2.4 Enzymes Flashcards
What are enzymes
Globular proteins that are biological catalysts, that interact with substrates
What are the chemical reactions for growth called. What are the chemical reactions for breaking down called?
Building up - Anabolic
Breaking down - Catabolic
What is metabolism
Sum of all the different chemical reactions happening in the cell
What is a Vmax
Enzymes can only increase the rate of reaction up to a certain point
What conditions effect enzyme action
Temperature, pressure, pH, concentration (of substrate and enzyme)
What happens to enzyme action when temperature and pressure increase
molecules have higher kinetic energy, resulting in more frequent successful collisions, increasing rate of reaction
What is the specificity of an enzyme
An enzyme can only catalyse one reaction
What is the activation energy of a reaction
Energy needed to be supplied for a reaction to start
What do enzymes do in terms of the activation energy
Enzymes help molecules collide successfully, reducing activation energy
Explain the lock and key hypothesis
Only a specific substrate can lock into the active site of the enzyme. When the substrate binds to an enzyme, The R groups interact, holding the substrate in place, a enzyme substrate complex is formed. Substrate reacts, forming an enzyme-product complex, products are released, enzyme remains unchanged.
Explain the induced fit-hypothesis
Enzyme changes shape slightly when substrate enters,
Why did the induced fit hypothesis become created
Initial interaction between enzymes and substrate is weak, however, this changes the enzyme’s tertiary structure, strengthening the binding and lowering activation energy
What are intracellular enzymes. What are extracellular enzymes
Intra - Enzymes in the cell.
Extra - Enzymes that work outside the cell, break down large molecules, so that they can enter the cell
Explain starch breaking down
Amylase breaks starch into maltose.
Maltose is broken down into glucose by maltase
Where is Amylase produced
Amylase is produced in salivary glands and pancreas, and released in pancreatic juice and small intestine
Where is maltase present
Small intestine
How does temperature impact enzyme action?
Increasing temperature increases the kinetic energy of particles, so collide successfully more frequently
What is the temperature coefficient (Q10)
How much the Rate of reaction increases with a 10oc rise
What does denatured means
Enzyme’s active site changes shape, meaning it is no longer complementary to the substrate
What happens if temperature increases too much
Enzyme becomes denatured, Temperature coefficient does not apply any more, as the enzymes has become denatured
What is the optimum temperature
temperature at which enzyme activity is at it’s highest
What adaptations have enzymes adapted if they are in temperature extremes
Cold - more flexible structure
Warm - les flexible structure (more bonds)
What is the impact of pH on enzyme action
pH above or below the optimum pH causes the active site to change, but if the pH returns, then active site resumes normal shape - renaturation
Significant pH change causes irreversible denature
What is the impact of substrate and enzyme concentration on enzyme action
Higher concentration of either increases rate of reaction
Substrate - higher collision rate with enzyme
Enzyme - increases available active sites
RoR increases to maximum Vmax - all active sites are occupied
What is the limiting factor
Factor that prevents more reactions occurring
Why is it important to control enzyme action
So that reactions do not occur too fast, reactions can be multi-step
how can enzymes be activated?
Cofactors
How can enzymes be inhibited?
inhibitors
What are the two types of inhibitors
Competitive, non-competitive
What are competitive inhibitors
Molecule with similar shape to the substrate fit into active site, blocking the substrate from entering the active site, so enzyme cannot carry out it’s function, slowing down rate of reaction
What are the impacts of competitive inhibitors
Reduces rate of reaction, without changing the Vmax, if substrate concentration is increased, there will be much more substrate than inhibitors, so Vmax can be reached
Give an example of a competitive inhibitors
Statins - CI of an enzyme used to synthesize cholesterol
Aspirin - Inhibits the active sites of COX enzymes preventing chemicals for pain/fevers
What are non competitive inhibitors?
Inhibitor binds to an enzyme at a location other then the active site, causing the tertiary structure of an enzyme, resulting in the active site no longer having a complementary shape, so the enzyme cannot carry out it’s function, they can be reversible or irreversible
What is the effect of non-competitive inhibitors on enzyme activity
Increasing the concentration of an inhibitor decreases rate of reaction, increasing enzyme or subsrate concentration will not overcome inhibitor
What is an example of an irreversible non-competitive inhibitor
Organophosphates - insecticides, inhibit acetyl cholinesterase, (enzyme necessary for nerve impulses)
What is end product inhibition.
Enzyme inhibition occurs when the product of a reaction acts as an inhibitor, negative feedback
What are cofactors
non protein ‘helper’ components
What are inorganic cofactors
Obtained via the diet, minerals, vitamins
What are prosthetic groups
Cofactors and are required by some enzymes, tightly bound to the enzyme, forming a permanent feature
What is precursor activation
Need to undergo a change in shape to be activated, through the addition of a cofactor or coenzyme
