Enzymes Flashcards
What are the characteristics of enzymes?
Biological catalysts
Specific
Speed up reactions without being used up
Complementary active site
Lowers activation energy required
What is the induced fit model?
Substrate collides with active site
Active site moulds around the substrate and forms an enzyme-substrate complex
Results in a change in the enzymes 3D shape which brings the two reactants closer together
Weakens chemical bonds allowing easy breaking and lowering activation energy
Product no longer fits in active site and is released
What are catabolic reactions?
Hydrolysis of larger molecules to smaller ones e.g. polypeptides into amino acids
What are anabolic reaction?
Condensation of smaller molecules into larger ones e.g. alpha glucose into starch
What are intracellular enzymes?
Enzymes which remain inside cell e.g. respiratory enzymes
What are extracellular enzymes?
Enzymes which are secreted from cells to function e.g. digestive enzymes
What is an enzymes turnover number referring to?
Max number of substrate molecules it can convert to product molecules per unit time
What must happen for an enzyme reaction to take place?
Successful collisions in order to form enzyme-substrate complexes
What factors affect an enzyme catalysed reaction?
Temp
pH
Substrate conc
Enzyme conc
Presence of inhibitors
What does a time graph show?
How long the reaction takes to occur
What does a rate graph show?
How fast the the reaction occurs
What does a concentration graph show?
How much product is formed (or product used)
What is the lock and key model?
Suggests enzymes have a specific complementary active site
What is activation energy?
Extra energy that is required to enable a reaction to occur
What is the effect of varying substrate concentration on a reaction?
Rate of reaction increases up to a certain point until all enzyme active sites are filled. Enzyme concentration is the limiting factor
What is the effect of varying enzyme concentration when excess substrate is present?
Linear gradient, because more active sites means more successful collision and more enzyme-substrate complexes formed
What are competitive inhibitors?
Have a similar shape to the substrate molecule therefore bind to active site and reduce amount of enzyme substrate complexes that can be formed and rate of reaction falls
What are non-competitive inhibitors?
Bind to allosteric site and alter the shape of the active site so enzyme-substrate complexes can no longer be formed. Rate of reaction will plateau
What are industrial enzymes?
Enzymes that are produced by culturing microbes in fermentation vessels. Enzymes produced as part of their normal metabolic activity
What happens after the enzymes have been produced by the microbes in the fermentation vessels?
Microbes removed. Enzymes immobilized and purified. Can then be added to substrate molecules to catalyse reactions that would’ve otherwise been difficult to carry out
Why are enzymes used in such a large scale industrial production?
Lower activation energy - save energy and increase efficiency.
Few side reactions so less waste products formed
What are immobilized enzymes?
Fixed, bound or trapped to an inert matrix
What are the advantages of using immobilized enzymes over free enzymes?
Easily recovered, product not contaminated, the inert-matrix is a microenvironment so more stable at high/low pH’s/temps, several can be used at the same time
What are two ways that enzymes can be immobilised on an inert matrix?
Entrapment - enzyme inclusion
Encapsulation - microcapsule
