Introduction to Cell: Its Main Parts and Human Cell

An introduction on cell, the basic unit of life.

1. CELLCELL
Fundamental unit of life

2. Cell
Basic and fundamental unit of life,
it possesses a highly organized
structure that enables it to carry
out its vital functions.

3. Cellulose cell wall;
chloroplasts and vacuoles.
Plant
Types
of Cells
Prokaryotic
Lack a defined
nucleus
Eukaryotic
Have a defined
nucleus
Rigid cell wall;
may have flagella.
Animal
They can have a cell wall,
without differentiated tissues.
Protist
Chitin Cell Wall;
they are heterotrophs.
Fungal
Dispersed genetic material
in the cytoplasm.
Prokaryotic

4. Prokaryotic cells have no nucleus. Instead,
some prokaryotes such as bacteria have a
region within the cell where the genetic
material is freely suspended. This region is
called the nucleoid.
1.
They all are single-celled microorganisms.2.
The cell size ranges from 0.1 to 0.5 µm in
diameter.
3.
The hereditary material can either be DNA or
RNA.
4.
Prokaryotes generally reproduce by binary
fission, a form of asexual reproduction. They
are also known to use conjugation – which is
often seen as the prokaryotic equivalent to
sexual reproduction (however, it is NOT sexual
reproduction).
5.
Prokaryotic Cell

5. Eukaryotic Cell
Eukaryotic cells are characterised by a true
nucleus.
1.
The size of the cells ranges between 10–100
µm in diameter.
2.
This broad category involves plants, fungi,
protozoans, and animals.
3.
The plasma membrane is responsible for
monitoring the transport of nutrients and
electrolytes in and out of the cells. It is also
responsible for cell to cell communication.
4.
They reproduce sexually as well as asexually.5.
There are some contrasting features between
plant and animal cells. For eg., the plant cell
contains chloroplast, central vacuoles, and
other plastids, whereas the animal cells do
not.
6.

6. Cell Theory
Cell Theory was proposed by the German scientists, Theodor Schwann,
Matthias Schleiden, and Rudolf Virchow. The cell theory states that:
All living species on Earth are composed of cells.
A cell is the basic unit of life.
All cells arise from pre-existing cells.
A modern version of the cell theory was eventually formulated, and it
contains the following postulates:
Energy flows within the cells.
Genetic information is passed on from one cell to the other.
The chemical composition of all the cells is the same.

7. Functions of a Cell
PROVIDES SUPPORT AND STRUCTURE: The cell wall and the cell
membrane are the main components that function to provide
support and structure to the organism.
Facilitate Growth Mitosis: In the process of mitosis, the parent cell
divides into the daughter cells. Thus, the cells multiply and facilitate
the growth in an organism.
Allows Transport of Substances: Various nutrients are imported by
the cells to carry out various chemical processes going on inside the
cells. The waste produced by the chemical processes is eliminated
from the cells by active and passive transport.

8. Functions of a Cell
Energy Production: Cells require energy to carry out various
chemical processes. This energy is produced by the cells
through a process called photosynthesis in plants and
respiration in animals.
Aids in Reproduction: A cell aids in reproduction through the
processes called mitosis and meiosis. Mitosis is termed as
the asexual reproduction where the parent cell divides to
form daughter cells. Meiosis causes the daughter cells to be
genetically different from the parent cells.

9. HUMANHUMAN
CELLCELL

10. human Cell
The body contains around 50—
100 trillion cells, and they vary
widely in size, number,
structure, and use.

11. Cell nucleus
An organelle that houses DNA, located
in the center of eukaryotic cells.
Its primary function is to store and
safeguard genetic information,
controlling gene expression and DNA
replication.
It also contains the nucleolus, which is
involved in ribosome synthesis.

12. Plasma membrane
To ensure each cell remains
separate from its neighbor, a
special membrane, known as the
plasma membrane, envelops the
cell. Phospholipids make most of
this membrane and prevent water-
based substances from entering
the cell.
The plasma membrane contains a range
of receptors, which carry out a number of
tasks, including being:
Gatekeepers: Some receptors allow
certain molecules through and stop
others.
Markers: These receptors act as name
badges, informing the immune
system that they are part of the
organism and not foreign invaders.
Communicators: Some receptors help
the cell communicate with other cells
and the environment.
Fasteners: Some receptors help bind
the cell to its neighbors.

13. Cytoplasm
The cytoplasm is a gel-like matrix
containing water, salts, proteins, and
other molecules. It occupies the
intracellular space between the cell
membrane and the nucleus.
It plays a crucial role in biochemical
reactions, energy production, and
substance transport. Essential for
cellular metabolism, it provides
structural support to the cell.

14. Cytoskeleton
It is composed of protein filaments
(microtubules, microfilaments, and
intermediate filaments) and provides
support and enables movement in
eukaryotic cells.
Its specific functions encompass stability,
intracellular transport, and contraction.
Furthermore, it regulates cellular shape
and plays a role in division, migration,
and communication.

15. Endoplasmic reticulum
The endoplasmic reticulum (ER) processes
molecules within the cell and helps transport
them to their final destinations. In particular, it
synthesizes, folds, modifies, and transports
proteins.
There are two main types of ER:
The Rough Endoplasmic Reticulum (RER) is
studded with ribosomes and is involved in
the synthesis and modification of proteins.
The Smooth Endoplasmic Reticulum (SER)
specializes in lipid synthesis, carbohydrate
metabolism, and detoxification.

16. Golgi apparatus
Key in the processing and packaging of
proteins and lipids produced in the
endoplasmic reticulum.
Composed of a series of flattened sacs called
cisternae, it acts as the 'shipping center' of the
cell, sorting and packaging proteins into
vesicles for transport and distribution.
It synthesizes carbohydrates and lipoproteins
and is essential for maintaining the cell's
internal balance and facilitating
communication with the outside.

17. Mitochondria
People may often refer to mitochondria as
the powerhouses of cells. They help turn
energy from food into energy that the cell
can use — adenosine triphosphate (ATP).
The double membrane of mitochondria
allows for the organization of various
stages of the respiratory chain, making it
crucial for cellular function and survival.

18. Ribosome
The nucleus transcribes segments of
DNA into ribonucleic acid (RNA), a
molecule similar to DNA, which directs
the translation of RNA into proteins.
Ribosomes read the RNA and translate
it into proteins by sticking together
amino acids in the order the RNA
defines.
Ribosomes are located in the
cytoplasm and the rough
endoplasmic reticulum.

19. The human body constantly replaces cells. Cells need to divide for a
number of reasons, including the growth of an organism and to fill
gaps that dead and destroyed cells leave after an injury, for instance.
There are two types of cell division: mitosis and meiosis.
cell division

20. Mitosis
Mitosis is how most of the cells in the
body divide. The “parent” cell splits into
two “daughter” cells.
Both daughter cells have the same
chromosomes as each other and the
parent. People refer to them as diploid
because they have two complete
copies of the chromosomes.

21. Mitosis
Mitosis is how most of the cells in the
body divide. The “parent” cell splits into
two “daughter” cells.
Both daughter cells have the same
chromosomes as each other and the
parent. People refer to them as diploid
because they have two complete
copies of the chromosomes.

22. Meiosis
In meiosis, the body produces sperm cells and egg cells.
In males, meiosis occurs after puberty.
Diploid cells within the testes undergo meiosis to produce
haploid sperm cells with 23 chromosomes. A single diploid cell
yields four haploidsperm cells. They contain one complete set
of 23 chromosomes.
In females, meiosis begins during the fetal stage, before the
individual is born. It happens in stages.

23. Meiosis
A series of diploid future egg cells enter meiosis. At the end of
the first stage of meiosis the process stops, and the cells
gather in the ovaries.
At puberty, one female egg cell resumes meiosis each month.
As meiosis completes, it yields a single haploid egg cell each
monthly cycle.
During human reproduction, the haploid sperm and haploid
egg combine. This temporarily doubles the number of
chromosomes. A small portion of each chromosome breaks off
and reattaches to its partner chromosome before fertilization
finishes.

25. Thank you!Thank you!
Any questions?