enzymes Flashcards
what are the two types of enzymes?
- anabolic; making bonds
- catabolic; breaking bonds
what are three properties of enzymes?
- biological catalysts that dont get permanently damaged
- globular proteins at the tertiary level
- effective in small amounts
- reaction specific
- denature at high temps
give an example of an enzyme-catalysed reaction
sucrose + water = glucose + fructose
what 3 conditions are needed for a typical chemical reaction to take place?
- substrates collide with enzyme with sufficient kinetic energy
- energy of products is lower than substrates
- initial boost of energy is needed
describe the structure of an enzyme?
- active site made of a small number of amino acids
- substrate fits neatly into active site
- hydrogen bonds maintain the shape
what are the two enzyme-substrate complex models?
- induced fit
- lock and key
how does the induced fit enzyme model work?
- proximity of substrate to enzyme causes enzyme to change shape due to bonds changing and form a functional active site
- enzyme moulds itself around the substrate
- as shape of enzyme changes, strain put on substrate which causes it to break apart
how does the lock and key enzyme model work?
- each enzyme has only one substrate that can fit into it
what are the advantages of the induced fit model?
fits the observations that enzymes are flexible and can change shape
what are the advantages of the lock and key model?
shows that enzymes and substrates are specific to each other
what are the disadvantages of the induced fit model?
may not show that enzymes and substrates are specific and complementary to each other
what are the disadvantages of the lock and key model?
it suggests that enzymes are rigid and inflexible, which is untrue
what two things must happen in order for an enzyme to work?
- must have a complimentary active site to the substrate
- must come into physical contact with the substrate
what are the two ways that the rate of enzyme controlled reactions can be measured?
- the rate of production of a product molecule
- the rate of disappearance of a substrate molecule
describe the effect of temperature on enzyme controlled reactions?
- at first as temperature increases, rate increases
- the rate peaks at around 40 degrees
- at temps higher than 40, rate rapidly decreases
describe why temperatures above 45 degrees often cause enzymes to denature?
- as temperature increases, kinetic energy increases
- as KE increases, the particles vibrate more
- too many vibrations cause the ionic, hydrogen and disulphide bonds that hold the active site in place to break
what is the optimum PH for the following enzymes;
a) pepsin
b) salivary amylase
a) 2
b) 7
describe the effect of PH on enzyme controlled reactions
- a change in PH causes the charged of the amino acids in the enzyme to change
- due to this, the substrate may no longer be able to become attached to the active site, so no ES complexes will be formed
- the PH changes could also cause a change in bonds which changes the active site, resulting in the same thing
describe the effect of enzyme concentration on the rate of an enzyme controlled reaction
- if there are too little enzymes, the reaction is slow because a very small amount of enzymes will have to break down or react with all of the substrate
- if there is a good amount of enzymes, the reaction will be fast
- too many enzymes will have no effect as there is only so much substrate that can be worked on, so extra enzymes will do nothing
what are enzyme inhibitors?
- molecules which have an altering effect on the active site of an enzyme
- this causes reduced activity of an enzyme so slows the rate of an enzyme controlled reaction
what are the two types of enzyme inhibitors?
- temporary
- permanent
what is a competitive enzyme inhibitor, and are they permanent or temporary?
- a molecule that is shaped similarly to the substrate, and then binds to the enzymes active site
- so is “competing” with the substrate
- temporary
what is a non-competitive inhibitor, and are they temporary or permanent?
- a molecule which binds to the enzyme at a point other than the active site, which changes the shape of the enzyme and active site so the substrate no longer fits
- temporary
