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Cellular component


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  • 1. Structure & Functions of Organelles bY SHALENI KAVIRAJAN STPM BIOLOGY
  • 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 & 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 & modifies the proteins through glycosylation & 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 cell’s 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 & prevents the release of enzymes which would destroy the cell contents  Contain high conc. of hydrolytic enzymes(ribonucleas, deoxyribonucleas, carbohydrase, protease, lipase & 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 & 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 & 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 & thylakoid membrane) provides large surface area for chlorophyll & accessory pigments to be located – traps light energy & carry out production of ATP & 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 & give certain firmness in the plant cells  The primary constituents of the cytoskeleton are microtubules, microfilaments and intermediate filaments
  • 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) & myosin(found in skeletal muscles as thick filaments)
  • 13.  Exists in bundles & found in layers in the cytoplasm  dynamic - can change their length very quickly(depends on their location & functions)  Functions in: i. assist in the cleavage process during cytokinesis ii. role in cellular movements Example: cytoplasmic streaming, cell motility – phagocytosis & pinocytosis iii. maintains cell shape