B1.2 - What happens in cells - Enzymes Flashcards
What is an enzyme?
a protein that functions as a biological catalyst
what is a catalyst?
a substance that speeds up a chemical reaction and is not changed by the reaction
metabolism
reactions that happen inside an organism
what is catalase?
an enzyme found in almost every type of living tissue e.g. liver
what does catalase break down?
what reaction does catalase speed up?
hydrogen peroxide
Hydrogen peroxide –> water + oxygen
catalase
how do enzymes speed up reactions?
- break larger molecules into smaller ones
- build larger molecules from smaller ones
- change 1 molecule into another
how do enzymes work - lock and key model
- substrate enters active site of enzyme
- substrate binds to enzyme forming enzyme-substrate complex
- the binding of substrate causes stress on glucose-fructose bond - bond breaks
- products are released - glucose and fructose - enzyme is now free to bind to another substrate
what enzyme breaks down starch?
Amylase breaks starch into maltose
where is amylase found?
saliva and small intestine
what colour will the iodine turn if amylase has not broken down the starch?
blue / black - shows starch is present
what colour will the iodine turn if amylase has broken down the starch?
brown
describe the denaturing of an enzyme
if temp changes sufficiently beyond enzymes optimum, the shape of the enzymes active sight irreversibly changes as bonds are broken - substrate will no longer fit
- if all enzymes are denatured the reaction stops
what are the effects of pH on enzymes?
- diff enzymes work best at diff pH’S
- enzymes become inactive (but not denatured) as pH varies either side of the optimum
- only in extreme pH’s are enzymes denatured
what does the optimum pH of an enzyme depend on?
the site of action
the rate of enzyme-controlled reactions is caused by…..
- Temperature
- pH
the higher the substrate concentration the faster the rate of reaction until….
- all enzyme molecules are locked with the substrate molecules - known as the saturation point
- rate is now at maximum and will not increase further unless more enzyme is added
what is collision theory
- when enzymes and its substrate move around they randomly collide
- some collisions result in reactions - fruitful / successful collisions - the more occurring the faster a reaction
- as temp increases so does rate of reaction
and fruitful collisions
what happens when temperatures are higher than the enzymes optimum?
enzyme denatures by breaking down their protein structure
how does substrate concentration effect rate of reaction?
the higher substrate concentration the faster the rate until - all enzyme molecules are locked with the substrate molecules (AKA saturation point) - rate is at max and wont increase further unless more enzyme is added
