Topic 1.4 Enzymes Flashcards
What is an enzyme?
a biological catalyst (globular proteins)
What is a catalyst?
a substance that speeds up the rate of a reaction without changing the substances being produced or being changed itself
What is an enzyme (long definition)?
proteins that have a very specific shape due to their primary, secondary, tertiary and quaternary structures. they act as biological catalyst and each enzyme will only catalyse a certain reaction
Enzymes show specificity, what is meant by this?
the characteristic of enzymes which means due to their very specific shapes as a result of their tertiary and quaternary, each enzyme only catalyses a specific reaction or group of reactions
What’s an anabolic reaction?
a reaction which builds up new molecules (synthesises) in a cell
What’s a catabolic reaction?
a reaction that breaks down substances within a cell
Describe what is meant by metabolism
the sum of anabolic and catabolic processes in a cell
What is a metabolic chain/pathway?
a series of linked reactions in the metabolism of a cell
Define intracellular and extracellular enzymes
intracellular catalyse reactions within the cell e.g. DNA polymerase
extracellular catalyse reactions outside of the cell in which they were made e.g. lysozyme
Define activation energy
the energy needed for a reaction to get started
What is a substrate?
the molecule or molecules on which the enzyme acts
What is the lock-and-key hypothesis?
the model that explains enzyme action by an active site in the protein structure that has avert specific shape. the enzyme and substrate slot together to form a complex as a key fits in a lock
What’s an active site?
the area of an enzyme that has a specific shape into which the substrate of a reactions fits
Describe the induced-fit hypothesis
a modified version of the lock-and-key theory where the active site is considered to have a more flexible shape. once the substrate enters the active site, the shape of the site is modified around it to form the active complex. once the products have left the active site it reverts to its inactive, relaxed form
What is the initial rate of reaction?
the measure taken to compare the rates of enzyme controlled reactions under different conditions
What is meant by molecular activity/ turnover number?
the number of substrate molecules transformed per minute by a single enzyme molecule
What is the temperature coefficient (Q10)?
the measure of the effect temperature has on the rate of reaction
What happens to Q10 between 10 degrees and 40 degrees?
it doubles for every 10 degree temperature rise
Give 3 examples of enzyme inhibition
- competitive
- non-competitive
- end-product
Give an example of a chemical that exerts irreversible inhibition on enzyme systems
cyanide, arsenic and mecury
Define enzyme inhibitors
substances that slow down enzymes or stop them from working
What is reversible inhibition?
inhibition of the action of an enzyme by an inhibitor which does not permanently affect the functioning of an enzyme and can be removed from the enzyme
What is reversible inhibition often used for?
to control the reaction rates within a cell
What is irreversible inhibition?
inhibition of the action of an enzyme that is permanent and cannot be undone (never used within cells to control the rates of reaction)
Define competitive inhibition
inhibition in which the inhibitor molecule is similar shape to the substrate molecule and competes with it for the active site of enzymes
Define non-competitive inhibition
inhibition in which the inhibitor doesn’t compete for the active site but forms a complex with the enzyme or enzyme/substrate complex and changes the shape of the active site so it can no longer catalyse the reaction
Define regulatory enzymes
enzymes that have a site separate to the active site where another molecule can bind to have either an activating or inhibitory affect
Define end-product inhibition
a control system in many metabolic pathways in which the enzyme at the beginning of the pathway is inhibited by one of the end products of the reaction
