This document discusses the key structures and functions of cells. It begins by describing how Robert Hooke first observed cells in 1665 when examining cork under a microscope. The main structures of animal cells are then outlined, including the cell membrane, cytoplasm, nucleus, nuclear membrane, and organelles. The types of cells are defined as prokaryotic and eukaryotic. Chromosomes, genes, and cell division are also summarized. The document provides a comprehensive overview of cellular structures and their functions at a basic level.

1. CELLS
STRUCTURE & FUNCTION

2. Topics
 Discovery of CELL
 The Cell
 Principal structures of an animal cell
 Number of cell
 Types of cell
 Shape & Size of cell
 Parts of cell and their function
 Cell Membrane
 Cell wall
 Cytoplasm
 Nucleus
 Nuclear membrane
 Chromosomes
 Dividing Chromosomes
 Gene

3. Discovery of
CELL
Robert Hooke
Born : July 18, 1635
Died : March 3, 1703
In 1665 he observed Slices of cork
Under a simple magnifing device.
Cork is a part of the bark of the bark
of a tree. He took thin slice of cork
and observed a under a microscope.
He noticed partitioned boxes or
compartments in the cork slice.
These box appeared like a honey
comb. Hooke coined the term ‘cell’
for each box. What hooke observed
as boxes or cell in
the cork were actually dead cells.

4. The Cell
In biology, the basic unit of which all living things are composed;
the smallest structural unit of living matter that is able to function
independently.
A single cell can be a complete organism in itself, as in bacteria
and protozoans. Groups of specialized cells are organized into
tissues and organs in multicellular organisms such as higher
plants and animals. There are two distinct types of cells:
prokaryotic cells and eukaryotic cells. Though the structures of
prokaryotic and eukaryotic cells differ (see prokaryote, eukaryote),
their molecular compositions and activities are very similar. The
chief molecules in cells are nucleic acids, proteins, and
polysaccharides. A cell is bounded by a membrane that enables it
to exchange certain materials with its surroundings. In plant cells,
a rigid cell wall encloses this membrane.

5. Principal structures of
an animal cell
Cytoplasm surrounds the cell's specialized structures, or
organelles. Ribosomes, the sites of protein synthesis,
are found free in the cytoplasm or attached to the
endoplasmic reticulum, through which materials are
transported throughout the cell. Energy needed by the
cell is released by the mitochondria. The Golgi complex,
stacks of flattened sacs, processes and packages
materials to be released from the cell in secretory
vesicles. Digestive enzymes are contained in lysosomes.
Paroxysms contain enzymes that detoxify dangerous
substances. The centrosome contains the centrioles,
which play a role in cell division. The microvilli are
fingerlike extensions found on certain cells. Cilia,
hairlike structures that extend from the surface of many
cells, can create movement of surrounding fluid. The
nuclear envelope, a double membrane surrounding the
nucleus, contains pores that control the movement of
substances into and out of the nucleoplasm. Chromatin,
a combination of DNA and proteins that coil into
chromosomes, makes up much of the nucleoplasm. The
dense nucleolus is the site of ribosome production.

6. Number of
cell
Human body or Animal body has Billions and trillions of cells which vary in
shapes and sizes. Different group of cells perform a variety of function.
Types of cell in organisma :
I. Organisms made of more than one cell are called Multicellular (Multi :
many; Cellular : Cell).
Ex : paramecium
ii. Organisms made of more than one cell are called Unicellular (Uni :
single or one; Cellular : Cell).
EX : amoeba

7. Types of cell in organisma :
UNICELLULAR MULTICELLULAR

8. Shape & Size of cell
Shape of cell :
I. The cell have no definite shape
For ex: Amoeba has no definite Shape, unlike other organisms. It keep
change its shape.
Size of cell :
I. The size of cell in living organisms may be as small as a millionth
of metre or may be as large as a few centimeters.
II. The smmallest cell is 0.1 to0.5 micrmetre in bacteria. The Largest
Cell Measuring 170mm to 130mm is the egg of ostrich.
III. The size of the cells has no relation with the size of the body of the
animal or plant.
IV. The size of cell is related to function.

9. Parts of Cell & their Function

10. Cell Membrene
The basic components of a cell are
Cell membrane, Cytoplasm and Nucleus.
The cytoplasm and nucleus are enclosed
within the cell membrane, also called
Plasma membrene.
In biology, the thin layer that forms the
outer boundary of a living cell or of an
internal cell compartment.
The outer boundary is the plasma
membrane, and the compartments
enclosed by internal membranes are called
organelles. Biological membranes have a
dual function: separation of vital but
incompatible metabolic processes
conducted in the organelles; and passage
of nutrients, wastes, and metabolic
products between organelles and between
the cell and the outside environment.
Membranes consist largely of a double
layer of lipids in which are embedded large
proteins, many of which transport ions and
water-soluble molecules

11. Cell wall
Cell Membrane (Plasma
membrane)
Covred by another thick
cobering called the cell wall.
Cell wall gives shape to the
cell.
Function:
This additional layer
surrounding the cell
membrane is required by
plant for protection. Plant cell
need protection against
variations in temperature,
high wind speed atmosphere
moisture etc. they are
exposed to these variaions
because they cannot move.

12. Cytoplasm
It is the jelly-like substance
present between the cell
membrane and the nucleus
Portion of a eukaryotic cell
outside the nucleus.
The cytoplasm contains all
the organelles . The
organelles include the
mitochondria, chloroplasts,
endoplasmic reticulum,
Golgi apparatus, lysosomes,
and peroxisomes. The
cytoplasm also contains the
cytoskeleton and the cytosol
(the fluid mass that
surrounds the various
organelles).

13. Nucleus
It is an important component
of the living cell. It is the
generally spherical and
located in the centre of the
cell. It can be stained and
seen easily with the help of a
microscope. Nucleus is
separated from the
cytoplasm by a membrane
called the nuclear membrene.
FUNCTION :
Its role in inheritance, acts
as control centre of the
activities of the cell. The
entire content of a living cell
is known as protoplasm.

14. NUCLEAR
MEMBRANE
Specialized structure occurring in
most cells (except bacteria) and
separated from the rest of the cell
by the nuclear membrane.
This membrane seems to be
continuous with the cell's
endoplasmic reticulum and has
pores that permits the passage of
large molecules. The nucleus
controls and regulates the cell's
activities (e.g., growth and
metabolism) and carries the genes.
Nucleoli are small bodies often
seen within the nucleus that play an
important part in the synthesis of
RNA and protein. A cell normally
contains only one nucleus.

15. Prokaryotic
I. Any cellular organism that lacks a
distinct nucleus.
II. Organisms classified in the domains
Bacteria (including blue-green algae,
or cyan bacteria) and Achaea are
prokaryotes; all other organisms are
eukaryotes and are placed in the
domain Eukaryote. Prokaryotic cells
lack a nuclear membrane and most of
the components of eukaryotic cells.
The cytoplasm includes ribosome's
that carry out protein synthesis and a
double-stranded DNA chromosome,
usually circular. Many prokaryotes
also contain additional circular DNA
molecules called plasmids. The
flagella are distinct from those of
eukaryotes in design and movement.
Eukaryotic
I. Any organism composed of
one or more cells, each of
which contains a clearly
defined nucleus enclosed by a
membrane, along with
organelles (small, self-
contained, cellular parts that
perform specific functions).
II. The organelles include
mitochondria, chloroplasts, a
Golgi apparatus, an
endoplasmic reticulum, and
lissome. All organisms except
bacteria and archaea are
eukaryotes; bacteria and
archaea are prokaryotes.

16. Chromosomes
The Nucleus contain thread-like structures called Chromosomes.
The structure and location of chromosomes differentiate
prokaryotic cells from eukaryotic cells (see prokaryote,
eukaryote). Every species has a characteristic number of
chromosomes; humans have 23 pairs (22 pairs of autosomal, or
nonsex, chromosomes and one pair of sex chromosomes).
Human chromosomes consist primarily of DNA. During cell
division (see meiosis, mitosis), chromosomes are distributed
evenly among daughter cells. In sexually reproducing
organisms, the number of chromosomes in somatic (nonsex)
cells is diploid, while gametes or sex cells (egg and sperm)
produced by meiosis are haploid (see ploidy). Fertilization
restores the diploid set of chromosomes in the zygote.

17. Dividing chromosome
During the first stages of cell
division, the recognizable double-
stranded chromosome is formed
by two tightly coiled DNA strands
(chromatids) joined at a point
called the centromere. During the
middle stage of cell division, the
centromere duplicates, and the
chromatid pair separates.
Following cell division, the
separated chromatids uncoil; the
loosely coiled DNA, wrapped
around its associated proteins
(histones) to form beaded
structures called nucleosomes, is
termed chromatin.

18. gene
Unit of heredity that occupies a fixed position on a chromosome.
Genes achieve their effects by directing protein synthesis. They
are composed of DNA, except in some viruses that contain
RNA instead. The sequence of nitrogenous bases along a
strand of DNA determines the genetic code. When the product
of a particular gene is needed, the portion of the DNA molecule
that contains that gene splits, and a complementary strand of
RNA, called messenger RNA (mRNA), forms and then passes to
ribosomes, where proteins are synthesized. A second type of
RNA, transfer RNA (tRNA), matches up the mRNA with specific
amino acids, which combine in series to form polypeptide
chains, the building blocks of proteins. Experiments have
shown that many of the genes within a cell are inactive much or
even all of the time, but they can be switched on and off.
Mutations occur when the number or order of bases in a gene
is disrupted.

19. Thank you
Name : Mukul
Class : X ‘B’
K.V.S sec-14 Gurgaon
Second Shift