lab final Flashcards
what is a biuret test?
tests for the presense of proteins
- uses copper ions in an alkaline solution to form a complex with peptide bonds in proteins
- color change (blue to violet)
what is the significance of color in a biuret test?
blue - no protein
middle colors indication varying concentrations of proteins
violet - protein
relationship between absorbance and concentration?
higher conc, higher absorbance
how to calculate Km from graph:
x-intercept = 1/Km
how to calculate Vmax from graph:
y-int = 1/Vmax
slope =
Km / Vmax
what is ONPG?
- a false substrate
- full name: ortho-nitro-phenyl-galactoside
why is ONPG used?
b/c it’s difficult to accurately measure lactose/glucose in a solution
- ONPG has a similar structure to lactose and can bind to the enzyme/be cleaved
products of ONPG…
ONP and galactose
ONP’s color
yellow
can ONP be measured by…
spectrophotomery
what is an activator?
when substance increases activity of an enzymatic rxn
what is an inhibitor?
when a substance decreases the activity of an enzymatic rxn
categories of inhibitors:
competitive inhibition, noncompetitive inhibition
competitive inhibition is…
inhibitor resembles chemical structure of substrate
- competes with substrate for binding to active site
- inhibitor is only able to bind to free enzyme and can’t bind substrate-enzyme complex
- Km increases
how can comp inhibition be overcome?
adding substrate in large amts till there is more substrate than inhibitor (Vmax is unchanged)
noncompetitive inhibition is…
when the inhibitor binds to the enzyme at a site other than the active site (allosteric site)
- changes the overall shape of enzyme
- apparent Vmax decreases
- Km is unchanged - no prevention of substrate binding
can noncomp inhibition be overcome?
no
what does the iodine number tell us?
- the degree of unsaturation
- # of iodine grams consumed by 100g of fat
- sees how much iodine will react to the double bonds present in the 100g of fat/oil
what has the higher iodine number?
unsaturated fats (greater than 70)
- range: 125-150
- vegetable products
what has the lower iodine number?
saturated fats (lower than 70)
- close to zero as saturated fats take up little to no iodine
- animal fats/oils
how is DNA cut with restriction enzymes?
- cut DNA at specific sites to create restriction fragments
how does agarose gel work?
traps molecules to show bands/fragments
negatively charged molecules migrate to…
positive pole, the anode (right)
