2: Enzymes Flashcards
What do catalysts do?
- speed up chemical reactions without being changed themselves
Define ‘enzyme’.
- biological catalysts produced by living organisms that speed up and control the rate of reactions of metabolism
- globular proteins
Define ‘substrate’.
a reactant in an enzyme-catalysed reaction
What makes it possible for enzymes to catalyse reactions?
- special region called the active site
catalysis only occurs if the substrates are in a liquid:
- molecules are in continual random motion
= chance of collusions between the substrates and the active site on the surface of the enzyme
What do collisions between active site and substrate result in? Why?
binding
- the shape and chemical properties of the active site complement those of substrates
= they are chemically attracted to each other and fit together
State and define a key characteristic of enzymes.
enzymes are “substrate specific”
= molecules other than the substrate do not fit or are not attracted so do not bind
How do enzymes speed up metabolic reactions?
- binding of substrates to the active site reduces the energy needed for them to be converted into products
What happens to the substrate once it binds to the active site of an enzyme?
- substrate converted into products
- products released, freeing it up to catalyse reactions with more substrates
How fast can an enzyme catalyse its reaction?
many times a second
Where else, outside living organisms, are enzymes widely used? What for?
in industry for catalysing specific reactions
What type of enzymes are the enzymes used in industry?
immobilized enzymes - enzymes attached to another material or into aggregations (groups) to restrict their movement
State 5 benefits of using immobilised enzymes in industry.
- catalysis can be controlled by adding/ removing enzymes promptly from reaction mixture
- enzyme concentrations can be higher
- enzymes can be reused, saving money
- enzymes are resistant to denaturation over greater ranges of pH and temperature
- products are not contaminated with enzymes
Name some methods of immobilising enzymes.
- attachment to surfaces such as glass (absorption)
- entrapment in a membrane or a gel (e.g. alginate)
- aggregation by bonding enzymes together into particles of up to 0.1mm diameter
What molecule is the sugar in milk?
lactose
What does lactase do to lactose?
lactase hydrolyses lactose into: glucose + galactose
How is lactose-free milk produced?
- either by adding free lactase to milk
- or by using lactase that has been immobilised on a surface or in beads of a porous material
Draw a diagram of ‘making alignate beads containing lactase’. (p26)
- syring
- mixture of sodium alignate and lactase
- 2% calcium chloride solution
- bead
Draw a diagram of ‘adding lactase that has been immobilised on a surface or in beads of porous material’ (p26)
- aliginate beads containing lactase
- syringe barrel
- screw gate clip
- glucose test strip
How is lactase obtained?
from microorganisms such as Kluveromyces lactis, a yeast that grows in milk
Name some advantages of lactose-free milk.
- many people are lactose intolerant and cannot drink more than 250ml of milk per day unless it is lactose-reduced
- galactose and glucose = sweeter than lactose, so less sugar needs to be added to sweet foods containing milk, such as milk shakes or fruit yoghurt
- lactose tends to crystallize during production of ice cream, giving it a gritty texture. Because glucose and galactose are more soluble than lactose they remain dissolved, giving a smoother texture
- bacteria ferment glucose and galactose more quickly than lactose, so the production of yoghurt and cottage cheese is faster
