Cell organelles (2)

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  • 2. Dr.Shazia 2
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  • 6.  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
  • 7.  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
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  • 9. The main cell structures are: Plasma membrane or cell membrane. The Cytoplasm and The cell organelles. 9
  • 10.  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. 10
  • 11.  Organelles meaning “little organs”. A membrane -bound compartment or structure in a cell that performs a special function. 11
  • 12.  Cell organelles are of 2 types.. Membranous Organelles:1. Rough Endoplasmic reticulum.2. Smooth endoplasmic reticulum.3. Mitochondria.4. Golgi.5. Lysosomes. 12
  • 13.  Non membranous Organelles.1. Ribosomes.2. Cytoskeletal structures. 13
  • 14.  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
  • 15.  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
  • 16.  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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  • 18.  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 . 18
  • 19.  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
  • 20.  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
  • 21.  Mitochondrial damage in βcells- diabetes. Dysfunction in heart- cardio myopathy. Dysfunction in neurodegenarative diseases- parkinsons disease..etc 21
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  • 23.  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. 23
  • 24.  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
  • 25.  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
  • 26.  Defects in the function of ribosome may cause:1. Anemia( 5 infants in 1 million are affected)2. Cartilage hair hypoplasia3. Shwachman diamond syndrome.(1 child in every 100,000 is born with ribosomal disorder)4. 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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  • 28.  Garnier named ergastoplasm Claude named microsomes. Porter named endoplasmic reticulum . Endoplasmic- within the cytoplasm. Reticulum- 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. 28
  • 29.  Two morphologically and functionally distinct differentiation of organelle are identified as1. Rough endoplasmic reticulum/granular/α- cytomembranous.2. Smooth endoplasmic reticulum/agranular/β-cyto membranous. 29
  • 30.  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. 30
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  • 32.  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. 32
  • 33.  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
  • 34.  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. 34
  • 35.  Smooth ER is very abundant in1. leydig cells of testies2. Cells of corpus luteum3. 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
  • 36.  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 36
  • 37.  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
  • 38.  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 possess1. Forming face(Cis – face)2. Maturing face(Trans- face) 38
  • 39.  Defects in various aspects of golgi function leads to1. Congenital glycosylation disorders.2. Muscular dystrophy.3. Diabetes.4. Cancer.5. Cystic fibrosis.(UNGAR.D. GOLGI PROTEIN GLYCOSYLATION AND ASSOCIATED DISEASES, CELL AND DEVELOPEMENTAL BIOLOGY20,762-769(2009) 39
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  • 41.  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”) 41
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  • 44.  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
  • 45.  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
  • 46.  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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  • 49.  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
  • 50.  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 cells activities and stores DNA. 50
  • 51.  Nucleolus is a "sub organelle" of the cell nucleus discovered by Fontana. Nucleolus comprises theIrregular 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
  • 52.  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 52
  • 53.  Kennedys disease- mutation of karyopherins. Emery dreifuss muscular dystrophy. Huntingtons disease. Fragile-x-syndrome. 53
  • 54.  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. 54
  • 55.  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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  • 57.  Ham`s histology david H .cormark,9th 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 17th edition. Robbins pathologic basis of disease 8th edition. Concise medical physiology by chaudhari. 57
  • 58.  Anthony`s textbook of anatomy and physiology 14th edition. Physiological basis of medical practise 12th edition B.I.Waverly. Moffett schauf- human physiology 2nd edition. British society of cell biology.UK Guyton text book of medical physiology 9th edition Mitochondria as therapeutic targets in diseases, jin han , shey-shing sheu, seoul national university ,korea 58
  • 59.  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 8th edition. Shafers textbook of oral pathology 6th edition. Images from Google. 59
  • 60. THANK YOU 60