3. 1. 4. 2 Many Proteins are Enzymes Flashcards
What does the enzymes do to the activation energy?
Each enzyme lowers the activation energy of the reaction it catalyses.
What does the induced fit model of enzyme action state?
It states that a substrate binds to an active site and both change shape slightly - an ideal fit for catalysis.
What does the properties of an enzyme relate to?
The properties of an enzyme relate to the tertiary structure of its active site and its ability to combine with complimentary substrates to form an enzyme-substrate complex.
Describe the specificity of enzymes.
Enzymes have an active site where specific substrates bind forming an enzyme-substrate complex.
Active site of enzymes have specific shape to fit a substrate.
What is the effect of enzyme concentration on the rate of enzyme-controlled reactions?
rate of reaction increases as the enzyme concentration increases, until a limiting point is reached.
Why does rate increase?
More enzyme molecules can bind to more substrate molecules and catalyse the reaction.
Why does it reach a limiting point?
All the substrate has bound and adding more enzymes won’t affect reaction rate as there are no more substrates to bind to.
How does the substrate concentration effect the rate of enzyme-controlled reactions?
rate of reaction increases as the substrate concentration increases, until a limiting point is reached.
Why does rate of reaction increase?
There are more/plenty of substrates to bind to the active site of an enzyme.
Why does it reach a limiting point?
So much substrate is present that all of the enzyme active sites have substrates bound to them; enzyme molecules saturated with substrate.
How do competitive inhibitors work?
- Compete with substrate for the binding site on enzyme
- Binds to an enzyme and prevents real substrate from binding
- occupy only some of enzyme active site; gradual increase in reaction rate
- Decrease reaction rate when there’s not much substrate (can be out-competed by many substrates)
- given enough substrate, enzyme can still reach max reaction rate
How do non-competitive inhibitors work?
- Decreases rate of enzyme controlled reaction by binding to an allosteric site
- Changes shape of enzyme active site
- Unable to bind to substrate
- Slows down product formation
- Doesn’t affect activation energy
What is an allosteric site?
An allosteric site is a location on an enzyme molecule where a nonsubstrate molecule can bind and affect the enzymes activity.
How does the pH affect the rate of enzyme-controlled reactions?
- Deviating from the optimum causes the enzymes active site to become denatured (change charge on enzymes, affects ionic bonding)
- This leads to a decrease in enzyme activity; no enzyme-substrate complexes formed
What is the effect of temperature on the rate of enzyme controlled reactions?
- Rate increases as temperature increases
- Kinetic energy increases
- More collisions between enzyme and substrate
- Beyond optimum- rate will decrease as enzyme becomes denatured (H-bonds break)
