Enzymes Flashcards
What is an anabolic reaction?
building up / synthesis (e.g. protein synthesis)
What is a catabolic reaction?
breaking down / degrading (e.g. respiration , digestion)
What is the specific shape of enzymes?
They are globular proteins which have a specific 3D structure.
Name two types of enzyme inhibitors
-Competitive inhibitors
-Non-competitive inhibitors
What happens when an enzyme is denatured?
There is a permanent change in secondary and tertiary structure of the enzyme. This is caused by high temperatures of extreme changes in pH
What is a cofactor?
A substance which is essential for efficient function of an enzyme.
How do you measure initial rate?
- Draw a tangent at t = 0 (long as possible)
- Calculate change in Y / Change in X
What are the 4 factors affecting the rate of an enzyme controlled reaction?
- Enzyme concentration
- Substrate concentration
- Temperature
- Ph
What is the effect of enzyme concentration on an enzyme controlled reaction?
Increasing enzyme concentration:
-increases number of AS available
-this increases the frequency of successful collisions
-more ESC formed
-more product formed per second
-increases the initial rate
Once it has reached the V-max the initial rate will not increase further as enzyme conc. no longer the limiting factor
What is the effect of substrate concentration on an enzyme controlled reaction?
Increasing the substrate concentration:
-increases the frequency of collisions between the AS and substrate
-increases ESC formed
-more product produced per second
-increases the initial rate
After the V-max is reached the initial rate will not increase further as every AS is occupied so substrate concentration is not a limiting factor
What is the effect of temperature on an enzyme controlled reaction?
- At low temperatures the enzyme is inactivated
- Molecules have less KE at lower temperatures which decreases the
number of successful collisions and the frequency of collisions - As temperature increases, KE increases which increases the frequency
of successful collisions between AS and S. - More ESC formed
- Increases the initial rate
- Above the optimum temperature the rate drops sharply as there are
more vibrations so bonds are broken ( loss of 2* and 3* structure) so
the AS changes shape, no ESC formed and enzyme denatured
What is the effect of pH on an enzyme controlled reaction?
-Small changes either side of the optimum pH decreases the rate as the shape of the AS is disrupted (not denatured)
-Extreme changes either side of optimum pH will make enzyme denature (rate = 0)
-In too acidic environments, H+ ions are attracted to negatively charged ions / molecules. Excess H+ interfere with hydrogen and ionic bonds (2* and 3* structure) which changes shape of AS so S no longer fits.
How do competitive inhibitors work?
-They are a similar shape to the substrate
-Compete with the substrate for the active site
-This is usually reversible
-The reaction can still reach its normal V-max as they usually bind for a short period then leave
How do non competitive inhibitors work?
-They do not compete for the AS
-They combine with the enzyme at an allosteric site
-This distorts the AS meaning the substrate can no longer fit the AS
-Increasing the substrate conc. will not help to increase the rate in this reaction
-This reaction will never reach its normal V-max
-This is an irreversible reaction
What is the shape of a competitive inhibitor graph vs a non-competitive inhibitor graph?
