Enzymes Flashcards
What is a catalyst?
A substance that increases the rate of a chemical reaction but does not get used up/changed/altered
What is an enzyme?
A protein molecule made by cells and acts as a catalyst
How are enzymes made?
By protein Synthesis
What are intracellular enzymes?
Only work inside of cells
What are extracellular enzymes?
Only work outside of cells (either in environment or in lumen)
What is specificity?
The relationship between an enzyme and the only type of molecule that fits into its active site
What are active sites made of?
A few amino acids within a polypeptide
What two things do eynzymes catalyse?
The breakdown and buildup of biological molecules
What three things can you infer from the name of an enzyme?
First part is the substrate, second is the reaction, and should end in ‘ase’
What do we know about carbohydrase?
The substrate is carbohydrates, the reaction is hydrolysis, and it is an enzyme (its a hydrolase enzyme - catalyses hydrolysis)
If an enzyme is less specific?
Can catalyse a number of reactions of the same type
How specific is subtilisin - breaks peptide bonds between any AA?
Not very
How specific are trypsin and chymotrypsin?
Quite, only breaks bonds between certain AA, chymotrypsin (more specific)
What is an enzyme-substrate complex?
Complex formed when a substrate fits into an enzymes active site
Lock and key hypothesis?
Active site is complementary in shape to the substrate like a lock (enzyme) and key (substrate)
Enzyme-product complex?
Complex formed in the active site after the reaction is complete but before product(s) leaves
Induced-fit hypothesis?
Active site of an enzyme changes shape during binding of a substrate molecule, putting a strain on the substrate molecule and contributing to the reaction
Activation energy?
Energy needed to overcome the energy barrier to allow a reaction to occur
How do enzymes effect the activation energy of a reaction?
Provide alternative pathway with a lower activation energy
Model of activation energy?
Energy barrier is the hump at the top of a hill, AE is the energy needed to push a ball over the hump (EB) and down the hill (the reaction), with an enzyme the energy barrier and energy needed is decreased (smaller hump) m
Investigating enzyme activity for milk protein solution with protease?
10cm3 of milk solution to tube 1, 10cm3 of protease to test tube 2, put both in 25 degrees water bath for 5 mins, mix together the two tubes, time how long it takes for cloudiness to disappear
Rate of reaction?
1/time taken for substrate to disappear or product to to appear
Why put enzyme and substrate both in bath separate?
To equilibrate them
Optimum temp?
Temp when ROR is at max and a decrease or increase in temp will decrease the ROR
Increase in temp?
Increase KE of molecules, mols move faster, chance of collisions is higher, more successful collisions occur = more product formed
How do enzymes denature?
Molecules vibrate, increased KE and vibration strains the enzyme and weakens hydrogen and ionic bonds which hold the tertiary structure, once tertiary structure alters = active site is not complementary
Temp coefficient?
Ratio between the ROR of two different temps for the same reaction (ROR at x + 10 degrees/ROR at x degrees =Q10)
What is ph?
Concentration of H+ ions in a solution (A decrease of 1 PH is a x10 difference in H+ ions)
How does ph effect enzymes?
Due to the active sites hydrogen bonds, a big change in H+ ions will break some of the AS bonds, enzyme can lose shape and get denatured also far away from neutral
How does ph differ from temperature when denaturing enzymes?
Reversible
When might PH cause a permanent denature?
When at extreme PH
How does low substrate concentration effect ROR?
Few substrate molecules, fewer collisions, fewer enzyme substrate complex’ formed
How does high enzyme concentration effect the ROR?
More AS’ available for substrates to fit in, more enzyme-substrate complexes form,
What is an issue with increasing substrate or enzyme concentration?
At some point there will be a limiting factor (whichever is not being increased) where there is not enough of the other reactant to collide with, or it is at its max ROR at that temp/ph
