3. Cytoplasm

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Ajman University of Science & Technology

Histology & Cell Biology

08 01 112

Dr. Al-Moutassem Billah Khair


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THE CYTOPLASMCytoplasm is a part of protoplasm, the interior of the cell

except the nucleus.

Cytoplasm is composed of a matrix in which areembedded several components, frequently called organelles. Plus

, , .*Cytoplasmic organelles & Cytosol " fluid surrounding organelles".

The cytoplasmic organelles of two types:

Membranous organelles:

n op asm c e cu um, o g o es, oc on r a, ysosomes,Peroxisomes (Microbodies)

Non-membranous organelles:

Ribosomes, Cytoskeletal elements, Centrioles


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I. Endoplasmic Reticulum (ER):

A delicate network of membranous sacs, which- .

The connection between two sacs is an anastomosis.

It is a membrane of lipoprotein have two surfaces: one

facing the cytoplasmic domain, surrounding the ER another.

ER: membrane 5 nm thick, more stable and less fluid

vesicular, tubular .

ER is of two specialized types: Rough ( RER ) andSmooth ( SER ).


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1. Rough Endoplasmic Reticulum:The name RER alludes to the presence of ribosomes on

the cytoplasmic surfaces of the endoplasmic reticulummembranes, giving them a rough or granular appearance. Thisform of ER is prominent in cells specialized for protein

.

RER consists mainly of lamellar forms interconnected byshort tubular se ments.

The principal function of the RER is to segregateproteins destined for export or intracellular use.

Additional functions : initial glycosylation of glycoproteins, the , ,

posttranslational modifications of newly formed polypeptides.


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2. Smooth Endoplasmic Reticulum:

SER is a membranous network, which lacks the ,

appears smooth rather than granular.

of interconnected channels of variable shape and sizes than as

stacks of flattened cisternae.

SER has a variety of specialized functions such as:

*Metabolism of small molecules* Synthesis of lipids & steroids

* Cellular detoxification


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II. Ribosomes: Ribosomes are small electron-dense cytoplasmic

par c es, a ou x nm n ze. ey are compose o types of ribosomal RNA ( rRNA ) and almost 80 ribosomal

.

Each ribosome consists of two different-sized u un s. o u un s are orme w n e nuc eo us, then they leave the nucleus to the cytoplasm and

.Ribosomes play a crucial role in translating the

message ur ng pro e n syn es s.


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II. Ribosomes:

A. free or ,

B. attached to the


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Proteins synthesized for use within the cell are synthesized on

in the cell are synthesized on RER ribosomes.


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III. Gol i A aratus GA :

of three distinct smooth- membrane-limited compartments: slightly

curved stacks of 3-10 f attened cisternae, numerous of small

vacuoles at one pole of the GA.


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III. Golgi Apparatus ( GA ):

The GA completesposttranslationalmodifications andpackages and

on products thathave been

synthesized by thecell.


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III. Golgi Apparatus:

GA has convex, forming,face near the RER and

concave, maturing, faceon the opposite side.Transitional vesiclesfrom RER are

forming face for furtherprocessing in GA. after

that they detach fromthe maturing face as

.


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III. Golgi Apparatus:

GA produces three kindsof products:

Primary lysosomes

Lipoprotein vesicles


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IV. Mitochondria:

Mitochondria are spherical or filamentous mem ranous organe es . -

m wide and up to 10 mlength. These organelles

trans orm t e c emicaenergy of metabolites present

in the cytoplasm into energy that is easily accessible to the cell.

Mitochondria are

chemically composed of protein, lipids, and small

uantities of DNA & RNA.


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IV. Mitochondria:

Mitochondria are

outer mitochondrialmembrane and an innermitochondrial membrane,the latter projects folds,termed cristae, into the

interior of themitochondrion. The spacelocated between the twomembranes is calledn ermem rane space, w e

the space enclosed by theinner membrane is called

, ,space.


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IV. Mitochondria:Between the cristae is an

amorphous matrix, rich in proteinand containing some DNA and RNA.Also the matrix exhibits roundedelectron-dense granules rich in suchcations and enzymes for the citricacid (Krebs) cycle and fatty acid -oxidation.

, combined activity of extramitochondrial glycolysis and the

transport system gives rise to 36 molecules of ATP per molecules of

obtainable under anaerobic conditions(glycolysis).


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IV. Mitochondria:

Mitochondria divide toform new mitochondriaby accretion of materialthat leads to growth and

(fission) of itself.


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V. Lysosomes:

Lysosomes are membrane-limited vesicles, usually s herical about 0.05-0.5 m in size. The contain more than ort

types of hydrolytic enzymes whose main function isintracytoplasmic digestion.

Lysosomal enzymes are synthesized and segregated ine en rans erre o e , w ere e enzymes aremodified and packaged as lysosomes.

,fuse with phagocytotic vacuole or vacuole of cytoplasmic debristo form secondary lysosomes ( SL). SL are those in whichdigestion occurs.


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V. Lysosomes:After digestion,

metabolites diffuse tothe cytoplasm andundigestible compoundsare re a ne w nvacuoles, which may

dischar e outside thecell or accumulate in thecytoplasm.

Lysosomes are sites of intracellular digestion

components.


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VI. Peroxisomes: Peroxisomes (or

Microbodies): are spherical membrane-limited

organelles, about 0.5-1.2 m. Peroxisomes contain

oxidases & catalase which regulate O2 and H2O2

which could causeirreversible damage to

many important cellular constituents.

The peroxisomal enzymes are synthesized on free

transferred to peroxisomes.


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VII. Cytoskeletal Elements:

The cytoplasm contains a com lex

network of microtubules, microfilaments, and intermediate i aments.The are called the

responsible for promoting movement

and maintaining the shape and organization

.


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VII. CytoskeletalElements:

Variet of filaments

Maintain & change cell'sshape

ro uce ce movements

Types:

- Microfilaments e. . actin- Intermediate filaments

(many)

- c amen s myos n

- Microtubules: each of 13protofilaments, which containpolymere of tubulin proteins.


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VII. C toskeletal Elements: Microtubules in addition to their role in cytoskeleton

they form specialized structures, like: cilia, flagella,centrioles and basal bodies.

diameter & 0.3-0.5 m in length). Centrioles have nine

eri heral tri lets of microtubules arran ed in apinwheel fashion. Centrioles form the microtubules of mitotic spindles.


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VII. C toskeletal Elements:Cilia & flagella are movable organelles with a highly

organized microtubule core; they extend from thesurface of some cell types. Ciliated cells usually possessa large number of cilia ( 300) that are 2-10 m long.

Flagellated cells normally have only one flagellum,which ranges in length from 50 to 200 m. Both cilia &flagella have a diameter of 0.2-0.5 m and have the

same organ ze core. s core cons s s o n ne ou e sof microtubules surrounding two central microtubulespa e , axo e e .

l


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Cilia


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. y

asa o es are en ca o cen r o es an oun athe base of each cilium or flagellum. The outerm cro u u e o a r p e en s a e ap ca en o ebasal body, while the other two microtubules of the

microtubules of the ciliary or flagellar axoneme. Basal

flagella axoneme.


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3. Cytoplasm

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