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CHAPTER 1
CELLULAR BIOLOGY
AND CELLS
I. Introduction
Molecular Biology and Molecular Genetics
The fast developed
branches of modern
biology
Cellular Biology
Immunology and Molecular Immunology
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II. Properties of cells
Before longer than 80 years ago, Wilson said that every key
problem can be discovered in cells!
CELL
1. Most basic and smallest unit to exhibit life, and life is the most basic property of cells.
2. Can be cultured in vitro where they will grow and reproduce for extended periods of time.
3. Can renew and expand themselves in vivo under exact regulation by their community.
The first culture of human cells was begun by George Gey of Johns Hopkins
University in 1951, and that was named as Hela cell from human malignant tumor
because the donor’s name is Henrrietta Lacks. Hela cells are still used in many labs now
in the world.
The cell culture in vitro has become an essential tool of cellular or molecular
biologists. Cell culture in vitro is so important that if you can not do it you can not do any
life research almost!
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Dimensions of some example cells. 1 mm = 10−3 m; 1 μm = 10−6 m; 1 nm
= 10−9 m
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Two Fundamentally Different Classes of Cells
Human cells
Animal cells
Eukaryotic Cells
Parasite or parasite cells (Protozoa)
Plant cells
Fungi
Cells
Acidophiles
Archaebacteria
Menthanogens
(Extremophiles)
Halophiles
Thermophiles
Prokaryotic Cells
Bacteria
Eubacteria
Mycoplasts*
Rickettsia
Chlamydia
Others
*Mycoplast is the smallest cell type in the world.
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Differences Between Prokaryotic and Eukaryotic Cells
A The tiny chromosomes of mitochondria and chloroplasts are exceptions; like prokaryotic chromosomes they are often circular.
B The S value, or Svedberg unit, is a sedimentation rate. It is a measure of how fast a molecule moves in a gravitational field, and
therefore in an ultracentrifuge.
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Basic Properties of Cells
Structural properties of cells:
1. Cells are highly complex and organized
2. Cells have membrane with specific permeability, dialysis, or penetration
3. Cells have genetic substance (DNA/RNA)
4. Cells have ribosome (For protein synthesis)
Functional properties of cells:
1. Cells possess a genetic program and the means to use it (Heritance). Human
genetic program contains enough information, if converted to words, to fill
millions of pages of text. But the information is packaged into the
space of a cell nucleus —— thousands of times smaller than the
dot on this i.
2.
3.
4.
5.
6.
7.
Cells are capable of producing more of themselves (Proliferation).
Cells acquire and utilize materials and energy for every function.
Cells carry out a variety of chemical reactions. Enzyme, Reaction, Metabolism
Cells engage in numerous mechanical activities: Mobility, changes in shapes.
Cells are able to respond to stimuli.
Cells are capable of self-regulation for maintaining a complex, ordered state.
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Morphological properties of cells:
Cells are very variable in size and shape.
Cells have highly complex and ordered
parts inside.
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Animal Cell
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Plant Cell
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E. coli
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A bacterial cell
model
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Gonococci
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E coli
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A bacterium with filament
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E. coli
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Plants are composed of several tissues
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The Chemical Basis of Life
(Molecular Basis of Cells)
The chemical components of a cell (Bacterial cell)
Components
Ratio to the cell weight (%)
Water
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Salts
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Sugar and their precursors
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Amino acids and their precursors
0.4
Nucleotides and their precursors
0.4
Fatty acids and their precursors
1
Other small molecules
Big molecules (Proteins, Nuclear acids, Polysaccharides)
0.2
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The basic components of a cell includes O, C, H, N, Si, K, Ca, P and
Mg. the ratio of O, C, H and N is over 90 percent of the cell weight. All
components can be divided into two parts as organics and inorganics.
Water: The importance of water to cells can not be
evaluated enough anyhow:
1. Resolve salts and proteins for forming a reaction system
2. Regulate temperature
3. Participate in enzyme reactions
4. Participate in metabolism
5. Maintain the cell structure
6. Maintain the cell function
Free water
Water in cell
Combined with protein (4.5%)
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Covalent bonds
The molecule of water is polarized, with partial negative charge on
the oxygen and partial positive charges on the two hydrogens
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Salts:
Roles of the Salts in Cells
1. Components of the cell structure: C, H, N, O, P and S.
2. Necessary to the enzyme reactions: Ca2+, Cu2+, Mg2+, K+,
Na+ and Cl-.
3. Necessary to the enzyme activities: Co2+, Cu2+, Fe3+, Mn2+
and Zn2+.
4. Maintaining the pH and osmotic pressure in cells.
5. The proteins or lipids that combined with some salts are
necessary to some special cell functions.
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Cl
Cl
Chlorine gas consists of two chlorine atoms, each of which consists
of a positively charged nucleus surrounded by negatively charged
electrons. Like oxygen, chlorine atoms tend to accept electrons when
they become available, but the battle is equal in the chlorine molecule:
The two atoms share their electrons equally and the molecule is nonpolar
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Ionic compounds will dissolve only in polar solvents. The
solutions are formed as the result of the interaction between
the polar molecules and non-polar molecules:
Acids are molecules that give H+ to water.
Bases are molecules that take H+ from water.
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Formation of sodium chloride solution
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Formation of sodium chloride solution
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Four types of important organic molecules and
biological macromolecules:
1. Sugars
Carbohydrates—sugars and the macromolecules built from them—have
many different roles in cells and organisms. All carbohydrates are formed
from the simple sugars called monosaccharides or glucose.
Sugars: Monosaccharide (Glycose, Glucose, Monosaccharose), Simple
sugars (Disaccharide, Disaccharose, Oligosaccharide, Oligosaccharose),
Polysaccharide (Polysaccharose, Polyose).
Glucose is the basic energy provider to cells by serial oxygenic reactions
to release energy, water and CO2, and basic molecule component to
polysaccharose.
Polysaccharose is big bio molecule involved with cell structure, immunity
(Antigen or semi-antigen), nutrition and others.
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Glucose (monosaccharide)
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The disaccharide lactose
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The polysaccharides glycogen and cellulose
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Cellulose
Structural polysaccharose
Membrane component
Chitin
Polysaccharose
Starch (Plant cell)
Nutritive storage polysaccharose
Glycogen (Animal cell)
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2. Proteins
Generally, proteins are the macromolecules composed by
amino acids that carry out virtually all of a cell’s activities;
they are the molecular tools and machines that make things
happen. It is estimated that a typical mammalian cell may
have as many as 10,000 different proteins having a diverse
array of functions.
Proteins in cell can play roles as enzyme, structural cables,
hormones, antibodies, antigens, cytokines, gene activators,
transmitters, receptor, toxins and many others. So, “The
nature of life is protein, the property of life is motility,
and the motility is the essential of protein” is well known
as a phrase.
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Structure of protein:
Proteins are capable of such a wide variety of activities
because they can exhibit such a great variety of structures.
Proteins have shapes that allow them to interact
selectively with other molecules. Proteins, in other words,
exhibit a high degree of specificity.
Proteins have four grades of structure shown as the
following fig:
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Primary structure: Polypeptide sequence composed of 20
amino acids by peptide bond
Secondary structure: Polypeptide chain forms the α-helix and
β-pleated sheet by hydrogen bonds
Tertiary structure: The conformation of the entire protein.
Tertiary structure is unlimitedly stabilized by an array of
noncovalent bonds between the diverse side chains of the protein.
In results, the function domains or motifs are formed.
Quaternary structure: Some proteins are composed of only
one polypeptide chain, such as myoglobin. But most are made up
of more than one chain, or subunits. It is called as quaternary
structure that the subunits linked together often by noncovalent
bonds between hydrophobic “patches” on the complementary
surface of neighboring polypeptides.
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3. Lipids
Lipids of importance in cellular function include fats,
steroids, and phospholipids.
Fats:
Fats consist of a glycerol molecule linked by ester bonds to
three fatty acids forming triglyceride.
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Steroids:
One of the most important steroids is cholesterol, a
component of animal cell membranes and a precursor for the
synthesis of a number of steroid hormones. Cholesterol is largely
absent from plant cells, that is why vegetable oils are considered
“cholesterol free”.
Phospholipids:
Phospholipids contain two ends: The end containing the
phosphate group has a distinctly hydrophilic character; the other
end composed of the two fatty acid tails has a distinctly
hydrophobic character. Based on the characters above,
phospholipids are the basic components of bio membranes, and
also, they participate in cell metabolism.
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4. Nucleic acids
Components of nucleic acids
Nucleosides
Nucleotides
Adenine (A)
Adenosine monophosphate (AMP)
Deoxygenated adenosine monophosphate (dAMP)
Guanine (G)
Guanine monophosphate (GMP)
Deoxygenated guanine monophosphate (dGMP)
Thymine (T)
Deoxygenated thymine monophosphate (dTMP)
Cytosine (C)
Cytosine monophosphate (CMP)
Deoxygenated cytosine monophosphate (dCMP)
Uracil (U)
Uracil monophosphate (UMP)
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The nucleotides triphosphate used to synthesize DNA
are as the follows:
Deoxygenated adenosine triphosphate (dATP)
Deoxygenated guanine triphosphate (dGTP)
Deoxygenated thymine triphosphate (dTTP)
Deoxygenated cytosine triphosphate (dCTP)
Denaturation: The step by that the closed DNA helixes is opened
and separated.
Melting temperature (Tm): The temperature that makes DNA
denaturated. The higher G+C ratio, the higher Tm. The higher A+T ratio,
the lower Tm.
Renaturation or annealing: The procedure by that the opened
DNA double strands assemble together.
So, the steps of a Polymerase Chain Reaction (PCR) should be
denaturation, annealing and extension.
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Structure of DNA molecule
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Three molecular structural types of DNA
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III. Viruses
1. Not cellular organism
2. Smallest organism in the world
3. Parasite in cells
4. Simplest organisms that contain nucleic acids
inside only
5. Simplest life cycle that shows nucleic acids
replication only
6. Usually, viruses are very harmful to humans,
animals and plants
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Viruses
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Polio virus
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T4 bacterial phage
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HIV
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DNA viruses
RNA viruses
Viruses
Phages
Reverse transcription viruses (RT-viruses)
Tumor viruses (Oncoviruses)
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