Cell & Its Orgenells

1. DR. ASHISH PATEL
Assistant professor
Dept. AGB, Veterinary College, AAU,
Anand

2.  Cell is the structural and functional unit of living organism
 There are two main groups of cells. and eukaryotic cells.
Prokaryotic cell Eukaryotic cell
• Cells that have membrane-bound
nucleus
• Cells also contain internal
membrane-bound structures called
organelles, such as mitochondrion
or chloroplast
• The genetic information is on a
chromosome which are found in
nucleus
• Prokaryotic cells shapes: irregular
e.g. Animals, Plants, Fung, Algae,
Protozoa
• Cells that lack a membrane-
bound nucleus
• The genetic information is in a
circular loop called a plasmid.
• Prokaryotic cells shapes: rod
shaped, spherical, and spiral.
• Replication by binary fission.
•E.g. Bacteria

3. Prokaryotic cell Eukaryotic cell
Animal Cell
Plant Cell

4.  Animal cells are typical of the eukaryotic cell, enclosed by a
plasma membrane and present in different shapes and
containing a membrane-bound nucleus and cell organelles.
 Cell contents are called the protoplasm.
 Most cells, both animals and plants, range in size between 1
and 100 micrometers and are thus visible only with the aid of a
microscope.
 In 1665, Robert hook discovered “Cell”.
 In 1839 Theodor Schwann formulated the Cell Theory which set
the concept that “the elementary parts of all tissues are formed
of cells through much diversified in manner”.
 Animal cell is distinct from other eukaryotes especially plant
cells by lack of cell walls and chloroplasts, and have smaller
vacuoles.

7. Cell Organelles
Various membrane bound structures found within a cell are
know
Cell Membrane (Plasma membrane/Plasmalemma/ phospho-lipid
bilayer)
 Cell membrane is of double layer of phospholipids.
 It physically separates the intracellular components from the
extra cellular environment and also serves as a protection layer
for the interior of the cell.
 The phosopholipids are "hydrophobic" (water fearing), so
the cell membrane acts as a protective barrier to the
uncontrolled flow of water.
 The cell membrane is selectively permeable, which allowing
some substances to pass into the cell and blocking others.

8.  The membrane contains numerous proteins which include
receptors for odours, tastes and hormones, as well as pores
responsible for the controlled entry and exit of ions like sodium
(Na+) potassium (K+), calcium (Ca++) and chloride (Cl-).
Cytoplasm
 Cytoplasm is a collective term for the cytosol plus the
organelles suspended within that cytosol.
 The cytoplasm has three major elements as follows,
• Cytosol
• Organelles and
• Inclusions

9. Cytosol
 The cytosol is the gel like fluid within which all the other
cell organelles reside. It is the internal fluid of the cell.
 Most of the cellular metabolism occurs within it.
 Proteins in cytosol control cell metabolism including
signal transduction pathways, glycolysis, intracellular
receptors and transcription factors.

10. Centrosome
 It also called the "microtubule organizing center (MTOC)".
 It is a small body located near the nucleus where microtubules
are produced.
 The centrosome is duplicated during cell division resulting in
two centrosomes, each with its own pair of centrioles.
Centriole
 Centrioles are barrel shaped self-replicating organelles found in
most animal eukaryotic cells (absent in plants and fungi).
 Centriole is made up of ring of nine bundles of microtubules
and each bundle is composed of three microtubules (protein of
the cytoskeleton).
 Centrioles are involved in the organization of the mitotic
spindle.

11. Golgi Apparatus
 It also called as Golgi body or Golgi complex or Dictyosome.
 It is an organelle composed of membrane-bound stacks known
as cisternae.
 The Golgi body processes and packages the macromolecules
such as proteins and carbohydrates synthesized by the cell into
membrane bound vesicles for cell secretion (exocytosis) or for
use within the cell.
 The enzymatic or hormonal contents of lysosomes,
peroxisomes and secretory vesicles are packaged in
membrane-bound vesicles at the periphery of the Golgi
apparatus.

12. Endoplsmic Reticulum
 The cytoplasm contains an extensive network of membrane
enclosed spaces; these spaces along with the membrane
enclosing them are known as Endoplasmic Reticulum (ER).
 The main functions of ER are
(1) It provide structural base for synthesis of proteins (Rough ER),
hormones (Smooth ER), lipids, phospholipids (both rough ER
and smooth ER)
(2) It provides channel for the transport of materials synthesized in
association with ER to various parts of cell.
 ER grouped in to two categories.
Smooth Endoplsmic Reticulum
 The smooth endoplasmic reticulum is named because its outer
and inner surfaces are appears smooth and regular.
 In those cells where only smooth ER found, where there are
little or no any protein synthesis occurs.

13.  Smooth ER plays different functions depending on the cell type
like lipid and steroid hormone synthesis, breakdown of lipid-
soluble toxins in liver cells and control of calcium release in
muscle cell contraction.
Rough Endoplasmic Reticulum
 The surface of the rough ER is found with protein-manufacturing
ribosomes giving it a "rough" appearance.
 Proteins synthesized on these ribosomes are collected in the
endoplasmic reticulum for transport throughout the cell.

14. Ribosomes
 Ribosomes are packets of RNA and protein that are sites for
protein synthesis (that process called as Translation).
 Messenger RNA from the cell nucleus is moved at the ribosome
where transfer RNA adds individual amino acid molecules to
form a protein chain.
 Each ribosome comprises of two parts - a large subunit and a
small subunit.
 Ribosomes are classified as being either "free" (anywhere in the
cytoplasm) or "membrane-bound" (endoplasmic reticulum).
Mitochondria
 Mitochondria also called as “Power House of Cell".
 Mitochondria are spherical to rod-shaped organelles with a
double membrane.

15.  The inner membrane is infolded many times, forming a series of
projections called as cristae. On these cristae the food (sugar) is
combined with oxygen to produce ATP - the primary energy source for
the cell.
 The most prominent role of the mitochondria is production of energy,
which stored in the form of glucose by conversion into ATP (adenosine
triphosphate) - the primary energy source for the cell.
Lysosome
 It is also known as cell vesicles/suicide-bags/suicide - sacs.
 Lysosomes are organelles that contain digestive enzymes
necessary for intracellular digestion.
 They are common in animal cells, but rare in plant cells.
 They digest excess or useless organelles, food particles, and
engulfed viruses or bacteria, which are transferred to the
cytoplasm as new cell-building materials.

16. Peroxisome
 Peroxisomes are membrane-bound packets of oxidative
enzymes.
 Peroxisomes break down organic molecules by the process of
oxidation to produce hydrogen peroxide and then quickly into
water and oxygen.
 They are called peroxisomes because they all produce hydrogen
peroxide.
Secretory vesicle
 It is a membrane bounded vesicle derived from the golgi
apparatus and cell secretions viz. hormones, neurotransmitters
are packaged in secretory vesicles at the Golgi apparatus.
 The secretory vesicles are then transported to the cell surface for
release.
Vacuoles
 A vacuole is a membrane-bound sac that plays roles in
intracellular digestion and the release of cellular waste products.
 Vacuoles are generally small in animal cell but large in plant
cells.

17. Cytoskeleton
 Cytoskeleton is a network of protein filaments and motor
proteins in the cytoplasm that give shape to a cell, hold and
move organelles, and typically involved in cell movement.
 The cytoskeleton maintains the cell shape.
Nucleus (Controlling center of the cell)
 Generally there is a single nucleus per cell that is spherical or
oval in shape.
 The nucleus is the largest cellular organelle that includes the
nucleolus.
 It is enclosed by a nuclear envelope, a double membrane and
communicates with the surrounding cytosol via numerous
nuclear pores.
 The viscous liquid within the nucleus is called nucleoplasm.
 Nucleus contains most of the cell's genetic material, double helix
DNA molecules held in complex manner with proteins, (histones
protein) to form chromosomes.

18.  Nucleus has DNA within it. The DNA is similar in every cell of
the body, but depending on the specific cell type, some genes
may be turned on or off – that is why a liver cell is different from
a muscle cell and a muscle cell is different from a fat cell.
 The main function of the nucleus is the coordination of the cell's
activities, which include growth, intermediary metabolism,
protein synthesis, and reproduction (cell division).
 A nucleus consists of three main parts, viz., nuclear membrane,
nucleolus and chromation
Nuclear Membrane (perinuclear envelope /nucleolemma /
karyotheca)
 It is a double membrane surrounds the nucleus and separates
the contents of the nucleus (DNA in particular) from the cytosol
(cytoplasm).

19. Nuclear Pores
 They are formed at sites where the inner and outer
membranes of the nuclear envelope are joined.
Nucleolus
 The nucleolus is a membraneless organelle found in the
nucleus.
 The main function of the nucleolus is the biogenesis and
assembly of ribosome components.
 Some cells have more than one nucleolus, but some cell do
not have any.
 Nucleolus is a spherical body found in the nucleus. It
disappears during prophase of mitosis and meiosis and
reappears during telophase.
 Nucleolus consists of three parts, viz., granules, fibrils and
matrix. Granular region contains proteins and RNA. The matrix
contains scattered granules and fibrils.

20. Functions of Nucleolus:
 Formation of ribosomes
 Synthesis of RNA.
Chromatin:
 Chromatin refers to partly clumped and tangled mass of nuclear
chromosomes.
 The chromatin fibre contains about 55 per cent proteins, 40 per
cent DNA and 4-5 per cent RNA.
 Chromatin is a basic unit of chromosomes, contains genes and
thus plays an important role in the inheritance of characters from
the parents to their offspring.

21. We studied which structures of an animal cell ?
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