Enzymes Flashcards
What does Catalase do?
Catalyses breakdown of hydrogen peroxide into water and oxygen
Is the breakdown of hydrogen peroxide intracellular or extracellular?
Extracellular
What does Amylase do?
Catalyses breakdown of carbohydrates from Starch to Maltose
What does Pepsin do?
Catalyses breakdown of proteins to peptides
Outline the Lock and Key hypothesis
- Enzyme’s active site is formed by its’ tertiary structure and is complementary to substrate.
- Substrate fits exactly in active site
Outline the induced fit hypothesis
- Active site isn’t exactly matched to the substrate
- Active site changes slightly to better accommodate the substrate
What do Cofactors do?
Stabilise the E+S complex
Name the two ways in which cofactors can act to stabilise the E+S complex
- As Co-substrates
- alter charge distribution
What is the definition of a ‘Prosthetic Group’?
A type of Cofactor
permanently bound to the enzyme
What cofactor is used by Carbonic Anhydrase?
Zinc
What is the definition of a Coenzyme?
A type of cofactor which is a non-protein molecule that is necessary for the function of the enzyme
Are coenzymes chemically changed in a reaction?
Yes
Where does a coenzyme bind to?
Temporarily, to the active site
When is an ES complex formed?
When the enzyme and substrate collide with enough kinetic energy
What bonds hold the ESC together?
Hydrogen bonds
Non-covalent
What is the effect of PH on enzyme activity?
- PH change interferes with hydrogen bonding in in the enzyme’s tertiary structure
- The enzyme’s tertiary structure is optimal for most efficient action
What is the effect of temperature on enzyme activity?
- Increase in temp means increase in rate
- more likely to collide with enough kinetic energy to form ESC
What happens when temp increases beyond the enzymes’ optimum temp?
Enzyme becomes denatured. Hydrogen bonds maintaining the tertiary structure are broken, so active site changes shape
What happens when an enzyme becomes denatured?
Active site no longer complementary to substrate, enzyme becomes totally inefficient
What is the effect of enzyme concentration on enzyme activity?
ROR and enzyme concentration are directly proportional
What is the effect of substrate concentration on enzyme activity?
ROR and substrate concentration are directly proportional, up to a point = Vmax
What is Vmax?
At Vmax, all enzyme active sites are occupied, with no available active sites are free to bind with substartes
What happens at Vmax?
The amount of enzyme becomes the limiting factor
What is the definition of a Cofactor?
A non-protein component of an enzyme that is required in order for the enzyme to function
What can inhibitors do?
Decrease the ROR of enzyme controlled reactions
Describe Competitive inhibitors
- Fits in Active site, but does not react
- Competes with substrate for active sute
- Effect is concentration dependant
- Effects are reversible/minimised by raising substrate conc.
Describe Non-Competitive inhibitors
- Binds to allosteric site
- Changes molecule shape preventing it working
- This is permanent and cannot be rectified
- Effect is dependant of substrate concentration
What is Q10 temperature coefficient?
It shows how much the rate of reaction changes when the temperature is raised by 10 degrees
What is the Q10 value of most enzyme-controlled reactions?
2
What is End-product inhibition?
When the final product in a metabolic pathway inhibits an enzyme that acts earlier on in the pathway
