CHAPTER 5
THE STRUCTURE AND FUNCTION
OF MACROMOLECULES
Polymer principles
And
Macromolecules
Page 62
1
Polymers principles
• Cells join ‫ تربط‬smaller organic molecules
(Monomers) together to form larger molecules
(macromolecules) (Polymers), which may be
composed of thousands of atoms.
• The four major classes of macromolecules are:
1)-Carbohydrates,
2)-Lipids,
3)-Proteins,
4)-Nucleic acids (will be studied later)
2
• Monomers are connected by covalent
bonds by a dehydration reaction ‫تفاعل‬
‫نزع الماء‬.
– One monomer provides a hydroxyl
group and
the other provides a hydrogen to form
water.
– This process requires energy and is
aided by
enzymes.
•
The covalent bonds connecting monomers in a polymer are disassembled
‫ســر‬
َ ‫ تـُك‬by hydrolysis (hydration) reaction ‫تفاعل إضافة الماء‬.
– In hydrolysis as the covalent bond is broken a
hydrogen atom and hydroxyl group from a split
water molecule attaches where the covalent
bond used to be.
– Hydrolysis reactions dominate the digestive
process, guided by specific enzymes.
Fig. 5.2a & b, Page 63
3
(Carbohydrates, Lipids, Proteins and nucleic acids)
Mono-mer
Di-mer
Poly-mer
‫أحادى‬
‫ثنائى‬
‫عديد‬
Polymer is a long molecule consists of a chain of similar
building molecules (monomers) covalently bounded together.
4
Page 62 – 63, Fig. 5.2
1- Carbohydrates
Fuel and Building Material (‫) مادة الطاقة و البناء‬
• Monosaccharides, are the simplest
carbohydrates (simple sugars).
• Disaccharides, double sugars, consist of
two monosaccharides joined by
dehydration.
• Polysaccharides, are polymers of many
monosaccharides.
5
Aldehyde sugars
1- Monosaccharides
Aldose
H
Glucose
C6H12O6
Asymmetric C
O
C
O
C
H
C
OH
H
C
OH
OH
C
H
OH
C
H
H
C
OH
OH
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
Page 64, Fig. 5.3
H
Aldose
H
Galactose
C6H12O6
Asymmetric C
6
Triose Sugar
Pentose Sugar
Hexose Sugar
H
H
O
H
C
H
H
C
C
OH
OH
H
Glyceraldehyde
O
H
OH
C
Ketone sugar
C
O
H
C
OH
OH
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
Page 64, Fig. 5.3
Ketose
C
Fructose
C6H12O6
Ribose
H
7
Monosaccharides are classified as following :A- Based on the location of C=O
Aldoses: are the monosaccharides of carbonyle group (C=O)
at the end of C chain (e.g. Glucose).
Ketoses: are the monosaccharides of C=O carbonyle
group within ‫ داخل‬the C chain (e.g. Fructose).
B- Based on the number of C in the skeleton
Triose (3C): e.g. Glyceraldehyde.
Pentose (5C): e.g. Ribose.
Hexose (6C): e.g. Glucose, Fructose and Galactose.
8
2- Disaccharides ‫السكر الثنائى‬
Consisted of 2 monosaccharide molecules during a
dehydration reaction ‫تفاعل نزع الماء‬.
Sucrose (table sugar): consists of Glucose + Fructose.
9
Fig. 5.5, Page 65
FIG. 5.5a, Page 65
3- Polysaccharides ‫السكر العديد‬
Consisted of few hundreds to few thousands of
monosaccharides.
They are two types:
1- Storage ‫تخزينية‬.
Provide sugar for cell by hydrolysis ‫إضافة ماء‬.
2- Structural ‫تركيبية‬.
Serve as building materials for the organism.
10
A)- Storage ‫ نخزينية‬Polysaccharides
I- Starch (in plants) ‫النشا‬
A storage polysaccharide of plants (within plastids).
It is consisted of thousands of  glucose molecules.
Thus, it gives glucose when hydrolysed ‫ بإضافة الماء‬by special enzymes in human .
Potatoes and grains are the major source of starch.
Fig. 5.7, Page 67
11
II- Glycogen (in animals) ‫الجليكوﭽـين‬
Stored in animal cells (e.g. liver and muscle cells in Human).
It is consisted of thousands of glucose molecules.
Thus, it gives glucose when hydrolysed.
12
Fig. 5.7, Page 66
B)- Structural ‫ تركيبية‬Polysaccharides
I- Cellulose
It is the building material of plants (cell wall).
Forms the micro-fibrils and cell wall in plants.
It is consisted of thousands of β glucose molecules.
Human cannot digest it, but some bacteria and protozoa can (e.g.
in Termites and Cows stomach).
Fig. 5.7c, Page 67
13
II- Chitin ‫الكيتين‬
It is the building material of the cuticle ‫ ال ُجـلَيد‬in insects.
It is consisted of thousands of glucose molecules with a N atom
in one end.
It is used to manufacture the surgical threads.
14
Fig. 5.9, Page 68
Carbohydrates
No. of C atoms
Triose (3C)
Glyceraldehyde
Pentose (5C)
Ribose
Monosaccharides
Glucose & Fructose
Location of
Carbonyl Group
Aldose
C=O on top
Ketose
No. of sugar molecules
Hexose (6C)
Glucose
Disaccharides
Polysaccharides
Maltose & Sucrose
Storage
Starch (in plants)
&
Glycogen (in animals)
Structural
Cellulose (in plants)
&
Chitin (in insects)
C=O in chain
15
2-Proteins
- Protein is a polymer of amino acids (constructed from 20 amino
acids) (to form Polypeptides).
- These components include a hydrogen atom, a carboxyl group, an
amino group, and a variable ‫ متغيرة‬R group (or side chain).
H
H
General Formula
of the Amino
Acid:
N
Amino
group
H
C
R
O
C
OH Carboxyl
group
Side chain
- The side chain R links with ‫ ترتبط بـ‬different compounds
- Differences in R groups produce the 20 different amino acids.
16
Amino acids ‫األحماض األمينية‬
1.
Hydrophobic: the amino acids that have hydrophobic R groups
(non-polar).
2-
Hydrophilic: the amino acids that have polar R groups, making
them hydrophilic.
3- Ionized: the amino acids with functional groups that are charged
(ionized) at cellular pH (7). So, some R groups are bases, others are
acids.
17
Fig. 5.15, Page 72
The Peptide Bond ‫الرابطة‬
‫البيبتيدية‬
Peptide bond formed between the carboxyl group of one amino acid
and the amino group of the other by dehydration.
H
N
H
H
O
H
H
C
C
N
C
R
OH H
Peptide bond
Amino acids
Peptide
O
C
OH
R
Dehydration
‫نزع الماء‬
Polypeptide (Protein)
18
Page 73, Fig. 5.16
•
Amino acids are joined together when a dehydration reaction removes a
hydroxyl group from the carboxyl end of one amino acid and a hydrogen
from the amino group of another. The resulting covalent bond is called a
peptide bond.
•
•
•
The repeated sequence (N-C-C) is the polypeptide backbone.
Attached to the backbone are the various R groups.
Polypeptides range in size from a few monomers to thousands.
19
Fig. 5.16, Page 73
Hydrophobic (non-polar R group)
Amino
acids
Hydrophilic (polar R group)
Ionized (charged functional groups)
Polypeptides
Proteins
20
3-Lipids;
1. Fats store large amounts of energy
2. Phospholipids are major components of cell membranes
3. Steroids include cholesterol and certain hormones
21
Pages 69-71
Glycerol
O
H
C
OH
Ester link
H C
OH
H
OH
C
OH
H C
H
C
H
H
C
H
H
C
H
H
C
H
H
C
Fatty Acid
H
H
Dehydration
H
In a fat, three fatty acids are joined to glycerol by an ester linkage, ‫رابطة‬
‫ إستيرية‬creating a triacylglycerol.
22
Fig. 5.10, Page 69
A)- Saturated Fats ‫الدهون المشبعة‬
The Fatty acid components are saturated (there is no double bonds
between the carbons. All C are linked with H.
Thus, it is saturated with H.
Most animal fats are saturated.
They are solid at room temperature.
Saturated fats-rich diet results in Atherosclerosis ‫التصلب الشريانى‬.
B)- Un-saturated Fats ‫الغير مشبعة‬
‫الدهون‬
These double bonds are formed by the removal of H atoms.
Most vegetable fats (oils) and fish fats are unsaturated.
They are liquid at room temperature.
They can be synthetically converted to saturated (solid) by adding H
(Hydrogenation ‫)ال َهد َْرﭽـَة‬.
23
Phospholipids;
Are major components of cell membranes
• Phospholipids have two fatty acids attached to glycerol and a
phosphate group at the third position.
– The phosphate group carries a negative charge.
• The fatty acid tails are
hydrophobic, but the
phosphate group and
its attachments form a
hydrophilic head.
• Thus, it is amphipathic
24
Fig. 5.12, Page 70
• At the surface of a cell, phospholipids are arranged as a bilayer
‫طبقة مزدوجة‬.
– Again, the hydrophilic heads are on the outside in contact with the
aqueous solution ‫ المحلول المائى‬and the hydrophobic tails from the
core ‫المركز‬.
– The phospholipid bilayer ‫ طبقة مزدوجة‬forms a barrier ‫ حاجز‬between
the cell and the external environment ‫البيئة الخارجية‬.
• They are the major component of cell membranes.
25
Fats
(Composed of Lipids)
Saturated
Unsaturated
Phospholipids
Steroids
Animal Fats
Vegetable Fats
Bi-layer of cell
membrane
Sex Hormones
& Cholesterol
Hydrogenation
‫َهـد َْرﭽـَــــــــة‬
26