Cellular component

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<ul><li> 1. Structure &amp; Functions of Organelles bY SHALENI KAVIRAJAN STPM BIOLOGY </li></ul> <p> 2. GOLGI APPARATUS are stacks of flattened, hollow cavities enclosed by membranes, which are often continuous with the membranes of the ER usually located near to the nucleus &amp; ER these stacks of flattened sacs / cavities are called cisternae. Each sac in the organelle contains enzymes that modify proteins Functions in modification, assembly, packaging, storage and secretion of substances. Golgi Apparatus 3. Cis-end(convex) receives newly manufactured proteins from ER, stores &amp; modifies the proteins through glycosylation &amp; adds sugar molecules to form glycoprotein.The modified proteins are then transported into vesicles that bud off at the trans-end(concave) carrying secretion of protein, glycoprotein / lipid. The contents are released to the cells exterior by exocytosis. 4. LYSOSOMES special vesicles(spherical) which are formed by the Golgi apparatus. The membrane(single layer of lipoprotein) is resistant to digestion &amp; prevents the release of enzymes which would destroy the cell contents Contain high conc. of hydrolytic enzymes(ribonucleas, deoxyribonucleas, carbohydrase, protease, lipase &amp; phosphatase) at pH value of 4 to 5(acidic) functions in : 1) cellular digestion 2) autophagy or disposal of damaged cell/worn out components like mitochondria 3) breakdown of a whole cell/autolysis (ex: happens in the tail of tadpole where the digestion products are used for building lungs &amp; adult skin). For this reason, they are sometimes called suicide sacs. 5. are known to contain over 40 different enzymes that can digest almost anything in the cell,including proteins, RNA, DNA, and carbohydrates. also appear to perform other digestive processes, such as those connected with phagocytosis and pinocytosis. Lysosomes also helps in destroying bacteria invasion 6. RIBOSOMES Found attached to the ER forming RER Occur singly or group together forming polysomes consist of rRna(produced in the nucleolus) and proteins each ribosome is made of 2 non-identical subunits large &amp; small (spheroid in shape) Provide site for synthesis of proteins(formation of peptide bonds - amino acid are joined to form polypeptide/protein) 7. Ribosome Structure Front View Large Subunit { Stalk, Centra Ridge, Wing} Small Subunit { Platform, Cleft,, Head} 8. CHLOROPLAST large plastids found only in the photosynthetic tissues of plant cell these are the double-membrane bound organelles has a system of membranous flattened sacs(thylakoids) stacked to form granum(where chlorophyll is located). site of photosynthesis 9. Intergranal lamella connects one thylakoid of a granum to another granum. The fluid outside the thylakoid is the stroma. It(grana &amp; thylakoid membrane) provides large surface area for chlorophyll &amp; accessory pigments to be located traps light energy &amp; carry out production of ATP &amp; NADPH stroma has enzymes to carry out light-independent reaction(Calvin cycle) forming high energy organic molecules such as ; sugar molecules 10. CYTOSKELETON The network of filamentous proteins structures within the cell that determines the 3-D shape of animal cells &amp; give certain firmness in the plant cells The primary constituents of the cytoskeleton are microtubules, microfilaments and intermediate filaments 11. MICROTUBULES 12. MICROFILAMENT long, thin, contractile rods(6-7 nm in diameter) that appear to be responsible for the movement of cells (both external and internal movement). composed of one/two types of protein-actin(found in skeletal muscles as thin filaments) &amp; myosin(found in skeletal muscles as thick filaments) 13. Exists in bundles &amp; found in layers in the cytoplasm dynamic - can change their length very quickly(depends on their location &amp; functions) Functions in: i. assist in the cleavage process during cytokinesis ii. role in cellular movements Example: cytoplasmic streaming, cell motility phagocytosis &amp; pinocytosis iii. maintains cell shape 14. INTERMEDIATE FILAMENTS </p>

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