Cell organelles

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Basic unit- CELL AND ITS ORGANELLES

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GOOD AFTERNOON 1

Cell organelles:

Dr.Shazia Pg student C ell organelles 2

CONTENTS:

INTRODUCTION. THE HUMAN CELL. CELL MEMBRANE. CELL ORGANELLES. ENDOPLASMIC RETICULUM. RIBOSOMES. GOLGI APPARATUS. LYSOSOMES. MITOCHONDRIA. CONTENTS 3

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NUCLEUS. PEROXISOMES. REFERENCES. 4

THE HUMAN CELL:

THE HUMAN CELL 5

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The word “cell” derived from a latin word “ cella ” meaning ‘store room’ or a ‘chamber’. The term cell was first introduced in biology by a british scientist- robert hooke (1663) CELL is the smallest living unit of organisation in the body Cell is the structural and functional unit of the living matter and is capable of carrying on the processes of life independently. 6

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The human body has an estimated cell population of 100 trillion cells. Cell is not merely a bag of fluid, enzymes and chemicals. It also contains highly organized physical structures called intracellular organelles Most mammalian cell lie within the size range 5-50 micrometers in diameter; e.g resting lymphocytes are amongst the smallest and megakaryocytes of the bone marrow the largest (200 micrometers). 7

Prokaryotes and Eukaryotes:

P rokaryotes and Eukaryotes 8

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The main cell structures are: Plasma membrane or cell membrane. The Cytoplasm and The cell organelles. 9

Cell membrane- specialists in communicating:

Remarkable structure that surrounds the cell. Nucleus and cytoplasm are covered by cell membrane. Cell membrane consists mainly of phospholipids and protein molecules. Cell membrane is about 7.5nm thick. Its function is to take part in the maintenance of the internal environment by active transport of ions and nutrients. Cell membrane- specialists in communicating 10

Cell organelles:

Organelles meaning “little organs”. A membrane -bound compartment or structure in a cell that performs a special function . C ell organelles 11

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Cell organelles are of 2 types.. Membranous Organelles: Rough Endoplasmic reticulum. Smooth endoplasmic reticulum. Mitochondria. Golgi. Lysosomes. 12

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Non membranous Organelles . Ribosomes . Cytoskeletal structures. 13

Mitochondria- cellular power plants:

M itochondria- cellular power plants Mitochondria has highly organised molecular structure. Ovoid, elongated thread like structures of 0.5µm to 1µm in diameter and roughly 5µm to 10µm in length mitochondria are the only organelles to have their own genetic material. In EM it can be seen that mitochondria are bounded by double unit membrane. These membrane are separated by narrow intramembranous space 14

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Inner membrane is four or five times larger than outer membrane. Outer membrane is fairly permeable, inner membrane is highly selective . Interior of the mitochondrian is filled with mitochondrial matrix of slightly higher electron density than the surrounding cytoplasm. Mitochondria are renewed on a continuous basis throughout the cell cycle. 15

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Mitochondria surronded by trilaminar double membrane, the inner one of which remains folded and forms number of partitions- Cristae Mitochondriales . The number and size of mitochondria give an indication of the energy requirements. Mitochondria primarily concerned with the chemical process by which energy is made available to the cell in the form of ATP ATP is often referred to as the energy “currency of cell” main site of aerobic respiration. 16

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Mitochondrial DNA:

This DNA is inherited maternally . Mitochondrial matrix contains 2r RNA and 22 tRNA`s used in translation of mRNA (synthesizes 37 proteins of their own). encodes 13 enzymes , involved in oxidative phosphorylation ( cytochrome b and 3 subunits of cytochrome : 7 subunits of NADH dehydrogenase ) The mutations of mtDNA are more likely to cause muscular dysfunctions . M itochondrial DNA 18

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Mitochondria are also significant participants in many versions of apoptosis , and altered mitochondrial function appears to be associated with various cancerous changes in cells. In cell hypertrophy- increase in number of mitochondria in cells In cell atrophy- decrease in no. of mitochondrias in cells. Mitochondria are comparatively rare in cancer cells which derive their energy from anaerobic glycolysis . 19

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Mega mitochondria seen in liver in alcoholic liver disease and nutritional deficiency. In mitochondrial myopathies - increased no. of mitochondria, large in size, abnormal cristae , crystalloids Bening tumors found in salivary glands thyroid, parathyroid, kidneys consists of abundant large mitochondria giving eosinophilic appearance . 20

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Mitochondrial damage in β cells- diabetes. Dysfunction in heart- cardio myopathy . Dysfunction in neurodegenarative diseases- parkinsons disease..etc 21

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Ribosomes:

Also called as claude`s particles. Ribosomes are the structures where proteins are made. A ribosome is an organelle composed of ribosomal RNA and ribosomal proteins known as a Ribonucleoprotein , at which protein synthesis takes place. It has approximately 37 - 62% RNA, and rest are made up of proteins. Ribosomes are tiny particles which are about 200Å. Ribosomes 23

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They are produced in the nucleolus The ribosomes has two categories: Those free to roam in the cytoplasm . Those bound to endoplasmic reticulum. Prokaryotes have 70S ribosomes (large) 50S subunit,and (Small) 30s subunit . Eukaryotes have 80S ribosomes (large) 60S subunit. (small) 40S 24

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Ribosomes are composed entirely of rRNA and ribosomal proteins and are classified under n0n-membranous organelles as they themselves possess no membrane component. Ribosomes are indistinguishable at LM level In EM cytoplasm contains abundance of free ribosomes . 25

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Defects in the function of ribosome may cause: Anemia( 5 infants in 1 million are affected) Cartilage hair hypoplasia Shwachman diamond syndrome.(1 child in every 100,000 is born with ribosomal disorder) Dyskeratosis congenita (1 child in 1 million is affected) ( Williams hematology marshall lichtman , thomas kipps M.D. et al 2010.) 26

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ENDOPLASMIC RETICULUM:

Garnier named ergastoplasm Claude named microsomes . Porter named endoplasmic reticulum . Endo plasmic- within the cytoplasm. Reti culum- strands and vesicles arranged in network. Consists of parallel membrane bound channels. All the membranes of ER are interconnected with plasma membrane on one hand and outer nuclear membrane on the other hand. ENDOPLASMIC RETICULUM 28

Types of Endoplasmic reticulum:

Two morphologically and functionally distinct differentiation of organelle are identified as Rough endoplasmic reticulum/ granular / α - cytomembranous . Smooth endoplasmic reticulum/ agranular / β - cyto membranous. Types of E ndoplasmic reticulum 29

Functions of endoplasmic reticulum:

They may serve specialized functions in the cell including protein synthesis, sequestration of calcium, production of steroids, storage and production of glycogen, and insertion of membrane proteins. F unctions of endoplasmic reticulum 30

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Rough Endo-reticulum:

Reticulum is studded with osmeophilic granules which were earlier called as palade granules- ribosomes . Large parallel flattened membranous sacs called cisternae studded with ribosomes . It is involved in protein production and protein folding . 13 million ribosomes are present on RER in an average liver cell RER is found throughout the cell but the density is higher near the nucleus and golgi . In the lumen of RER , quality control checking is carried out. R ough Endo-reticulum 32

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Functions of rough ER: Proteins synthesized in the attached ribosomes enter the lumen of the reticulum, from which they are ultimately distributed to other organelles. 33

Smooth endoplasmic reticulum:

Do not possess osmeophilic granules- the ribosome Smooth ER is devoted almost exclusively to the manufacture of lipids e.g .. liver cells and steroid hormones. e.g.. adrenal cortex and endocrine glands. It also plays a pivot role in detoxifying a number of organic chemicals converting them to safer water soluble products.eg. In Liver cells smooth ER are found in larger quantities. S mooth endoplasmic reticulum 34

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Smooth ER is very abundant in leydig cells of testies Cells of corpus luteum Parietal cells of gastric mucosa (Alberts et al,molecular biology of the cell garband publishing 1994) Functions of smooth ER: Contains enzymes for fatty acid and steroid synthesis. Stores and releases calcium, which controls various cell activities. 35

GOLGI APPARATUS:

In 1898, an Italian neurologist Camillo Golgi named this structure as Golgi apparatus, Golgi complex or simply as Golgi. The structure looks like a network of fine threads(Golgi network) or irregular granular material The main structural unit of Golgi body is a flattened membranous vesicle described as Golgi saccule It is usually located near the nucleus and in the gland cells found between the nucleus and the apex of the cell GOLGI APPARATUS 36

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Cisternae stack have five functional regions Cis golgi network, cis golgi,medial golgi , trans golgi , trans golgi network. Vesicles from ER fuse with the cis golgi network,, travel upto trans golgi network where they are packaged and sent to the required destination. GERL complex does not appear to be functionally separate from the Golgi apparatus. ( THE JOURNAL OF CELL BIOLOGY " VOLUME 90, 1981) Part of the GERL complex : Intracellular stack of membrane bounded vesicles in which glycosylation and packaging of secreted proteins  takes  place. 37

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3 main structures can be observed under EM : Flattened vesicles. secretory vesicles. Microvesicles . The main structural unit of golgi apparatus is flattened membrane vesicle described as GOLGI SACCULE. Golgi saccules arranged in golgi stacks. Each stack of saccules in golgi complex possess Forming face( Cis – face) Maturing face(Trans- face) 38

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Defects in various aspects of golgi function leads to Congenital glycosylation disorders. Muscular dystrophy. Diabetes. Cancer. Cystic fibrosis. (UNGAR.D. GOLGI PROTEIN GLYCOSYLATION AND ASSOCIATED DISEASES, CELL AND DEVELOPEMENTAL BIOLOGY20,762-769(2009 ) 39

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LYSOSOMES:

Vesicles of 0.5µm in diameter is manufactured in the Golgi apparatus. Size and shape of the lysosomes change with the stage of their activity. pH within the lysosome is distinctly acidic . Enzymes of lysosomes are potent enough to digest its own cellular contents in which it inhabits , (“suicide bag”) lysosomes that digest the degenerated mitochondria are referred to as cytolysosomes ,( “digestive bags” ) Lysosomes hauls away unusable waste and dumping it outside the cell . (“cellular garbage disposal`s”) LYSOSOMES 41

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Contain 50 different hydrolytic enzymes that can breakdown bacteria and debris that have been taken into the cell. Enzymes found are ribonucleus , deoxyribonucleus , phosphatase , collagenase and cathepsins A lysosome that buds from the trans face of a golgi stack is termed as primary lysosome . 44

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The staining reveals a crystal like matrix in spherical vesicles. The crystalloid matrix is urate oxidase. All enzymes of lysosomes are produced in the endoplasmic reticulum, and transported and processed through the Golgi apparatus. Each acid hydrolase is targeted to lysosome by phosphorylation. Cytochemically , the enzyme alkaline phosphatase (beta- glyceryle phasphatase ) is used as a marker of lysozymes for light & EM. Lysosomes required to digest tails of tadpoles and to remove the web from the fingers of a 3-6 month old fetus. 45

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The most common LSDs are: Tay sachs diesase Niemann - pick disease Krabbe`s disease Gaucher disease. Pompe`s disease. Slicosis and asbestosis Rhematoid arthritis. Lysosomes are involved in the pathogenesis of gout Tay- sachs disease is the most progressive in the major group of genetic diseases. 46

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NUCLEUS - THE CELL`S BRAIN:

NUCLEUS - THE CELL`S BRAIN 48

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In cell biology, the nucleus (from Latin nucleus or nuculeus , kernel) is found in all eukaryotic cells. The nucleus was discovered around 1833 by botanist Robert Brown. The nucleus varies in diameter from 11 to 22.25 micrometres Usually the nucleus is round and is the largest organelle in the cell. 49

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Structure / Components- Nuclear envelope- regulate what enters and leaves nucleus ( Nuclear pores ) Nucleolus -makes ribosomes Genetic Material- DNA Chromatin – DNA uncoiled, threadlike, Not Divisional Chromosomes –DNA is condensed, Divisional Nucleoplasm -fluid inside nucleus Function The nucleus of a eukaryotic cell directs the cell's activities and stores DNA. 50

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Nucleolus is a "sub organelle" of the cell nucleus discovered by Fontana. Nucleolus comprises the Irregular network or rows of fine granules nucloelonema as seen in EM The nucleolus loses its identity during cell division. Nucleolus contains still smaller nucleus known as nucleo-lolus or nucleo-linus or nucleolo -nucleus . Mark.c.alliegro et al M.C.proc.natl.acad.sci.U.S.A,(2010) 51

Disorders of nucleus:

Defective nucleoli have been implicated in several rare hereditary diseases, mostly neurodegenerative disorders such as Alzheimer’s and Huntington’s disease. nucleoli also plays a role in this disease, which is also known as “shaking palsy”. Parkinson’s disease may be caused by oxidative stress within cells due to defective nucleoli. The Journal of Neuroscience, January 12, 2011, 31(2):453– 460, DOI:10.1523/JNEUROSCI.0590-10.2011 D isorders of nucleus 52

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Kennedys disease- mutation of karyopherins . Emery dreifuss muscular dystrophy. Huntingtons disease. Fragile-x-syndrome. 53

PEROXISOMES:

They are generally less than 1 µm in diameter. Unit membrane bound organelles. Peroxisomes are also called microbodies . Contains the enzymes peroxidase and catalase which are important in metabolic reactions involving ribose peroxide. Destroy certain products formed from oxygen, notably hydrogen peroxide that can be toxic to the cell. Often seen in kidney and liver cells. PEROXISOMES 54

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Peroxisomes ar relatively large in hepatocytes and kidney cells but very small in intestine cells so called microperoxisomes Peroxisomal disorders: Zellweger cerebrohepatorenal syndrome Neonatal adreno leukodystrophy . Infantile refsum disease . 55

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REFERENCES:

Ham `s histology david H .cormark,9 th edition Human physiology vander sherman luciano 8 th edition. Human physiology volume 1 by dr.c.c . chatterjee Review of medical physiology william F. Ganong 17 th edition. Robbins pathologic basis of disease 8 th edition. Concise medical physiology by chaudhari . REFERENCES 57

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Anthony `s textbook of anatomy and physiology 14 th edition. Physiological basis of medical practise 12 th edition B.I.Waverly . Moffett schauf - human physiology 2 nd edition. British society of cell biology.UK Guyton text book of medical physiology 9 th edition Mitochondria as therapeutic targets in diseases, jin han , shey - shing sheu , seoul national university , korea 58

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Neuropathology by dimitri d agamanolis , northeast ohio medical university. Composition and Dynamics of the Nucleolinus, a Link between the Nucleolus and Cell Division Mark C. Alliegro , steven Hartson and  Mary Anne Alliegro received December 27, 2011. Campbell and rece , book of biology 8 th edition. Shafers textbook of oral pathology 6 th edition. Images from Google. 59

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THANK YOU 60

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