Medical Biology
Lec -1-
Shorooq Wessam
Introduction
The term biology derived (from Greek"life" and logos "knowledge") , also
referred to as the biological sciences , is the scientific study of life . biology
examines the structure , function , growth , origin , evolution and distribution
of living things it classifies and describes organisms ,their functions , how
species come into existence and the interactions they have with each other
and with the natural environment.
Biology as a separate science was developed in the nineteenth century , as
scientists discovered that organisms shared fundamental characteristics . Most
biological sciences are specialized discipline . Traditionally, they are grouped by
the type of organism being studied Zoology, the study of animals; and
microbiology,the study of microorganisms .The fields within biology are
further divided based on the scale at which organisms are studied and the
methods used to study them like biochemistry examines the fundamental
chemistry of life;molecular biology studies the complex interaction of system
of biological molecules ; cellular biology (cytology) examines the basic building
block of all life the cell ; physiology examines the physical and chemical
functions of the tissues and organ systems of an organism and histology
examines the types and shape of tissues , ecology examines how various
organisms interrelate , anatomy and taxonomy .
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Microscope
Is an instrument for viewing objects that are too small to be seen by the
naked or unaided eye . the science of investigating small objects using such an
instrument is called microscopy . the term microscopic means minute or very
small , not visible with the eye unless aided by a microscope .
1- Compound microscope (Optical microscopes)
2- Dissection microscope
3- Transmission Electron microscope
4- Scanning Electron microscope
5- Scanning probe microscope
6- Point- projection microscope
The cell
In 1663 an English scientist , Robert Hooke, discovered cells in a piece of
cork, which he examined under his primitive microscope actually , Hooke only
observed cell walls because cork cells are dead and without cytoplasmic
contents. The word CELL is derived from tge Latin word ' cellula' which means
small compartment in the human body , there are more than 200 different
Kinds of cells,each specialized for such distinctive functions as memory ,
movement and digestion, all cells share common fundamental properties that
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have been conserved throughout evolution. For example, all cells employ DNA
as their genetic materials, are surrounded by plasma membranes , and use the
same basic mechanism for energy metabolism . On the other hands, presntday cells have evolved
Many organisms , such as bacteria, amoeba and yeast consist of single cells that are
capable of independent self-replication . The more complex organisms are
composed of collection of cells that function in a coordinated manner, with different
cells specialized to perform particular tasks. E.g . human body. The cells are divided
into two types( classes), initially defined by whether they cont ains anucleus:)
1-Prokaryotic cells : they lack the nuclear envelope e.g.bacteria.
2- Eukaryotic cell: they have nucleus in wlich the genetic materials
The prokaryotic cells are generally smaller and simple than eukaryotic cells, in
addition to the absence of a nucleus, their genomes are less complex and do
not contain cytoplasmic organelles or a cytoskeleton.
Claracteristic
Nucleus
Diameter of typical cell
Cytoskeleton
Cytoplasmic organelles
DNA content ( base pair)
Chromosomes
prokaryotic
absent
About lum
absent
absent
1x10
Single circular DNA
Eukaryotic cells
present
About 10-100 um
present
present
1.5 x10 to 5x 10
Mutltiple linear DNA
CELL THEORY: the cell doctrine states that all organisms are composed of
similar units of orginzation, called cells. The concept was formally articulated in
1839 by schleiden & Schwann and has remained as the foundation of modern
biology . Ultra structural research and modern molecular biology have added
many tenets to the cell theory , but it remains as the preeminent theory of
biology . The cell throry is to Biology as Atomic theory is to Physics.
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Formulation of the cell theory
In 1838 , Schleiden summarized his observations into three conclusions about
cells :
1- The cell is the unit of structure , physiology and organization in living things .
2- The cell retains a dual existence as a distinct entity and a building block in
the construction of organisms .
3- Cells form by free – cell formation , similar to the formation of crystals
(spontaneous generation) . but the first two tenets are correct , but the third is
clearly wrong .
The modern tenets of the cell theory include:
1- All knowen living things are made up of cells .
2-The cell is structural & fuctional unit of all living things .
3- All cell come from pre- exitsting cells by division (spontaneous generation
does not occur)
4- Cells contains hereditary information which is passes from cell to cell
during cell division .
5- All cell are basically the same in chemical composition .
6- All energy flow (metabolism & biochemistry) of life occurs .
Cytoplasm
Is a gelatinous semi - transparent fluid that fills most cells. The cytoplasm has
three major elements ; the cytosol , organelles and inclusions . the cytosol is
the gooey , semi – transport fluid in which the other cytoplasmic elements are
suspended . cytosol makes up about 70% of the cell and is composed of water ,
salts , organic molecules and enzymes that are nessary for the cell to catalyze
reactions .The organelles are the metabolic machinery of the cell and are like
little organs themselves . the major organelles that are suspended in the
cytosol consists of the mitochondria , proteins , ribosomes , endoplasmic
reticulum , colgi apparatus , lysosomes and cytoskeleton .the inclusions are
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chemical substances that store nutrients , secretory products and pigment
granules . the cytoplasm is the site where most cellular activities are done . all
functions for cell expansion , growth and replication are carried out in the
cytoplasm of the cell . the cytosol has enzymes that take molecules and break
them down , so that the individual organelles can use them as they need to .
cytosol also contains the cytoskeleton which gives the cell its shape and can
help in the movment of the cell.
Generalized human cell
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