Paper 23
iha
.N

~ X
X X -
·

X ~ X -
Dr

H20
Dr. Nihal Gabr
87
Biology 9700 AS Paper 2 Biological molecules

r
ab
23 May/June 2017 Syllabus- 9700 Paper 23

lG
iha
.N
Dr

Dr. Nihal Gabr

88
Biology 9700 AS Paper 2 Biological molecules

24 Oct / Nov 2017 Syllabus- 9700 Paper 22

r
C

ab
C

C -
lG
iha
Linked
to cell
membra
ne in
.N

topic 4
Dr

Dr. Nihal Gabr

89
Biology 9700 AS Paper 2 Biological molecules

Both have glycerol

Both have ester bonds
Both have C, H, and O

r
ab
Triglycerides has no phosphate group
Triglyceride has no choline

lG
Triglyceride has 3 fatty acids Us 2
iha
.N

Linked to Smooth endoplasmic reticulum

A single membrane bound organelle
cell
structure
in topic 1 Tubular sacs
Dr

No ribosomes attached

Dr. Nihal Gabr

90
Biology 9700 AS Paper 2 Biological molecules

25 March 2016 Syllabus- 9700 Paper 22

Sucrose

r
Peptide

ab
Cellulose

lG Biuret

Glycerol
iha
.N
Dr

Dr. Nihal Gabr

91
 Biology 9700 AS Paper 2 Biological molecules

15 May/ June 2015 Syllabus- 9700 Paper 21

-Phospholipid

r
• hydrophilic
-Triglyceride

ab
phosphate head
-Non polar
• One saturated ,
-With
one
hydrophobic
hydrocarbon tail
-no carbon to
carbon double
lG ge
e
unsaturated
hydrocarbon
tail

bond
iha
( saturated )
.N

Number of fatty acids 2

3
Dr

2
Number to double bonds 0 1
j
Number of saturated fatty acids
3
1

Number of ester bonds 3 2

Dr. Nihal Gabr

79
Biology 9700 AS Paper 2 Biological molecules

r
ab
lG
iha
Linked to
cell
.N

structure
( Golgi
apparatus
function)
Dr

Dr. Nihal Gabr

80
Biology 9700 AS Paper 2 Biological molecules

r
S
Polar / dipolar

ab
-

Hydrogen bonds

lG
iha
16 Oct/Nov 2015 Syllabus- 9700 Paper 23
.N
Dr

Dr. Nihal Gabr

81