1.4 Enzymes And Biological Reactions Flashcards
What do enzymes do?
Speed up a reaction
Not used up
Not changed
What are enzymes made up of?
Protein chain folded into a globular or spherical shape with hydrophilic R groups outside molecule
What is the active site?
A small area with a specific 3D shape
Where can enzymes act?
Extracellular - they are secreted from cells by exocytosis and catalyse reaction. Eg amylase
Intracellular ( solution) - enzymes act in solution inside cells.
Intracellular (membrane bound )
Enzymes attached to membranes Eg on Christie of mitochondria
Induced fit model
Shape of active site is not complimentary to the shape of the substrate
Therefore the shape of the active site alters to bind to the substrate
Then products are released
What is the activation energy?
The minimum energy required for molecules to react, breaking existing bonds in the reactants to make new ones in the products
What effect does temp have on enzyme action?
Increased temp increases KE as molecules collide with more energy more often which increases r of r.
What happens when the reaction reaches optimum temp?
After optimum temp the reaction decreases because the vibration breaks hydrogen bonds and tertiary shape of enzyme changes shape
What happens to the active site of the enzyme?
Active site is altered so substrate does not fit.
Enzyme denatures and structure changes.
What happens to the enzyme at low temps?
At low temps the enzyme is inactivated as the molecules have low KE.
Shape does not change and enzyme will work again if temp increases
What effect does low PH have on the enzyme?
Excess H+ ions are attracted to the negative charges and neutralise them
What effect does high PH have on enzymes?
Excess OH- ions neutralise the positive charges and
Shape of enzyme changes and enzyme denatures
No enzyme substrate complexes form as there is no enzyme activity
What happens to the enzyme when substrate concentration increases?
Enzyme conc is constant and rate of reaction increases
What happens to the enzymes when substrate concentration is low?
The enzyme molecules have only a few substrate molecules to collide with so the active sites are not working at full capacity.
What is the limiting factor?
The substrate concentration as it controls the rate of reaction decreases because
What happens when the substrate concentration as it is at its maximum?
The active sites are occupied and rate of reaction is at its max so enzyme is saturated
What happens to the enzyme as enzyme conc increases?
There are more active sites so rate of reaction increases
What is enzyme inhibition?
The decrease in rate of enzyme controlled activity by another molecule an inhibitor.
What does an inhibitor do?
Combines with an enzyme to stop it forming enzyme substrate complexes form as
What is competitive inhibition?
They have a molecular shape complimentary to the active sites and similar to the substrate so they compete for the active site.
What is non competitive inhibition?
They bind to the enzyme at an allosteric site so they do not compete with the substrate. This alters the shape of the active site
What happens as the inhibitor concentration increases?
The rate of reaction and final mass of product decreases
What are immobilised enzymes?
When enzymes are fixed on an inert surface and substrate molecules move over them
