Key Difference – Kd vs Km
Kd thiab Km yog qhov sib npaug. Qhov sib txawv tseem ceeb ntawm Kd thiab Km yog Kd yog qhov ntsuas kub tsis tu ncua thaum Km tsis yog qhov ntsuas kub tsis tu ncua.
Kd hais txog kev sib cais tas li thaum Km yog Michaelis tas li. Ob qho tib si no tseem ceeb heev hauv kev txheeb xyuas qhov ntau ntawm cov tshuaj tiv thaiv enzymatic.
Kd yog dab tsi?
Kd yog dissociation tas li. Nws tseem hu ua equilibrium dissociation tas li vim nws siv nyob rau hauv equilibrium systems. Lub dissociation tas li yog qhov sib npaug ntawm qhov kev xav uas qhov sib xyaw loj hloov mus rau hauv cov khoom me me reversibly. Cov txheej txheem ntawm kev hloov dua siab tshiab no tseem hu ua dissociation. Ib qho ionic molecule ib txwm dissociates rau hauv nws cov ions. Ces qhov dissociation tas li los yog Kd yog ib tug kom muaj nuj nqis qhia txog qhov uas ib yam khoom nyob rau hauv cov tshuaj dissociates rau hauv ions. Yog li, qhov no yog sib npaug rau cov khoom ntawm cov concentrations ntawm cov ions sib faib los ntawm cov concentration ntawm un-dissociated molecule.
AB ↔ A + B
Nyob rau hauv cov lus teb dav dav saum toj no, qhov kev sib cais tsis tu ncua, Kd tuaj yeem muab tau raws li hauv qab no.
Kd=[A][B] / [AB].
Ntxiv mus, yog tias muaj kev sib raug zoo stoichiometric, ib qho yuav tsum suav nrog cov stoichiometric coefficients hauv kab zauv.
xAB ↔ aA + bB
Qhov kev sib npaug ntawm qhov tsis sib xws, Kd rau cov tshuaj tiv thaiv saum toj no yog raws li hauv qab no:
Kd=[A]a[B]b / [AB]x
Tshwj xeeb, hauv kev siv tshuaj lom neeg, Kd pab txiav txim siab cov khoom lag luam muab los ntawm cov tshuaj tiv thaiv tshuaj nyob rau hauv lub xub ntiag ntawm ib qho enzyme. Kd ntawm cov tshuaj tiv thaiv enzymatic qhia txog ligand-receptor affinity. Hauv lwm lo lus, nws hais txog lub peev xwm ntawm lub substrate tawm ntawm receptor ntawm ib qho enzyme. Ntawm qhov tod tes, nws piav qhia yuav ua li cas muaj zog substrate khi rau cov enzyme.
Km yog dab tsi?
Km yog Michaelis tas li. Tsis zoo li Kd, Km yog kinetic tas li. Nws daim ntawv thov tseem ceeb yog nyob rau hauv enzyme kinetics, uas yog, los txiav txim siab affinity ntawm lub substrate los khi nrog ib tug enzyme. Qhov tsis tu ncua yog qhia los ntawm kev cuam tshuam cov substrate concentration rau cov tshuaj tiv thaiv tus nqi nyob rau hauv lub xub ntiag ntawm ib tug enzyme. Raws li, Michaelis tas li los yog Km yog qhov concentration ntawm substrate thaum qhov ceev ntawm cov tshuaj tiv thaiv mus txog ib nrab ntawm nws qhov siab tshaj plaws ceev.
Daim duab 1: Kev sib raug zoo ntawm cov tshuaj tiv thaiv kev tshaj tawm thiab cov txheej txheem hauv qab hauv cov tshuaj tiv thaiv enzymatic.
Thaum lub sijhawm cov tshuaj tiv thaiv ntawm enzyme (E) thiab substrate (S), tsim cov khoom (P) yog raws li hauv qab no:
E + S ↔ E-S complex ↔ E + P
Yog tias qhov sib npaug ntawm cov tshuaj tiv thaiv saum toj no yog raws li hauv qab no, koj tuaj yeem muab Km los ntawm cov khoom qub no.
Km=K-1 + K+2 / K+1
Kev txiav txim siab Km Raws li Michael's Concept
Michaelis tsim kev sib raug zoo uas siv cov concentration ntawm substrate, [S] thiab qhov siab tshaj plaws cov tshuaj tiv thaiv tshaj tawm, Vmax. Kev sib raug zoo ntawm substrate concentration thiab Km ntawm cov tshuaj tiv thaiv enzymatic yog raws li nram no:
v=Vmax[S] / Km + [S]
v yog qhov nrawm txhua lub sijhawm, thaum [S] yog lub substrate concentration ntawm lub sijhawm tshwj xeeb, thiab Vmax yog qhov siab tshaj plaws ntawm cov tshuaj tiv thaiv. Km yog Michaelis tas li rau cov enzyme hauv cov tshuaj tiv thaiv. Tus nqi ntawm Michaelis tas li nyob ntawm qhov enzyme. Yog li ntawd, tus nqi me me ntawm Km qhia tias cov enzyme tau saturated nrog me me ntawm substrate. Tom qab ntawd Vmax tau txais ntawm qhov qis substrate concentration. Nyob rau hauv sib piv, tus nqi siab Km qhia tau hais tias lub enzyme yuav tsum tau ib tug ntau ntawm substrate kom saturated.
Kd thiab Km txawv li cas?
Kd vs Km |
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| Kd is the dissociation constant. | Km yog Michaelis tas mus li. |
| Nature | |
| Kd yog qhov ntsuas kub tsis tu ncua. | Km is a kinetic constant. |
| Details | |
| Kd sawv cev rau kev sib koom ua ke ntawm lub substrate ntawm ib qho enzyme. | Km sawv cev rau kev sib raug zoo ntawm substrate concentration thiab cov tshuaj tiv thaiv ceev. |
Summary – Kd vs Km
Kd thiab Km yog qhov sib npaug uas piav txog cov khoom ntawm cov tshuaj tiv thaiv enzymatic. Qhov sib txawv tseem ceeb ntawm Kd thiab Km yog Kd yog qhov ntsuas kub tsis tu ncua thaum Km tsis yog qhov ntsuas kub tsis tu ncua.
