Enzymes Flashcards
Are enzymes globular or fibrous?
Globular
What two things can enzymes affect in an organism?
Structure
Function
What is intracellular enzyme and example?
Works inside cells
Catalase- hydrogen peroxide breakdown catalysed
Extra cellular enzymes and example?
Work outside of cells
Amylase- catalyses hydrolysis of starch into maltose
What is an enzyme substrate complex?
A substrate bonded to an active site
What is an enzyme product complex?
Formed after reaction is catalysed, when product molecule is released from complex
Two models for enzyme action and explanation?
Lock and key- active site and substrate complementary in shape
Induced fit- active site undergoes conformational change after substrate binds, completing the fit
Two models for enzyme action and explanation?
Lock and key- active site and substrate complementary in shape
Induced fit- active site undergoes conformational change after substrate binds, completing the fit
How do enzymes speed up reactions?
By reducing activation energy
How does temperature affect rate of reaction at first?
Enzyme and substrate gain kinetic energy
More collisions and more enzyme- substrate complexes form
Rate of reaction increases to optimum temperature
How does temperature affect rate of reaction after optimum temperature?
-Molecules in enzyme begin to vibrate more
-Bonds in tertiary structure (ionic/hydrogen) break
-active site changes shape, no longer complementary to substrate
-enzyme denatures
What is the temperature coefficient (Q10)?
Unit-less value
Which indicates how much reaction changes if the temperature is increased by 10•C
Equation for temperature coefficient?
Q10= R2/R1
R2- rate at higher temp
R1- rate at lower temp
How do low pH’s affect rate of reaction?
H+ ions cause hydrogen and ionic bonds in tertiary structure in enzyme to break
How do high pH’s affect rate of reaction?
Presence of OH- causes ionic and hydrogen bonds in tertiary structure of enzyme to break
What is H+ and OH- ions overall affect on enzymes?
Enzyme may denature, shape of active site changes
What does increasing enzyme concentration have on rate of reaction?
More successful collision
More enzymes substrate complexes form
Rate or reaction increase s
Why does rate of reaction plateau when enzyme concentration increases?
Amount of substrate is limited, so adding more enzymes has no affect
What effect does increasing substrate concentration have on rate of reaction?
More successful collision with active site
Rate increases
More enzyme-substrate complexes form
Why does rate of reaction plateau when substrate is increased?
All available active sites are occupied
What is Vmax?
Maximum rate of reaction
What are inhibitors and what are the two types?
Molecules which bind to enzyme to reduce their activity
Competitive and non competitive inhibitors
What do competitive inhibitors do?
Similar shape to substrate
Bind reversible to active site and block it, preventing substrate binding
What affect does substrate concentration have on rate of reaction, when competitive inhibitors are involved?
-Increasing substrate concentration, increases rate of reaction
-As substrate concentration increases, there is a higher chance of substrate colliding with active site, instead of inhibitor molecule
How do non competitive inhibitors work?
-They bind to allosteric site
-This causes active site to change shape, substrate can no longer bind
What affect does increasing substrate concentration have on rate of reaction, when non competitive inhibitor is involved?
Little effect, as inhibitor and substrate do not compete
Vmax is dependant on inhibitor concentration
For each type of inhibition, do the molecules bind reversible or irreversibly?
Both bind irreversibly and reversibly
For each type of inhibition, do the molecules bind reversible or irreversibly?
Both bind irreversibly and reversibly
What is a metabolic pathway?
Sequence of enzyme controlled reactions, where the product of one reaction, is reactant for next
What is end product inhibition?
Final product of metabolic pathway acts as a reversible non competitive inhibitor for first enzyme
What is the use of end product inhibition?
Regulates pathway, preventing build up of final product
When the levels of product start to fall, the inhibition levels decrease
What are co factors and co enzymes?
Non protein molecules, which bind to enzymes, allowing them to function
What are inorganic co factors?
Example?
Ions which bind to active site alongside substrate
They are not involved in reaction
Cl- ions are cofactors for amylase
What are co enzymes?
Example?
-Organic molecules, bind alongside substrate
They are involved in the reaction, and are changed by it
-NAD removes H from ethanol via ethanol dehydrogenase
Where are co enzymes sourced from?
Vitamins e.g. NAD comes from vitamin B3
