BIOLOGY Form 4 CHAPTER 2.1Cellular Structures and Functions1. Nucleus ( Largest Organelle in cell )i.Large, spherical and dense organelleii.Control all the cellular activities.iii.Three main components a.nuclear membrane/nuclear envelope ( inner membrane / outer membrane ) -seperate the contents of nucleus from cytoplasmb.chromatin ( uncondensed chromosome ) - Carry genetic information in form of DNA( deoxyribonucleic acid ).Information carried by DNA directs and controls cellular activities, like protein synthesis. These proteins determine characteristics and metabolic functions of cell.c.Nucleolus - a darker and dense region2. Endoplasmic reticulum ( ER )i.consists of an entensive network of folded membrane forming interconnected tubes and sacs in the cytoplasmii.membrane of ER physically continuous with nuclear membrane.iii.two types of ERrough ER + smooth ERa. Rough ERHas ribosomes attacted to surfaceTransport proteins synthesised by ribosomes and enclose them into versicleb. Smooth ERSynthesises and transport lipids ( phospholipids and steroids ).Carry out detoxification of drugs and metabolis by-products.3. Ribosomei.Compact,spherical organelle attached to rough ER or free in cytoplasm.ii.2 types : a. Free - unbound in the fluid cytoplasm, produce protein for use in cell. b. Bound - attached to the RER, produce protein for export or for plasma membrane.iii.Consists of 2 sub-units(large+small)made of RNA(ribonucleic acid)+protein.iv.Synthesises proteins that store in chromatin.4. Plasma membranei.Made of phospholipids bilayer with proteinsii.Thin, flexible layers form outer boundry.(seperates contents of cell from its external environment)iii.Semi-permeable barrier.(regulate the movement of substances in and out of the cell / control the movement of substances across the cell)iv.Allows the exchange of nutrients, respiratory gases and waste products between the cell and its external environment.5. Cytoplasmi.Fluid portion = "cytoplasm"ii.Jelly-likeiii.Contains organic+inorganic substances(water with dissolved salts, nutrients and enzymes)iv.Acts as a medium for biochemical/metabolic reactions.v.Provide substances obtained from external environment to the organelles6. mitochondrioni.Cylindrical-shaped/oblong-shapedii.Double membrane(outer+inner membrane)iii.Sites of cellular respiration.iv.Release energy in form of ATP(adenosine triphosphate) through oxidation of food substances.7. Golgi apparatusi.Consists of a stack of flattened membrane-bound sacswith budding vesicle around itii.Transport vesicle from ER fuse into GA modifies, sorts and packages proteins into secretory vesicle.iii.Secretory vesicle buds off, leave GA and travel to mitochondrion, other organelles or plasma membrane.8. Centriole (animal only)i.Small cylindrical structures outside nucleus that occur in pairs in animal cellii.Composed of microtubulesiii.Form spindle fibres during cell division in animal celliv.Synthesise cilia and flagella of small organism9. Chloroplast (plant cell only)i.Lens-shaped organelleii.Internal chloroplast membranes contain green pigment,chlorophyll.iii.Chlorophyll traps sunlight to carry out photosynthesis.10. Vacuolei.Fluid-filled sac surrounded by tonoplast (semi-permeable membrane)ii.Fluid in vacuole in cell sap (water+dissolved substances)iii.Fresh water microorganisms like paramecium sp. have contractile vacuole and food vacuole.iv.Contractile vacuole regulates the balance of water in cell(osmoregulation).11. Lysosomei.Sphericalii.Formed by pinching off from GAiii.Membrane-bound sacs with hydrolytic enzymes(digestive enzymes).iv.Hydrolytic enzymes break down/digest unwanted molecules or worn out organelles for cell renewal.12. Cell wall (plant cell only)i.Rigid outer layerii.Composed of cellulose, tough, fibrous CHOiii.Permeable to all fluids- has tiny pores that allows substances to move freely in and out of plant cell.iv.Maintain the shape of plant cell.v.Provides mechanical strength to support the plant cell.vi.Protect plant cell from bursting when too much water entering the cell.