2.5 Enzymes

Question 1

what is an enzyme

Answer 1

enzymes are gloubular proteins that act as catalyst - sped up reactions and remain unchanged

substrate –> product faster

an enzyme only catalyses one biochemical reaction

ENZYME SUBSTRATE SPECIFICITY

Question 2

why are enzymes substrate specific?

Answer 2

substrates bind to a special region on teh surface of the enzymes called an active site

shape and chemical properties match the two together

substrates are converted to products while bound to the active site and then released

Question 3

what are the stages of enzyme catalysis and how does the collision occur

Answer 3

1. the substrate binds to teh active site of the enzyme. Some enzymes have two substrates that bidn to different parts of the active site (needs to move very close to it and a collision must occur)
2. while the substrates are bound to the active site they change into different chemical substances
3. products seperate from teh active site leaving it vacant and the process repeats

collision

substrates are dissolved in water around enzyme

water is a liquid so in continual motion and each partical can move seperately

teh direction of movement is random and repeatedly changes

substrates are smaller than enzymes so move faster

substrate may be at any angle when collision occursbut need correct alignment for collision to be successful

Question 4

how does temp affect enzyme activity

Answer 4

in liquids particles have continual random motion

so when heated kinetic energy is gained so substrate and enzymes move faster and chance of collision is increased

when an enzyme is heated the bond in the enzyme vibrate and the bond is more likely to break . when it breaks this causes a change in the shape of the enzyme and active site . this is permanent and is called denaturing . as temp increases this happens to more and more enzymes

Question 5

how does PH affect enzyme activity

Answer 5

pH 5 is 10 time more acidic than pH6

optimum pH at which activity is highest

when teh h ion conc is higher or lower than optimum level structure of enzyme is altered - denatures- active site

wide range of optimum ph reflects wide range of PH environments

bacillus licheniformis secrets protease for PH between 9 and 10

this bacterium is cultured to produce alkaline tolerant protease for use in biological laundry detergents

Question 6

how does substrate conc affect enzyme activity

Answer 6

if conc is increased there are more substrate active site collisions so rate of enzyme catalysing is increased

however finite number of enzymes and as more conc more active sites are occupied so rate increases by less

–> greater proportion of active site are blocked

Question 7

how and why to produce lactose free milk

Answer 7

lactose is a sugar in milk and can be converted ot glucose and galactose by the enzyme lactase

lactase is obtained from kluveromyces lactis

a typeof yeast that grows in milk

bio tech extract the lactase from the yeast and purify it for sale to food manufacturers

1. some people are lactose intolerant and cannot drink more than 250 ml of milk a day
2. galactose and glucose are sweeter than lactose so you need to add less sugar to sweet foods
3. lactose crystallises when producing ice cream making it gritty. glucose and galactose are more soluble and remain dissolved so the texture is smooth
4. bacteria ferment glucose and galactose more quickly than lactose, so the production pf yogurt and cottage cheese is faster

peopel with lactose intolerance most to least

thailand

france

sweden

Question 8

what are immobilised enzymes and how where they invented

Answer 8

hans and eduard buchner showed that an extract of yeast with no yeast cells could convert sucrose to alcohol showing that you can use enzymes outside of living cells

contrast to louis pasteures theory of vitalism that you need living cells

use of enzymes in industry

the enzyme attaches to another material or into aggregations so the enzyme do not move too much

e.g. attaching enzymes to glass surface, trapping them in alginated gel, bonding them together to form enzyme aggregation of up to 0.1 mm in diameter

advantage

1. can be seperated from teh products of reaction and stop reaction at ideal time and prevent contamination of products
2. after being seperated form the reaction mixture the enzyme can be recycled so cost can be saved, enzyme are expensive
3. immobilization increases the stability of enzymes to changes in temp and pH which reduces the rate of degradation and if they need to be replaced
4. substrates can be exposed to higher enzyme conc than with dissolve enzymes, speeds up the reaction rate