INTRODUCTIONTO STRUCTURE
OF CELL

CELL THEORY
 In biology, it describes the properties of a cell
 Robert Hooke was discovered the cell theory in 1665 by using the
microscope.
 Robert Hooke published a book name is Micrographic in 1665.
 All cells come from preexisting cells through cell division.

Types of cells
• Prokaryotic
• Eukaryotic
 Prokaryotic:-These are those cells which do not have a membrane-bound nucleus. In
prokaryote comes from (pro) means 'before’ and (karyon) means ‘nut or kernel'. Examples
are , Bacteria, E. coli, cyan bacteria(blue-green algae).
 Eukaryotic:-These are those cells which cells contain a nucleus and other organelles
enclosed within membranes. It comes from the Greek word which means
“true nucleus.”Examples are,plant,animal,protozoa.
Prokaryotic cell Eukaryotic cell

Characteristics
• Prokaryotic
1)The absence of a membrane around the nuclear material.
2)The absence of clearly defined membrane-limited organelles like mitochondria,
chloroplast, Golgi complex and lissome.
3)The genetic material is located on a single chromosome which consists of a
circular double strand of DNA.
• Eukaryotic
1) The nucleus houses the cell's DNA and directs the synthesis
of proteins and ribosome's.
2) Mitochondria are responsible for ATP production; the
endoplasmic reticulum modifies proteins and synthesizes lipids; and theGolgi
apparatus is where the sorting of lipids and proteins takes place.
3) Perixisomes carry out oxidation reactions that break down fatty acids and amino
acids and detoxify poisons; vesicles and vacuoles function in storage and
transport.

FUNCTION OF CELLS
• Prokaryotic cell
 The cell membrane (or plasma membrane or plasma lemma) surrounds
the cytoplasm of living cells, physically separating the intracellular components
from the extracellular environment.The cell membrane also plays a role in
anchoring the cytoskeleton to provide shape to the cell, and in attaching to
the extracellular matrix and other cells to hold them together to form
tissues. The cell employs a number of transport mechanisms that involve
biological membranes:
1. Passive osmosis and diffusion: Some substances (small molecules, ions) such as
carbon dioxide (CO2) and oxygen (O2), can move across the plasma membrane
by diffusion, which is a passive transport process. Because the membrane acts as
a barrier for certain molecules and ions, they can occur in different
concentrations on the two sides of the membrane. Such a concentration
gradient across a semi permeable membrane sets up an osmotic flow for the
water.
2.Tran membrane protein channels and transporters Nutrients, such as sugars or
amino acids, must enter the cell, and certain products of metabolism must leave
the cell.

• Such molecules diffuse passively through protein channels such
as aquaporins (in the case of water (H2O)) in facilitated diffusion or are pumped
across the membrane by transmembrane transporters. Protein channel proteins,
also calledpermeases, are usually quite specific, recognizing and transporting
only a limited food group of chemical substances, often even only a single
substance
3. Endocytosis: Endocytosis is the process in which cells absorb molecules by
engulfing them.The plasma membrane creates a small deformation inward,
called an invagination, in which the substance to be transported is captured.The
deformation then pinches off from the membrane on the inside of the cell,
creating a vesicle containing the captured substance. Endocytosis is a pathway
for internalizing solid particles ("cell eating" or phagocytosis), small molecules
and ions ("cell drinking" or pinocytosis), and macromolecules. Endocytosis
requires energy and is thus a form of active transport.
4. Exocytose: Just as material can be brought into the cell by imagination and
formation of a vesicle, the membrane of a vesicle can be fused with the plasma
membrane, extruding its contents to the surrounding medium.

• This is the process of exocytose. Exocytose occurs in various cells to remove
undigested residues of substances brought in by endocytosis, to secrete
substances such as hormones and enzymes, and to transport a substance
completely across a cellular barrier. In the process of exocytose, the
undigested waste-containing food vacuole or the secretary vesicle budded
from Golgi apparatus, is first moved by cytoskeleton from the interior of the
cell to the surface.The vesicle membrane comes in contact with the plasma
membrane.The lipid molecules of the two baitlayers rearrange themselves
and the two membranes are, thus, fused. A passage is formed in the fused
membrane and the vesicles discharges its contents outside the cell.
• Eukaryotic cell
 All cells are surrounded by a plasma membrane.The membrane is
composed of a phospholipids belayed arranged back-to-back.
The membrane is also covered in places with cholesterol molecules and
proteins.The plasma membrane is selectively permeable and regulates
which molecules are allowed to enter and exit the cell.

PLANT CELL
• All animals and plants are made of cells.
• Animal cells and plant cells have features in common, such as a nucleus,
cytoplasm, cell membrane, mitochondria and ribosome's.
• Plant cells also have a cell wall, and often have chloroplasts and a
permanent vacuole.

ANIMAL CELL
 An animal cell is a type of cell that dominates most of the
tissue cells in animals.
 Animal cells are different from plant cells because they don't have cell walls
and chloroplasts, which are relevant to plant cells.

CELL MEMBRANE
 It is a type of membrane which allows certain substances to pass through
the cytoplasm.
 In animal cells, it is always in the outer boundary of the cells. But in plant
cells, it is usually covered with cell wall.
 Also known as the semi permeable because those are made up of
phospholipids and proteins.

CELL WALL
 It is a type of a layer in which it cannot able to be changed or adapted.
The carbohydrate (e.g. starch, cellulose, or glycogen) whose molecules
consist of a number of sugar molecules bonded together in lying outside the
plasma membrane of the cells of plants, fungi, and bacteria.

NUCLEUS
 It means that in a positive way charging the central core of an atom,
consisting of protons and neutrons and containing nearly all its mass.

NUCLEAR MEMBRANE
 It is also known as the nuclear envelope. In this membrane it is double lipid
belayed membrane which surrounds the genetic material and nucleolus in
eukaryotic cell. It consists of two lipid baitlayers—the inner nuclear
membrane, and the outer nuclear membrane.

CHROMOSOMES
 It is a thread-like structure of nucleic acids and protein which are found in
the nucleus of most living cells, which carries genetic information in the
form of genes.

ENDOPLASMIC RETICULUM
 It is a type of a network in which look like a membrane which is a minute
tube inside the cytoplasm of a eukaryotic cell, which are forming like an
unbroken whole with the nuclear membrane. It usually has ribosome's
attached which involves in protein and lipid synthesis.
 It is divided into 2 types :
 RER{ rough endoplasmic reticulum}
 SER{ smooth endoplasmic reticulum}

Rough endoplasmic reticulum
 A membrane system which is folded sacs and is interconnected with
channels.
 It serves as a site for protein and lipid synthesis.
 It is Cellular organelles which is like tiny organs found in a cell that perform
specific functions like the large organs in our bodies.

Smooth endoplasmic reticulum
 A network of tubular membranes within the cytoplasm of the cell.
 It is occurring either with a smooth surface (smooth endoplasmic
reticulum) or studded with ribosome (rough endoplasmic reticulum)
involved in the transport of materials.
 It functions in several metabolic processes. It synthesizes lipids,
phospholipids, and steroids.

MITOCHONDRIA
 A organelle found in large numbers in most cells, in which the biochemical
processes of respiration and energy production occur in double membrane,
the inner part being folded inwards to form layers (cristae).

GOLGI BODIES
 a complex of a small fluid-filled bladder and folded membranes within the
cytoplasm of most eukaryotic cells, involved in a process by which
substances are produced and discharged from a cell, gland, or organ for a
particular function in the organism or for excretion which are take to
located.
 Helps to carry out materials within the cell and outside the cell.

VACUOLE
 a small fluid-filled bladder within the material of a cell, surround by a
membrane and typically have a substance that has no fixed shape and yields
easily to external pressure.

Reference
 Albert., & Bruce. (n.d). Cell biology. Retrieved 27 May, 2016, from
https://en.Wikipedia.org./wiki/cell_(biology)