ENZYMES Flashcards
What are enzymes
Biological catalysts
Globular proteins
Cause substrate molecules to interact at a faster rate
What are metabolic reactions
All the chemical reactions that take place in a cell
What is a catalyst
Substance that increases rate of reaction
Doesn’t take part in reaction
Can be reused
What is the Turnover number
Number of substrate moecluels an enzyme can catalyse per second
What is the Vmax
Enzymes can only increase rate up to a certain point
Max rate of enzyme catalysed reaction
What is a catabolic enzyme
Break substances down into smaller products
Releasing energy
E.g. Glucose
WHat is an anabolic enzyme
Build up reactants
Suing energy
E.g. Synthesis of large polymer base compounds
What is a modifying enzyme
Change substrate slightly
E.g. Alpha to beta glucose
What are intercellular enzymes
Enzyme action takes place inside cells
E..g synthesis of plumbers from monomers
E.g. Polysaccharides from glucose
Extra cellar enzymes
Nutrients need to provide substrate to cells for produc making
Nutrients in the form of polymers often - too large - have to be broken down before entering the cell
Enzymes released from cell and work outside cell they were released from
Examples of extra cellular enzymes
For fungi and bacteria
Trypsin
Amylase
Trypsin - digestion of protein
Breaks down protein into smaller peptides
Then broke. Down into amino acids
Trypsin produced by Pancras, released within pacreatic juices into small intestine
Amino acids absorbed by cells lining digestive system
Digestion of starch
Broken down into maltose using amylose
Amylose produced y salivary glands and pancreas
Maltose broken down in small intestine into glucose by Maltase
Glucose - absorbed by cells into blood stream
What part of the enzyme determines the specificity
Active site
Tertiary structure
What are the 2 hypothesises for enzyme action
Induced fit
Lock and key
Explain the induced fit hypothesis
New
Enzyme shape changes slightly as substrate enters
Initial enzyme - substrate interaction is weak but these interactions induc changes in tertiary structure, strengthening binding putting strain on substrate moecluels - weakening bands
Lock and key hypothesis
WHne the substrate is bond to active site, enzyme subs state complex is formed
Substrates react adn product formed( enzyme product complex)
Products released and enzyme unchanged
Substrate held by enzyme -atom groups close enough to react. R groups within the active site of the enzyme will also interact with TEH substrate, forming temporary bonds = put strain on bonds in substrate
Temperature- how does it affect enzyme activity
INCREASING temperature increases kinetic energy of particles
More frequently collide
Too hot - bonds in protein vibrate and strain, break and change 3D shape and active site
Q10 no longer applies
Q10
Temperature coefficient
Measure of how rate of relation increases with a 10 degree rise in temperature
What are thermophiles and how are their enzymes different
Extreme temperatures
Enzymes are more stable, high number of h bonds and sulphur bridges in tertiary structure, more resistance to change
How does ph affect enzyme activity
Change in h+ concentration
Hydrogen and ionic bonds between Amino acid r groups old protein in precise 3D shape, bonds result from interaction between Omar and charged r groups resent on amino acids forming primary structure
Hydrogen ions interact with polar positively charged r groups
Renaturation
Ph
Returns from post optimum shape,
BUT IF CHANGED SIGNIFICATNLY - denatured
How specifically does ph affect interactions
Changes degree of interaction and interaction of r groups with each other
MORE h+= less r groups are able to interact with each other, bonds in enzyme. Break , changes shape
Less h+- lots of bonds, changes shape
Ph buffer
Resists change in ph, mopping up excess h+ ions
How does substrate and enzyme concentration affect enzyme activity
Increased substrate particles = higher collision rate between susbryaet and active site, more enzyme substrate complexe formed
What does a graph look like for increasing. Substrate or enzyme concentration wand the effect on reaction rate
Rate of reaction increases up to a certain point
At this point, all active sites are occupied form substrate particles adn no more esc’s can be formed until products are released from active site
If enzyme conc is increased, substrate conc becomes limiting factor
Why do we need inhibitors
ENSURES NOT WASTING RPDOUCTS
So reaction don’t happen too fast
Leads to build up of excess products
WHat is a competitive inhibitor
Molecule or part of molecule has similar shape to substrate fo enzyme
Ca to into active site Blocks substrate from entering TEMPOARILY binds ( few exceptions e.g. Aspirin)
How do competitive inhibitors affect reaction rate
Susstrate and inhibitor moecluels present in solution will compete with each other to bind to active site
THis reduces number of substrate molecules binding to active site in given time and reduces rate
Vmax can still be reached ,when susbryaet concentration is increased, so much more substrate tan inhibitor
How does aspirin work
Irreversibly inhibits active site of COX enzymes
Competitive
Prevents synthesis of thromboxane, responsible for producing pain and fever
Non competitive inhibition
Inhibitor binds to the enzyme at a site other than the active site
Allosteric
The binding of the inhibitor causes the tertiary structure of the enzyme to change = active site changes shape
Active site no longer complementary to substrate
Enzyme can’t carry out function and doesn’t compete with inhibitor for active site
Some irreversible and some not
Vmax - non competitive inhibitors
after a certain point, increasing concentration of substrate has no effect
Vmax can’t be reached because substrate isn’t competing with enzyme for active site
Organosphates
Used as insecticides and herbicides
Irreversibly inhibit the enzyme acetyl chlorinetease an enzyme necessary for nerve impulse transition, can lead to muscle cramps, paralysis and even death
What is end product inhibition
Non competitive reversible inhibition
Enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme
Serves as negative feedback mechanism for the reaction , excess RPDOUCTS are not made and resources not wasted
E.g. Respiration and PSK and glucose
What is a COFACTOR
Non protein helper
May transfer atoms or groups from one reaction to another or form part of active site of the enzyme
Some cofactors change the charge distribution of the surface of the substrate// active site making temporary bonds in the ESC form more easily
How are inorganic cofactors obtained
Via diet as minerals e,g, iron, calcium ad chlorine
Coenzymes
Organic cofactors ( contain C) Binds temporarily to sub rate Chemically changed Derived from vitamins E.g. Vitamin b3 used to synthesise NAD, responsible for transfer of H atoms between moecluels involved in restoration
Prosthetic group cofactors
Cofactors containing prosthetic group
Permenantly bound
E.g. Zn2+ , to form part of carbonic anhydrase ( enzyme for metabolism of co2)
Precursors activation
Many enzymes produced in an inactive form = inactive pecurosor enzymes
Particularly damaging enzymes
Need to undergo a change in tertiary shape -atctive site
What is an inactive precursor enzyme called before and after COFACTOR is added?
Apoenzyme
After- halo enzyme
COFACTOR example
Amylase contains cl- ions, necessary for correctly formed activ site
What are zymogens and pro enzymes
Precursor enzymes activated by change in tertiary structure by another enzymes action or change in conditions such as ph or temperature
