Molecular Biology - 2.5 Enzymes Flashcards
What is an enzyme?
- They are catalysts
- They are proteins
- They are used in all cell metabolic reactions (eg. photosynthesis, respiration, cell division, food metabolism, digestion and protein synthesis)
-> they lower the activation every required for a reaction to take place (rate = amount of reactant used up in a given amount of time)
The shape and chemical properties of the active site are highly dependent on the tertiary structure of the enzyme
Enzyme Understandings:
- Enzymes have an active site to which specific substrates bind
- Enzyme catalysis involves molecular motion and the collision of substrates with the active site
- Enzymes lower the activation energy of the chemical reactions that they catalyse
Breakdown of how enzymes work and the key terms/components
3 things
Enzymes work due to their shape = they have an area called the ACTIVE SITE that brings the reactive parts of molecules together (ie the substrate) (either breaking them apart or clicking them together)
They temporarily form a ENZYME-SUBSTRATE COMPLEX - a change is induced in the shape of the enzyme molecule (ie INDUCED FIT) ie causing a strain on the chemical bonds between the substrate moles = they react and the product is released
The enzyme is UNCHARGED and UNCHANGED ie. can catalyse another creation straight away
- > “lock and key fit”
- > “induced fit”
Information about the reactions between substrate and enzyme
Reactions can only occur if the substrate and enzyme are in a LIQUID and in RANDOM MOTION and they can COLLIDE with one another.
- > “lock and key fit”
- > “induced fit”
Enzymes are SPECIFIC (and only catalyse one reaction - the active site and the specific substrate are chemically attracted to one another. Other molecules will not be attracted and bind)
Denaturation of enzymes
Understanding: enzymes can be denatured
Denaturation = a structural change in a protein that results in the loss (USUALLY PERMANENT) of its biological properties. (eg. the DNA strands unravel (eg. cooking an egg))
Things that cause denaturation = heat, pH
Explain enzyme substrate specificity
The enzyme will only catalyse one reaction - ie. lock and key fit or enduced fit - therefore, the enzyme only reacts with a certain type of substrate
Factors that affect enzymes
Understanding: - Temprepreture - pH - substrate concentration affect the rate of acticity of enzymes
YOU NEED TO BE ABLE TO EXPLAIN AND DRAW/RECOGNISE EACH OF THESE (ON GRAPHS)
FAE = Tempreture
Low temps = reaction is slow ( insufficient thermal energy for the activation of an enzyme-catalysed reaction to proceed) due to few collisions
As temp rises = action speeds up (movement of both enzymes and substrates) until an OPTIMUM temp is reached = higher enzyme activity
OPTIMUM = the peak
Past OPTIMUM temp = action of collisions is slowed down until above 50 degrees celcius (this is when the protein is denatured) - disulfide bonds are broken
(although, some enzymes can operate at high temps)
FAE = pH
Enzymes catalyst reactions at a specific pH - for most enzymes, OPTIMUN pH = between pH 5 and 9
Changing the pH will alter the charge of the enzyme, which in turn will alter protein solubility and overall shape
Changing the shape or charge of the active site will diminish its ability to bind the substrate, abrogating enzyme function
Enzymes have an optimal pH (may differ between enzymes) and moving outside this range diminishes enzyme activity
Examples:
- Pensin (stomach enzyme) = best at pH 2
- Amylase (mouth starch enzyme) = best at pH 7
- Trypsin (duodenum enzyme) = best at pH 9`
FAE = Enzyme/substrate concentration
(the reactant = the thing that the enzyme is acting on)
Beginning = lots of reactants and enzymes
Ending = enzymes/substrates used (there is excess substrate concentration and not enough enzymes)
Increasing SC = increase the activity of a corresponding enzyme -> more substance = increased chance of enzyme and substrate colliding and reacting
After a certain point, the rate of activity will cease to rise regardless of any further increases in substrate levels
This is because the environment is saturated with substrate and all enzymes are bound and reacting (Vmax)
- can incluse co-factors and/or co-enzymes
Co-factors and co-enzymes
The activity of some enzymes requires co-factors
These may include metal ions, vitamins, minerals are inorganic and organic chemicals that assist enzymes during the caralusis of reations
Co-factors and co-enzymes
Co-factors = metals (no carbon = inorganic)
Co-enzymes = (have carbon = organic) eg. organic vitamins
Use of enzymes in industry
Understandings: immobilized enzymes are widely used in industry
Application: Methods of production of lactose-free milk and its advantage
Enzymes are extensively used in industry for the production of items from fruit juice to watshing powder
Enzymes are usually immobilised by attachment to another material (eg. glass beads to restrict their movement so they can be easily separated from the product and used again)
Methods of producing lactose-free milk
Lactise us a disaccgaride of glucose and galactose which can be broken down by the enzyme lactast
It is produced by purifying lactase (eg. from yeast or bacteria) and binding it to an inert substance (such as algineate beads) - milk is passed over the immobilised enzyme and will become lactose=-free
Advantages of lactose free milk:
- as a source of milk for lactose-intorlerant people
- as a means to increast the sweetness of milk (glucose/galactose are sweeter in flavour) = no need for artifical sweeteners
- As a way of reducing the crystallisation of ice-creams (glucose and galactose are more soluble than lactose)
- As a means of shortening the production time for yogurts or cheese (bacteria ferment glucose and galactose more readily than lactose.
