Enzymes 1A Flashcards
What is an enzyme
A biological catalyst which speeds up metabolic reactions by lowering the activation energy
What is the lock and key theory
Where the substate binds to the active site of the enzyme and forms an enzyme substate complex so that the reactants can be catalysed into products
What is the induced fit theory
Where the substrate doesn’t only have to be the right shape to fit the active site, it has to make the active site change shape in the right way as well.
How do an enzymes properties relate to its tertiary structure
Enzymes are very specific - they usually only catalyse one reaction. This is because only one complementary substate will fit into the active site. The active site’s shape is determined by the enzymes tertiary structure if this is altered then the enzymes active site will change shape. This means that the substate will no longer fit into the active site and enzyme substate complexes cannot be made, meaning no reaction can taken place. An enzymes tertiary structure can be altered by things like temperature or PH. The primary structure of a protein is determined by a gene. If a mutation occurs in that gene it could alter the enzymes tertiary structure
How does temperature influence enzyme activity
Increase in temperature causes the enzymes molecules to vibrate more. If the temperature goes above a certain level the vibration breaks some of the bonds holding the enzyme in shape this denatures the enzyme
How does PH influence enzyme activity
All enzymes have an optimum PH. Above and below the optimum PH the H+ and OH- ions found in acids and alkalis can mess up the hydrogen and ionic bonds that hold the enzymes tertiary structure together. This means the enzyme is denatured
How does enzyme concentration affect rate of reaction
The more enzyme molecules there are in a solution the more likely a substate is to collide with one and form an enzyme substate complex so increasing the concentration increases the rate of reaction but if the substate is the limiting reactant then adding more enzyme with have no further effect
How does substate concentration affect rate of reaction
The higher the substate concentration the faster the reaction more substate means a collision is more likely and so more active sites are used. However there comes where all the active sites are all full so adding more substate will have no further effect. Rate of reaction decreases over time
How does competitive inhibition affect enzyme activity
Competitive inhibitor similar shape to substate. They compete with the substate molecules to bind to the active site but no reaction takes place and they block the active site so no substates can bind
How does non competitive inhibition affect enzyme activity
Non competitive inhibitors bind to an allosteric site changing the shape of the enzymes active site so no substate can bind and no enzyme substate complexes can be made so no reaction takes place
How do you measure the rate of enzyme controlled reactions
- Catalase catalyses the breakdown of hydrogen peroxide into water and oxygen.
Set up a boiling tubes containing the same volume and concentration of hydrogen peroxide add a buffer
set up an upside down measuring cylinder with a boiling tube attached to a bung
Put each boiling tube in a water bath set to a different temperature along with another tube containing catalyse
Use a pipette to add same volume and concentration of catalase to each boiling tube
Attach bung and measure oxygen produced in one minute calculate a mean
How to measure how fast a substate is broken down
Add a drop of iodine in potassium iodide to each spotting tile mix together a known concentration of starch and amylase and add a drop to each spotting tile then measure how long it takes for the solution turning from orange to blue black
