A cell is the fundamental unit of life. It is capable of independent existence and carries out all functions necessary to sustain life. The document defines cells and describes their key components. It explains that cells come in various shapes and sizes, and are enclosed by a membrane with a nucleus and cytoplasm inside. The document distinguishes between prokaryotic and eukaryotic cells, and describes several important cell organelles like the nucleus, mitochondria, chloroplasts, and their functions.

1. THE FUNDAMENTAL UNIT OF LIFE.
PRESENTEDBY: SMARANDAS.
CLASS: 9-C.
SCHOOLNO.: 2507.

2. A cell is capable of independent existence and can carry Out all the
functions which are necessary for a living being. A cell carries out
nutritious, reproductions; the way an individual Organisms are capable
of independent existence which show a cell’s Capability to exit
independently. Due to this, a cell is called The fundamental and
structural unit of life .All living being are composed of the basic unit of
life.
WHAT IS A CELL ?

3. The cell is the smallest unit of life. All organisms are composed one or
more cells. New cells arise from previously existing cells. Cell wall is
made of cellulose. It is somewhat hard but permeable to most of the
substances. Cell wall is available in plant cells & in cells of bacteria &
fungi.
CELL WALL.

4. A cell is a tiny mass of protoplasm which is surrounded by a membrane & is capable of performing
all functions of life . Cells come in all shapes and size . While most of the Cells are spherical in
shapes, cell of various other shapes are also found. Most Of the cell are microscopic in size, i.e. it is
impossible to see them with Naked eyes. Some cells are fairly large, e.g. a neuron in human body
can Be as long as 1 meter. The egg of an ostrich is the largest known cell of a Living animal and an
average egg is 15 cm long and 13 cm wide . A cell is enclosed in a membranous casing and is filled
with a Liquid Substance which is called the cytoplasm. There are many cell Organelles In a typical
cell. Some of the main structures of a cell are as follows:
 Plasma membrane or cell membrane.
 Nucleus.
 Cytoplasm.
WHAT IS CELL MADE UP OF ?

5. Plasma membrane or cell membrane is the outermost covering of the cell that separates the
contents of the cell from its external environment. The plasma membrane allows or permits the
entry and exit of some materials in and out of the cell. The cell membrane , therefore is called a
selectively permeable membrane.
PLASMA MEMBRANE OR CELL
MEMBRANE.

6.  It gives definite shape to cell.
 It separates the contents of the cell from it’s surrounding medium.
 It provides mechanical barrier for the protection of the internal
contents of the cell.
 It is selectively permeable.
 It regulates the movement of ions in & out of the cell.
FUNCTIONS OF PLASMA
MEMBRANE OR CELL MEMBRANE.

7. The nucleus is a membrane bound structure that contains the cell's hereditary information and
controls the cell's growth and reproduction. It is commonly the most prominent organelle in the
cell. The nucleus is surrounded by a structure called the nuclear envelope. This membrane
separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed
within the nucleus. Chromosomes contain DNA which provides the genetic information necessary
for the production of other cell components and for the reproduction of life.
NUCLEUS.

8.  The nucleus controls all metabolic activities of the cell.
 It regulates the cell cycle.
 It is concerned with the transmission of heredity traits from the
parent offspring's.
FUNCTIONS OF NUCLEUS.

9. There are two fundamental types :
1. Prokaryotic.
2. Eukaryotic.
CELLS.

10. PROKARYOTIC CELL.

11.  Prokaryotic cells are less complex.
 It is unicellular.
 It does not have nucleus.
 It has a cell wall surrounding the cell membrane.
 It include bacteria & blue- green bacteria.
PROKARYOTES.

12. EUKARYOTIC CELL.

13.  It is more complex cell.
 It includes both multicellular and unicellular organisms.
 It does not have a true nucleus.
 Organelles are internal structures in cell’s that perform specific
functions.
 Eukaryotes include plant cells, animal cells, fungi, algae etc.
EUKARYOTES.

14. The protoplasmic mass of the inner cell to plasma membrane and excluding nucleus is
called cytoplasm. When the cell is young , the cytoplasm completely fills the space
between nucleus and plasma membrane. As it increases in size, a number of small
cavities called vacuoles appear in the cytoplasm. It also contains many specialized cell
organelles. Each of these organelles performs a specific function for the cell.
CYTOPLASM.

15. Every cell has a membrane around it to keep its own contents separate
from the external environment. Large and complex cells, including cells
from multicellular organisms, need a lot of chemical activities to
support their complicated structure and function. To keep these
activities of different kinds separate from each other , these cells use
membrane bound little structures (or organelles) within themselves.
CELL ORGANELLES.

16. • Endoplasmic reticulum.
• Golgi apparatus.
• Lysosomes.
• Mitochondria.
• Plastids.
• Vacuoles.
TYPES OF CELL ORGANELLES.

17. This is a complex network of tubes, the lumen of which is filled
with fluid. The two types of endoplasmic reticulum are seen . They
are :
Rough Endoplasmic Reticulum.
Smooth Endoplasmic Reticulum.
ENDOPLASMIC RETICULUM.

18. RER looks rough under a microscope because it has particles called
ribosomes attached to its surface. The ribosomes , which are present
in all active cells , are the sites of protein manufacture.
SER helps in the manufacture of the fat molecules , or lipids,
important for cell function. Some of these proteins & lipids helps in
building the cell membrane.
FUNCTIONS OF (RER) & (SER).

19. It is also known as Golgi complex or Golgi bodies , they consists of tiny elongates ,
flattened sacs (cisternae) , which are sacked parallel to one another along with
some vacuoles and clusters of vesicles. The function of the Golgi body is to secrete
certain hormones and enzymes . It also forms lysosomes . The Golgi body is usually
found close to the nucleus.
GOLGI APPARATUS.

20. These are membrane bound vesicular structures found in the cytoplasm . Each lysosome is
surrounded by a single membrane and contains powerful digestive enzymes. These enzymes are
made by RER .Lysosomes are involved in intracellular digestion of foreign food or microbes and
are called DIGESTIVE BAGS. These are involved in autolysis or self- digestion of cells after their
death, hence they are also called SUICIDAL BAGS. They are a kind of waste disposal system of a
cell.
LYSOSOMES.

21. Cells need to make proteins. Those proteins might be used as enzymes or as support for other cell functions.
When you need to make proteins, you look for ribosomes. Ribosomes are the protein builders or the protein
synthesizers of the cell. They are like construction guys who connect one amino acid at a time and build long
chains. Ribosomes are found in many places around the cell. You might find them floating in the cytoplasm
(cytosol). Those floating ribosomes make proteins that will be used inside of the cell. Other ribosomes are
found on the endoplasmic reticulum. Endoplasmic reticulum with attached ribosomes is called rough. It
looks bumpy under a microscope. Those attached ribosomes make proteins that will be used inside the cell
and proteins made for export out of the cell.
RIBOSOMES.

22. MITOCHONDRIA.

23. FUNCTION OF LYSOSOMES.
They are called digestive bags. They destroy any foreign material which enter the
cell such as bacteria and virus.
They remove worn out and poorly working cellular organelles by digesting them to
make way for their new replacements. They are called suicide bags of cell.

24. Chloroplast, structure within the cells of plants and green algae that is the site of photosynthesis,
the process by which light energy is converted to chemical energy, resulting in the production
of oxygen and energy-rich organic compounds. Photosynthetic cyanobacteria are free-living close
relatives of chloroplasts; endosymbiosis theory posits that chloroplasts and mitochondria (energy-
producing organelles in eukaryotic cells) are descended from such organisms.
CHLOROPLAST.