1. LIFE CYCLE OF CELLSLIFE CYCLE OF CELLS
A cell in a adult org is considered as steady state ystem.The systemA cell in a adult org is considered as steady state ystem.The system
is balanced that the cell niether grows, shrinks, nor change itsis balanced that the cell niether grows, shrinks, nor change its
function .A new cell arise when one cell divides or when two cellsfunction .A new cell arise when one cell divides or when two cells
fuse.Both events are set by DNA replication and proteinfuse.Both events are set by DNA replication and protein
formation.The cell cycle includes period of cell growth, duringformation.The cell cycle includes period of cell growth, during
which protein are made and DNA is replicated, followed by cellwhich protein are made and DNA is replicated, followed by cell
division. In adult org replaces the worn out cells or make moredivision. In adult org replaces the worn out cells or make more
cells in response to a new need for eg the proliferation of RBC incells in response to a new need for eg the proliferation of RBC in
higher altitudes is due to increase need of oxygen to cells andhigher altitudes is due to increase need of oxygen to cells and
tissues. Most eukaryotic cells have internal clock called cell cycle ,tissues. Most eukaryotic cells have internal clock called cell cycle ,
during which DNA is duplicated during the synthesis (s) phase andduring which DNA is duplicated during the synthesis (s) phase and
the copies are distributed to opposite end of the cell duringthe copies are distributed to opposite end of the cell during
Mitotic (M) phase .Mitotic (M) phase .

2.  The prokaryotic cell cycle is simple and fast .Replication ofThe prokaryotic cell cycle is simple and fast .Replication of
the single chromosome start at a particular DNA sequencethe single chromosome start at a particular DNA sequence
which is anchored to the cell membrane .After replication iswhich is anchored to the cell membrane .After replication is
complete ,assembly of new membrane and cell wall forms acomplete ,assembly of new membrane and cell wall forms a
septum to divide the cell into two. Few types of eukaryoticseptum to divide the cell into two. Few types of eukaryotic
cells can grow and divide as quickly as bacteria .In plants andcells can grow and divide as quickly as bacteria .In plants and
animal cell take 10-20 hours to double in number . And someanimal cell take 10-20 hours to double in number . And some
duplicate at slow rate .Many cells in animals like nerve andduplicate at slow rate .Many cells in animals like nerve and
striated muscle cells do not divide at all. A specialisedstriated muscle cells do not divide at all. A specialised
mechanism coordinates their replication of genome DNA,mechanism coordinates their replication of genome DNA,
distribution of chromosomes, and cell division. In cytokinesisdistribution of chromosomes, and cell division. In cytokinesis
process, the plant and animal cells show difference. Cellprocess, the plant and animal cells show difference. Cell
differentiation create diverse type of cells from fertilised egg.differentiation create diverse type of cells from fertilised egg.

3. 
UncheckedUnchecked cell growth and multiplication produce a mass ofcell growth and multiplication produce a mass of
cells called tumor. Programmed cell death play an role in cellcells called tumor. Programmed cell death play an role in cell
growth control.It also eliminates unnecssary cells for eggrowth control.It also eliminates unnecssary cells for eg
during embryogenesis, the digits of our fingers and toes areduring embryogenesis, the digits of our fingers and toes are
sculpted by the death of cells in the intervening spaces.If thesesculpted by the death of cells in the intervening spaces.If these
cells remained alive, our hands and feet would becomecells remained alive, our hands and feet would become
webbed. Thus the cell growth and division are under control.webbed. Thus the cell growth and division are under control.
Cell death follow an internal program of events calledCell death follow an internal program of events called
apotosis.apotosis.
 In this processIn this process first sign is condensation of the nucleus andfirst sign is condensation of the nucleus and
fragmentation of the DNA.fragmentation of the DNA.

4. PURIFICATION OF CELLSPURIFICATION OF CELLS
 Both animal and plant tissue contain many cells which are inBoth animal and plant tissue contain many cells which are in
mixture ,the seperation of each cell type is based on somemixture ,the seperation of each cell type is based on some
physical property. A Flow cytometer can indentify differentphysical property. A Flow cytometer can indentify different
cells by measuring the light they scatter or fluorescence theycells by measuring the light they scatter or fluorescence they
emit, as they flow through a laser beam and cells are sortedemit, as they flow through a laser beam and cells are sorted
from the mixture.from the mixture. Fluorescent activated cell sorter ((FACSFluorescent activated cell sorter ((FACS),),
an instrument based on flow cytometry which can one cellan instrument based on flow cytometry which can one cell
from thousand of other cells. For eg any antibody specific to afrom thousand of other cells. For eg any antibody specific to a
particular to cell surface molecule is linked to a fluorescentparticular to cell surface molecule is linked to a fluorescent
dye then cell bearing this molecule will bind with antibody getdye then cell bearing this molecule will bind with antibody get
seperated from other cells when it fluoresce in the facs.Afterseperated from other cells when it fluoresce in the facs.After
sorting of cell, it can be cultured for further study.sorting of cell, it can be cultured for further study.

5.  This procedure is commonly used to purify the types of WBCThis procedure is commonly used to purify the types of WBC
since each of which bear on its surface one or more distinctivesince each of which bear on its surface one or more distinctive
proteins and bind with monclonal antibody specfic for thatproteins and bind with monclonal antibody specfic for that
protein .FACS seperation on culture cells or cells from animalprotein .FACS seperation on culture cells or cells from animal
tissues, which interact with adjacent cells surrounded by antissues, which interact with adjacent cells surrounded by an
extracellular matrix . First sample must treated with proteaseextracellular matrix . First sample must treated with protease
to degrade the extracellular matrix protein and cell-surfaceto degrade the extracellular matrix protein and cell-surface
proteins that attach cells in tissue to one another .proteins that attach cells in tissue to one another .
 The function of FACS is to measure cell’s DNA and RNAThe function of FACS is to measure cell’s DNA and RNA
content and the determination of its shape and size .content and the determination of its shape and size .

6. MITOCHONDRIAMITOCHONDRIA

8.  Mitochondria are called the 'powerhouse of theMitochondria are called the 'powerhouse of the
cell'. Mitochondria contain a number ofcell'. Mitochondria contain a number of
enzymes and proteins that help in processingenzymes and proteins that help in processing
carbohydrates and fats obtained from food wecarbohydrates and fats obtained from food we
eat to release energy. Mitochondria are presenteat to release energy. Mitochondria are present
in every cell, they are found in highin every cell, they are found in high
concentrations in the muscle cells that requireconcentrations in the muscle cells that require
more energy .more energy .

9.  Mitochondria are rod-shaped structures that areMitochondria are rod-shaped structures that are
enclosed within two membranes - the outerenclosed within two membranes - the outer
membrane and the inner membrane. The membranesmembrane and the inner membrane. The membranes
are made up of phospholipids andare made up of phospholipids and proteinsproteins. The space. The space
in between the two membranes is called the inter-in between the two membranes is called the inter-
membrane space which has the same composition asmembrane space which has the same composition as
the cytoplasm of the cell. However, the proteinthe cytoplasm of the cell. However, the protein
content in this space differs from that in thecontent in this space differs from that in the
cytoplasm.cytoplasm.

10.  Outer MembraneOuter Membrane
The outer membrane is smooth unlike the innerThe outer membrane is smooth unlike the inner
membrane and has almost the same amount ofmembrane and has almost the same amount of
phospholipids as proteins. It has a large numberphospholipids as proteins. It has a large number
of special proteins calledof special proteins called porinsporins that allowthat allow
molecules of 5000 daltons or less in weight tomolecules of 5000 daltons or less in weight to
pass through it. The outer membrane ispass through it. The outer membrane is
completely permeable to nutrient molecules, ions,completely permeable to nutrient molecules, ions,
ATP and ADP moleculesATP and ADP molecules

11.  Inner MembraneInner Membrane
The inner membrane is more complex in structure thanThe inner membrane is more complex in structure than
the outer membrane as it contains the complexes of thethe outer membrane as it contains the complexes of the
electron transport chain and the ATP synthetase complex.electron transport chain and the ATP synthetase complex.
It is permeable only to oxygen, carbon dioxide and water.It is permeable only to oxygen, carbon dioxide and water.
It is made up of a large number of proteins that play anIt is made up of a large number of proteins that play an
important role in producing ATP, and also helps inimportant role in producing ATP, and also helps in
regulating transfer of metabolites across the membrane.regulating transfer of metabolites across the membrane.
The inner membrane has infoldings called theThe inner membrane has infoldings called the cristaecristae thatthat
increase the surface area for the complexes and proteinsincrease the surface area for the complexes and proteins
that aid in the production of ATP, the energy richthat aid in the production of ATP, the energy rich
molecules.molecules.

12.  MatrixMatrix
The matrix is a complex mixture of enzymes thatThe matrix is a complex mixture of enzymes that
are important for the synthesis of ATP molecules,are important for the synthesis of ATP molecules,
special mitochondrial ribosomes, tRNAs and thespecial mitochondrial ribosomes, tRNAs and the
mitochondrial DNA. Besides these, it has oxygen,mitochondrial DNA. Besides these, it has oxygen,
carbon dioxide and other recyclable intermediates.carbon dioxide and other recyclable intermediates.

13. FUNCTIONSFUNCTIONS
 The most important function of the mitochondria isThe most important function of the mitochondria is
to produce energy. The food that we eat is brokento produce energy. The food that we eat is broken
into simpler molecules like carbohydrates, fats,etc.,into simpler molecules like carbohydrates, fats,etc.,
in our bodies. These are sent to the mitochondrionin our bodies. These are sent to the mitochondrion
where they are further processed to producewhere they are further processed to produce
charged molecules that combine with oxygen andcharged molecules that combine with oxygen and
produce ATP molecules. This entire process isproduce ATP molecules. This entire process is
known as oxidative phosphorylation.known as oxidative phosphorylation.

14.  It is important to maintain proper concentration ofIt is important to maintain proper concentration of
calcium ions within the various compartments ofcalcium ions within the various compartments of
the cell. Mitochondria help the cells to achievethe cell. Mitochondria help the cells to achieve
this goal by serving as storage tanks of calciumthis goal by serving as storage tanks of calcium
ionsions
 Mitochondria helps in the building of certain partsMitochondria helps in the building of certain parts
of the blood, and hormones like testosterone andof the blood, and hormones like testosterone and
estrogen.estrogen.
 Mitochondria in the liver cells have enzymes thatMitochondria in the liver cells have enzymes that
detoxify ammonia .detoxify ammonia .

15.  Mitochondrial DNAMitochondrial DNA
DNA is generally present in chromosomes within theDNA is generally present in chromosomes within the
nucleus, but mitochondria too have small amounts ofnucleus, but mitochondria too have small amounts of
their own DNA called as, mitochondrial DNA. Thetheir own DNA called as, mitochondrial DNA. The
mitochondrial DNA (mtDNA) is present in cytoplasm ofmitochondrial DNA (mtDNA) is present in cytoplasm of
the cell. Mthe cell. Mitochondrial DNA is a double strandeditochondrial DNA is a double stranded
circular molecule, which is inherited from thecircular molecule, which is inherited from the
mother in all multicellular organisms. It ismother in all multicellular organisms. It is
because, during fertilization, all mtDNA comesbecause, during fertilization, all mtDNA comes
from oocyte.from oocyte.

16.  Compared to chromosomes, it is relativelyCompared to chromosomes, it is relatively
smaller, and contains the genes in a limitedsmaller, and contains the genes in a limited
number. Changes in mtDNA can causenumber. Changes in mtDNA can cause
maternally inherited diseases, which leads tomaternally inherited diseases, which leads to
faster aging process and geriatric disorders.faster aging process and geriatric disorders.