2.4 Enzymes Flashcards
What is an enzyme?
A biological catalyst made of protein. They are used in metabolic reactions and lower the activation energy, not used up in the reaction
Describe anabolic and catabolic
Anabolic - require energy and combine simple molecules to form new molecules
Catabolic - release energy used to drive chemical reactions and break down larger molecules
Describe intracellular and extracellular reactions
Intracellular - reactions that occur within a cell
Extracellular - reactions that occur outside cell
Compare intracellular and extracellular enzymes
Both made inside a cell but extracellular enzymes must be released by exocytosis.
Intracellular - catalase
Extracellular - trypsin, amylase
How do enzymes work?
Enzymes combine reversibly with substrate molecules to form an enzyme substrate complex.
The ESC breaks down to give the product and release the enzyme in an unchanged form.
Describe the lock and key hypothesis and Induced fit
- The substrate is exactly the same shape as the enzyme active site
- The active site changes shape to accommodate the complementary substrate
How does temperature affect enzyme action?
- As temperature increases the enzyme and substrate gain kinetic energy so there are more successful collisions between the substrate and the active site so there are more ESC’s.
- However, if temperature exceeds the optimum the active site will change shape so it is no longer complementary to the substrate, tertiary structure changes, fewer ESC’s form
How PH impacts enzymes
Enzymes have an optimum PH. If out of range, denaturation occurs.
In a solution which is too acidic H+ ions interact with hydrogen and ionic bonds and breaks them.
In a solution which is too alkali OH attracts positive charges in bonds.
Change tertiary structure, active site no longer complementary, fewer ESC’s formed.
Describe the effect of substrate concentration in enzyme activity
As substrate concentration increases there are more successful collisions between the active site and substrate so more ESC’s form until all the active sites are saturated and enzyme concentration becomes the limiting factor.
Describe the effect of enzyme concentration on rate.
As enzyme concentration increases there are more successful collisions between the active site and the substrate so more ESC’s form until all of the substrate is used and substrate concentration becomes the limiting factor.
What are coenzymes (organic)?
Not permanently bound to the enzyme, needed to activate the enzyme, produce the specific shape of the active site, take part in the reaction e.g. vitamins
Describe cofactors (inorganic)
Permanently bound to enzyme, needed to form holoenzyme, produce specific shape of active site, NOT involved in the reaction e.g. Cl- for amylase
Describe prosthetic groups
Non protein group that is permanently bound to the enzyme e.g. Zn2+ for carbonic anhydrase
Describe competitive inhibitors
Substrate competes with inhibitors, both the substrate and the inhibitor have a complementary specific shape to the active site, fewer ESC’s form, increasing substrate concentration increases chances of the successful ESC’s
Describe non competitive inhibitors
The inhibitor binds to a site away from the active site known as the allosteric site resulting in a change in shape of the active site, substrate is no longer complementary to the active site, fewer ESC’s form
