Enzymes and the Digestive System Flashcards
(36 cards)
what is an enzyme?
a biological catalyst that speeds up a reaction without being used up, lowers activation energy, bends the bonds within the substrate
fun facts about enzymes (6):
- they’re globular proteins
- proteins of high weight to have substantial stability and strength
- sensitive to both temperature and PH hydrogen and ionic bonds specifically impacted
- catalyse both anabolic (building up) and catabolic (breaking down) reactions
- soluble in water - dependent on the R-group
- enzymes can be extracellular and intracellular
groups of enzymes:
lyases: splitting of bonds other than hydrolysis or oxidation
hydrolases: hydrolysis of bonds - all digestive enzymes
ligases: joining of two molecules by formation of covalent bonds
isomerase: isomerisation of molecules
what are activators?
inorganic groups permanently bound to enzymes and are a type of prosthetic group
what are co-enzymes?
organic molecules that bind only temporarily to the enzyme transferring a chemical group necessary required for a reaction
what is the active site?
3D specific tertiary structure complementary to the substrate
what’s the substrate function?
the substrate binds to the active site -> creates enzyme/substrate complex bends bonds of substrate -> enzyme/product complex -> active site will release products they diffuse away - we know this as the lock and key theory
what is the lock and key theory?
substrate is an exact complimentary shape to the active site
what is the Induced Fit Model?
- this model takes into account the fact that protein active sites have some three-dimensional flexibility
- substrate binds to the enzyme at the active site similar complimentary shape to substrates but NOT exact
- binding of substrate induces the enzyme to change shape such that there is an exact fit in the active site once the substrate has bound
- reactions can only take place AFTER induced fit has occurred
what are factors effecting the rate of reaction (6)?
- temperature
- PH (log-[H+])
- concentration of substrate
- concentration of enzyme
- inhibitors
- activators
describe the temperature graph?
bottom of curve: rate of reaction at its slowest, the internal kinetic energy of the molecules don’t reach the activation energy. Fewer successful collisions, fewer enzyme/substrate complexes, enzymes and substrate kinetic energy have little kinetic energy
mid of curve: increased temperature more kinetic energy, high number of successful collisions, high number of enzyme/substrate complexes, more product formed per second and a higher rate of reaction
optimum: fastest rate of reaction, most successful collisions per rate, highest rate of enzyme/substrate complexes and highest rate of product formation
after optimum: active site denatures - its 3d tertiary structure is no longer complimentary to the substrate, fewer successful collisions per second, lower rate of enzyme/substrate complexes forming, lower rate of product formation, decrease in rate of reaction -> structure of active site is no longer complimentary to the substrate temperature overcome tertiary structure bonds - hydrogen, ionic, disulphide are broken and this changes the 3d tertiary structure of the active site
Describe the Ph graph:
pAll enzymes have an optimum Ph at which they operate best
Enzymes are denatured at exrmtreames of Ph:
Hydrogen and ionic bonds hold the tertiary structure of the protein together
Below and above the optimum Ph of an enzyme, solutions with an excess of H+ ions and OH- ions can cause these binds to break
This alters the shape of the active site, which means enzyme-substrate complexes form less easily. Eventually, enzyme-substrate complexes can no longer form at all at this point compleate denaturation has occurred
Describe a substrate concentration graph:
Increase concentration of substrates high rate of reaction because there are available active sites. Substrate concentration is limiting the rate of reaction. As the graph levels off, all active sites are occupied, and the rate of reaction is at its fastest. High concentration of substrate doesn’t increases the rate of reaction, as active sites are the limiting factor, resulting in a maximum number of enzyme-substrate complexes
Describe an enzyme concentration graph:
The rate of reaction is directly proportional to the enzyme concentration. As the enzyme concentration increases, so does the rate of reaction as more active sites are available
What are inhibitors function?
They slow down the rate of reaction by inhibiting the enzyme
Describe a competitive inhibitor graph:
At low substrate concentration the rate of reaction is reduced in the presence of an inhibitor there is increased probability that the competitive inhibitor will bind to the active site- reducing the number of enzyme-substrate complexes which decreases the rate of reaction.
The effect of the inhibitor is overcome by very high substrate concentration. At high concentrations, the inhibitor is out-compeated by the substrate, and the max rate of reaction is achieved. Max number of enzyme-substrate complexes formed. All active sites occupied by substrates which result in the highest rate of reaction
what is a competitive inhibitor?
competitive inhibitors have a similar 3D shape to the substrate or a complimentary 3D shape to the active site. when the competitive inhibitor binds to the active site it prevents enzyme-substrate complexes from forming, active sites are occupied –> fewer products are formed per second –> lowers rate of reaction
what is a non-competitive inhibitor?
a non-competitive inhibitor binds to the binding site away from the active site, which causes a 3D shape change to the active site. this prevents the active site from bending the bonds, which further prevents successful enzyme-substrate complexes forming, which lowers the rate of reaction. the active site is no longer a 3D complimentary shape to the substrate
Describe a non-competitive inhibitor graph and the function of a non-competitive inhibitor?
the graph of a non-competitive inhibitor levels off very early on because the maximum rate of reaction is never achieved.
the effect of a non-competitive inhibitor is not overcome by increasing the substrate concentration. all enzyme molecules with bound non-competitive inhibitors do NOT convert substrate to product.
what is end product inhibition?
products often act as a regulator. when the concentration of product is high it binds non-competitively to an enzyme in pathway, blocking further production of itself. when concertation of the products falls it leaves the binding site and the active site/ enzyme is the available
What is an activator?
- molecules that bind to enzymes and increase their activity
- they are often involved in the allosteric regulation of enzymes
- they bind to an alternate site on an enzyme, changing the shape of the active site cause the 3D tertiary structure of the active site to become complementary to the substrate
About Salivary amylase:
1-4/1-6 glycosidic bonds, hydrolyses starch into shorter chains which increase the surface area. It’s found in the salivary glands which transport the salivary amylase into the mouth, found in saliva (enzyme and buffer). Ph 7 environment
About endopeptidases:
hydrolyse peptide bonds within the peptide chain. Hydrolyses proteins into shorter chain polypeptides, which increases the number of terminal ends which increases the surface area. It’s found in the stomach - enzymes and HCl likes a Ph 2
About pancreatic enzymes:
endopeptidases - shorter chains into di-peptides
exopeptidases - hydrolyses peptide binds at terminal ends of the shorter polypeptide chains
pancreatic amylase - short chain starch into disaccharides e.g. maltose
lipase - hydrolyses the ester bond, hydrolyses lipids into a mono-glyceride and two fatty acids
all found in the pancreas - all made in the pancreas and delivered by the pancreatic duct to the duodenum -the upper part of the small intestine. bile made in the liver stores in the gallbladder: emulsifies, and neutralises the acidic food the Ph 8/9
all these enzymes like a Ph 8/9
