This document discusses the structure and function of macromolecules. It focuses on proteins, which are polymers of amino acids that fold into complex shapes to perform various functions in the body. The four levels of protein structure are described as primary, secondary, tertiary, and quaternary. Lipids are also covered, with details about their hydrophobic nature and roles as fats, phospholipids in cell membranes, and steroids like cholesterol.

1. THE STRUCTURE AND FUNCTION
OF MACROMOLECULES
2) Proteins :- Many Structures, Many Functions
1. A polypeptide is a polymer of amino acids connected in a specific sequence
2. A protein’s function depends on its specific conformation

2.  Their functions include structural support, storage, transport of other
substances, intercellular signaling ‫اإلشارات‬‫بين‬‫الخلوية‬ , movement, defense
against microbes and work as enzymes in the cell that regulate
metabolism ‫األيض‬.
 Humans have tens of thousands of different proteins, each with their
own structure and function.
 All protein polymers are constructed from ‫تتركب‬‫من‬ the same set of 20
monomers, called amino acids.
 Polymers of proteins are called polypeptides ‫ببتيدات‬‫عديدة‬ .
 A protein consists of one or more polypeptides folded and coiled
into a specific conformation

3. - The physical and chemical characteristics ‫صفات‬of the R group
determine ‫تحدد‬the unique characteristics of a particular amino acid.
Side chain
Amino
group
Carboxyl
group
General Formula
of the Amino
Acid: C
H
R
N
H
H
C
OH
O
- The side chain R links with ‫ترتبط‬‫بـ‬ different compounds
***
- Monomer of amino acid includes a hydrogen atom, a carboxyl group,
an amino group, and a variable ‫متغيرة‬R group (or side chain), all
covalently bonded to C atom.
- Differences in R groups produce the 20 different amino acids.

4. 1. Hydrophobic: the amino acids that have hydrophobic R groups
(non-polar).

5. 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.

6. The Peptide Bond ‫الرابطة‬‫البيبتيدية‬
Peptide bond formed between the carboxyl group of one amino acid
and the amino group of the other by dehydration.
OH
C C
H
R
N
H
H
O
H
C
H
R
N
H
C
OH
O
Peptide bond
Polypeptide (Protein)
Dehydration
‫نزع‬‫الماء‬
Amino acids Peptide

7.  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.
• Repeating the process over and over ‫عدة‬‫مرات‬ creates a long polypeptide chain.
– At one end is an amino acid with a free amino group the (the N-terminus)
and at the other is an amino acid with a free carboxyl group the (the C-
terminus).
• 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.

8.  The folding ‫إلتفاف‬of a protein from a chain of amino acids
occurs spontaneously ‫ذاتيا‬.
 There are three levels of structure:
primary ‫أولى‬, secondary ‫ثانوى‬, and tertiary ‫ثالثى‬structure, are
used to organize the folding within a single peptide
chain.
 Quaternary ‫باعى‬ُ‫ر‬structure arises when two or more
polypeptides (proteins) join to form another kind of
protein.

9. 1. Primary structure:
It is a single peptide chain
of amino acids.
 Lysozyme, an enzyme that
attacks bacteria, consists of a
polypeptide chain of 129 amino
acids.
 A slight change ‫تغيير‬‫طفيف‬ in the
primary structure can affect a
protein’s conformation and
ability to function.

10.  Sickle cell disease ‫المنجلية‬‫خاليا‬‫الدم‬ :
an abnormal hemoglobin because of a single amino acid
substitution ‫تغيير‬.
 These abnormal hemoglobin crystallize, deforming ‫كسر‬ُ‫ي‬the red blood
cells and leading to clogs ‫إنسداد‬in tiny blood vessels ‫.أوعية‬

11. 2. The secondary structure:
Results from hydrogen bonds at regular intervals ‫على‬‫أبعاد‬‫متساوية‬ along the
polypeptide backbone.
A. Coils ‫الحلزونى‬(α-helix)
are typical shapes
that develop from
secondary structure
B. Folds (β-pleated sheets)
‫الشيت‬‫جعـد‬ُ‫م‬‫ال‬ . Composed
of several parallel α-helix
coils attached by H bonds

12. An example for folds (β-pleated sheets) ‫الشيت‬‫جعد‬ُ‫م‬‫ال‬ :
Is the structural properties of silk ‫الحرير‬because of the presence of so
many hydrogen bonds makes each silk fiber stronger than steel.

13. 3. Tertiary structure:
is determined by a variety of interactions among ‫خالل‬R groups and
between R groups and the polypeptide backbone.
 These interactions include weak bonds like hydrogen bonds
among polar areas, ionic bonds between charged R groups, and
hydrophobic interactions and Van der Waals interactions among
hydrophobic R groups.
- Also include disulfide bridges,
strong covalent bonds that form
between the sulfhydryl groups
(SH) of cysteine monomers,
stabilize the structure.

14. 4- The quaternary structure:
Results from the aggregation ‫تجمع‬of two or more
polypeptide chains.
Collagen is a fibrous protein of three polypeptides that are
supercoiled, and function in connective tissues.
Hemoglobin
is a globular protein with
two copies of two kinds
of polypeptides (2α and
2β).
Collagen Hemoglobi
n

15. The 4 forms of protein

16.  It is the change of protein’s conformation in response to
‫إستجابة‬‫لـ‬ the physical and chemical conditions.
 For example, alterations ‫تغيير‬in pH, salt concentration,
temperature, or other factors can denature ‫يفرد‬a protein.
 These forces break the hydrogen bonds, ionic bonds, and disulfide
bridges that maintain the protein’s complicated shape.
 Some proteins can return to their original shape again
after denaturation, but others cannot.

17. ‫مفرود‬
‫فرد‬
‫إعادة‬‫إلى‬‫طبيعته‬

18. Amino
acids
Primary
structure
Secondary
structure
Tertiary
structure
Quaternary
structure
1- Hydrophobic
Interaction
(Van der Waals
interaction);
2- H bonds;
3- Ionic bonds;
4- Di-sulfide
bridges;
Single chain
of amino acids
e.g. Lysozyme
Coils &
Folds
H bonds
e.g. silk
e.g. Collagen
& Hemoglobin
two or more
polypeptide
chains
Peptides
Hydrophobic (non-polar R group) ***
Hydrophilic (polar R group)
Ionized (charged functional groups)
ProteinsPolypeptides

19. Lipids;
The Hydrophobic Molecules
1. Fats store large amounts of energy
2. Phospholipids are major components of cell membranes
3. Steroids include cholesterol and certain hormones

20.  Lipids are an exception among macromolecules because
they do not have polymers.
 The unifying feature ‫الصفة‬‫زة‬ٍ‫ـ‬‫ي‬َ‫م‬ُ‫م‬‫ال‬ of lipids is that they all
have little or no affinity for water ‫ال‬‫متزج‬َ‫ـ‬‫ت‬‫بالماء‬ .
 This is because their structures are dominated by non-polar
covalent bonds.
 Lipids are the components ‫كونات‬ُ‫م‬of fats, and are highly
diverse in form and function.
 Although fats are not polymers, they are large
molecules assembled from ‫تتكون‬‫من‬ smaller molecules by
dehydration reactions.
 A fat is constructed from two kinds of smaller
molecules, glycerol and fatty acids ‫أحماض‬‫ُهنية‬‫د‬ .

21. A fat is composed of three fatty acids linked with one glycerol molecule.
Fats are classified into Saturated ‫مشبع‬and Un-saturated ‫غير‬‫مشبع‬ fats
OH
H H
C
C
CC
C
C H
HH
H
H H
H
H
H
O
OC
C
C
H
H
H
H
OH
OH
H
H
Dehydration
Fatty AcidGlycerol
Glycerol consists of a three C skeleton with an OH group attached to each C.
A fatty acid consists of a carboxyl group (COOH) attached to a long carbon
skeleton, often 16 to 18 carbons long.
Ester link

22.  The many non-polar C-H bonds in the long hydrocarbon skeleton
make fats hydrophobic.
 In a fat, three fatty acids are joined to glycerol by an ester linkage, ‫رابطة‬
‫إستيرية‬creating a triacylglycerol( = triglyceride) .

23.  Fatty acids may vary ‫تختلف‬in length (number of carbons) and in the
number and locations of double bonds.
 If there are no carbon-carbon double bonds, then the molecule is a
saturated fatty acid ‫(مشبع‬has H at every possible position).
•If there are one or more carbon-carbon double bonds, then the
molecule is an unsaturated fatty acid ‫حامض‬‫دهنى‬‫غير‬‫مشبع‬ - formed by the
removal of H atoms from the carbon skeleton.

24. 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 ‫التصلب‬‫الشريانى‬ .
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 ََ‫ْر‬‫د‬َ‫ه‬‫ةﭽال‬َ‫ـ‬).
B)- Un-saturated Fats ‫الغير‬‫مشبعة‬‫الدهون‬

25.  The major function of fats is energy storage.
 A gram of fat stores more than twice as much energy as
a gram of a polysaccharide.
 Humans and other mammals store fats as long-term
energy reserves ‫كمخزون‬‫طاقة‬‫طويل‬‫المدى‬ in adipose cells ‫خاليا‬‫دهنية‬ .

26.  Phospholipids have two fatty acids attached to glycerol and a
phosphate group at the third position.
 The phosphate group carries a negative charge.
• The interaction of
phospholipids with
water is complex.
• The fatty acid tails are
hydrophobic, but the
phosphate group and
its attachments form a
hydrophilic head.

27.  When phospholipids are added to
water, they self-assemble ‫تتشكل‬‫ذاتيا‬
into aggregates ‫تجمعات‬with the
hydrophobic tails pointing toward
the center and the hydrophilic
heads on the outside.
 This type of structure is called a
micelle ‫.الزهرة‬
• At the surface of a cell phospholipids
are arranged as a bilayer ‫طبقة‬‫مزدوجة‬ .
– Again, the hydrophilic heads are on
the outside in contact with the aqueous
solution ‫المحلول‬‫المائى‬ and the
hydrophobic tails in the core ‫.المركز‬
– The phospholipid bilayer ‫طبقة‬‫مزدوجة‬
forms a barrier ‫حاجز‬between the cell
and the external environment ‫البيئة‬
‫.الخارجية‬
• They are the major component of cell
membranes.

28.  Steroids are lipids with a carbon skeleton consisting of four fused
‫ملتحمة‬carbon rings.
 Different steroids are created by varying functional groups attached to
the rings.
• Cholesterol, an important
steroid, is a component in
animal cell membranes.
• Cholesterol is also the precursor ‫المادة‬‫الخام‬ from which all other
steroids are synthesized.
• Many of these other steroids are hormones, including the sex
hormones.
• While cholesterol is clearly an essential molecule, high levels of
cholesterol in the blood may contribute to Atherosclerosis ‫تصلب‬‫الشرايي‬‫ن‬

29. F a t s
(Composed of Lipids)
Saturated Unsaturated Phospholipids
Animal Fats Vegetable Fats Bi-layer of cell
membrane
Hydrogenation
ََ‫ْر‬‫د‬‫ـ‬َ‫ه‬‫ــــــــةﭽ‬َ‫ـ‬
Steroids
Sex Hormones
& Cholesterol
***

30. CHAPTER 5
THE STRUCTURE AND
FUNCTION OF
MACROMOLECULES
THE STRUCTURE AND FUNCTION
OF MACROMOLECULES
4- Nucleic Acids:
The Informational Polymers
1. Nucleic acids store and transmit
hereditary information ‫المعلومات‬‫الوراثية‬
2. A nucleic acid strand is a polymer
of nucleotides
3. Inheritance is based on
replication of the DNA
double helix