Enzymes Flashcards
What are enzymes ?
- biological catalysts
- globular proteins
- speed up chemical reactions without being used up
What are anabolic reactions ?
building of molecules
What are catabolic reactions ?
breaking of molecules
What is the lock and key hypothesis ?
- only a specific substrate will fit into the active site
- forms an enzyme-substrate complex
- substrate reacts and products are formed
- enzyme- product complex
- products are released
What is the induced fit hypothesis ?
- active site slightly changes to fit the substrate
- weaken the bonds in the substrate and lowers the activation energy
What is activation energy ?
the amount of energy that needs to be supplied to chemicals before the reaction will start
How does the formation of the enzyme substrate complex lower the activation energy ?
- ## when catalysing a breakdown reaction the substrate fitting into the active site puts a strain on the bonds and the substrate can break more easily
What are intracellular enzymes ?
- enzymes that act within cells
- catalase breaks down harmful hydrogen peroxide into water and oxygen
What are extracellular enzymes ?
- secreted by cells and catalyse reactions outside of cells
- digestion of proteins and starch
How is starch digested ?
- starch is broken down into maltose by amylase
- maltose is broken down into glucose by maltase
How are proteins digested ?
-trypsin catalyses the digestion of proteins into smaller peptides
- trypsin is produced in the pancreas and released with pancreatic juice
what is the effect of temperature on enzymes
- increasing temperature increases kinetic energy and the particles move faster and collide frequently
- more frequent collisions between the substrate and enzyme
Enzyme denaturation from temperature
- increasing temperature increases vibrations until the bonds strain and break
- breaking of the bonds changes the tertiary structure
Enzymes and optimum temperature
- temperature at which the enzyme has the highest rate of activity
- once denaturation occurs the decrease in the rate of reaction is rapid
- decrease in the rate of reaction below the optimum is less rapid as the enzyme is less active
what is temperature coefficient
- measure of hoe much the rate of reaction increase with 10 degrees
- rate of reaction doubles with a 10 degree increase
what is the effect of pH on enzymes
- when pH changes from the optimum causes denaturation and a change in shape
- renaturation - pH returns to the optimum
- more hydrogen bonds (low pH) the R-groups interact less and bonds break and changes shape
- shape of the enzyme changes as pH changes
- only functions within a narrow pH range
what is the effect of enzyme concentration
- higher the concentration the greater number of active sites available and greater likelihood of an enzyme substrate complex formation
- sufficient amount of substrate available the initial rate of reaction increases linearly
- limited amount of substrate any further increase in enzyme concentration won’t increase the reaction rate
what is the effect of enzyme concentration
- greater substrate concentration the high the rate of reaction
- no. substrate molecules increase likelihood of enzyme substrate complex formation
- all active sites become saturated and any increase in substrate concentration won’t increase the rate of reaction
What are enzyme inhibitors
- molecules that prevent enzymes from carrying out their normal function as catalysts
what are competitive inhibitors
- molecule has a similar shape to substrate
- blocks substrate from entering active site
- cannot carry out its function
- reduces the number of substrate molecules binding to active sites and slows rate of reaction
- reversible
what is the effect of competitive inhibitors on the rate of reaction
- high concentration of inhibitor reduces rate of reaction
- high concentration of substrate increases the rate of reaction
what are non competitive inhibitors
- inhibitor binds to allosteric site
- causes tertiary structure of the enzyme to change and the active site
- active site no longer has a complementary shape
what is the effect of non competitive inhibitors on the rate of reaction
- increasing the concentration of enzyme / substrate won’t overcome the effect
- increasing concentration of the inhibitor decreases the rate of reaction
what is end - product inhibition
- enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that it produces
- regulates metabolic pathways
What is an example of a metabolic pathway
- glucose is broken down by the addition of two phosphate groups
- addition of the second phosphate group is catalysed by phosphofructokinase
- high ATP levels more ATP binds to the allosteric site on PFK preventing the addition of the second phosphate to glucose
- As ATP is used up less binds to the PFK and the enzyme catalyses the second addition
what are co factors
- inorganic non-protein substances
- help the enzyme function properly
- help enzyme and substrate to bind together
- aren’t used up or changed
- can be permanent or temporary
what are co enzymes
- organic non-protein cofactors
- changed by the reaction
- move chemical groups between enzymes aiding in catalysis
what are prosthetic groups
- cofactors that are a permanent structure of the enzyme they assist
- essential to the enzyme functioning properly
- form the final 3D shape of the enzyme
