2. OBJECTIVES:
At the end of the session the students will be able to:
•Define cell
•Describe structure and function of cell
•List the cell organelles
•Explain the process of cell division
3. Cell
• “Cell is the basic structural and functional unit of life”.
• A cell is the smallest and basic unit that is capable of
performing life functions.
4. Introduction
• Cells vary considerable in size, shape, and function.
• The shape of cells in the body vary based on their function.
• Humans contain about 100 trillion cells.
• Most plant and animal cells are between 1 and 100 µm and
therefore are visible only under the microscope.
5. Cell history
• The cell was discovered by Robert Hooke in 1665.
• The word cell comes from the Latin cella, meaning "small
room".
• The descriptive term for cell was used by Robert Hooke
when he observed the cork cells through microscope.
6. Cell theory
The Cell Theory is one of the basic principles of biology. It
is formulated by a german scientists Theodor Schwann,
Matthias Schleiden, and Rudolph Virchow.
The Cell Theory states:
All living organisms are composed of cells. They may be
unicellular or multicellular.
The cell is the basic unit of life.
Cells arise from pre-existing cells.
7. Modern version of the Cell Theory
• The modern version of the Cell Theory includes the ideas
that:
• Energy flow occurs within cells.
• Heredity information (DNA) is passed on from cell to cell.
• All cells have the same basic chemical composition.
8. Composite Cell
Because cells vary so greatly in size, shape,
content, and function, describing a “typical” cell is
impossible.
All of the structures described in the composite cell
can NOT be found in every cell regardless of
function.
The organelles are found in the cytoplasm of the
cell.
9. Cell structure
A cell has three main parts (plasma membrane,cytoplasm,and
nucleus).
Inside which there are a number of organelles floating in a
watery fluid called cytosol.
Organelles are small structures with highly specialized
functions. cell growth, maintenance and reproduction)
Many of which are membrane bounded.
11. Cell Membrane
• Extremely thin and semi permeable membrane forms the
Cell‘s Outer surface.
• The cell membrane contains many kinds of proteins, each
with a special function.
12. Structure:
• The basic framework of the cell membrane consists of a
(bilayer) double layer of phospholipid, with fatty acid tails
turned in.
13. Plasma membrane
• Phospholipids molecules have a head which is electrically
charged and hydrophilic (water loving)
• And a tail which has no charge and hydrophobic (water
hating).
• The phospholipids bilayer is arranged like a sandwich with
the head and tail.
• Forming a central water repelling layer.
14. Cell Membrane
• The Phosphate Head is HYDROPHILIC meaning
"WATER LOVING". Because of its hydrophilic nature,
the head of a Phospholipid will orient itself so that it is as
close as possible to water molecules.
• The Lipid Tails are HYDROPHOBIC meaning "WATER-
FEARING", the Hydrophobic tails will tend to orient
themselves away from water.
15.
16. Functions of Plasma membrane
• The membrane allows some substances to enter and leave the
cell but not others (selective transport)
• participates in signal transduction,
• helps cells adhere to other cells.
• forms a boundary around the cellular contents
• Branched carbohydrate molecules attached to the some
membrane protein molecules give immunological identity to the
cell.
• It plays a key role in communication among cells and between
the cell.
• Can act as specific receptors for hormones and other chemical
messenger.
17.
18. Cytoplasm
• Gel-like mixture
• It consist of all the cellular content between the plasma
membrane and the nucleus.
• Has two components ,cytosol (intracellular fluid portion) and
organelles
19. Cytoplasm
• Cell activities occur mainly in the cytoplasm, where nutrients
are received, processed, and used.
20. Endoplasmic Reticulum
ER is a network of membrane in the
Form of flattened sac Or tubules.
It is made up of membrane-bounded flatten sacs and elongated canals.
21. Endoplasmic Reticulum
Cell contain two Distinct form of ER.
• Rough ER:
Has ribosome on its outer layer and is attached to nuclear
envelope
It synthesizes glycoproteins and phospholipids that are
transferred to cellular organelles.
its function in the synthesis and transport of PROTEIN
22. Smooth ER
• No ribosomes.
• it function in the transport of LIPIDS
• Smooth ER synthesize fatty acids and steriods.
• inactivate drugs.
• store and release calcium ions in muscle cell.
• ER provides a tubular transport system inside the cell.
23.
24. Ribosome
•Composed of two subunits containing ribosomal
RNA and proteins.
•May be free in cytosole or attached to rough ER.
•Function is protein synthesis.
25. Ribosomes
• Each cell contains
thousands.
• Make proteins
• Found on ribosomes
& floating throughout
the cell
26.
27. Golgi Apparatus
• Composed of about 3-20 flattened, membranous sacs (cistea).
• Cup like shape
• Stractually and functionally divided into entry face medial
sisternae,and exit face.
• Function is to refine, package, and deliver proteins synthesized
on ribosome.
• It forms Vesicles that have a role in secretion.
• Plays a central role in the transport of molecules.
29. Golgi Bodies
• Protein 'packaging
plant'
• Move materials
within the cell
• Move materials out
of the cell
30. Mitochondria
• Is the POWERHOUSE of the cell.
• It contain enzymes that catalyze reactions that release energy
in the form of ATP from glucose.
• Adenosine Triphosphate (ATP) energy.
32. Mitochondria
• Consist of outer and
inner mitrochondrial
membrane,cristae and
mitrix.
It is the power house
Of the cell.
33. Mitochondria
• Produces energy through chemical reactions
• Controls level of water and other materials in cell
• Recycles and decomposes proteins, fats, and carbohydrates
34. Lysosome
• Vesicle formed from
golgi complex.
Contain digestive
Enzymes.
Digestive 'plant‘
for proteins, fats,
and carbohydrates
35. Lysosomes
• The "garbage disposals of the cell“
• They contain powerful enzymes to break up old cell
components and bacteria. Example white blood cells can engulf
bacteria to fight bacterial infections.
37. Microfilaments and microtubules
• Thin, threadlike processes within the cytoplasm that function
in various kinds of cell movement and that serve as the
cytoskeleton of the cell.
• Microfilaments, made of the protein actin, cause various
cellular movements.
• Mictotubules, made of the globular protein tubulin.
38.
39. Centrosome
• It is a structure made up of two hollow cylinders called
centrioles.
• Function in cell reproduction.
40. Cilia and flagella
• They are motile extensions from the cell.
• Cilia is short and move “to-and-fro”.
• Cilia function is to move fluids.
• Flagella are longer and move in an undulating wavelike
motion.
• What is the only flagellated cell in the body? SPERM
41.
42. Vesicles
• Or vacuoles are formed by part of the cell membrane.
• They contain some liquid or solid material formerly outside
the cell.
• Golgi and ER also form vesicles.
43. Nucleus
It is an oval shaped organelle.
Every cell in the body has a nucleus.
Except mature RBC.
it is the largest
organelle.
It has a tiny pores
through which some
substances can pass
between the nucleus and the
cytoplasm.
44. Nucleus, nuclear envelope
• Is bounded by a double-layered nuclear membrane (nuclear
envelope) containing relatively large nuclear pores that allow
the passage of certain substances.
45. Nucleolus
• Inside the nucleus are one or more spherical bodies called
nucleoli.
• Single is nucleolus.
• That function in producing ribosomes.
• Nucleoli are quit prominent in cell that synthesize large
amounts of protein.
46.
47. Chromosomes and Genes
‘Chroma’ color ‘soma’ bodies
Inside the nucleus the chromatin material condense to form
chromosome.
Human cell contain 46 chromosome arrange in pair in the
nucleus of each cell.
Each chromosome is a long molecule of DNA that is coil
together with several proteins. the complex of DNA,protein and
some RNA is called chromatin.
GENES:
Gene is the segment of DNA
each chromosome carries many genes
The site on chromosome on which a particular gene is located is
called locus
Genome all gene possessed by one individual.
48. Nucleus structure and functions
• Each nucleus is simply a cluster of protein ,DNA,and RNA.
• Nucleoli are the sites of synthesis of RNA.
• Within the nucleus are most of the cell's hereditary units,
called genes. which control cellular structure and direct
cellular activities.
• Genes are arranged with chromosomes.
49. Nucleus structure and functions
• Human body cells have 46 chromosomes.23 inherited from
each parents.
• Each chromosome is a long molecule of DNA, that is coiled
together with several protein.
• Nucleoli produce ribosomes, and chromosomes consist of
gene. that control cellular structure and functions.
50. What Cells Do?
• Cells are the basic units of all living things.
• Cells make up bones, muscles, skin, and blood.
• As the organism grows, the cells must reproduce.
• Cell reproduction is called mitosis
51. Cell division
•The process by which cells reproduce
themselves
•Two type of cell division
a) somatic cell division division
b) Reproductive cell division
52. Somatic cell division
•A somatic cell is any cell of the body except
germ cell i.e. Gamete (sparm or oocyte)
•In sometic cell division a cell undergoes a
nuclear dicision called mytosis
53. Reproductive cell division
•A reproductive cell division is the machanism that
produce gametes
•This process consist of a special two steps division
called meiosis, in which the number of cromosoms
in the nucleus is reduced by half.
54. Mitosis
• Mitosis is a process of cell division which results in the
production of two daughter cells from a single parent cell.
• The daughter cells are identical to one another and to the
original parent cell.
• Occurs in somatic cells
56. Prophase
•Early phase.
•Chromatin fibers condense into paired chromatids.
•nucleolus,and nuclear envelope disappear.
•Each centrosome moves to an opposite pole of the
cell.
57.
58. Prophase cont…
• 3 major events.
i) chromosomes condense
ii) spindle fibers form
iii) chromosomes are captured by
spindle
60. Anaphase
• In anaphase centromere split
• identical set of chromosomes move to opposite pole of cell.
• They appear V shape.
61. Telophase
• Begins after chromosomal movement stop.
• Nuclear envelopes and nucleoli reappear
• Mitotic spindle disappear.
• Chromosomes resume chromatin form.
62. • Cytokinesis (division of cell cytoplasm and organelles into two
identical cell)
• The final stage of mitosis.
63. Mitotic Cell Division
• Functions:
• Growth, maintenance, repair of body tissues.
• Forms the basis of
Asexual Reproduction
64. Meiosis
• Meiosis is a reductive cell division.
• It involves two divisions to produce four non-identical daughter
cells each containing half the number of chromosomes of the
parent cell.
• Takes place in reproductive cells
65. MEIOSIS
• Meiosis occur in two successive stage.
• Meiosis I and meiosis II.
• During the interphase that precedes meiosis I, the
chromosomes of the diploid starting cell replicate.
• Two sister chromatids are attached at their centromeres.
66. Meiosis I
• It begins once chromosomal replication complete.
• Consist of four phases.
• prophase I
• metaphase I
• anaphase I
• telophase I
67. Meiosis 1
First division of meiosis.
• Prophase 1:
o Each chromosome duplicates and remains closely associated. These
are called sister chromatids.
oCrossing-over can occur during the latter part of this stage.
• Metaphase 1:
oHomologous chromosomes align at the metaphase plate.
68.
69. • Anaphase 1:
oHomologous pairs separate with sister chromatids remaining together.
• Telophase 1:
o Two daughter cells are formed
oeach daughter containing only one chromosome of the homologous
pair
77. Telophase 2: Cell division is complete. Four
haploid daughter cells are obtained.
78.
79.
80. Meiosis I Mitosis
Prophase I Prophase
Pairing of chromosomes No pairing
Metaphase I Metaphase
Homologous chromosomes at Duplicated chromosomes at
Metaphase plate metaphase plate
Anaphase I Anaphase
Homologous chromosomes separate Sister chromatids separate, becoming
Daughter chromosomes
Telophase I Telophase
Daughter cells are haploid Daughter cells are diploid
81. Meiosis II Mitosis
Prophase II Prophase
No pairing of chromosomes No pairing
Metaphase II Metaphase
Haploid # of chromosomes at metaphase Diploid # of duplicated
chromosomes at plate metaphase plate
Anaphase II Anaphase
Sister chromatids separate, becoming Sister chromatids separate, becoming
daughter chromosomes daughter chromosomes
Telophase I Telophase
4 haploid daughter cells Daughter cells are diploid
82. Mitosis and Meiosis
• Mitosis:
-division of somatic (body) cells
• Meiosis
-division of gametes (sex cells)
83. Movements through cell membranes
• Passive mechanisms do
not require energy.
1. Diffusion
2. Facilitated diffusion
3. Osmosis
4. Filtration
• Active mechanisms
require cell energy.
1. Active transport
84. Passive (diffusion)
• Diffusion is the process by which molecules or ions scatter or
spread spontaneously from high concentration to low
concentration.
• Oxygen and carbon dioxide can diffuse readily through the
cell membrane.
• Equilibrium is reached.
85. Passive
• Substances that are not able to pass through the lipid bilayer
need the help of membrane proteins to get across, this is
called facilitated diffusion.
• Carrier molecules “revolving doors” are used to carry large
molecules (glucose) across the membrane.
86.
87. Passive
• Osmosis is the diffusion of water.
• Solutions with a higher osmotic pressure than body fluids are
called hypertonic.
• Solutions with a osmotic pressure equal to body fluids are
called isotonic.
• Solutions with a lower osmotic pressure than body fluids are
called hypotonic.
88. Active
• Active transport is a process that moves particles through
membranes from a region of low concentration to high
concentration.
• Equilibrium is never reached.
89. Cell Death
• Apoptosis is a form of cell death that is actually a normal
part of development, sculpting organs from overgrown
tissues.
90. • The Cell Cycle; G1, S, G2 & Mitosis:
http://highered.mcgraw-
hill.com/sites/0072495855/student_view0/chapter2/animation__how_t
he_cell_cycle_works.html
Mitosis & Cytokinesis:
• http://highered.mcgraw-hill.com/olc/dl/120073/bio14.swf
• Stages of Meiosis:
http://highered.mcgraw-hill.com/olc/dl/120074/bio19.swf
http://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf.
( Website used for my class presentation)
Ross and Wilson and Tortora
Refrences
