3. Enzymes Flashcards
Define activation energy
Energy needed in a chemical reaction for a product to form
(Q1) What is the activation energy of the reaction in the presence of the enzyme?
A
(Q2)Which statement explains how the substrate is able to enter the active site of the enzyme?
Contact between the substrate and the enzyme causes a change in the enzyme shape.
(3) why did the actual rate of reaction decrease over time?
Substrate molecules were used up
(4) Catalase is an enzyme that catalyses the conversion of hydrogen peroxide into water and oxygen.
Two students investigated the effect of enzyme concentration on the rate of reaction of the
enzyme catalase. The students predicted their results would show the same trend. The graphs
show the rates obtained by each student.
Student 2 used a lower concentration of substrate in the investigation
can’t be temp bc that’s not what they’re studying and changing
can’t be pH bc that’s also kept constant
can’t be inhibitor bc that’s not what they’re studying
What is an enzyme inhibitor?
Something that inhibits the rate of enzyme activity
What is a competitive inhibitor?
It has a similar shape to the substrate and temporarily fits into the enzymes active site, competing with the substrate
What can make a competitive inhibitor reversible?
Increasing the substrate concentration will reduce effect of inhibitor
What is non-competitive inhibition? 2
It doesn’t bind to the active site, but another part of the enzyme
causing a change in the enzymes shape so it’s no longer complementary
Increasing substrate has no effect
What level of protein structure is always involved in competitive and non-competitive inhibitors of enzymes?
tertiary
How do you calculate mean?
Sum of terms divided by number of terms
what is an enzyme-substrate complex?
a temporary molecule formed when the substrate binds to the enzyme
(7) which graph shows the change in concentration of enzyme substrate complex?
A
not B bc not just concentration but CHANGE in concentration
What is the lock and key hypothesis
Active site has perfectly complementary shape to substrate
What is induced-fit hypothesis?
Active site, or sometimes substrate, can change shape slightly to fit together better for more efficient enzyme activity
What do the lock and key and induced fit hypotheses have in common
Substrate is converted to product by specific R groups in the active site
Lysozyme is secreted from tear glands & forms deposits in contact lenses. How would one clean this?
Protease dissolves lysozyme
(13) Which graph statement is correct?
Between X & Y, the number of enzyme molecules is limiting
What is involved in enzyme regulation? 3
Change in enzyme concentration
Change in substrate concentration
Inhibition by final product of reaction
What type of bond is formed between an enzyme and a substrate?
Hydrogen bond
How do you plot the initial rate of reaction? 3
draw a tangent to the curve at the start of the reaction
Find an easy- to read part of the scale to stop drawing
Make triangle as big as possible
How do you calculate the initial rate of reaction? 2
Calculate the gradient of line
Change y / change x
(18) which graph represents action of a non-competitive inhibitor?
A
Which orders of protein structure control the shape of the active site
Primary, secondary, tertiary & quaternary
(20) n an experiment, 5cm^3 of 1% salivary amylase is added to 100cm^3 of different concentrations of starch
Which graph shows the results of plotting the initial rate of reaction (y axis) against substrate concentration (x axis)
A
