Week 6: Enzymes Flashcards
(31 cards)
What are enzymes?
Protein molecules which act as biological catalysts.
Enzymes have a specific region on their surface, called?
an active site
The active site has a shape that is complementary to the shape of the?
Reactants/substrates that the enzyme catalyses
Enzymes are not consumed in their reaction, therefore…
they can be used over and over again.
Most enzymes work inside cells. Why?
This is the site of cell metabolism
All reactions involve the breaking of bonds, as well as?
The reforming of bonds
Enzymes aid in the breaking/reforming of bonds by…
lowering the amount of energy needed for the reaction
How do enzymes lower activation energy?
The substrate binds to the active site of the enzyme by weak bonds, forming an enzyme-substrate complex
- Active site changes slightly to form an exact fit
- Bonds are subjected to pressure which reduces energy and increases likelyhood of reaction
- The product forms and breaks away from the enzyme
The specificity of an enzyme is caused by?
The complementary fit between enzyme and substrate
What is the induced fit?
The change in the enzyme caused by the substrate binds to the active site of the enzyme
Factors that affect enzyme activity:
- Temperature
- pH
- Inhibitors
Most human enzymes operate effectively at:
Body temp (35-40*)
A higher temperature is generally a good way to speed up reactions. Why?
As temperature increases the substrate molecules will collide more frequently, thus are more likely to interact with the active site
What happens if the temperature exceeds the ideal temp?
The enzyme denatures: Active site changes shape so substrates can no longer bind
At lower temperatures, the rate of reaction…?
slows down - fewer collisions happen between substrate and enzymes
The optimum pH for human enzymes:
6-8
Changing pH can alter binding at the active site, therefore:
enzyme denatures
Extreme temperature or pH causes reduced enzyme activity due to…
enzyme denaturing
Extreme conditions do what to the enzyme bonds?
Break bonds and change the structure of the protein, and alter the shape of the active site
What are inhibitors?
Inhibitors are chemicals that reduce the action of enzymes.`
Competitive inhibitors:
- Inhibitors block the substrate entering the active site by binding to the active site. They mimic the shape of the substrate (complementary to the shape of some of the active site)
- EG: Cyanide
Non-competitive inhibitors:
- Inhibitors bind elsewhere on the enzyme and this changes the shape of the enzyme and thus reduces enzyme-substrate binding.
- EG: Lead, mercury
Increasing the concentration of the substrate therefore increases:
the chance of colliding with the enzyme, therefore increasing the reaction rate
What is a metabolic pathway?
- Biological reactions usually occur as a series of small regulated steps called a metabolic pathway
- EG: aerobic respiration
