LS23L Week 3 - Biochemical Assay of B-
Galactosidase Exam | Questions with
100% Correct Answers | Verified | Latest
Update 2026/2027
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Terms in this set (26)
What does beta-galactosidase It is an enzyme that catalyzes the
do? hydrolysis of lactose (a disaccharide
found in milk) to glucose and galactose.
,Lac Operon The Lack I gene, which produces the
repressor, is constantly activated. The
repressor that is produced binds to the
operator (LacO) gene, prohibiting the
production of beta-gal. However, when
allolactose is present, it binds to the
repressor, causing a conformational
change that makes it fall off of the
operator region. Once the repressor is
gone, RNA polymerase is free to bind to
the promotor (LacP) and transcribe the
operon. There are three structural genes,
including LacZ, which encodes lactase.
Lactase not only breaks down lactose,
but also isomerizes it into allolactose,
which is the form that binds to the
repressor.
, How does Glucose affect the Many cells prefer to use glucose as an
Lac Operon? energy source than lactose because it is
simpler and requires less energy to break
down. If it is available, cells use it first
before resorting to other resources.
When little glucose is present, there is an
increase in cAMP, which binds to a
protein called CAP. This causes a
conformational change that allows CAP
to bind to a region near the promotor of
the Lac operon (the activator) which
makes it easier for RNA polymerase to
bind and start transcribing. Therefore,
there must be low glucose and high
lactose in order for beta-gal to be
produced.
Galactosidase Exam | Questions with
100% Correct Answers | Verified | Latest
Update 2026/2027
Save
Terms in this set (26)
What does beta-galactosidase It is an enzyme that catalyzes the
do? hydrolysis of lactose (a disaccharide
found in milk) to glucose and galactose.
,Lac Operon The Lack I gene, which produces the
repressor, is constantly activated. The
repressor that is produced binds to the
operator (LacO) gene, prohibiting the
production of beta-gal. However, when
allolactose is present, it binds to the
repressor, causing a conformational
change that makes it fall off of the
operator region. Once the repressor is
gone, RNA polymerase is free to bind to
the promotor (LacP) and transcribe the
operon. There are three structural genes,
including LacZ, which encodes lactase.
Lactase not only breaks down lactose,
but also isomerizes it into allolactose,
which is the form that binds to the
repressor.
, How does Glucose affect the Many cells prefer to use glucose as an
Lac Operon? energy source than lactose because it is
simpler and requires less energy to break
down. If it is available, cells use it first
before resorting to other resources.
When little glucose is present, there is an
increase in cAMP, which binds to a
protein called CAP. This causes a
conformational change that allows CAP
to bind to a region near the promotor of
the Lac operon (the activator) which
makes it easier for RNA polymerase to
bind and start transcribing. Therefore,
there must be low glucose and high
lactose in order for beta-gal to be
produced.
