Cytology- The Cell

1. B Y - N I H A R I K A V E R M A
CYTOLOGY

2. CYTOLOGY
 The human body develops from a single cell called
the ‘Zygote’- the result of the fusion of ovum and
sperm.
 All cells, tissues organs and systems of our body
originate from a Zygote Cell is a smallest living
structural unit in the body.
 Cell is the structural and functional unit of life
because whole body is made up of cell.
 The cell is a Latin word for a ‘little room’.
 Discovered by Robert Hook (1665).

3. CELL
 The cell is the structural and functional unit of all known
as living organisms.
 It is the smallest unit of an organism that is classified as
living, and is often called the building block of life.
 Some organisms, such as most bacteria, are unicellular
(consists of a single cell).
 Other organisms, such as human, are multicellular.
 It consists of : minerals, carbohydrates, lipids, and
proteins (amino acids)
 The protoplasm is surrounded by fine membrane (Wall)
of protein threads and lipids.

5. CELL FORMATION
 Female – ovum
 Male – sperm Fusion
Single cell (ZYGOTE) unit of
human  Tissue  Organ  Organ System
• Human- animal cell
• Nuclic acid – Protein
• Living cell – Protoplasm (non color jelly like fluid).

7. PROTOPLASM
 Different substances that make a cells are collectively
called Protoplasm.
 Protoplasm is composed of :
1. Water – 70-80% is present in cell.
2. Carbohydrates
3. Lipids
4. Proteins
5. Electrolyte – Sodium (Na+), Potassium (K+),
Magnesium (Mg2+), Calcium (Ca2+), Phosphate,
Chloride (C1-1), and Bicarbonate (HCo3-).

8. CELL DIVISION
 Cell divide  Daughter Cell
|
Mitosis – division of somatic cells.
life long [genes thread like structure in the bundle
called Chromosomes (DNA)].
|
Meiosis – creation of new sex cells.
46 Pair  23 Father : 23 Mother
(exceptional cases – 24:23)

9.  SOMATIC CELL- A body cell- a cell whose genes will
not be passed on to future generations.
 GERM CELL- A cell that is destined to become a
gamete (egg or sperm), a cell whose a genes can be
passed on to future generations.

10. AEROBIC RESPIRATION
ANAEROBIC
RESPIRATION
 It is the process of
breakdown of food in
the presence of oxygen.
 Its end products are
CO2 and H2O.
 It takes longer time to
energy.
 It is the process of
breakdown of food in
the absence of oxygen.
 End products can be
lactic acid or CO2 and
alcohol.
 It is a fast process as
compared to aerobic
respiration.

11. ANAEROBIC
RESPIRATION
 It produces large
amount of energy.
 Example : Occurs
mostly in plants and
animals.
 It produce small
amount of energy as
compared to aerobic
respiration.
 Example : Yeast,
Bacteria, Human
muscle, Cells, etc.
AEROBIC RESPIRATION

12. MITOSIS
 4 stages in total (plus
interphase)
 Happens in somatic cells.
 Purpose is cellular
proliferation.
 Produces 2 diploid
daughter cells.
 Chromosome number
remains the same
 Genetic variation doesn’t
change.
MEIOSIS
 8 stages in total (plus
interphase).
 Happens in germ cells.
 Purpose is sexual
reproduction.
 Produces 4 haploid
daughter cells.
 Chromosome number is
halved in each daughter
cell.
 Genetic variation
increased.

13. MITOSIS AND MEIOSIS (SAME)
 Produce new cells.
 Similar basic steps.
 Start with a single parent cell.

14. MITOSIS
 Mitosis is a process where a single cell divides into
two identical daughter (cell division).
During mitosis one cell divides once to form two
identical cells
The major purpose of mitosis is for growth and to
replace worn out cells.
If not corrected in time, mistakes made during
mitosis can result in changes in the DNA that can
potentially lead to genetic disorders.

15. MITOSIS IS DIVIDED INTO FIVE PHASES:
1. INTERPHASE
2. PROPHASE
3. METAPHASE
4. ANAPHASE
5. TELOPHASE

16. Interphase
 The DNA in the cell is copied in preparation for cell
division, this results in two identical full sets of
chromosome.
 Outside of the nucleus are two centrosome, each
containing a pair of centrioles, these structures are
critical for the process of cell division.
 During interphase, microtubes extend for these
centrosomes.

17. Prophase
 The chromosome condense into X-shaped structures that
can be easily seen under a microscope.
 Each chromosome is composed of two sister chromatids,
containing identical genetic information.
 The chromosome pair up so that both copies of
chromosome are together, both copies of chromosome 2
are together, and so on.
 At the end of prophase the membrane around the
nucleus in the cell dissolves away releasing the
chromosomes.
 The mitotic spindle. Consisting of microtubules and
other proteins, extends across the cell between the
centrioles as they move to opposite poles of the cell.

18. Metaphase
 The chromosomes line up nearly – to – end – along
the centre (equator) of the cell.
 The centrioles are now at opposite poles of the cell
with the mitotic spindle fibers extending from them.
 The mitotic spindle fibers attach to each of the sister
chromatids.

19. Anaphase
 The sister chromatids are thin pulled apart by the
mitotic spindle which pulls one chromatid to the
opposite pole.

20. Telophase
 At each pole of the cell a full set of chromosomes
gather together.
 A membrane forms around each set of chromosome
to create two new nuclei.
 The single cell then pinches in the middle to form
two separate, daughter cells each containing full set
of chromosomes within a nucleus.
 This process is known as Cytokines.

22. MEIOSIS
 Meiosis , on the other hand, is used for just one
purpose in the human body.
 The production of gametes, sex cells, or sperm and
eggs. It goal is to make daughter cells with exactly
half as many chromosome as the starting cell.
 To put that another way, meiosis in humans is a
division process that takes us from a diploid cell, one
with two sets of chromosomes to haploid cells, ones
with a single set of chromosome.

23. PHASES OF MEIOSIS
 In many ways, meiosis is a lot like mitosis. The cell
goes through similar stages and uses similar
strategies to organize and separate chromosome. In
meiosis, however, the cell has a more complex task.
It still needs to separate sister chromatids (the two
halved of a duplicated chromosome) as in mitosis.
But it must also separate homologous chromosomes,
the similar but non identical chromosomes pairs an
organism receives from its two parents.
 These goals are accomplished in meiosis using a two-
step division process.

24.  Homologue pairs separate during a first round of cell
division, called Meiosis I, sister chromatids separate
during a second round, called Meiosis II.ng cell can
 Since cell division occurs twice during meiosis, one
starting cell can produce four gametes (egg or
sperm). In each round of division, cells go through
four stages : PROPHASE, METAPHASE,
ANAPHASEM AND TELOPHASE.