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Transcript of Organelles




OBJECTIVESDescribe the structure and function of cytoplasm, cytosol and organelles

INTRODUCTIONCytoplasm 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)

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.

CYTOSOL Is the fluid portion of the cytoplasm that surround organelles Site of many chemical reactions required for a cells existance enzyme in cytosol catalyze glycolisis (a series of 10 chemical reactions that produces 2 molecules of ATP from one molecules glucose)

ORGANELLESPerform specific function in cellular growth, maintenance and reproduction Its own set of enzyme that carry out specific reactions Serves as a functional compartment biochemicalto maintain homestasis Cooperate process for specific


CYTOSKELETONa 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

WHAT ARE SOME DISTINGUISHING CHARACTERISTICS?The cytoskeleton is composed of at least three different types of fibers: Microfilaments Intermediate Microtubules


COMPARISONCytoskeleto Dian type meter Structure Subunit examples (nm) Microfilame 6 double helix actin nts Intermediat 10 two anti- vimentin (mesenchyme) e filaments parallel glial fibrillary acidic protein helices/dimers (glial cells) , forming tetramers neurofilament proteins (neuronal processes)

keratins (epithelial cells)

Microtubule s


nuclear lamins protofilaments - and -tubulin , in turn consisting of tubulin subunits

MICROFILAMENTSresisting tension maintaining cellular shape forming cytoplasmatic protuberances participation in some cell-to-cell or cell-tomatrix junctions essential to transduction produce cytoplasmic streaming in most cells


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


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


MITOCHONDRIAsmall, 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.

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.


Membrane enclosed vesicle form from Golgi complex (GA)

Lysosom eGolgi apparat us

Contain digestive and hydrolytic enzyme Brake down of molecules once lysosomes fuse with vesicles formed during endocytosis The interior of lysosome has a pH of 5 (more acidic than cytosol) Lysosomal enzyme work best at acidic pH Includes transporter that move the final products of digestion into cytosol glucose, fatty acid Also known as "suicide-bags"

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

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

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.

Action of Lysosomes

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

Disorder : Tay Sachs Disease

Caused of faulty or absent lysosomal enzymes Inherited condition characterized by the absence of single lysosomal enzyme called Hex A 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


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 reticulum ii) Smooth endoplasmic reticulum

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

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..



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


suspended in the cytosol-called free ribosome bound to RER-called bound ribosome

FUNCTION OF RIBOSOMESite 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


STRUCTUREConsist of a stack of flattened,slightly curved,membraneenclosed 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.

FUNCTIONSModifies,sorts,packages and received from the rough ER transport protein

Forms secretory vesicles that discharge processed proteins via exocytosis into extracellular fluid Forms membrane vesicles that molecules to the plasma membrane ferry new

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

References:3.Seeley, Stephens, Tate (2005) Essentials of Anatomy and Physiology, 5th edition, Mc Graw Hill 5.Gerard J. Tortora (2008) Principles of Anatomy and Physiology. 11th edition,Wiley Higher Education, page 74 - 82