Why do E. coli cells with a defective lacZ gene fail to show galactoside permease activity after the addition of lactose in the absence of glucose?

The purified OXA-M290 enzyme can now be tested to determine which β-lactamase inhibitor is most effective. This inhibitor could be prescribed in combination with a β-lactam antibiotic to treat the infection caused by the E. coli KGH1 strain. Before testing inhibitors against OXA-M290, the kinetic activity of this enzyme must first be measured. The activity of OXA-M290 is measured using nitrocefin, a chromogenic β-lactam antibiotic. When nitrocefin is hydrolyzed by a β-lactamase, it changes from yellow to red in colour. The nitrocefin hydrolysis product has an extinction coefficient of 20,500 M-1 cm-1 at 486 nm. The hydrolysis of 60 μM nitrocefin by 1 nM OXA-M290 is monitored using a microplate reader. The absorbance of the wells in the plate is measured at 486 nm every 30 seconds. This experiment is carried out with three replicates, generating the following data: Time (min) Absorbance of Replicate 1 Absorbance of Replicate 2 Absorbance of Replicate 3 0.5 0.0984…

What is the significance of the pentose monophosphate shunt to synthesis of nucleotides? What is a difference between synthesis of purine and pyrimidine nucleotides?

Which three amino acids are substrates or products of serine hydroxymethyltransferase?

In E. coli, a protein called Lac permease (encoded by lacY) imports lactose into cells so that a protein called beta-galactosidase (encoded by lacZ) can digest it into galactose and glucose. What are some similarities and differences between how you and E. coli import and metabolize lactose?

Is there a way to classify or identify the tests needed in order to differentiate C12H22O11 and galactose from each other?

CTP synthetase catalyzes the glutamine-dependent conversion of UTP to CTP. The enzyme is allosterically inhibited by the product, CTP. Mamma- lian cells defective in this allosteric inhibition are found to have a complex phenotype: They require thymidine in the growth medium, they have unbal- anced nucleotide pools, and they have an elevated spontaneous mutation rate. Explain the likely basis for these observations.

Which statement is true for the active site residues of RNase A, lysozyme, or trypsin? Select any/all answers that apply. O A. His12 (RNase A) initially acts as an acid. O B. His119 (RNase A) initially acts as an acid. O C. Glu35 (lysozyme) initially acts as an acid. O D. His57 (trypsin) initially acts as an acid. O E. Ser195 (trypsin) initially acts as an acid.

The pathway shown below is used by a fungus to create Fructose-1,6-diphosphate from glucose. A silent mutation occurs in the gene that encodes enzyme 3. This fungus is grown on media that only contains the precursor. Discuss the effects of this mutation on: (i) The function of Enzyme 3 (ií) The production of Fructose-1,6-diphosphate Enzyme 1 Glucose-6- Enzyme 2 fructose-6- Enzyme 3 Fructose-1,6- Glucose phosphate phosphate diphosphate

Ferritin levels are controlled in cells to ensure that free iron levels do not surpass a toxic threshold. Its levels must never be too high or it will titrate too much iron and jeapardize critical cellular iron-dependent enzyme activities. How is this achieved? Choose one. a) Elements present in the 5' UTR contribute to its translational block in low iron conditions. b) The Ferritin mRNA is under IRE-BP control so that in high iron conditions IRE-BP is not in its active conformation an has no negative effect on Ferritin mRNA translation c) IRE-BP can effectively bind to destablizing elements in the 3'UTR of the Ferritin mRNA, thus drastically reducing the half life of the transcript 4) a and b only 5) a, b and c