About cell ,cell cycle and basics of cell division and stages of cell division and cell Apoptosis, cell growth factor.

1. CELL CYCLE

2. Cells are the basic building
blocks of all living things.
The human body is composed of
trillions of cells.
They provide structure for the
body, take in nutrients from food,
convert those nutrients into
energy, and carry out specialized
functions. ...
Cells have many parts, each with
a different function.
Introduction

3. Animal Cell

4. Cell organelles
• Cell membrane: protects inner cell and
regulates entry and exit of substances
• Mitochondria: power house of cell, site for cellular
respiration and ATPgeneration
• Ribosome:site for protein synthesis
• Endoplasmic reticulum:
– Rough: contains ER so site for protein
synthesis
– Smooth: lipid synthesis and drug
detoxification

5. • Golgi apparatus: packages proteins inside
the cell before send to destination.
• Lysosome: k/a suicidal bags, responsible
for cellular digestion by hydrolysis
• Microtubules : maintain the cellular
structure
• Microfilaments: cell motility

6. Nucleus
•Brain of cell
•Control all activities
within cell
•Contains genetic
material in the form
of nucleic acids

7. Nucleic acids
• Deoxyribonucleic acid(DNA)
• Ribonucleic acid (RNA)
• Nitrogen bases:
– Purines: Adenine, Guanine
– Pyrimidines: Thymine(DNA), Cytosine , Uracil(RNA)
• Pentose Sugar:
– Deoxyribose (DNA)
– Ribose(RNA)
Structure

8. Chromosome
•Organised structure
of DNA , protein and
RNA.
•Total 23 pairs of
chromosomes in
human beings with
21 somatic and 2
pairs of sex
chromosomes.

9. Animal Cell Types
There are numerous types of animal cells, each designed
to serve specific functions. The most common types of
animal cells are:
Skin Cells
Melanocytes, keratinocytes, Merkel cells and Langerhans
cells
Muscle Cells
Myocyte, Myosatellite cells, Tendon cells, Cardiac muscle
cells
Blood Cells
Leukocytes, erythrocytes, platelet
Nerve Cells
Schwann cell, glial cells etc
Fat Cells
Adipocytes
white blood cell
red blood cell
cheek cells
sperm
nerve cell
muscle cell

10. Cell division and cell cycle

11. Cell growth:
Increase in size and/or weight, whereas in an isolated metazoan cell growth implies
proliferation which means increase in cell number.
In mammals there are 200 different specialized cell types all these cells are derived from a
single cell ( zygote) with a total number of cells more than 1018 in adult humans.
Cells grow and divide independently with exceptions for central & peripheral nerve cells,
epithelium of lung etc
Bone marrow is the most proliferating tissue in the body. Muscle and skin epithelial cells
multiply to increase cells, tissue injury, wound healing.
These are achieved by a combination of various cell signals actuated extracellular and
intracellular factors.

12. The reasons for cell division in multicellular
organisms are;
i) Growth
ii) Repair & Replacement of damaged parts
iii) Reproduction of the species.

13. PHASES OF CELL CYCLE
• G0 Phase
• Interphase (90% of cell cycle)
– Gap 1 (G1)
– Synthetic phase (S)
– Gap 2 (G2)
• Mitosis (10% of cell cycle)

14. Interphase:
Interphase The longest stageof aCell’s life
The timespent between divisions
Produces all materialsrequired for growth
Preparation for division

15. Cell Cycle:
In order to divide, each cell passes through a complete
cell cycle. It is divided into fundamental parts;
Interpahase – Occupies majority of cell cycle. Further
divided into
o G1 (growth1),
o S (synthetic) &
o G2 (growth2) phases.
Mitosis – ending with the division of cell. Divided into
4-5 stages;
prophase, metaphase, anaphase & telophase.
The regulation of cell cycle must ensure that the
events in each phase are complete before moving to
the next. Thus cell cycle must have check points to
monitor the integrity of DNA and prevent progression
and propagation of damaged or mutated cells. Phases of Cell Cycle

16. Cell Cycle Control: Three checkpoints,
– G1 – assesses cell size, environment (contact inhibition)
– G2 – assesses success of DNA replication
– M – assesses have spindle fibres attached correctly to the
chromosomes

17. • G1 checkpoint: is the most significant
because the cell is committed to divide once
it passes this checkpoint
– If the cell does not pass this checkpoint,
1. It could enter G0 where it continues to perform its
normal functions but does not divide
2. Initiate DNA repair if DNA is damaged
3. Death by apoptosis (programmed death)
o G2 checkpoint: the cell verifies that DNA
has replicated and mitosis can proceed
o M checkpoint: pauses between metaphase
and anaphase to allow the proper attachment
of chromosomes to spindle fibers
o This also ensures that the chromosomes will be
distributed accurately to the daughter cells

18. G1 phase
• G1 is an intermediate phase occupying the time between the end of cell division in mitosis and the beginning of DNA
replication during S phase.
• During this time, the cell grows in preparation for DNA replication, and certain intracellular components, such as the
centrosomes undergo replication.
• Before a cell begins DNA replication, it must ensure that it is biologically ready to take on such a process. G1 is the
phase when this cellular monitoring takes place.
• During G1, the cell reviews the cellular environment and the cell size to ensure that the conditions are appropriate to
support DNA replication.
• Not until the cell is ready does it leave G1. If all is not ready to undergo DNA replication, cells can pause during G1
and enter a phase called G0.
• Depending on a cell's preparedness to continue in the cell cycle, G0 can last days, weeks, or even years. When the cell
has reached an appropriate size and is in a supportive environment for DNA replication, it will exit either G1 or G0 and
enter the next phase of interphase called S phase.

19. Apoptosis
• Apoptosis is the process of programmed cell death.
• It is used during early development to eliminate unwanted cells; for
example, those between the fingers of a developing hand.
• In adults, apoptosis is used to rid the body of cells that have been
damaged beyond repair. Apoptosis also plays a role in preventing
cancer.
• If apoptosis is for some reason prevented, it can lead to uncontrolled
cell division and the subsequent development of a tumor.

20. WhyApoptosis?
Apoptosis is needed to destroy cells
Examples:
Cells infected with viruses
Cells of the immune system
Cells with DNA damage
Cancer cells

21. S phase
• S phase, or synthesis, is the phase of the cell cycle when DNA packaged into chromosomes is replicated.
• This event is an essential aspect of the cell cycle because replication allows for each cell created by cell division
to have the same genetic make-up.
• During S phase a number of events additional to chromosome replication take place.
• Cell growth continues through S phase, as does the rate of synthesis of a number of proteins and enzymes that
are involved in DNA synthesis.
• Once DNA replication is complete the cell contains twice its normal number of chromosomes and becomes
ready to enter the phase called G2.
G2 phase
• Similar to G1, G2 is an intermediate phase, a time for the cell to ensure that it is ready to proceed in the cell
cycle.
• Occurring between the end of DNA replication in S phase and the beginning of cell division in mitosis, G2 can
be thought of as a safety gap during which a cell can check to make sure that the entirety of its DNA and
other intracellular components have been properly duplicated.
• In addition to acting as a checkpoint along the cell cycle, G2 also represents the cell's final chance to grow before
it is split into two independent cells during mitosis.

22. • The Cell begins the division process
• In Early Prophase of Mitosis the Chromosomes get small, centrioles move to the poles of the nucleus, and spindle fibers
develop
• The nucleolus disappears, The nuclear membrane breaks apart
Prophase :

23. The Second Phaseof Mitosis.
The Nuclear Membrane is completely gone.
During Metaphase theChromosomes line upacrosscenterofthecell,alsocalledthe equator,orMetaphase plate.
Spindle Fibers
Chromosomes
Equator, or Metaphase Plate
Metaphase

24. • The third phase of Mitosis
• Diploid sets of daughter chromosomes separate
• In Anaphase the Chromatids that make up each Chromosome move apart and travel to opposite ends
of cellular spindle
• They are pushed and pulled toward opposite poles of the cell by the spindle fibers
Anaphase :
Daughter Chromosomes
Chromatid

25. • Nucleus and the Cytoplasm starts to divide
• Cytokinesis is nearly complete,
• The nuclear membrane and nucleoli (nucleus) reform.
Telophase :
• The Cell Plate begins to form
• The Cell prepares for finial division
Cleavage Furrow

26. The finalstageof Mitosis
The cytoplasm,organelles,andnuclear material areevenlysplitandtwo new cellsare formed.
Daughter Cells
Cytokinesis :

27. Prophase
Metaphase
Anaphase
Telophase
Interphase

28. Growth Regulation:
Growth in mammalian cells is controlled at 3 different levels;
a) Intrinsic: Intracellular regulations (cell mass & conformation) to decide whether mitosis
will take place or cells will maintain in resting state of G0 phase
b) Intracellular: Space and nutritional factors within a cell population
c) Inter-population: Hormones, growth factors and inhibitors that act between populations.
 Cells divide to control their volume otherwise the size would become too large. In cell
culture conditions the cells show;
 Anchorage dependent
 Anchorage independent behaviour
 Normal fibroblast cells exhibits ‘contact inhibition’ (cells stop dividing when they are in
contact with other cells).

29.  Epithelial and endothelial cells do not stop proliferating even in touch with each
other.
 Cessation of growth also occur due to over crowding of cells.
 Density Dependent Inhibition (DDI) of growth:
Every cell type exhibits DDI, but Sub-culturing cells avoid DDI.
Three mechanisms have been proposed;
a) Competition between neighbouring cells for the same limiting growth factors.
b) Accumulation of toxic metabolic end products
c) The limitation of space for the attachment of cells.

30. • https://www.genome.gov/genetics-
glossary/apoptosis#:~:text=Apoptosis%20is%20the%20process%20of,a%20role%20in%2
0preventing%20cancer
• https://www.slideshare.net/SayantiSau/cell-cycle-and-its-check-points-and-regulation
• https://www.slideshare.net/MerlynH/cell-cycle-46934137
• https://www.slideshare.net/DeepaGautam/cell-cycle-29468534
Reference