2. Discovery of Cells
 The first observations of cells were made in 1665 by
English scientist Robert Hooke, who used a crude
microscope of his own invention to examine a variety
of objects, including a thin piece of cork.

3.  While Hooke was the first to observe and describe
cells, he did not comprehend their significance.
 At about the same time, the Dutch maker of
microscopes Anton Van Leeuwenhoek pioneered the
invention of one of the best microscopes of the time.
Using his invention, Leeuwenhoek was the first to
observe, draw, and describe a variety of living
organisms, including bacteria gliding in saliva, one-
celled organisms cavorting in pond water, and sperm
swimming in semen.

4. The cell is the structural and
functional unit of all known
living organisms. It is the
smallest unit of an organism
that is classified as living, and
is often called the building
brick of life.Some organisms,
such as most bacteria, are
unicellular (consist of a single
cell). Other organisms, such
as humans, are multicellular.

5. Major components of the Cell
Theory
a. All living things/ organisms are composed of one or
more cells and cell products
b. All living cells come from other living cells by the
process of cell division

6. Cell Functions
 1. Nutrition – process by which cells obtain food
molecules to support their other activities.
 2. Digestion- food particles are broken down into
smaller soluble units suitable for cell use with the help
of the ENZYMES
 3. Absorption- is the process by which cells absorb
water, minerals & other matl’s essential to life
 4. Biosynthesis- process by which cells organize
complex chemicals from simple building units to
complex

7.  5. Excretion- process by which by products of all cell
activities which are not needed for further cell fxning
are eliminated
 6. Egestion-insoluble, non digested particles are
eliminated by the cell
 7. Secretion- process by which substances that are
synthesized by the cells are expelled from the
membrane (e.g Hormones)
 8. Movement- process by which includes the
locomotion of cells by means of special structures like
cilia of flagella

9.  9. Irritability- process by which cells respond or
react to external factors.
 10. Respiration- is the process of breaking down
food molecules into chemical energy needed by all
cells in order to fxn
11. Reproduction- process by which cells copy or
replicates its DNA and increases its number by cell
division.

10. Anatomy of cells
 There are two types of cells: eukaryotic and prokaryotic.
 Prokaryotic cells are usually independent, while
eukaryotic cells are often found in multicellular
organisms.

11. Prokaryotic cells
 prokaryote cell is simpler
than a eukaryote cell,
lacking a nucleus and
most of the other
organelles of eukaryotes.
There are two kinds of
prokaryotes: bacteria
and archaea; these share
a similar overall
structure.

13.  A prokaryotic cell has three architectural regions:
on the outside, flagella and pili project from the
cell's surface. These are structures (not present in
all prokaryotes) made of proteins that facilitate
movement and communication between cells;

14.  Eukaryotic cells
Eukaryotic cells are about 10 times the size of a typical
prokaryote and can be as much as 1000 times greater in
volume. The major difference between prokaryotes and
eukaryotes is that eukaryotic cells contain membrane-
bound compartments in which specific metabolic
activities take place. Most important among these is the
presence of a cell nucleus, a membrane-delineated
compartment that houses the eukaryotic cell's DNA. It is
this nucleus that gives the eukaryote its name, which
means "true nucleus."

15. Animal Cell

16.  An animal cell typically contains several types of
membrane-bound organs, or organelles. The nucleus
directs activities of the cell and carries genetic
information from generation to generation. The
mitochondria generate energy for the cell. Proteins
are manufactured by ribosomes, which are bound to
the rough endoplasmic reticulum or float free in the
cytoplasm. The Golgi apparatus modifies, packages,
and distributes proteins while lysosomes store
enzymes for digesting food. The entire cell is
wrapped in a lipid membrane that selectively permits
materials to pass in and out of the cytoplasm.

19. Table 1: Comparison of features of prokaryotic and eukaryotic cells
Prokaryotes Eukaryotes
Typical organisms bacteria, archaea protists, fungi, plants, animals
~ 10-100 µm (sperm cells, apart from
Typical size ~ 1-10 µm
the tail, are smaller)
Type of nucleus nucleoid region; no real nucleus real nucleus with double membrane
linear molecules (chromosomes) with
DNA circular (usually)
histone proteins
RNA-synthesis inside the nucleus
RNA-/protein-synthesis coupled in cytoplasm
protein synthesis in cytoplasm
Ribosomes 50S+30S 60S+40S
highly structured by endomembranes
Cytoplasmatic structure very few structures
and a cytoskeleton
flagella and cilia containing
Cell movement flagella made of flagellin microtubules; lamellipodia and
filopodia containing actin
one to several thousand (though some
Mitochondria none
lack mitochondria)
Chloroplasts none in algae and plants
single cells, colonies, higher
Organization usually single cells multicellular organisms with
specialized cells
Mitosis (fission or budding)
Cell division Binary fission (simple division)
Meiosis

20. Comparison of structures between animal and plant cells
Typical animal cell Typical plant cell
Organelles •Nucleus •Nucleus
•Nucleolus (within •Nucleolus (within
nucleus) nucleus)
•Rough endoplasmic •Rough ER
reticulum (ER) •Smooth ER
•Ribosomes •Ribosomes
•Cytoskeleton •Cytoskeleton
•Golgi apparatus •Golgi apparatus
•Cytoplasm (dictiosomes)
•Mitochondria •Cytoplasm
•Vesicles •Mitochondria
•Lysosomes
•Centrosome
•Centrioles
•Vacuoles
•Smooth ER

21.  The Plasma Membrane—A Cell's Protective Coat
 The outer lining of a eukaryotic cell is called the
plasma membrane. This membrane serves to
separate and protect a cell from its surrounding
environment and is made mostly from a double layer
of proteins and lipids, fat-like molecules. Embedded
within this membrane are a variety of other molecules
that act as channels and pumps, moving different
molecules into and out of the cell. A form of plasma
membrane is also found in prokaryotes, but in this
organism it is usually referred to as the cell
membrane.

22.  The plasma membrane
(cell membrane) is
made of two layers of
phospholipids. The
membrane has many
proteins embedded in
it.
 The plasma membrane
regulates what enters
and leaves the cell.
Many molecules cross
the cell membrane by
diffusion and osmosis.

23. The Cytoskeleton—A Cell's
Scaffold
The cytoskeleton is an
important, complex, and dynamic
cell component. It acts to organize
and maintain the cell's shape;
anchors organelles in place; helps
during endocytosis, the uptake
of external materials by a cell; and
moves parts of the cell in
processes of growth and motility.
There are a great number of
proteins associated with the
cytoskeleton, each controlling a
cell’s structure by directing,
bundling, and aligning filaments.

24.  The Cytoplasm—A Cell's Inner Space
 Inside the cell there is a large fluid-filled
space called the cytoplasm, sometimes
called the cytosol. In prokaryotes, this
space is relatively free of compartments.
In eukaryotes, the cytosol is the "soup"
within which all of the cell's organelles
reside. It is also the home of the
cytoskeleton. The cytosol contains
dissolved nutrients, helps break down
waste products, and moves material
around the cell through a process called
cytoplasmic streaming. The nucleus
often flows with the cytoplasm changing
its shape as it moves. The cytoplasm also
contains many salts and is an excellent
conductor of electricity, creating the
perfect environment for the mechanics
of the cell. The function of the
cytoplasm, and the organelles which
reside in it, are critical for a cell's
survival.

25.  Genetic Material
 Two different kinds of
genetic material exist:
deoxyribonucleic acid
(DNA) and ribonucleic
acid (RNA). Most
organisms are made of
DNA, but a few viruses have
RNA as their genetic
material. The biological
information contained in an
organism is encoded in its
DNA or RNA sequence.

26.  The Nucleus—A Cell's Center
 The nucleus is the most
conspicuous organelle found in a
eukaryotic cell. It houses the cell's
chromosomes and is the place
where almost all DNA replication
and RNA synthesis occur. The
nucleus is spheroid in shape and
separated from the cytoplasm by a
membrane called the nuclear
envelope. The nuclear envelope
isolates and protects a cell's DNA
from various molecules that could
accidentally damage its structure or
interfere with its processing.
During processing, DNA is
transcribed, or synthesized, into a
special RNA, called mRNA. This
mRNA is then transported out of
the nucleus, where it is translated
into a specific protein molecule. In
prokaryotes, DNA processing takes
place in the cytoplasm.

27.  The Ribosome—The
Protein Production
Machine
 Ribosomes are found in
both prokaryotes and
eukaryotes. The ribosome
is a large complex
composed of many
molecules, including RNAs
and proteins, and is
responsible for processing
the genetic instructions
carried by an mRNA

28.  The mitochondria are
specialised for energy
production (respiration).
Chloroplasts are organelles
found in plant cells which
produce sugar using light.
Light is the ultimate source of
energy for almost all life on
Earth. The area of the cell
outside the nucleus and the
organelles is called the
cytoplasm. Membranes are
complex structures and they
are an effective barrier to the
environment, and regulate the
flow of food, energy and
information in and out of the
cell

29. Transport, "intracellular highway".
Ribosomes are positioned along the rough
ER, protein made by the ribosomes enter the
ER for transport.
Processes, packages and secretes proteins.
Like a factory.

30. Animal cell

31. Plant cell