Transcript Cell structure and functions

Cell structure & functions
Department of Applied Science
King Saud University/ Community College
By: Murad Sawalha
Outline
 Introduction
 Eucaryotic cell structure
 Procaryotic cell structure
 Differences between Procaryotic &


Eukaryotic cells.
Reproduction of organisms & their
cells.
Gram stain
Introduction
- Cell is defined as the fundamental living unit of any organism.
- Cell is important to produce energy for metabolism (all chemical
reactions within a cell)
- Cell can mutate (change genetically) as a result of accidental
changes in its genetic material (DNA).
- Some microrganisms are procaryotic, some are eucaryotic, &
some are not cells at all (Viruses)
- Viruses are composed of only a few genes protected by a
protien coat, & may contain few enzymes.
- Cytology: the study of the structure and functions of cells.
Eucaryotic cell structure
• Eucaryotic cells: have a
true nucleus, & the DNA
is enclosed by a nuclear
membrane.
• They are 10 times larger
than Procaryotic cells.
Cell membrane
• It’s composed of large
•
•
molecules of protiens &
phospholipids (certain types
of fats).
The cell membrane is
seperating the contents of
the cell from the outside
world.
It has the property of
selective permiability: only
certain substances may
enter & leave the cell
Cell Membrane
• Phospholipid bi-layer
that separates the cell
from its environment.
• Selectively permeable
to allow substances to
pass into and out of
the cell.
Nucleus
• Double membrane-control,
& integrates the functions of
the entire cell.
• Consider the command
center of the cell.
• Separates the genetic
material from the rest of the
cell.
Parts of the nucleus:
• Chromatin - genetic material of cell in its non-dividing
•
•
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state.
Nucleoplasm is the gelatenous matrix of the nucleus,
like cytoplasm.
Nucleolus - dark-staining structure in the nucleus that
plays a role in making ribosomes.
Nuclear envelope - double membrane structure that
separates nucleus from cytoplasm.
Cytoplasm
• Is a gel-like matrix of water, enzymes,
nutrients, wastes, and gases and contains
cell structures (organelles).
• Fluid around the organelles called cytosol.
• Most of the cells metabolic reactions occur
in the cytoplasm.
The Endoplasmic Reticulum
• The endoplasmic reticulum (ER)
– Accounts for more than half the total
membranes in many eukaryotic cells
– The ER membrane: is continuous with the
nuclear envelope
• There are two distinct regions of ER
– Smooth ER, which lacks ribosomes
– Rough ER, which contains ribosomes
Rough Endoplasmic Reticulum
• Network of continuous
•
•
sacs, studded with
ribosomes.
Manufactures, processes, and transports
proteins for export from
cell (vesicles)
Continuous with nuclear
envelope.
Smooth Endoplasmic Reticulum
• Similar in appearance to rough ER, but
without the ribosomes.
• Involved in the production of lipids,
carbohydrate metabolism, and
detoxification of drugs and poisons.
• Stores calcium.
Ribosomes
• Are the sites of protein synthesis.
• Found attached to the Rough
endoplasmic reticulum or free in
the cytoplasm.
• 60% RNA and 40% protein.
• Protein released from the ER are
not mature, need further
processing in Golgi complex before
they are able to perform their
function within or outside the cell.
Golgi Apparatus
• Modifies proteins and lipids
made by the ER and
prepares them for export
from the cell (exocytosis).
• Encloses digestive enyzymes
into membranes to form
lysosomes.
• Consists of flattened
membranous sacs called
cisternae
Lysosome
• Single membrane bound
•
•
•
structure.
Contains digestive
enzymes that break down
cellular waste and debris
and nutrients for use by
the cell.
Originate at the Golgi
complex.
Are the
Lysosome
• They contain lysozymes & other digestive
enzymes that breakdown foreign material taken
into the cell by phagocytosis (e.g Amebas, and
certain types of WBCs “phagocyte”).
• Also these enzymes may breakdown parts of the
cell or destroy the entire cell by process called
autolysis if the cell damaged or deteriorated.
• They contain up to 40 enzymes for digestion
Peroxisomes
• They are similar to lysosome but smaller.
• Peroxisomes contain the enzyme catalase,
which breakdown of hydrogen peroxide
into water and oxygen.
• Found mainly in liver and kidney cells
• Main function is detoxification of toxic
materials.
Mitochondrion
• Membrane bound
organelles that are the
site of cellular respiration
(ATP production)
• Mitochondria are
enclosed by two
membranes
– A smooth outer membrane
– An inner membrane folded
into cristae
Chloroplast
• Site of photosynthesis
• Membrane bound
•
•
structure.
Contains chlorophyll
Found only in plants
Cytoskeleton
• The cytoskeleton
– Is a network of fibers extending throughout
the cytoplasm
Microtubule
0.25 µm
Microfilaments
Roles of the Cytoskeleton: Support,
Motility, and Regulation
• The cytoskeleton
– Gives mechanical support to the cell
– Is involved in cell motility, which utilizes motor
proteins
Components of cytoskeleton:
1) Microfilaments
• Solid rods of globular
•
proteins.
Important component
of cytoskeleton which
offers support to cell
structure.
Components of cytoskeleton:
2) Microtubules
• Microtubules
– Shape the cell
– Guide movement of organelles
– Help separate the chromosome copies in
dividing cells
Components of cytoskeleton:
2) Microtubules
Centrosomes and Centrioles
• The centrosome
– Is considered to be a “microtubule-organizing
center”
– Contains a pair of centrioles
Components of cytoskeleton:
2) Microtubules
Centrioles
• Found only in animal
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•
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cells.
Self-replicating
Made of bundles of
microtubules.
Help in organizing cell
division.
Cell Wall
• Protects and gives
•
rigidity to plant cells
Formed from fibrils of
cellulose molecules in
a “matrix” of
polysaccharides and
glycoproteins.
Cilia and Flagella
• External appendages
•
from the cell
membrane that aid in
locomotion of the cell.
Cilia also help to
move substance past
the membrane.
Animal Cell vs. Plant Cell
Prokaryotic vs. Eukaryotic
Procaryotic cell strucure
• Are about 10 times smaller than
eucaryotic cells.
• Reproduction of these cells by binary
fission.
• Binary fission: the simple division of one
cell into two cells, following DNA
replication, & the formation of a
separating membrane & cell wall.
Procaryotic cell strucure
• Cytoplasm is surrounded by a cell
membrane, a cell wall (usually), &
sometimes a capsule or slime layer.