 Robert Hooke (mid-600s)
observed cell in cork
 Cell is the basic
structural, functional and
biological unit
 Cell- The smallest unit of
life that can replicate
independently, and are
often called the "building
blocks of life"
Structure of Cell
• Each cell is formed by a cell body and membrane covering the
cell body called cell membrane.
• Cell body has two part
a- Nucleus
b-Cytoplasm
•
Cell membrane
Structure Of Animal Cell
Structure of Plant Cell
Cell Size
Characteristics of Cell
 A surrounding membrane
 Protoplasm – cell contents in thick fluid
 Organelles – structures for cell function
 Control center with DNA
Cell Membrane
 The cell membrane surround the cell; work as gatekeeper.
membrane serves to separate and protect a cell from its
surrounding environment
 also known as plasma membrane or plasma lemma
 selectively permeable and able to regulate what enters and
exits the cell.
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Cell membrane is composed of three type of substance
1-Protein-55%
2-Lipid-40%
3-Carbohydrate-5%
Cell membrane
Structure of Cell Membrane- cell membrane is called unit membrane.
Electron microscope study reveals three layer of cell membrane
 One central electron-lucent layer-protein layer
 Two electron dense layer-lipid layer.
Cytoplasm- Gel-like fluid that take up most of the space inside the cell
containing organelles
components of cytoplasm
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Interconnected filaments & fibers
Fluid = cytosol
Organelles (not nucleus)
storage substances
Microtubules
 Filamentous intracellular structure with 20-30 nm in diameter
that are responsible for various kinds of movements in all
eukaryotic cells.
 Microtubules are composed of a single type of globular
protein- tubulin.
Function of microtubules
 Long rigid shape - which enables microtubules to support
other structures within the cell
 Ability to generate movement - various kinds of movements
in all eukaryotic cells. both within cells (conveyer belts) and of
the whole cells themselves ( microtubules that form structures
such as cilia and flagella).
 Role in nucleic and cell division (Spindle –Mitosis, centiole
movements)
 Inter mediate Filaments: Forms network around
nucleus extend towards periphery.
 Diameter- 10 nm.
 Rope like polymer
 Five Classes:
1. Keratins (epithelial Cells)
2. Glial filaments (Astreocytes).
3.Neurofilaments(nerve cells).
4. vimentin
5. desmin (muscle fibers)
 Microfilaments: Long fine thread like 3-6 nm.
 Non tubular contractile proteins. (actin & myosin)
Ectoplasm-Actin
Endoplasm- Actin & myosin
Functions:
structural strength.
Resistance against pulling force
Cellular Movements- contraction, gliding, cytokinesis.
Nucleus
 Nucleus control center of cell, is the
largest organelle.
 Double membrane
Nucleus Contains
 Chromosomes
 Nucleolus
Function of nucleus
 Control of all activities of the cell
 Synthesis of RNA
 Sending genetic instruction to
cytoplasm for protein synthesis
 Formation of subunits of ribosome
 Control of cell division
 Storage of hereditary information in
genes
Mitochondria
 Known as power house, bound by
double membrane
 Have their own DNA
 0.5-1.0 micron.
 Cristae
 Matrix
Function of mitochondria
• Production of energy
• Synthesis of ATP
• Initiation of apoptosis
Cytochrome C
Caspases
• Storage of Ca & Detoxification of
Ammonia.
Endoplasmic Reticulum
Endoplasmic reticulum (ER)- an interconnected
network of tubules, vesicles, and cisternae within cells.
The phospholipid membrane encloses a space, the
cisternal space (or lumen), from the cytosol, which is
continuous with the perinuclear space .
Two types
 Rough endoplasmic reticulum
 Smooth endoplasmic reticulum
 Ribosome-15 nm dot like without membrane.
 35% protein & 65% RNA.
 Functions: Protein Factories.
 Bound Ribosome- Enzyme, Hormone, lysosomal
protein & cell membrane protein.
 Free Ribosome-Hb , peroxisomal & mitochondrial
protein.
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
 Ribosomes attached to
 No attached ribosomes
surface
 Manufacture proteins
 Not all ribosomes attached to
rough ER
 May modify proteins from
ribosomes
 Has enzymes that help build
molecules
 Carbohydrates
 Lipids
Function of Rough endoplasmic Function of Smooth endoplasmic
reticulum
reticulum
 Synthesis of protein
 Degradation of worn out
organelles
 Synthesis of lipid and steroids
 Role in cellular metabolism
 Storage and metabolism of calcium
 Catabolism and detoxification of toxic
substance
Golgi Apparatus
 The Golgi apparatus also known as the Golgi
complex, Golgi body, or simply the Golgi, is
an found in most eukaryotic cells.
 Involved in synthesis of plant cell wall
 Labeling, Packaging & shipping station of cell
Golgi Apparatus Functional mechanism:
1. Molecules come in vesicles
2. Vesicles fuse with Golgi membrane
3. Molecules may be modified by Golgi
4. Molecules pinched-off in separate vesicle
5. Vesicle leaves Golgi apparatus
6. Vesicles may combine with plasma membrane to
secrete contents
Lysosomes
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Lysosomes - cellular organelles which contain acid hydrolase enzymes to break up
waste materials and cellular debris. They are found in animal cells, while in yeast and
plants the same roles are performed by lytic vacuoles.
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Some (50) important enzymes found within lysosomes include:
Lipase, which digest lipids
Amylase, which digests amylose, starch, and maltodextrins
Proteases, which digest proteins
Nucleases, which digest nucleic acids
phosphoric acid monoesters.
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Functions of Lysosomes
Aid in cell renewal
Break down old cell parts (autography)
Digests invaders (hetrography)
Secretary-Perforin, Granzymes, Melanin, Serotonin
Vacuoles
vacuole- membrane-bound organelle which is present in
all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles
are essentially enclosed compartments which are filled with water containing
inorganic and organic molecules including enzymes in solution , though in
certain cases they may contain solids which have been engulfed.
Function of Vacuole
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Isolating materials that might be harmful or a threat to the cell
Containing waste products
Containing water in plant cells
Maintaining internal hydrostatic pressure or turgor within the cell
Maintaining an acidic internal pH
Containing small molecules
Exporting unwanted substances from the cell
MULTIPLE
CHOICE
QUESTIONS
Q-1 The maximum size of a cell is limited by
 a. its need for enough surface area for exchange with
its environment.
 b. the number of organelles that can be packed inside.
 c. the materials needed to build it.
 d. the amount of flexibility it needs to be able to move.
 e. the amount of food it needs to survive
Ans –a
 Q-2 Generally accepted features of biological
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membrane include all of the following except
a-asymmetric arrangement of lipid
b-rapid diffusion of inorganic ions across lipid bilayer
c- lateral diffusion of lipid
d-lateral diffusion of integral and peripheral proteins.
Ans-b
Q-3 the major function /feature of the golgi
apparatus in eukaryotic cells are
 a-its carries out glycosylation of the proteins being
transported
 b-it is the major protein sorting centre of the cell
 c-it forms secretary vesicles in its trans compartment
 d-all of the above
Ans-d
Q-4 which one of the following organelles is
enclosed by a single membrane
 a-mitochondria
 b-nucleus
 c-chloroplast
 d-lysosome
Ans-d
Q-5 A distinctive features of the lysosome is that it
has
 a- a lower pH than cytoplasm
 b- a reduced hydrolase activity
 c- DNA
 d- ribosome
Ans-a
 Q6- The following are membranous cell
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organelles except
a- mitochondria
b- cell membrane
c- microtubules
d- lysosomes
E-secretory vesicles
Ans-c
 Q7-The organoids that can duplicate themselves
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are
a- Ribosomes
b- Lysosomes
c- Mitochondria
d- Golgi apparatus
e- none of the above
Ans-c
 Q8- The number of mitochondria present in a cell
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depends on its
a- size
b- shape
c- energy requirements
d- capability of division
E- none of the above
Ans-c
 Q9- To enter or leave a cell, substances must pass
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through
a. a microtubule.
b. the Golgi apparatus.
c. a ribosome.
d. the nucleus.
e. the plasma membrane
Ans-e
Q.10-The largest cell in human body
 a- lymphocytes
 b- fat cells
 c- RBCs
 d- Mature ova
Ans-a