Enzymes Flashcards
What is an enzyme?
An enzyme is a globular protein which acts as a biological catalyst by speeding up the rate of chemical reaction
What are 2 special features of enzymes?
- Enzymes are not changed or consumed by the reactions they catalyze
- Enzyme-substrate specificity explains the fact that enzymes can only catalyze one biochemical reaction
What are substrates?
The substances that enzymes convert into products
What is an active site?
The active site is the region on the surface of the enzyme which binds to the substrate molecule
What are the steps during enzyme catalysis?
- The substrate binds to the active site and an enzyme-substrate complex is formed
- The enzyme catalyzes the conversion of the substrate into product by lowering the reaction’s activation energy and an enzyme-product complex is formed
- The enzyme and product dissociate with enzyme not being altered
What is collision?
The coming together of a substrate molecule and an active site.
Successful collisions are ones in which the substrate and active sites are correctly aligned.
What condition is required for catalysis?
Catalysis only occurs if the substrates are in a liquid, so their molecules are in continual motion and there is a chance of collisions
What are the factors affecting enzyme activity?
- Temperature
- Low temperatures => insufficient thermal energy for
the activation of reaction (i.e. activation energy) - Increasing the temperature => increase in average
kinetic motion of substrates => increase frequency of
collisions => increased enzyme activity - Higher than optimum temperatures will eventually
cause enzyme to denature due to changes in the
enzyme’s bonds
- Low temperatures => insufficient thermal energy for
- pH
- changing the pH will alter the charge of the enzyme,
which in turn will alter protein structure (and so
function)
- changing the pH will alter the charge of the enzyme,
- Substrate concentration
- Concentration increases => frequency of collisions
increases => enzyme activity increases - After a certain point, the rate of activity will cease to
rise because the solution will be saturated with
substrate
- Concentration increases => frequency of collisions
What is denaturation?
Denaturation is when enzymes are irreversibly altered. Any change to the structure of the active site will negatively affect the enzyme’s capacity to bind to the substrate.
What are immobilized enzymes?
Enzymes fixed to a static surface
Why are immobilized enzymes used widely in industrial processes?
Immobilized enzymes are more efficient as:
- products can be easily separated from enzymes
- immobilization increases the stability of enzymes to changes in temperature and pH
- catalysis can be controlled by controlling amount of enzymes
- enzyme concentrations can be higher
What are the 3 methods of enzyme immobilization?
- Attachment to surfaces such as glass
- Entrapment in a membrane or a gel
- Aggregation by bonding enzymes together into particles of up to 0.1 mm diameter
What are three industrial processes where immobilized enzymes are used?
- Food production: enzymes are used in the production and refinement of beers and dairy products
- Textiles: enzymes are utilized in the processing of fibers
- Paper: enzymes assist in the pulping of wood for paper production
How is lactose-free milk produced?
Lactose-free milk can be produced by treating the milk with the enzyme lactase:
- the lactase is purified from yeast or bacteria and then bound to an inert substance
- the milk is then repeatedly passed over this enzyme, becoming lactase free
What are the benefits of lactose-free milk?
- Source of dairy for lactose-intolerant individuals
- Galactose and glucose are sweeter than lactose, so less sugar needs to be added to milk shakes or yogurt
- Avoiding crystallization of ice creams as monosacccharides are more soluble
- Reduces production time for cheese and yogurt as bacteria ferment monosaccharides more readily
