Bio 173 Exam 1 Flashcards
Hypothesis
a testable prediction based on observations and assumptions
must be falsifiable
Prediction
a description of an expected outcome in the test (experimental) group and in each control group – Confirming a prediction supports (but does not “prove”) that hypothesis – Negating a prediction suggests that it may be wrong
positive control
response expected, ensures that the setup works properly and provides a baseline (antibiotics)
negative control
no response expected, ensures results are due to the variable being tested and not something else (placebos)
enzyme
catalytic protein (think lock and key/puzzle piece)
How do enzymes lower the activation energy barrier?
Lowering the activation energy (alternate pathway)
What is an exergonic reaction?
A spontaneous reaction, happens naturally
factors that influence catalysis
temperature
pH
substrate concentration
enzyme concentration
activator presence
inhibition presence
What reaction does polyphenoloxidase catalyze?
catechol to orthoquinone
how to measure reaction rate
slope
initial reaction rate is the first 2 min slope
how does enzyme conc affect the reaction rate
Determines how fast the rate of the reaction will be
Low concentration - fewer available active sites, reaction is limited by the number of enzymes
High concentration - reaction is faster because enzymes can find substrates to bind to quicker
Vmax
where the reaction levels off on the chart
maximum rate of reaction when all the enzyme have been used up, adding substrate wont do anything past this point
Km
[substrate] when the reaction is at halfway
cofactor role
required for the reaction to occur, it primes/shapes the activation site
competitive inhibitor
goes into the enzyme - increases Km but not vmax - % inhibition varies at different concentrations
non-competitive inhibitor
goes into an alternate area (allosteric site) and changes the overall shape - decreases vmax but not Km - % inhibitor is constant for all concentrations of substrates
how is Vmax affected by inhibitors
noncompetitive inhibitors - decreases Vmax
competitive - none
calculate % inhibition
(Rate without inhibitor - rate with inhibitor)/(rate without inhibitor) x 100%
what does % inhibition means
how much of enzyme is used up
Effect of running the reaction at extreme temperatures (very hot, very cold)
45 C fastest rate, 20 C (control), 0, 65
At 45, the molecules are excited - more collisions make it more likely for the reaction to occur, making it happen faster (shift the chart left)
At 0 molecules have a lot less kinetic energy, very slow
At 65, the enzyme is denatured (there is low to no reaction)
Effect of freezing and thawing the enzyme vs boiling it and letting it cool
Control - never frozen or boiled
Fastest reaction is cold tied with the control, then boiled (denatured)
Is Potassium arsenite an inhibitor
6mm catecol with inhibitor
6mm catecol without inhibitor
24 mm catecol with inhibitor
24 mm catecol without inhibitor
If we vary the substrate concentration and its a competitive inhibitor, we expect less inhibition
Less substrate to compete with inhibitor for active site
If its a noncompetitive inhibitor, % inhibition is the same
It is barely an inhibitor for PPO, % inhibitor was ~5 ish on each
No sulphohydride groups in polyphenoloxidase
Does polyphenoloxidase have a metal cofactor?
Cofactor - required for the reaction to occur
primes/shapes active site
Regulates things in the body
Blood - iron is a cofactor for hemoglobin
Isolate the cofactor (if it is even there)
Add a keylator (substance that pulls it out)
PTU is copper only
Potassium cyanide is copper and iron
Control, ptu and potassium cyanide
PTU and potassium cyanide both had slowed reactions, meaning that copper is the cofactor of pilyphenoloxidase
The effect of increasing salt
Ions in salt solutions can destabilize ionic bonds but its not an inhibitor
It is a universal inhibitor but not specific to an enzyme, it does not change the shape or go into the enzyme to prevent the substrate
Salt is denaturing the enzyme
Needs to be pretreated (denaturation doesn’t happen immediately)
Run with increasing salt concentration
Control, high concentration, low concentration
As salt increases, reaction rate decreases (to a point)
Biologically relevant because of saltwater ecosystems have very specific concentrations
Ice caps are melting, diluting the salt concentration, impacting these systems
