Topic 1A- Biological Molecules (Enzymes) Flashcards
What type of proteins are all enzymes?
What is the full definition of a catalyst?
What are all enzymes?
What two things are most chemicals?
What is the activation energy?
How do enzymes work by?
What biologically are enzymes and what is their function?
What is the most important fact about enzymes?
What can each type of enzymes only do?
Globular proteins
A catalyst is a chemical that increases the rate of a chemical reaction, but does not get permanently altered in the reaction
Catalysts
Stable and require energy to make them react with each other
The energy you need to put in to get a reaction started is the activation energy
Reducing the activation energy needed for a chemical reaction to occur
Biological catalysts which reduce the activation energy of chemical reactions
They are highly specific
Only catalyse one chemical reaction.
What is the shape of enzymes of like?
What is the active site?
What can enzymes also do to a reaction?
What is the name of the first theory for enzymes?
What does this theory propose?
What does this mean would happen if this is right?
What happens when scientists examine the shape of the active site?
What does this then suggest?
What is the only difference in the induced fit theory?
What does this change then do to the enzyme resulting in what?
Enzymes have a very precise shape (part of the protein’s tertiary structure)
The part of the enzyme that fits the substrate (or substrates)
Enzymes can also catalyse the reaction in the opposite direction
Theory 1: The Lock and Key Theory
That the active site is rigid
The substrate molecules would have to be exactly complementary to the active site
It’s not exactly complementary to the substrate
That the active site must actually be a bit flexible
That as the substrate binds with the active site, it causes the enzyme to change shape slightly
Puts a strain on the bonds in the substrate molecule(s), and this lowers the activation energy.
What is formed when the substrate binds to the enzyme?
What does the active site have?
What happens to the products after the reaction?
Why are enzymes known as specific?
What is the shape of the active site determined by?
What will change the shape of the active site?
What will this result in and then lead to?
When do we say that the protein has been denatured?
What are the two ways to measure the rate of chemical reactions?
What are rates always measured in and give an example?
It forms an enzyme-substrate complex
A complementary shape
The products leave the enzyme because they no longer bind with the active site
Because they only catalyse one reaction
The tertiary structure of the enzyme
Anything that affects the tertiary structure of a protein (eg high temperature, high/low pH)
The substrate will no longer bind to the enzyme and the enzyme won’t catalyse the reaction
When the tertiary structure of a protein changes
- We can measure the amount of substrate being used up
- We can measure the amount of product being made
Per unit time (eg mile per hour).
What is the rate of reaction on a graph and what does this show?
What four things change once a reaction has started?
What will all of these things affect?
What is pH a measure of?
What can pH changes cause in enzymes?
What does this cause?
What does this cause to the enzyme?
What happens as a result of the substrate no longer fitting the active site?
What do we need to do to determine a rate?
What does higher temperature do to particles?
What two things does this result in?
The rate of the reaction is the slope (gradient) of the graph) that shows the amount of product or reactant
- The concentration of substrate
- The concentration of product
- Temperature
- pH
The rate of the reaction
A measure of the concentration of hydrogen ions
Can cause hydrogen and ionic bonds in the enzyme to break
Denaturation
Cause the enzymes to change shape
So the rate of the reaction becomes less
We need to calculate the amount of substrate used per unit of time
Increases the kinetic energy of the particles
More frequent collisions between substrate and enzymes, so a faster reaction rate.
What two things happen as the atoms in the enzyme move more rapidly?
What does this then change?
What then happens to the rate of the reaction and why?
What is the optimum temperature for many human/mammalian enzymes?
What is this not?
Ionic and disulphide bonds within the protein break (called denaturation)
Changes the tertiary structure of the protein
The substrate no longer fits the active site, so the rate of the reaction decreases
Around 40 oC
This is not the optimum for enzymes generally.
What can a small change in pH cause to enzymes?
What then happens if the pH returns to “normal”?
What therefore can a small change in pH result in?
What happens to enzymes if there’s a large change in pH?
What does this then change?
What does this then cause to the enzyme?
What therefore does a large change in pH result in?
H+ / OH- ions to block the active site
The H+ / OH- ions will move away and the active site will be unblocked
A reversible effect on enzyme activity
Causes hydrogen and ionic bonds to break
The tertiary structure of the enzyme
An irreversible change to the shape of the active site
A irreversible effect on enzyme activity (the enzyme is denatured).
What are and describe the two types of reactions that enzymes are involved in?
What is the full definition of denaturation?
What is and describe the collision theory in enzymes?
Describe the two features of competitive inhibitors?
What is an example of a competitive inhibitor?
Describe the two features of non-competitive inhibitors?
What are two examples of non-competitive inhibitors?
- Anabolic reactions (building)
- Catabolic reactions (breaking)
Denaturation is the irreversible changing of the active site’s shape due to breaking of hydrogen and other bonds in the molecules secondary, tertiary and quaternary structures
Small increases in temperature increase the energy and frequency of successful collisions between an enzyme and substrates, so the rate of reaction increases
- Similar shape to substrate
- Binds to active site of enzyme
Antibiotic sulphanilamide
- Binds to the enzyme (not in the active site) and changes its shape
- Substrate then no longer fits
Arsenic or Cyanide.
What happens at high substrate concentrations?
What happens at low substrate concentrations?
What happens as you increase the concentration of the enzyme?
What happens for any given substrate concentration?
What two things cause the maximum rate of reaction to still be limited?
Adding more substrate has no effect because all of the active sites are occupied, so rate plateaus
There are not many substrate molecules to collide with the enzymes. Adding more substrate increases the rate of reaction
There is more chance of a collision between substrate and enzyme
The rate of reaction will be faster the more enzyme molecules there are
Still limited by the amount of enzyme- or the number of active sites.
What is the saturation point?
The point at which all active sites are occupied by substrate molecules.
