UNIT 2: Enzymes Flashcards
enzymes
folded, globular shaped protein catalysts that speed up reactions without being used up.
examples of catabolic enzymes
pepsin - digests proteins into peptides
amylase - digests starch into maltose
lipase- digests fats into fatty acids and glycerol
examples of anabolic enzymes
potato phosphorylase - makes starch from glucose
DNA polymerase - makes DNA from its building blocks (nucleotides)
active site theory of enzyme action
all enzymes have an active site when the enzyme combines with its specific substrate.
involves two models of enzyme action; 1. lock and key model, 2. induced fit model
active site
area of the enzyme where substrate enters and is changes into products
specificity
refers to the enzymes ability to react with only one substrate
substrate
substance upon which the enzyme acts
product
substance that results from the action of the enzyme
lock and key model
- enzyme has a rigid shape.
- the substrate enters the active site of the enzyme and fits snugly, much like a key fits in a lock,
- an enzyme-substrate complex is formed.
- substrate is changed into product(s)
- products exit the active site.
induced fit model
- substrate enters active site.
- the enzyme changes its shape slightly to accept substrate.
- an enzyme substrate complex is formed.
- substrate is changed into products
- products exit the active site upon which point the enzyme returns to its original shape
optimum activity of an enzyme
refers to the conditions under which an enzyme works best.
generally most human enzymes work best at 37˚C at a pH 7. An exception is pepsin, which acts on proteins in the stomach at a pH of 1-2.
Plant enzymes work bets between the temperatures of 10-30˚C depending on their natural habitat.
denaturation
involves a permanent change in the shape of an enzyme so that it does not act on its substrate.
Human enzymes will begin to denature at around 40˚C. During infections the temperature of the human body can reach 42˚C.
bioprocessing
the use of enzyme-controlled reactions to produce a product
e. g.
- production of beer using yeast
- production of insulin using genetically-modified E coli bacteria.
- production of cheese using the enzyme rennin
- production of fructose from glucose using glucose isomerase
bioreactor
a vessel or container in which living cells or their products are used to make a product
immobilized enzymes
enzymes that are attached to or trapped in an inert insoluble material.
- carrier-blinding method;
- physical adsorption
- ionic binding
- covalent binding - cross-linking method
- entrapment method
uses of immobilized enzymes
- immobilized lactase breaks down lactose in milk for lactose-intolerant people
- immobilized rennin is used in the cheese-making process
- immobilized glucose isomerase is used in sweet manufacture as fructose is sweeter than glucose
advantages of immobilized enzymes
- immobilized enzymes are more stable
- efficiency of the enzyme is unaffected
- easy recovery of product and enzyme at end of reaction
- immobilized enzymes can be reused many times reducing costs to manufacturers
Batch culture
- a fixed amount of substrate is placed into bioreactor
- reaction is allowed to proceed.
- product is collected at end of reaction
- bioreactor is then cleaned out for next batch
continuous flow culture
- substrate is continually infused into the bioreactor
- reaction proceeds and conditions within are strictly controlled using sensors
- product is continually collected
Cellular energy
The energy stored in the bonds of biomolecules
Catalyst
A substance that speeds up a reaction, without itself being used up in the reaction
