Chapter One
Introduction
Objectives:
At the end of this chapter, students will be able to:







Identify eukaryotes & prokaryotic cells
List the structure of cells & describe their function
Describe the phases of the cell cycle
Distinguish the difference between mitosis &
meiosis
Explain control of cell cycle
List macromolecules of cells & their monomers
Describe the function of macromolecules
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Objectives cont’d








Describe the phases of the cell cycle
Distinguish the difference between mitosis & meiosis
Explain control of cell cycle
List macromolecules of cells & their monomers
Describe the function of macromolecules
Describe the composition, chemistry, & function of nucleic
acids
Explain the steps leading from DNA to Proteins
Discuss the central dogma of Molecular biology & the basic
chemical structure of DNA/RNA
Definition of terms




Chromosome :The structure by which hereditary
information is physically transmitted from one
generation to the next
Gene: the basic unit of heredity; a sequence of
DNA nucleotides on a chromosome
Genotype: the genetic makeup of an organism, as
characterized by its physical appearance or
phenotype
Heredity: the transmission of characteristics from
one generation to the next
1. Introduction
Molecular biology is the study of life at a molecular
level. It overlaps with genetics & biochemistry.
branch of biology that seeks to understand the
molecular basis of life. In particular, it relates the
structure of specific molecules of biological
importance—such as proteins, enzymes and the
nucleic acids DNA and RNA—to their functional
roles in cells and organisms.
 Biochemistry: It is the study of the chemical
substances & vital processes occurring in living
organisms or is study of the substances found in living organisms and of
the chemical reactions underlying life processes.
Genetics


5
It means the study of heredity & the effect of
genetic differences (variation) among generation
of organisms.
 study of the function and behavior of genes.
Genes are bits of biochemical instructions found
inside the cells of every organism from bacteria
to humans.
Thus, Molecular biology use specific techniques
native to molecular biology, but increasingly
combine these techniques with techniques & ideas
of genetics & biochemistry.
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2. History overview of molecular biology

1866, Gregor Mendel provide the fundamental principle
of heredity.

1909, Johannse coined the term gene to denote the
basic unit of heredity.

1910, Morgan describe unit of heredity, the gene,
contained in chromosome.


6
In 1944, Oswald Avery, working at the Rockefeller
institute of New York, demonstrated that genes are
made up of DNA
In 1953, James Watson & Francis Crick discovered the
double helical structure of the DNA molecule.
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History cont’d



7
In 1961, Francois Jacob & Jacques Monod hypothesized
the existence of an intermediary between DNA & its
protein products, which they called messenger RNA
Between 1961 & 1965, the relationship between the
information contained in DNA & the structure of proteins
was determined: there is a code, the genetic code , which
creates a correspondence between the succession of
nucleotides in the DNA sequence & a series of amino
acids in proteins.
In 1966, gene transcription described
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History cont’d…………………
In 1975, southern blotting invented.
 In 1977, DNA sequencing methodology discovered
 In 1981, Kan & Chang shown genetic diagnose of sickle
cell anemia.


In 1985, PCR developed by Millis & co-workers

In 2001 Draft of human genome sequence was revealed

In 2003, Human Genome Project was launched
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3. Overview of cells & Biologically important
molecules
3.1 Overview of cells
 All genetic diseases involve defects at the
level of the cell such as errors in replication of
genetic materials, translation of gene into
proteins, or in cell division.
 For this reasons, one must understand the
basic cell biology to understand genetic
diseases.
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1.


Types of Cells
Prokaryotic cells
Bacteria(eubacteria) & the Archae
(Archaebacteria)
Are smaller size and structurally simple as compared
to eukaryotic cells
 Have single Circular DNA
 They have no definite nucleus
 They don't have membrane bound organelles
 Have no histones and their DNA is ‘naked’
 Their DNA has no interones




10
Most of them have cell wall
Their nuclear region is called nucleoid
There is no nucleolus
Have smaller and less complex ribosomes(3 kinds of rRNA
:30S,50 &70 sub unit proteins)
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2. Eukaryotic cells
 Protists,fungi,plants and animals are eukaryotes

Are larger size and structurally complex
compared to prokaryotic cells

Have definite nucleus

Have linear chromosomes(DNA complexed with
histone)

Have histones (H1, H2A, H2B, H3, H4) & nonhistones proteins

Their DNA have intrones and exons

A nucleolus is present
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4. Cytoplasmic structures: prokaryoticribosome
(40%)
(60%)
+
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Eukaryotic cell ribosomes
Site of protein synthesis
Free: produce intra cellular proteins
Fixed: synthesize extracellular proteins
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Types of human cells
Somatic cells

are diploid, contain 46 (23 pairs) chromosomes
 1 pair = sex chromosomes
 22 pair = autosomes, which are said to be homologs
or homologous, because their DNA is very similar
 23 from egg (mother) & 23 from sperm (father)
b. Gametes (germ cells): sperm cells & egg cells
 Have haploid number of chromosomes, 23.
 Haploid cells have one complete set of chromosomes
obtained through meiosis
1.
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The Cell cycle

Cell cycle alternates between interphase & cell
division (karyokinesis; mitosis or meiosis &
cytokinesis)
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Phases of the Cell cycle cont’d
1.
Interphase

non-dividing phase
 Cell
is preparing for division
 nucleus
is visible & chromosomes are uncoiled &
invisible.
 Includes
G 1, S & G 2
a.
G1 phase =

Each chromosome has one chromatid

The cell grows in size

Synthesis of organelles4/24/2022
occurs.
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b. S phase

DNA duplicates when DNA synthesis occurs
c. G2 phase


The chromosomes have two chromatids.
synthesis of enzymes & other proteins in
preparation for mitosis
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2. Cell division
A. Mitosis/one nuclear division

Produces two daughter cells that are identical to the parent
cell.
Function of mitosis



single celled organisms: reproduction
multi-celled organisms:
• Growth/development (asexual reproduction),
• Differentiation: specialization & division of labor
• Repair: replacement of dying cells e.g. skin, RBCs
Reproduction (multi-cellular to produce sex cells (gametes)
(meiosis)
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Phases of Mitosis
1. Prophase (pro=before)
 Chromatin

19
condenses
Centrioles move to opposite poles of the cell
 The
spindle apparatus forms
 The
nuclear membrane disintegrates.
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Microtubules
forming mitotic spindle
Sister
chromatids
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Mitosis cont’d
2. Prometaphase/late prophase
Chromatids
begin to move toward the cell
equator, metaphase plate
Chromosome
kinetochore
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become more condensed
is formed at the centromer
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Mitosis cont’d
3. Metaphase (meta=middle)
 Chromosomes
aligned
at the cells equator
 Microtubules
attach at the
kinetochores
 spindle
apparatus
attached to each
chromosome.
22
Kinetochore
proteins
attached to
centromere
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Mitosis cont’d
4. Anaphase
23

centromers split making two sister chromatids free

Each chromatid move towards opposite poles

Once separated, the chromatids are again called
chromosomes

Cell begins to elongate
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Mitosis cont’d
5. Telophase (telo=end)

chromosomes reach opposite
poles

nuclear membrane reforms

chromosomes uncoil

spindle apparatus breaks
down

cleavage furrow formed
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Mitosis cont’d
6. Cytokinesis
 In plant cells, new cell wall forms to divide
the two daughter cells

In animal cells, cleavage furrow forms as the
cell membrane is pinched inward to divide
the cell into two daughter cells
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B. Meiosis/two nuclear division

It is the process of nuclear division that reduces
the number of chromosomes by half ( 2n---->n )

1.
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Phases of meiosis
First Division/reduction division
o
Prophase I
Metaphase I
o
Anaphase I
Telophase I
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Meiosis cont’d
2. Second Division/equational division
o
Prophase II
Metaphase II
o
Anaphase II
Telophase II
Meiosis I
 The step preceding the first cell division is the
'interphase'.
 The DNA is replicated into two identical copies,
just as in mitosis.
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Meiosis I cont’d
Prophase I:

Nuclear envelope & nucleolus disappears

Homologous chromosomes crosse-over & start to
move away from each other, but remain linked at
points called chiasmata.
Chromatin condenses & become visible, looking

very long, as they are not yet totally condensed &
become thicker & shorter, as they condense more &
more
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Prophase I
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Meiosis I
2. Metaphase I

Homologous chromosomes line up in pairs of chromosomes
(tetrads)

Spindle fibers attach to the centromeres

nuclear membrane has disappeared
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Meiosis I
3. Anaphase I:
 separation
 The
of homologous chromosomes
chromosomes migrate toward opposite
poles, not the chromatids as in mitosis
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5. Telophase I:

very short & often mistaken with prophase II
because there is no time for new cell membrane
formation, or for duplication of DNA.

The next step starts straight away but in some
species of cells nuclear envelope reforms, nucleoli
reappear & chromosomes may decondense.
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Telophase I cont’d
 The sister chromatids are still joined.



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Chromosomes arrive at spindle poles
Each cell has one each homologous chromosome,
cytokinesis occurs to split cells
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Meiosis II
 The
second division conserves the number of
chromosomes but divides the chromatids
 No
DNA replication, as a result no interphase II
so called interkinesis
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Phases of Meiosis II
1. Prophase II:
 It is very short because everything is ready
 The two centrioles migrate away
from each other, & a network
of microtubules forms
 The two networks are
parallel to each other,
 perpendicular to the previous one
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2. Metaphase II
 The sister chromatids
align up at the center of the cell.

Spindle fibers attach
to the centromeres
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3. Anaphase II
 Sister
chromatids are
separated & move
to opposite sides of the cell.
 The chromatids present
at the first cell division
separate now.
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4. Telophase II
Nuclear envelop reforms
in each daughter cell
 Nucleolus appears in
each nucleus
 Chromosomes
decondense
(lengthen & become
indistinct)
 Cytokinesis occurs.

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Difference between mitosis & meosis
Mitosis
Meiosis
Purpose
Produces somatic cells (Body,
growth)
produces reproductive cells
Process
cell duplication (Diploid -> diploid)
reduction division (Diploid ->
haploid)
Number of
Divisions
One cell division
Two cell division
Product
1 -> 2 identical daughter cells To
each other & mother cell
1 -> 4 cells (gametes) daughter cells
different
Occurrence
More often
At a certain time in the life cycle
Crossingover
No
Yes
Chromosome
separation
Sister chromatids
Homologous chromosomes
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Significance of meiosis
It Produce genetic variation, the raw material for evolution
as follows:
a) Independent Assortment
 The orientation of homologous chromosomes on one side of
the metaphase plate or the other in Meiosis I is random.
 The number of possible orientations is 2n possible
combination in daughter cells, where n is the haploid
number..
 For humans, the number is 223 = 8,388,608 ≈ 8.4 million
possible combinations.
 Variation is added by crossing-over; if only one cross-over
occurs within each bivalent, 423 or 70,368,744,000,000
combinations are possible

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b) Random fertilization

Any of a male’s 8.4 million sperm can fertilize any of a
woman’s 8.4 million eggs resulting a total number of
combinations over 70 trillion

Fertilization also contributes to genetic variation; (223)2 =
70,368,744,000,000 possible combination without crossingover
c) Crossing over
 When crossing over is considered with fertilization, the
number of combinations is nearly infinite
 (423)2 = 4,951,760,200,000,000,000,000,000,000
combinations are possible.
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Control of the cell cycle

42
Critical problem: how to tell cell to divide?
o
If too often --- cancer
o
If not often enough ---- death
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Control of the cell cycle cont’d
1. Telomeres
 Mammalian cells typically divide only about 50
times.
 This limit is set by the presence of repeated
sequences of DNA at the tips of the
chromosomes called telomeres
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Control of the cell cycle cont’d

In young cells, the sequence TTAGGG is
repeated 100s or 1000s times but each time the
cell divides, it loses 50 to 200 of these repeats.

Cells that have divided many times have fewer
of these repeats left & when it is reduced to a
certain size, the cells will no longer divide
Control of the cell cycle cont’d

Telomeres is restored to their original length by an
enzyme called telomerase.

This enzyme contains a single strand of RNA that is
used to synthesize the telomeres.

Telomerase is usually found in cells involved in the
production of gametes not normally found in
somatic cells.
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2. Cyclin-Dependent Kinases

Some cells stop dividing in G1 others stop in
G2.
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2. Cyclin-Dependent Kinases…………….

Kinases are enzymes that activate proteins by
transferring a phosphate group from ATP to the
protein being activated

An activated protein is needed for the cell cycle to
proceed from G1 to S

Similarly, another activated protein is needed to
move the cycle from G2 to mitosis.
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Cyclin-Dependent Kinases…………….
 Kinases activate these proteins & thus stimulate
the cell cycle to continue.
 Kinases are normally inactive & must be activated
before they can activate other proteins.
 Cyclin-dependent kinases become activated by
combining with a protein called cyclin.
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Cyclin-Dependent Kinases…………….
The activated complex is involved in stimulating the
cell cycle to resume
 The level of cyclin fluctuates (cycles)
 At low levels, kinases are not activated & the cell
cycle is halted
 At high levels, activation occurs & the cycle
resumes

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Growth Factors



50
Growth factors are special proteins produced in
extremely tiny amounts that stimulate nearby cells
to divide by promoting the binding of cyclin to
kinase.
Under normal conditions, cyclin combines with
kinase only when growth factors are present.
For example, damaged tissue releases growth
factors to stimulate cell division needed to repair
the tissue.
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Growth Factors
Some of these genes have been cloned allows
production of significant quantities, can use in
research & clinical applications
 Several growth factors have been isolated, tissue
specific.
 Nerve growth factor, fibroblast growth factor, etc.
a. S-Cyclin
 S-Kinase combines with S-cyclin & the resulting
active complex stimulates DNA replication.

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S-cyclin…….
The "S" in S-kinase & S-cyclin refers to DNA
synthesis.
Enzymes triggered by the active kinase-cyclin
complex then destroy the S-cyclin.
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b. M-Cyclin in M-Kinase combines with M-cyclin &
the active complex initiates several mitotic events:
• chromosome condensation (coiling)
• nuclear membrane disintegration
• the synthesis of the spindle apparatus
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M cyclin….
The active kinase-cyclin complex also activates
enzymes that destroy the M-cyclin.
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3.2 Overview Biological important molecules

56
Most organic molecules fall into one of four
classes:
 Carbohydrates
 Lipids
 Protiens
 Nuclic acids
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Polymers and their monomers
Class
Monomers
Carbohydrates sugars
Polymers
polysaccharides
Protein
amino acids proteins and polypeptides
Nucleic Acids
nucleotides DNA & RNA
Lipids
57
fatty acids
(membranes = non-covalent
structures)
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Function of CHO





58
Energy source- 1g= 4kcal/17kj
Cell structure (plants-cellulose & animalschitin)
Recognition markers-e.g. A,B,O blood
types
Structural component of nucleic acids
Part of plasma membrane
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Monosaccharides
A
Monosaccharide is made up of 1 sugar unit
which can not be hydrolyzed to a simpler form
 can be of varying length (3-7c long)
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Disaccharides
 two monosaccharides joined by a glycosidic
linkage
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3. Polysaccharides
 >10 monos joined together by glycosidic
bond
a. storage polysaccharide
Starch- in plant
 entirely of glucose monomers
 two types:
 amylose = unbranched starch
 amylopectin = branched starch
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Polysaccharides……….
starch: amylose- joined by α1,4- & α-1,6-glycosidic bond
 unbranched
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Polysaccharides……….
 Branched
starch: amylopectin - joined by
α-1,4- & α-1,6-glycosidic bond
CH2OH
CH2OH
O
H
H
OH
H
H
O
OH
CH2OH
H
OH
H
63
H
OH
H
1
H
OH
CH2OH
O
H
OH
H
OH
H
H
O
H
OH
H
H
O
O
H
OH
H
H
OH
H
O
amylopectin
O
6 CH2
H 5
H
4 OH
3
H
CH2OH
O
H 1
2
OH
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H H
O
CH2OH
O
H
4 OH
H
H
H
H
O
OH
O
H
OH
H
H
OH
H
OH
Polysaccharides……….
Glycogen
 Storage polysaccharide in animals (liver and muscles)
 Made up of glucose monomers but is more extensively
branched than starch.
 Both glycogen and starch polymers have a helical shape
CH2OH
CH2OH
O
H
H
OH
H
H
OH
H
O
OH
CH2OH
H
H
OH
H
64
H
OH
H
H
OH
CH2OH
O
H
OH
O
H
OH
H
H
O
O
H
OH
H
H
OH
H
H
O
4
glycogen
H
1
O
6 CH2
5
H
OH
3
H
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CH2OH
O
H
2
OH
O
H
H
1
4
O
CH2OH
H
OH
H
H
H
H
O
OH
O
H
OH
H
H
OH
H
OH
b. Structural polysaccharides
Cellulose
o
Major component of plant cell walls
o
Polymers of glucose
o
Very few organisms produce cellulose, enzyme
that hydrolyze cellulose
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6CH OH
CH2OH
H
O
H
OH
H
O
H
1
H
O 4 OH
OH
H
H
5
OH
3
H
H 1 O
2 H
OH
H
O
H
OH
H
H
O
O
H
OH
H
OH
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H
O
H
H
OH
O OH
H
H
H
H
cellulose
66
CH2OH
CH2OH
CH2OH
2
H
OH
H
OH
b. Chitin
 Glucose polymers with a nitrogen containing
group
 component of arthropod exosketeon & fungal
cell walls
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Proteins

Proteins are polymers of amino acid by a peptide
bond (20 different)

Denatured (change its structure) by temperature,
pH, or salt changes

Reversible & non-reversible denaturing can occur.
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Amino acid structure
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Function of proteins




70
Structural proteins: support body: tubulin, actin,
collagen, elastin
Storage proteins : (ovalbumin in eggs, zeins in
corn seeds, casein in milk)
Transport proteins : transport O2 by hemoglobin,
ion transporters in cell membrane
Defense proteins: provide protection against
disease e.g. antibodies
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Function of proteins cont’d




Receptor proteins : response of cell to chemical
stimuli: e.g. neurotransmitter receptors, hormone
receptors, etc...)
Contractile proteins: involved in movement, e.g.
actin & myosin.)
Hormonal proteins : coordination of organism's
activities: e.g. insulin, glucagon)
Enzymatic proteins: catalyst for most crucial of
functions; selective acceleration of chemical
reactions
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Levels of protein structure
When cells make a polypeptide, the chain
folds spontaneously to assume the
functional conformation of that protein
 4 superimposed levels of structure

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1. Primary protein structure



sequence of amino acids
Determined by the sequence of codons in DNA.
Single changes in amino acid sequence may have
profound impact on protein function (e.g. Sickle-cell
anemia)
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2. Secondary of protein
 Amino acid arrangement beta sheets or coils
resulting from H-bonds at regular intervals
 Alpha helix: coil held together by H-bonding
between every 4 a.a.
 Pleated sheet: chain folds back in parallel or
antiparallel orientation & H-bonds between parallel
regions hold structure together.
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20 structure
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3. Tertiary of protein
3D shape is due to hydrophobic reactions of R
groups resulting from bonding between side chains
(R-groups) of various amino acids.
 H-bonds, ionic interactions, & disulfide bridges of
side chains also involved in stabilizing the tertiary
structure.

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30 structure
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4. Quaternary proteins

It is the overall protein structure results from
the aggregation of polypeptide units
e.g. collagen = triple helix (3 subunits)
hemoglobin = 2 alpha & 2 beta subunits
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Types of Quaternary proteins
1. Fibrous, or structural (insoluble)
 Collagen: forms connective tissue, comprises 30%
of mammalian protein, lacks cysteine & tryptophan,
rich in hydroxyproline
 elastins -forms tendons & arteries
 keratins - forms hair, quills, hoofs, nails, rich in
cysteine & cystine
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2. Globular (soluble) protein

albumins eg, egg albumin & serum albumin

globulins eg, serum globulin

histones occur in glandular tissue & nucleic acids,
rich in lysine & arginine

protamines associated with nucleic acids, contain
no cysteine, methionine, tyrosine or tryptophan,
rich in arginine
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3. Conjugated proteins




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nucleoproteins combined with nucleic acids
Mucoproteins combined with more than 4%
carbohydrates
Glycoproteins combined with less than 4%
carbohydrates
Lipoproteins combined with lipids, such as
phosphoglycerides or cholesterol
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Lipids
 composed of monomers of alcohol (glycerol) &
fatty acids
 Fats (solid) & oils (liquid at room temp.)
Fats associated with animals - butter
Oils associated with plants - corn oil, olive oil
 Consist of hydrophobic molecules with
diverse structures & functions.
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Types of lipids
4 important families of lipids are:
1. Triglycerides (fats & oils) = 1 Glycerol & 3 fatty
acids
2. Phospholipids = 1Glycerol + 2 fatty acids +
Phosphate
3. Steroids = Lipids fused in rings (cholesterol)
 Cholesterol in animals & ergosterol fungi
 It is a precursor of all steroid hormones (e.g. sex
hormones - cortisone & aldosterone).
4. waxes (cutin, suberin) = Alcohol & 1 fatty acid

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Function of lipids






Store energy - fats & oils
Insulation (subcutaneous fat) & Cushions of
internal organs
Structure: part of cell membrane - phospholipids
Protection & water repellent (mycobacterium) waxes
Message (signaling) & membrane fluidity - steroids
Hormones (testosterone, estrogen) - steroids
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4. Cellular genetic components
Nucleic acids
 linear polymers of nucleotides (its primary
structure)
 Types of nucleic acids
1. DNA
2. RNA
1. Deoxyribonucleic acid (DNA)
 deoxyribose sugar
 double stranded helix
 have thymine rather than uracil
 Can replicate itself
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Ribonucleic acid (RNA)
•
ribose sugar
•
single stranded
•
uracil instead of thymine
•
Can not replicate itself
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Components of nucleotides
1. Phosphate group
 It is an acidic character of nucleotides
because it dissociate at the PH found in the
cells, freeing H+ ions & leaving the phosphate
negatively charged
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2. Pentose sugar
it is a 5-carbon sugar molecule
 The only difference between the two sugars
is that ribose has a hydroxyl group on carbon
2, whereas deoxyribose has only hydrogen in
that position.

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Pentose cont’d


In the configuration found in nucleic acids,
carbons 1 through 4 are part of a ring structure,
whereas carbon 5 is on a side chain.
The compound has five carbon atoms numbered
as 1', 2', 3', 4' & 5', using an apostrophe to
distinguish them from the numbering of the
nitrogen containing bases
Structure of pentose sugar
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3. Nitrogenous bases
o So
named base because they can combine with
hydrogen ions in an acid solution
a. Pyrimidines
◦ are single carbon-nitrogen rings
◦ The 6 atoms (4 carbons, 2 nitrogen) are
numbered 1-6
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b. Purines


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Are double carbon – nitrogen ring
The 9 atoms that make up the fused rings (5
carbons, 4 nitrogen atoms) are numbered 1-9.
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1.
Nucleosides
 Base (one purine or pyrimidine) + sugar (one
ribose or deoxyribose) combination
 Are formed upon the attachment of C1 of the
sugar molecule to the N1 of pyrimidine or N9
of purines
 Adenosine, Guanosine, Cystidine & Uridine
in RNA; & deoxyadenosine, deoxyguanosine,
deoxycytidine, thymidine in DNA
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Nucleosides’ structure
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a. Nucleoside monophosphate

Formed by the attachments of an – OH of
phosphate to an – OH of C5 of the sugar

Nucleoside + one phosphate group.

Ribonucleotides: AMP, CMP, GMP, & UMP

Deoxynucleotides: dAMP, dCMP, dGMP, TMP.
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b. Nucleoside diphosphates
Nucleosides + two phosphates.
 Nucleoside 5'-diphosphates are abbreviated ADP,
GDP, CDP, UDP, dADP, dCDP, dGDP, TDP
 It is also possible to have nucleoside 3'-, 5'diphosphates.
c. Nucleoside tri-phosphates
 Nucleosides + three phosphates.
 nucleoside triphosphates: ATP, CTP, GTP, UTP,
dATP, dCTP, dGTP, TTP.
 They are the immediate precursors for synthesis of
DNA & RNA

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2.Nucleotides

Base–ribose–phosphoric acid---- RNA

Base–deoxyribose–phosphoric acid—DNA

Can possess 1, 2, or 3 phosphate groups
& labeled with α, β & γ phosphate,
respectively.
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Repeating Nucleotide Subunits In DNA & RNA

Nucleic acids are often described as polymers
of nucleotides or polynucleotides

Nucleotides are joined by covalent bonds called
phosphodiester linkages, between α
phosphate of one nucleotide & sugar of next
monomer.
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
Structure of DNA is ideally suited to its function:

Encodes information

Replicates easily

Grooves allow for protein-specific mutates
(allows evolution).
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Polymerized Nucleotides
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Base
Nucleotide(Nucleoside
ribose
deoxyribose
ribose
deoxyides
ribose deoxyides
GMP
dGMP
GDP
DGPP
GTP
AMP
dGMP
ADP
dADP
CMP
dGMP
monophoplate
dTMP
dGMP
Uridine monophosphate
Ump
monophosphate)
Guanine
Guanasine monophosphate
Deoxyguonasine
monophosphate
Aderine
Adenosine monophosphate
Deoxyadenosins
DGTP
monophosphate
Cytosise
Cytidine monophosphate
Deoxycytidine monophosphate
Thymine
Uracil
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Deoxy
dADP
ATP
DATP
CDP
DCDP
CTP
DCTP
UDp
DTDP
UTP
DTTP
thymidine
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5. The Central dogma of molecular genetics

Defines the relationships between DNA,
RNA, & protein in the transmission of genetic
information into functional units of biological
activity
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Summary






All genetic diseases involve defects at the level of the cell
such as errors cell division, lack of cell cycle control &
lack of biologically important macromolecules
DNA is a polymer of nucleotides, storing genetic
information in the order of the nucleotide sequence
Nucleotides consist of a nitrogenous base, five carbon
sugar, and a phosphate group
Human DNA has two sets of chromosomes, and is a
single linear duplex DNA
Genetic information flows from generation to generation
through DNA replication
Genetic information flows with in a cell through
transcription & translation
quiz




What is central dogma of molecular biology?(2
points)
Why DNA replication is always from 5’ to 3’? (2
points)
What is advantage of primers during DNA
replication? (2 points)
Write types and advantages of enzymes that are
important for DNA replication? (4 points)