Book 3- enzymes Flashcards
What are enzymes?
biological catalysts enabling chemical reactions to take place in a cell at relatively low temperatures. They are not used up, just lower the activation energy
Explain the structure of proteins?
- globular proteins
- made up of amino acids joined together by peptide bonds forming a primary structure
- that is then folded into secondary structures then further into tertiary
- hydrogen, ionic and disulphide bonds hold the structure in place
How do enzymes function?
Enzymes have a specific tertiary structure, so have a specific active site that only complementary substrate can bind to. This forms an ES complex. Bonds in the substrate are either made or broken (condensation/hydrolysis reactions). The products are then released from the active site and the enzyme is free to take part in further reactions.
What is the lock and key theory?
this theory describes how the enzyme’s active site has a fixed shape. The active site is complementary before and after the substrate binds as the active site shape does not change shape.
What is the induced fit theory?
the active site is not complementary shape to the substrate. as the substrate moves into the active site, the active site shape changes and becomes complementary to the substrate.
What factors effect the rate of reaction?
enzyme conc, substrate conc, temperature, pH, inhibitrs
How does the enzyme conc affect the rate of reaction?
As the conc increases, the rate increases because more and more ES complexes form as more enzymes are added. Eventually the reaction would stop as the substrate would run out.
How does the substrate conc affect the rate of reaction?
rate increases as more ES complexes form. the rate slows down to a constant rate as all active sites have been occupied by substrate molecules.
How does the temperature affect the rate of reaction?
The rate increases as temp does because:
- enzyme substrate molecules have more kinetic
- move around faster making more collisions
- forming more ES complexes
As the temp rises above optimum temp, rate decreases because:
- enzyms denature
-breaking H and ionic bonds
-tertiary structure changes
-no longer complementary
How does the pH affect the rate of reaction?
variations from optimum can result in denatured enzymes. ph measures the H bonds, which forms the tertiary structure. a change causes a change in the structure so its no longer complementary.
Explain how competitive inhibitors work?
- The inhibitor is similar shape to the substrate.
- inhibitor binds to the active site, it prevents the substrate from binding to the active site.
- Some ES substrates will form but at a much slower rate.
What do inhibitors do?
reduce the rate of reaction
Explain how non-competitive inhibitors work?
- the inhibitor is different to the substrate
- inhibitor attaches to a binding site on the enzyme molecule away from the active site
- this causes the hydrogen and ionic bonds in the enzyme to break, causing the tertiary structure and active site to change.
- substrate is no longer complementary to the active site so doesn’t bind.
- ES complexes cannot form
