LS23L - Week 3 (B-gal) Exam Questions and
Answers with Verified Solutions | Latest
Updated 2026
What is the purpose of ONPG substrate that gives a yellow color when
in this lab? cleaved by beta-galactosidase
What type of blank should be "b-gal blank" made by your group
used for the b-galactosidase
enzyme activity assay?
What is the purpose of Z provides an optimum pH for enzymatic
buffer in this lab? reaction
According to the Lab Safety Safety goggles Correct
Sheet provided for this week, Gloves Correct
when working with E. coli cells Standard lab attire Correct
you must wear: (check all that Lab coat
apply)
According to the Lab Safety True
Sheet, in the b-galactosidase
assay lab, used gloves should
be disposed of in the
autoclave bag.
Microcentrifuge tubes with Capped and placed in the labeled
chloroform in the bottom must hazardous waste bin in the hood
be:
, Which of the following Add chloroform into tubes for enzymatic
procedures should be done in assay.
the hood?
Chemicals/materials you will E. coli cells
use in the b-galactosidase Z-buffer mix
assay lab include: Chloroform
ONPG (420 nm)
Na2CO3 (stops onpg reaction)
What is the purpose of partially disrupts cell membrane to allow
chloroform in this lab? substrate to enter the cell
In the presence of glucose, does not have to be produced because
Beta-galactosidase there is no need for it Correct
The lac operon is devised to The lac repressor is deactivated through
activate the transcription of allosteric change in the presence of
the enzyme beta- lactose allowing for transcription of the Z
galactosidase when needed. Gene to beta-galactosidase. Correct
What conditions begin this
process?
The bacteria grown in Luria Show marked B-galactosidase activity.
broth with only lactose were Correct
expected to:
Why is ONPG an ideal because it is cleaved by B-Gal into
substrate to assay for B-Gal galactose and o-nitrophenol, a yellow
activity? compound. Correct
Answers with Verified Solutions | Latest
Updated 2026
What is the purpose of ONPG substrate that gives a yellow color when
in this lab? cleaved by beta-galactosidase
What type of blank should be "b-gal blank" made by your group
used for the b-galactosidase
enzyme activity assay?
What is the purpose of Z provides an optimum pH for enzymatic
buffer in this lab? reaction
According to the Lab Safety Safety goggles Correct
Sheet provided for this week, Gloves Correct
when working with E. coli cells Standard lab attire Correct
you must wear: (check all that Lab coat
apply)
According to the Lab Safety True
Sheet, in the b-galactosidase
assay lab, used gloves should
be disposed of in the
autoclave bag.
Microcentrifuge tubes with Capped and placed in the labeled
chloroform in the bottom must hazardous waste bin in the hood
be:
, Which of the following Add chloroform into tubes for enzymatic
procedures should be done in assay.
the hood?
Chemicals/materials you will E. coli cells
use in the b-galactosidase Z-buffer mix
assay lab include: Chloroform
ONPG (420 nm)
Na2CO3 (stops onpg reaction)
What is the purpose of partially disrupts cell membrane to allow
chloroform in this lab? substrate to enter the cell
In the presence of glucose, does not have to be produced because
Beta-galactosidase there is no need for it Correct
The lac operon is devised to The lac repressor is deactivated through
activate the transcription of allosteric change in the presence of
the enzyme beta- lactose allowing for transcription of the Z
galactosidase when needed. Gene to beta-galactosidase. Correct
What conditions begin this
process?
The bacteria grown in Luria Show marked B-galactosidase activity.
broth with only lactose were Correct
expected to:
Why is ONPG an ideal because it is cleaved by B-Gal into
substrate to assay for B-Gal galactose and o-nitrophenol, a yellow
activity? compound. Correct
