Many Proteins Are Enzymes (3.1.4.2) Flashcards
Part of Proteins (3.1.4)
1
Q
What is the activation energy?
A
- The energy required for a chemical reaction to take place
2
Q
What are enzymes?
A
- Proteins that act as biological catalysts
- They speed up chemical reactions by providing an alternative reaction pathway of lower activation energy, increasing the rate of reaction
2
Q
What is the lock and key hypothesis?
A
- Suggests that the enzyme’s active site has a specific, rigid shape that is complementary to its substrate
- Only substrates that perfectly fit the active site can bind and form an enzyme-substrate complex
2
Q
What is the induced fit model?
A
- Suggests that the active site of the enzyme is not initially complementary to the substrate, but it changes shape to better fit the substrate
- As the enzyme changes shape a strain is placed on bonds within the substrate molecule, forming an enzyme-substrate complex, thus lowering the activation energy
2
Q
What factors can affect the rate of enzyme controlled reactions?
A
- Enzyme concentration
- Substrate concentration
- Temperature
- pH
3
Q
What is the effect of enzyme concentration?
A
- The rate of reaction increases as the enzyme concentration increases as there are more active sites for the substrates to bind to
- However, increasing the enzyme concentration beyond a certain point has no effect on the rate of reaction as there are more active sites than substrates so substrate concentration becomes the limiting factor
4
Q
What is the effect of substrate concentration?
A
- The rate of reactions increases as the substrate concentration increases as more enzyme-substrate complexes are formed
- However, increasing the substrate concentration beyond a certain point has no effect on the rate of reaction as all the active sites are occupied at one time so enzyme concentration becomes the limiting factor
5
Q
What is the optimum temperature?
A
- The temperature at which the rate of reaction is highest
6
Q
What is the effect of temperature?
A
- As the temperature increases, the rate of reaction rises, due to increased kinetic energy, resulting in more frequent collisions and more enzyme-substrate complexes are formed
7
Q
What happens beyond the optimum temperature?
A
- The enzyme begins to denature as the increased temperature breaks hydrogen and ionic bonds in the enzyme’s tertiary structure, altering the active site and preventing substrate binding
- Denaturation is often irreversible above 50°C, permanently altering the enzyme’s structure and preventing it from catalysing reactions
8
Q
What is the effect of pH?
A
- Enzymes are only active over a narrow pH range. At lower or higher pHs than the optimum, denaturation can occur
- Changes in pH alter hydrogen and ionic bonds in the enzyme’s tertiary structure, altering the active site and preventing substrate binding
9
Q
What is the effect of enzyme denaturation on its function?
A
- loss of tertiary structure → altering of active site → substrate no longer complementary to active site → fewer enzyme-substrate complexes formed
10
Q
What are competitive inhibitors?
A
- The inhibitor has a similar structure to the substrate
- Competes with the substrate for attachment to the active site
- The rate of reaction is reduced as the substrate cannot bind when the inhibitor molecule is occupying the active site
11
Q
What are non competitive inhibitors?
A
- Different shape to the substrate
- Binds to the enzyme at a position anywhere other than the active site to form an enzyme / inhibitor complex altering the tertiary structure and active site of the enzyme
- Substrate cannot bind to the altered active as it is no longer complementary to the substrate
12
Q
What is the effect of the addition of more substrates to competitive inhibitors?
A
- The effect is reduced, more substrates out competes the inhibitor molecules for attachment to the active site
13
Q
What is the effect of the addition of more substrates to non competitive inhibitors?
A
- The effect stays the same, adding more substrates has no effect on the inhibitor
