Biology 6093 (Text): Principles of Biology + Nutrition & Transport in Humans

Cells ● To view organelles, electron microscope (x200000) is used, ascomparedtolight microscope(x1000)● Longitudinal section: cutting across the length of the cell, viceversafor transversesection● Theprotoplasmconsistsof thecytoplasmandthenucleusPart Function&Structure PlasmaMembrane Madeof lipidsandproteins Partiallypermeablemembrane Controls substances entering and leaving the cell byallowing only substances smaller than its pores to passthrough Cytoplasm Siteof most cell activities Containsorganelles: RoughEndoplasmicReticulum(R.E.R.) Siteof proteinsynthesis Network of flattened spaces linedwith amembrane Appears rough because small ribosomesareattachedtoitsouter surface Outer surface is continuous with thenuclear envelope SmoothEndoplasmicReticulum Tubular anddonot haveribosomes Synthesisesfatsandsteroids Converts harmful substances intoharmlessmaterialsviadetoxification Ribosomes Attached ribosomes (R.E.R.) synthesiseproteinsthat aretransportedout of cells Free ribosomes (cytoplasm) synthesiseproteinsthat areusedwithinthecell

GolgiApparatus Stack of flattened spaces surroundedbyamembrane Chemically modifies substances madebytheendoplasmicreticulum Stores andpackages themin vesicles forsecretionout of thecell Vesicles Tiny spherical spaces enclosed by amembrane Transport substanceswithinthecell: 1. Small vesicles containingsubstances made by theendoplasmic reticulumare pinchedofromtheendoplasmicreticulum 2. The small vesicles fuse with theGolgi apparatus and release theircontentsintotheGolgi apparatus 3. The Golgi apparatus chemicallymodifies the substances made bytheendoplasmicreticulum 4. Secretory vesicles containing thechemically-modified substancesare pinched o from the Golgiapparatus 5. The secretory vesicles move to theplasmamembrane 6. The secretory vesicles fuse withtheplasma membrane and theircontents are released out of thecell Mitochondrion Sausage-shaped Performs aerobic respiration in which

glucose is oxidised in the presence ofoxygentoreleaseenergy Chloroplasts Contains chlorophyll which absorbs andconverts light energy tochemical energyduringphotosynthesis Nucleus Consists of nucleolus and chromatin in nucleoplasm,whichissurroundedbyanuclear envelope Controls cell activities such as cell growth and repair ofworn-out parts Essential for cell division NuclearEnvelope Separates the contents of the nucleusfromthecytoplasm Nucleoplasm Densematerial withinthenucleus Nucleolus Makeproteinsinthecell Chromatin Made up of deoxyribonucleic acid thatstoreshereditaryinformation Chromatin threads condense intochromosomesduringcell division Cell Wall Madeof cellulose Fullypermeablemembraneandinelastic Protectsthecellsfrominjuries Giveplant cellsafixedshape Vacuole (Animal cells) Numerous small vacuoles containingwaterandfoodsubstances, whichexiststemporarily (Plant cells) One large, central vacuole containing cellsap (sugars, mineral salts and amino acids), that issurroundedbythepartiallypermeabletonoplast● Only plant cells have acell wall, chlor