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PhysiologyofThe CELL (I)for pre-medic Mesir (July 2013)
DR. NUR FARIESHA MD HASHIM
MSc Radiation Biology (UCL), PhD Cancer Cell
Biology (KCL)
PHYSIOLOGY UNIT, DEPT. OF BIOMEDICAL SCIENCE, FACULTY OF MEDICINE
& HEALTH SCIENCES UPM
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Overview ofCELL PHYSIOLOGYat a glance
Cell Theory
Observation of cells
An overview of cell structure Endoplasmic Reticulum and Segregated Synthesis
Golgi Complex and Exocytosis
Lysosomes and Endocytosis
Peroxisomes and Detoxification
Mitochondria and ATP Production Centrosome, Centrioles and Microtubule Organization
Cytosol: Cell Gel
Cytoskeleton: Cell Bone and Muscle
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Learning OutcomesCell Physiology
At the end of the session, you will be able to :
1. Explain the parts of cells
2. Describe the functions of cell compartments
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Principles of the Cell Theory
The cell is the smalleststructural and functionalunit capable of carrying
out life processes
The functional activitiesof each cell depend onthe specific structuralproperties of the cell
Cells are the livingbuilding blocks of all
multicellular organisms
An organisms structureand function ultimately
depend on the collectivestructural characteristics
and functionalcapabilities of its cells
All new cells and new lifearise only from pre-
existing cells
Because of thiscontinuity of life,
the cells of all
organisms are
fundamentally
similar in
structure andfunction
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PART 1
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An Overview of Cell Structure- under an EM
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Cell Structure
Plasma
membrane
Encloses the cells
Nucleus
Contains the cells geneticmaterial
Cytoplasm
The portion of the cells interiornot occupied by the nucleus
Different cells share many common features. Most cells have 3 major subdivisions:
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The plasma membrane bounds the cell
Plasma
membrane
Very thin structurecomposed of mostly lipid
(fat)
It keeps the
intracellular fluid (ICF)within cells frommingling with the
extracellular fluid (ECF)outside the cells
Like gated walls that
enclosed ancient cities,the cell controls the entry
of nutrients and other
needed supplies and the
export of productsmanufactured within
Guard againstunwanted traffic into
or out of the cell
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The nucleus contains the DNA
1-Typically the largestsingle organized cell
component located nearthe center of the cell
2-Surrounded by nuclearenvelope- separates thenucleus from the rest of
the cell
3-Houses the cells geneticmaterial, DNA
4-DNA has 2 majorfunctions: directing proteinsynthesis and serves as
genetic blueprint during cellreplication
Nucleus
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Cytoplasm
Contains specialized organelles (cells little organs) and the cytoskeleton (ascaffolding of proteins , act as bone and muscle) dispersed within thecytosol
Organelles Highly organized structures. 2 categories: membranous and non-membranous organelles
Membranous organelles- 5 main types- endoplasmic reticulum, Golgicomplex, lysosomes, peroxisomes and mitochondria
Non-membranous organelles- ribosomes, vaults and centrioles
Cytoskeleton
Is an interconnected system of protein fibers and tubes that extendsthroughout the cytosol
Gives the cell its shape, provides for its internal organization, and regulatesits various movements
Cytosol
Semiliquid, gel-like mass.
Many chemical reactions that are compatible with one another are
conducted in the cytosol
The cytoplasm consists of various organelles, the cytoskeleton and cytosol
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PART 2
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Endoplasmic Reticulum and Segregated Synthesis
Endoplasmic Reticulum (ER) Fluid-filled membranous system distributed extensively throughout the
cytosol
Primarily a protein- and lipid-producing factory
Rough ER
Consists of stacks of relatively flattened interconnected sacs
Synthesizes glycoproteins and phospholipids that are transferred intocellular organelles, inserted into the plasma membrane, or secretedduring exocytosis
Smooth ER
Is a meshwork of tiny interconnected tubules
Synthesizes fatty acids and steroids, such as estrogens and testosterone;inactivates or detoxifies drugs and other potentially harmful substances;
removes the phosphate group from glucose-6-phosphate; and stores andreleases calcium ions that trigger contraction in muscle cells
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The roughendoplasmic reticulumsynthesizes proteins
for secretion andmembrane
construction
The outer surface of RER membrane is studded with smallparticles called ribosomes- the workbenches where
protein synthesis takes place
The RER synthesizes and releases a variety of newproteins which serve one of 2 purposes : 1-some proteinsare destined for export to the cells exterior as secretory
products, like protein hormones or enzymes 2- otherproteins are transported to sites within the cell for
constructing new cellular membrane
The RER is most abundant in cells specialized for proteinsecretion (i.e. cells that secrete digestive enzymes) or in
cells that require extensive membrane synthesis (i.e.rapidly growing cells like immature egg cells)
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The smoothendoplasmic
reticulum packagesnew proteins in
transport vesicles
No ribosomes. SER is rather sparse and primarily servesas a central packaging and discharge site for molecules
to be transported from the ER
Portions of the SER then bud off (balloon outward on thesurface, then are pinched off), forming transport vesiclesthat enclose the new molecules in a spherical capsule
derived from SER membrane
Vesicle= fluid-filled, membrane enclosed intracellularcargo container
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1-The RERsynthesizes
proteins to besecreted to the
exterior or to beincorporated intocellular membrane
2-The SER packagesthe secretory productinto transport vesicles,
which bud off andmove to the Golgi
complex
3-The transportvesicles fuse with
the Golgi complex ,open up, and emptytheir contents intothe closest Golgi
sac
4-The newly synthesized proteinsfrom the ER travel by vesiculartransport through the layers of theGolgi complex, which modifies the
raw proteins into final form andsorts and directs the finished
products to their final destination byvarying their wrappers
5-Secretory vesicles containingthe finished protein products
bud off the Golgi complex andremain in the cytosol, storingthe products until signaled to
empty
6-On appropriate stimulation,the secretory vesicles fuse withthe plasma membrane, open,
and empty their contents to thecells exterior. Secretion hasoccurred by exocytosis, withthe secretory products never
having come in contact with thecytosol
7-Lysosomesalso bud from
the Golgicomplex
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PART 3
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Golgi Complex
Consists of a stack of slightlycurved, membrane-enclosed sacs.
The vesicles at the dilated edges
of the sacs contain finished proteinproducts packaged for distribution
to their final destination
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Processing and packaging of proteins by the Golgi complex. All proteins exported fromthe cell are rocessed in the Gol i com lex
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(a) Exocytosis: A secretory vesicle
fuses with the plasma membrane,
releasing the vesicle contents to
the cell exterior. The vesicle
membrane becomes part of
the plasma membrane
(b) Endocytosis: Materials from the
cell exterior are enclosed in a
segment of the plasma membrane
that pockets inward and pinches off
as an endocytic vesicle
Exocytosis and endocytosis
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PART 4
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Lysosomes and endocytosis
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Endocytosis can be accomplished in 3 ways-pinocytosis,
receptor-mediated endocytosis and phagocytosis
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1- Pseudopods begin tosurround prey/solid
particle
2- Pseudopods closearound prey/ solid
particle
3- Prey/solid particle isenclosed in endocyticvesicle that sinks into
cytoplasm
4- Lysosome fuses withvesicle, releasing
enzymes that attackmaterial inside vesicle
Phagocytosis cell eating, large
multimolecular particles are internalised
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1- Solute moleculesand water molecules
are outside theplasma membrane
2- Membrane pocketsinward, enclosing
solute molecules andwater molecules
3- Pocket pinches offas endocytic vesiclecontaining sample of
ECF
Pinocytosis cell drinking, a drop of ECF is
taken up non-selectively
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1- Substances attachto membrane
receptors
2- Membrane pocketsinward
3- Pocket pinches offas endocytic vesicle
containing targetmolecule
A highly selective process that enables cells
to import specific large molecules that
it needs from its environment
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To be continued in CELL II