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Page 1: Organelles

UNIKL - MESTECH

NURUL NADIAH BT MOHD PAUZI (12273209046)NURASYIKIN BT MOHAMED (12273209113)ZILIYANI ATIFAH MOHAMAD ZABHI (12272209063)SITI NORFAEZAH AZLAN (12272209122)NURUL JANNAH MUHAMAD SIDEK (12272209082)SITI NOR IZ’ZAH MOHD IRAMZY (12272209072)

ORGANELLES IN CYTOPLASM

PREPARED BY:

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OBJECTIVES

Describe the structure and function of cytoplasm, cytosol and organelles

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INTRODUCTION

Cytoplasm consists of all cellular contents within the plasma membrane except for the nucleus

It has two (2) compartments:• The cytosol •Organelles (tiny sructures that perform different functions in the cell)

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CYTOPLASM

• The jellylike matrix within a cell. • Literally “cell-reforming” is the part of the cell that lies internal to the plasma membrane and external to the nucleus. • Most cellular activities are carried out in the cytoplasm.

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ORGANELLES

• Is the fluid portion of the cytoplasm that surround organelles

•Site of many chemical reactions required for a cell’s existanceenzyme in cytosol catalyze glycolisis (a series of 10

chemical reactions that produces 2 molecules of ATP from one molecules glucose)

CYTOSOL

•Perform specific function in cellular growth, maintenance and reproduction

•Its own set of enzyme that carry out specific reactions

•Serves as a functional compartment for specific biochemical process

•Cooperate to maintain homestasis

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CYTOSKELETON

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CYTOSKELETON a network of fibers throughout the cell's cytoplasm a dynamic structure that maintains:

cell shape protects the cell enables cellular motion

plays important roles in both intracellular transport cellular division

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WHAT ARE SOME DISTINGUISHING CHARACTERISTICS?

The cytoskeleton is composed of at least three different types of fibers:

Microfilaments Intermediate filamentsMicrotubules

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COMPARISON

Cytoskeleton type

Dia-meter(nm)

Structure Subunit examples

Microfilaments 6 double helix actinIntermediate filaments

10 two anti-parallel helices/dimers, forming tetramers

vimentin (mesenchyme)

glial fibrillary acidic protein (glial cells)

neurofilament proteins (neuronal processes)

keratins (epithelial cells)

nuclear laminsMicrotubules 23 protofilaments, in

turn consisting of tubulin subunits

α- and β-tubulin

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MICROFILAMENTS

resisting tension maintaining cellular shape forming cytoplasmatic protuberances participation in some cell-to-cell or cell-to-matrix

junctions essential to transduction produce cytoplasmic streaming in most cells

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INTERMEDIATE FILAMENTS

Found in parts of cells subject to mechanical stress Help anchor organelles such as nucleus Help attach cells to one another

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MICROTUBULES

They play key roles in: intracellular transport (associated with dyneins and

kinesins, they transport organelles like mitochondria or vesicles)

Participate in the movement of specialized cell projections such as cilia & flagella

the mitotic spindle synthesis of the cell wall in plants

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MITOCHONDRIA

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MITOCHONDRIA• small, bean shaped or rod shaped, threadlike organelles with inner and outer membranes seperated by a space.• made up of an unusual double membrane.• the outer membrane surrounds the entire organelles, the inner membrane contains numerous folds called cristae.• cristae increases the surface area exposed to the fluid contents or matrix of the mitochondria

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Metabolic enzymes in the matrix catalyze energy-producing reactions. the major sites of adenosine triphosphate (ATP) production within the cells ATP is the major energy source for most chemical reactions within the cells. Cells with a large energy requirement have more mitochondria than cells

that require less energy. Carry out aerobic respiration in which oxygen is required to allow the

reactions that produce ATP to proceed. Cells that carry out extensive active transport , contain many mitochondria. When muscles enlarge as a result of exercise, the mitochondria increase in

number within the muscle cells and provide the additional ATP required for muscle contraction.

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LYSOSOMES•STRUCTURE•FUNCTION •ACTION•DISORDER

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Lysosome

Golgi apparatus

The interior of lysosome has a pH of 5 (more acidic than cytosol)

Membrane – enclosed vesicle form from Golgi complex (GA)

Contain digestive and hydrolytic enzyme Brake down of molecules once lysosomes fuse with vesicles formed during endocytosis

Also known as "suicide-bags"

Lysosomal enzyme work best at acidic pH

Includes transporter that move the final products of digestion into cytosol glucose, fatty acid

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Functions:Digest substance that enter a cell via endocytosis

Transport final products of digestion into cytosol

Carry out autophagy ( digestion of worn out organelles)-engulf organelles, digest it and return the components to the cytosol for reuse- During the digestion, the organelles to be digested is enclosed by a membrane derived from ER to create a vesicle called AUTOPHAGOSOME, which then fuse with lysosome.

Carry out extracellular digestion-the head of sperm cell release lysosomal enzymes that aid its penetration of the oocyte by dissolving its protective coat

Carry out autolysis ( digestion of entire cell)-occur in some pathological condition-tissue deterioration that occur just after the death

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Action of Lysosomes

A vesicle forms around material the cell.

The vesicle is pinched off from the cell membrane and becomes a separate vesicle inside the cell.

A lysosome is pinched off the Golgi apparatus

The lysosome fuses with the vesicle.

The enzymes from the lysosome mix with the material in the vesicle, and the enzyme digest the material.

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Lysosome engulf organelle digest it and return the digested components to the cytosol to be reuse (AUTOPHAGY)

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Disorder : Tay – Sachs Disease

Inherited condition characterized by the absence of single lysosomal enzyme called Hex A

Caused of faulty or absent lysosomal enzymes

Hex A – broke down a membrane glycolipid called ganglioside GM2 that is prevalent in nerve cells

As the excess ganglioside GM2 accumulates,the nerve function less efficiently

Children with Tay – Sachs disease experience:• Seizure• Muscle rigidity• Gradually become blind • Demented

Test now can reveal weather an adult is a carrier of defective gene

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ENDOPLASMIC RETICULUM

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ENDOPLASMIC RETICULUM (ER)

Network of membranes in the form of flattened sacs or tubules.

Extends from the nuclear envelope (membrane around the nucleus), to which it is connected, throughout the cytoplasm.

So extensive that is constitutes more than half of the membranous surfaces within the cytoplasm of most cells.

Part of the endomembrane system. Two regions of the ER that differ in both structure and

function:i) Rough endoplasmic reticulumii) Smooth endoplasmic reticulum

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Rough endoplasmic reticulum RER receives its name from the appearance of ribosomes that attached to the cytoplasmic side of the membrane. Location : Connected to nuclear membrane and extending out into cytoplasm. Function : i) The outer surface of RER is studded with ribosomes and it made the RER responsible for protein synthesis. Protein synthesized by ribosomes attached to RER enter spaces within the ER for processing and sorting. ii) Produces secretory proteins, membrane proteins, and many organellar protein. iii) Incorporated into the membrane of organelles ,secreted into plasma membrane or secreted via exocytosis

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Smooth endoplasmic reticulum Extends from the RER to form a network of membrane tubules. Not have ribosomes on the outer surface of its membrane. Location : Located in the cytoplasm of cells. Function : i) synthesizes fatty acids and steroid, such as estrogens and

testosterone. ii) in the liver cells, enzymes of the smooth ER help release glucose

into the blood-stream and inactivate or detoxify lipid-soluble drugs and other potentially harmful substances, for example alcohol.

iii) stores and release calcium ions that trigger contraction in muscle cells..

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RIBOSOMES

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RIBOSOMES

STRUCTURE

ribosome compose of two unit : large subunit and small subunit

ribosomal subunit are synthesis by nucleolus

They are the most numerous organelles in almost all cells

Ribosomes are from 15 to 20 milimicrons in diameter (i.e. very small

ribosome usually aggregate to form polysome

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LOCATION

suspended in the cytosol-called free ribosome

bound to RER-called bound ribosome

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FUNCTION OF RIBOSOME

Site for protein synthesis -ribosome contain binding site for mRNA and tRNA molecules. ribosome move along mRNA strand to translate the genetic code and then synthesis a polypeptide chain

the protein produce by ribosome on Endoplasmid reticulum then transport to Golgi apparatus to be process into digestive enzyme and hormone for Exocytosis

besides, free ribosome in cytoplasm synthesis protein and enzyme for intracellular use

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GOLGI APPARATUS

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STRUCTURE•Consist of a stack of flattened,slightly curved,membrane-enclosed sacs or cisternae

•The sacs within each Golgi do not come into physical contact with one another

•One side of the stack faces the endoplasmic reticulum and serves as a site of entry for vesicle from the endoplasmic reticulum that contain cellular products.

•The opposite side of Golgi stack of sacs faces towards the plasma membrane.As the cellular product passes towards that side it is chemically modified and then released within vesicles that are buds off the sacs.

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FUNCTIONS

•Modifies,sorts,packages and transport protein received from the rough ER

•Forms secretory vesicles that discharge processed proteins via exocytosis into extracellular fluid

•Forms membrane vesicles that ferry new molecules to the plasma membrane

•Forms transport vesicles that carry molecules to other organelles such as lysosomes.

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References:

1.Seeley, Stephens, Tate (2005) Essentials of Anatomy and Physiology, 5th edition, Mc – Graw Hill

2.Gerard J. Tortora (2008) Principles of Anatomy and Physiology. 11th edition,Wiley Higher Education, page 74 - 82