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Sel adalah unit terkecil dari makhluk hidup yang membentuk struktur dan fungsi tertentu.

TRANSPOR PASIF(Transpor tanpa menggunakan energi)TRANSPOR AKTIF(Transpor dengan menggunakan energi) karena dari konsentrasi rendah tinggi Transport pada membranDIFUSIOSMOSISSederhanaTerfasilitasiDibantu dengan protein pembawa di membran palsma sehingga membentuk kanal dan molekul bergerak melintasi membranDifusi molekul air melintasi membran permeabelEndositosisEksositosismemakan(fagositosis)memuntahkanmeminum(pinositosis) STRUKTUR UMUM SELSELBAGIAN LUAR SEL (MEMBRAN DAN DINDING SEL)SITOPLASMA NUKLEUS/ INTI SELBAGIAN DALAM SEL (SITOPLASMA DAN ORGANEL)ORGANEL LAIN




GOGO2007-2008Sistem transport yang terjadi pada sel berlangsung melalui membran sel..


Extracellular fluidCholesterolCytoplasmGlycolipidTransmembraneproteinsFilaments ofcytoskeletonPeripheralproteinGlycoproteinPhospholipidsGO TO OUTLINEBAGIAN BAGIAN MEMBRAN SEL :9The carbohydrates are not inserted into the membrane -- they are too hydrophilic for that. They are attached to embedded proteins -- glycoproteins.Difusi Sederhana Mekanisme Difusi Sederhana :

DIFUSI: pergerakan molekul dari konsentrasi tinggi rendah

10Movement from high concentration of that substance to low concentration of that substance. Difusi Terfasilitasi (terbantu)Diffusion through protein channelschannels move specific molecules across cell membraneno energy needed

The Bounceropen channel = fast transportfacilitated = with helphighlow11Donuts!Each transport protein is specific as to the substances that it will translocate (move).For example, the glucose transport protein in the liver will carry glucose from the blood to the cytoplasm, but not fructose, its structural isomer.Some transport proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel through the membrane -- simply provide corridors allowing a specific molecule or ion to cross the membrane.These channel proteins allow fast transport.For example, water channel proteins, aquaporins, facilitate massive amounts of diffusion.Diffusion Mass flow process by which species change their position relative to their neighbours Driven by thermal energy and a gradient Thermal energy thermal vibrations Atomic jumpsConcentration / chemical potentialElectricGradientMagneticStress HUKUM FICKS Assume that only B is moving into A Assume steady state conditions J f(x,t) (No accumulation of matter) Flux (J) (restricted definition) Flow / area / time [Atoms / m2 / s]Ficks I law

No. of atoms crossing area Aper unit timeCross-sectional areaConcentration gradientMatter transport is down the concentration gradientDiffusion coefficient/ diffusivityAFlow direction As a first approximation assume D f(t)

Ficks first law Diffusivity (D) f(A, B, T)D = f(c)D f(c)C1C2Steady state diffusionx Concentration DiffusionSteady state J f(x,t)Non-steady stateJ = f(x,t)D = f(c)D = f(c)D f(c)D f(c)Ficks II lawJxJx+xx

Ficks first law

D f(x)

RHS is the curvature of the c vs x curvex c x c +ve curvature c as t ve curvature c as t LHS is the change is concentration with time

Solution to 2o de with 2 constantsdetermined from Boundary Conditions and Initial Condition

Erf () = 1 Erf (-) = -1 Erf (0) = 0 Erf (-x) = -Erf (x)u Exp( u2) 0AreaABApplications based on Ficks II lawx Concentration Cavg tt1 > 0 | c(x,t1)t2 > t1 | c(x,t1)t = 0 | c(x,0)A & B welded together and heated to high temperature (kept constant T0)Fluxf(x)|tf(t)|xNon-steadystate If D = f(c) c(+x,t) c(-x,t) i.e. asymmetry about y-axis C(+x, 0) = C1 C(x, 0) = C2C1C2 A = (C1 + C2)/2 B = (C2 C1)/2Determination of Diffusivity

Temperature dependence of diffusivityArrhenius typeApplications based on Ficks II lawCarburization of steel Surface is often the most important part of the component, which is prone to degradation Surface hardenting of steel components like gears is done by carburizingor nitriding Pack carburizing solid carbon powder used as C source Gas carburizing Methane gas CH4 (g) 2H2 (g) + C (diffuses into steel)x 0C1CS C(+x, 0) = C1 C(0, t) = CS A = CS B = CS C1Approximate formula for depth of penetration


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