biology cellular - the structure

8/13/2019 Biology Cellular - The Structure

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The structure and organization

of eukaryotic cell

By:

dr.Sutrisno Darmosumarto, Sp.A

Histology & Cell Biology Department

Gadjah Mada University


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CELL COMPONENTS

The cell is composed of 2 basic parts:

cytoplasm and nucleus

Individual cytoplasmic components not

clearly visible in HE-stained preparations

the nucleus intensely stained dark blue

or black


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The basic structure of cell

Cellular membrane ,covers

Cytoplasm ,contains nucleus,

organelles and inclusions


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Organelles

Permanent

Performing cell activities

E.g. : mitochondria, Golgi apparatus,lysosome, smooth and rough endoplasmic

reticulum etc.


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Inclusions

Temporary

Metabolic products

E.g.: glycogen granules, mucinogenglobule, zymogen granule, melanin

granule etc


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Basic activities of cell

Metabolism, divided into:

anabolism and katabolism Conserning irritability

Reproduction


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CELL COMPONENTS

The cell is composed of 2 basic parts:

cytoplasm and nucleus

Individual cytoplasmic components not

clearly visible in HE-stained preparations

the nucleus intensely stained dark blue

or black


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Cell Membrane

composed of phospholipids, protein, and, to alesser extent, polysaccharides.

The functions:

selective barrier regulates the passage ofcertain materials into and out of the cell.

facilitate the transport of specific materialsthrough this limiting barrier

carry out a number of specific recognition

and regulatory functions 7.5 to 10 nm in thickness visible only in the

EM.


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Cytoplasm

composed of a matrix embedded

several structures classified into 3 groups:

organelles

inclusions

other components


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The characteristics of

cytoplasmic components 1. organelles presents in all eukaryotic cellsenclosed in a membrane, and containenzymes that participate in cellular metabolicactivity permanent components of the

cytoplasm (the endoplasmic reticulum, themitochondria, the Golgi apparatus, and thelysosome).

2. The inclusions temporary components ,accumulations of pigment, lipids, proteins, orcarbohydrates

3. The other components the centrioles,microtubules, and microfilaments.


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Mitochondria.

composed of an external membrane andan internal membrane

Internal membrane projects folds the

crista.

These membranes surround a space

spaium intermembrane

Space between the cristae matrix


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Mitochondria

transform the chemical energy

into available energy stored in

ATP release energy required to

perform any type of work ( be of

osmotic, mechanical, electrical, or

chemical nature)


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E R & Ribosomes

flattened, rounded, or tubular vesicles anastomose with one another in a networkform

2 types of ER granular (rough) andagranular (smooth).

The membranes of the ER continuous

with the nuclear envelope membrane. usually arranged in the form of flattened

cisternae stacked in parallel


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Ribosome

small, electron-dense particles, 1520 nmin diameter, attached to the outer surfaces

of the membranes composed of RNAand protein the basophilia in thecytoplasm

Ribosomes can appear as isolatedgranules free in the cytoplasm, or linked ingroups called polysomes.


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Smooth ER

no ribosomes

very abundant in the liver cell

composed entirely of membranes that generally

appear as profusely anastomosing tubules or flatcisternae

participates in the contraction of muscle cells

also involved in the synthesis of the glycogen inliver cells glucose-6-phosphatase is found

within its membranes


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Golgi Apparatus

group of piled-up flat vesicles

with peripheral dilatations

occupies a finite and fixed area in

the cytoplasm of most cells(supranuclear)


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Golgi app.

plays a role in the process of synthesis,

concentration, and storage of secretory-

products of most glandular cells.

The proteins synthesized enclosed by a

membrane to form secretory granules.


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Lysosomes

membrane-bound vesicles contain lyticenzymes intracytoplasmic digestion.

particularly abundant in cells exhibiting

phagocytic activity (eg, macrophages, whiteblood cells).

usually spherical, diameter 0.2 to 0.5 /um,.

The enveloping single membrane serves to

separate the lytic enzymes from the cytoplasmprevents the attacking and digestingcytoplasmic organelles.


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MICROTUBULES, MICROFILAMENTS, & INTERMEDIATE

FILAMENTS

In addition to the membrane-bound organ-

elles, the cytoplasmic matrix exhibits a

complex network consisting of

microtubules, microfilaments, andintermediate filaments provide for the

form and shaping of cells , also important

in cytoplasmic and cellular movement.


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Microtubules

rod- or pipe-like organelles microtubules.

outer diameter of 24 nm consisting of adense wall 5 nm thick and a less dense

(possibly hollow) core 14 nm wide.

lengths are variable


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Microtubules

Composed of proteinaceous subunits ( tubulin ).

Tubulin, a heterodimer, is a molecule consisting

of 2 non-identical monomers ( alfa and beta

tubulins). Both tubulins , MW about 60,000

Under appropriate conditions tubulin subunits

polymerize into typical microtubules. A total of 13 protofilaments generally comprise

the wall of a microtubule .


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Cilia and flagella

motile processes highly organizedmicrotubule core extend from the surface ofmany different cell types.

Ciliated cells

possess a large number of cilia (2 to 10 /um in length).

Flagellated cells have only one or 2 flagella,range in length from 100 to 200 /um.

Cilia and flagella both have a diameter of 0.3 0.5 /um and possess the same complexlyorganized core of microtubules.


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Intermediate Filaments

known as tonofilamentsdiameter of 8-10 nm.

be involved with the "slow" component ofaxoplasmic transport, as a smooth muscle

cytoskeletal component, in pigment granulemovement, as a junctional complex structuralelement, and with cell spreading.

possess an actin corefollowing brief

trypsinization

the filaments bind heavymeromyosin ( a functional assay normally usedto identify actin)


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Cytoplasmic Inclusions

transitory components of the cytoplasm

lipid droplets, carbohydrateaccumulations (glycogen), secretory

granules, colored substances (melanin

pigment and lipofuscin)


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THE NUCLEUS

a rounded or elongated structure in the

center of the cell. its diameter varies 5 to 10 /um.

is composed of the nuclear envelope,

chromatin, the nucleolus, and nucleoplasm.


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The plasma membrane

Is about 8 nm thick

Surrounds the cell and controls chemical

traffic into and out of the cell

is selectively permeable; it allows some

substances to cross more easily than

others

Has a unique structure which determines

its function and solubility characteristics


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Lipid in plasma membrane

The lipids in the plasma membrane are

chiefly phospholipids like phosphatidyl

ethanolamineand cholesterol.

Phospholipids are amphiphilicwith the

hydrocarbon tail of the molecule being

hydrophobic; its polar head hydrophilic.
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Lipid bilayer

Cell membrane is made of a phospholipidbilayer sandwichedbetween two layers of globular protein.

The polar (hydrophilic) heads of phospholipidsare oriented towards the protein layersforming a hydrophilic zone.

The nonpolar (hydrophobic) tails of

phospholipids are oriented in between polarheads forming a hydrophobic zone.


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Role of membrane protein

transport of molecules/ions into or out of cells.

Three methods of doing this are through active,

facilitated or passive transport.

cell recognition, enzymatic activity

receptors,

cell to cell communication, attachment to the cytoskeleton and extracellular

matrix


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Role of membrane protein

transport of molecules/ions into or out of cells.

Three methods of doing this are through active,

facilitated or passive transport.

cell recognition, enzymatic activity

receptors,

cell to cell communication, attachment to the cytoskeleton and extracellular

matrix


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Types of transport

Passive Transport:

uncharged small molecules can move directly

through the membrane in the direction of high

concentration to low concentration. charge molecule (positive or negative) tend

to move to the side of the membrane that

have the opposite electrical potential.


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Types of transport

Facilitated Transport (these can be either

uniport or cotransport):

Using special channel protein to facilitate the

transport

moves with the electro-chemical gradient.
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Transport of large molecules

Endocytosis

Exocytosis


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Cell division

Mitotic division Meiotic division


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Mitotic division

During mitosis the mother cell divides

and each of the daughter cells receives achromosomal karyotype identical to that of

the mother cell


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Prophase

characterized by the gradual coiling up ofchromatin of the nucleusgiving rise to severalindividualized rod-shaped or hairpin-shapedbodies that stain intensely (the chromosomes)

The nuclear envelope remains unaltered, andthe chromosomes appear coiled in the nucleus.The centrioles duplicate and separate, and apair migrates to each pole of the cell.

Simultaneously, the microtubules of the mitoticspindle appear between the 2 pairs of centrioles.


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Metaphase

the nuclear envelope and the nucleolusdisappear.

The chromosomes migrate to the

equatorial plane of the cell, where each divides longitudinally to form 2 chromatids.

These attach to the microtubules of the

mitotic spindle at a special plaquelike,electron-dense region, the centromere(kinetochore) .


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Anaphase

the sister chromatids separate from

each other and migrate toward the

opposite poles of the cell, following the

direction of the spindle microtubules.

Throughout this process, the centromeres

move from the center, pulling along the

remainder of the chromosome .


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Meiotic division

Germinal cells (spermatogonium or

oogonium)

Goes through 2 successive divisions

Reduction by half of the number of

chromosomes and amount of DNA per cell

producing spermatid

Through an elaborate process of

cytodifferentiation spermatozoon

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