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, chloroplasts andalarge, centralvacuole● Onlyanimal cellshavecentriolesandnumeroussmall vacuoles

● Dierentiation is the process by whichacell becomesspecialisedfor aspecific functions (e.g. redbloodcells, xylemvessel androothair cells)● Dierent ___ forming ___ work together to performa specificfunction (except in the case of cells of the same type formingsimpletissues) Cells ➜ SimpleTissue ➜ Organs ➜ OrganSystem ➜ Organ-ismComplexTissue Movement of Substances Diusion Osmosis ActiveTransport Directionof netmovement Fromaregionof higherconcentrationtoaregionoflowerconcentration Fromasolutionof higher waterpotential toasolutionoflower waterpotential Fromaregionof lowerconcentrationtoaregionofhigherconcentration Downtheconcentrationgradient Downthewaterpotentialgradient Against theconcentrationgradient Particlesinvolved Any Watermolecules Any Energy? Not required Required Partiallypermeablemembrane? Not required Required ● At equilibrium, thereisnonet movement of substancesacrossthepartially permeable membrane, but there is still movement ofsubstances across the partially permeable membrane due toBrownianmotion● Only soluble substances can aect the water potential of asolution

Solution Dilute SameConcentration Concentrated Water potential Higher thancell Sameascell Lower thancell Typeof solution Hypotonic Isotonic Hypertonic Directionofmovement ofwater molecule Fromsurroundingsolutionintothecell viaosmosis Nonetmovement ofwatermolecules Fromthecellintothesurroundingsolutionviaosmosis Downthewaterpotentialgradient Downthewaterpotentialgradient Finalappearanceofcell Animal Cells Cell expandsandbursts Cell remainsthesameastheoriginal state Cell shrinkinsizeandbecomescrenated Plant Cells Vacuoleincreasesinsizeandpushesagainst thecellwall, exertingturgor pressureontheinelasticcell wall Cell remainsthesameastheoriginal state Vacuoledecreasesinsizeandshrinksawayfromthecell wall andthecell isplasmolysed Cell expandsandbecomesturgid Cell shrinkinsizeandbecomesflaccid● When a cell bursts, it is irreversible because the cytoplasmiccontentsarereleasedintothesolution● Importanceof turgidity:1. Plants remain upright due to turgor pressure within theircells

2. Lossof turgiditycausesplantstowilt● To reverse plasmolysis, water is addedtodilute ahypertonic soilsolution● Factorsaectingrateof diusionandosmosis:1. The steeper the concentration / water potential gradient,thefaster therateof diusion/osmosis2. The higher the surface areatovolume ratio, the higher therateof diusion/osmosis● As active transport requires energy, it only occurs in respiringlivingcells Nutrients Importanceof Humans Plants Nutrients Provideenergyfor metabolicactivities Supplyrawmaterialsfor repair of worn-out tissues Water Solvent inwhichchemicalreactiontakesplace Photosynthesis Control bodytemperaturethroughtheremoval oflatent heat whensweatevaporates Keepingplant cellsturgid,andhenceplantsupright Transport dissolvedfoodsubstances OrganicCompound Carbohydrates Fats Proteins Elements Carbon, hydrogen(H) andoxygen(O) Carbon,hydrogen, oxygenandnitrogen RatioofH: O 2:1 NilGeneral Cn H2n On

formula Simplemolecules Formed via hydrolysis in chemical digestion: a watermolecules is neededtobreak upacomplex molecule intosmaller molecules MonosaccharidesA. GlucoseB. FructoseC. Galactose FattyAcids Aminogroup(-NH2 ) Acidicgroup(-COOH)Glycerol Sidechain(R) Cannot befurther digestedintosmaller molecules Small enough to pass through the pores of plasmamembrane Complexmolecules Formed via condensation reaction: two simple moleculesare joined together to form a larger molecule with theremoval of onewater molecule Disaccharides:● Maltose(A+A)● Lactose(A+C)● Sucrose(A+B) Nil Aminoacidslinkupbypeptidebondstoformpolypeptides Polysaccharides:● Starch(A)● Cellulose(A)● Glycogen(A) Polypeptidescoiltoforma3D-molecule Tests Cut food intosmaller pieces, add1 cm 3 of water, mix wellanddecant toprepareafoodsample Reducingsugar: Ethanol emulsion Biuret Test

Benedict’stest test Starch: Iodinetest Uses Provideenergyfor cell activities Synthesisof newprotoplasmforgrowthandrepair Synthesiselubricants Insulatingmaterial toprevent excessiveheat loss Synthesisofenzymesandhormones FormnucleicacidsinDNA Reducewater lossfromskinsurface Synthesisofantibodiestocombat diseases● Benedict’stest:1. Add2cm 3 of Benedict’ssolutionto2cm 3 of foodsample2. Shakethemixtureandboil it for 2mins3. Observations:Colour Change Amount of ReducingSugar Bluesolutionremainsblue Noreducingsugar Bluetogreenprecipitate Tracesof reducingsugar Bluetoyellowprecipitate Moderateamount Bluetobrick-redprecipitate Largeamount● Iodinetest:1. Addafewdropsof iodinesolution2. Positivetest: blue-blackNegativetest: nochangeincolour● Ethanol emulsiontest:1. Add2 cm 3 of ethanol to2cm 3 of foodsampleandshakethemixture2. Positivetest: cloudywhiteemulsionNegativetest: solutionremainsclear● Biuret test:

1. Add 2 cm 3 of sodium hydroxide solution to 2 cm 3 of foodsampleandshakethemixture2. Positivetest: violet colourationNegativetest: