Question

Which of the following is TRUEregarding global control mediated by catabolite repression?

A.if glucose is present, then synthesis of other catabolic operons (lactose, maltose) are turned off

B.cyclic AMP is involved in the regulation

C.glucose inhibits cAMPsynthesis

D.all of the above

please explain

Answer 1

2 - 1 P . ... . . - Answer : The correct option for this provided option D question all of the above. Reason: The queestion provided is based on The catabolite repression t positive regulation with respect to the lactose operon. The positur regulations mainly takes place when glucose is related , en the réseence of Lactose, when Gelucose is i resent, then the lactose operon will be it off, and this phenonienon is called present Ke catabolite repression, Cabana called the in In the absence of glucose, an activator catabolile Activator protein CCAP) es produced by a regulatory' e, b uit. roeg is en inactive state CAP produced is eigen the of by binding AMP is activated which by produced Adeny cate cycle the enzyme any late Cyclase activated CAP-CAMP complex then binds to the CAP site of the operon. The bindeira I the CAP-CAMP complex eauses a bendin. the DNA that helps ir bending of the in the promoter region and also RNA pol to the promoter reason et easiles with the CAP-CAMP which increases increaser a the affinity of the RNA polymerase for the promoter when glucose is present in high concer tration I the cAMP concentration Th is. low and hence CAMP cannot be roduce CAP-CAMP with CAP to produce Capico complex x & CAP at CAP site. sile. Hence for binding the polymerase binding is not stabilized due to which, the gene expression is turned off. interact easilei complex, which

. 4. orodact - studie s this pathway , catabolic breakdown prod icore prevents the activation of the ron by lactose, so this effect was new called Cababolite repression? AIRES of glucose preu Lae operon by i origenally cace ori Gelreose effect L BORDE merase VALA - hac operon Z Y A » еxртеми - activated. glucose absent) Amp level night mRNA M STE DETER -CAP up e AMP 0.oo activated) :> WAJ I = . complex - . CAP inactive) L > RRA Pol cannot bind CAP Site 7 y. A - o T i i no no gene ression, OY Xpre bur t no binding inactive . AmRNA . CAP (positive regulation) CAMP lend low. blucose present CAP MRNA. no cAMP.' e CAP protein Cinactive) Thus the process clearly tells that all or the options - A> Glucose present a process turned on > true By gelie Arup involved - Frue . Glucose inhobits camp sun its camp synthesis L, Таи accordi all the options are true rocess desanbed , hence o o call of the above is most answer to the question, ERS As, all the option to the process descon option D call on . appropriate ansever to th W

The catabolite repression has been a greatly observed in E.coli,when both lactose and glucose is present.Untill and unless the glucose is used up lactose is not metabolised by the bacteria.This causes a growth curve characterised by two lag and log phases and intervened by a single stationary phase.This type of growth is called Diauxic growth.