Enzyme action

Question 1

What are enzymes and why are they important?

Answer 1

• Globular proteins
• Biological catalysts (speed up the rate of reaction by interacting with substrate molecules)
• Reduce the activation energy needed for reactions to start

Question 2

What is the Vmaxx?

Answer 2

The point at which adding more enzymes will not have an affect on the rate of reaction (highest point)

Question 3

What is the lock and key hypothesis?

Answer 3

An area within the tertiary structure of an enzyme has a shape which is complementary to the shape of a specific substrate molecule

Question 4

Equation for the reaction?

Answer 4

Enzyme+ substrate = enzyme substrate complex = enzyme product complex
The product is then released, leaving the enzyme to take part in another reaction

Question 5

How do enzymes lower the activation energy of a reaction?

Answer 5

Temporary bonds form between the substrate molecule and the amino acids on the surface of the active site which weaken the bonds of the substrate

Question 6

What is the induced fit hypothesis?

Answer 6

As the substrate molecule starts to form bonds with the amino acids on the surface of the active site, the tertiary structure of the active site changes to adjust to the substrate molecule
This weakens bonds in the substrate, reducing the activation energy for the reaction

Question 7

What is an intracellular enzyme?

Answer 7

Enzymes that act within the cell.

Eg: catalase breaks down hydrogen peroxide to oxygen and water

Question 8

What is an extracellular enzyme?

Answer 8

Enzymes that are released from cells and act outside the cell
Eg: amylase breaks starch down into maltose
maltase breaks maltose down into glucose
trypsin breaks proteins down into peptides

Question 9

How does temperature affect enzyme activity?

Answer 9

Increase temp= increase KE of the particles= particles move faster and collide more often= more frequent and successful collisions between particles

Question 10

What is the Q10

Answer 10

Measure of how much the rate of reaction increases with a 10c rise in the temperature

Question 11

What is denaturing and how does it happen?

Answer 11

Temperature increases= bonds holding protein together vibrate= bonds strain and break= change in the tertiary structure of protein= protein changes shape= denatured
Active site changes shape and is no longer complementary to the shape of the active site (Q10 no longer applies) Enzyme can no longer function as a catalyst.

Question 12

What is the optimum temperature?

Answer 12

Temperature at which the enzyme has the highest rate of activity

Question 13

How does pH affect enzyme activity?

Answer 13

Change in pH= change in hydrogen ion concentration
Change in hydrogen ion concentration affects the ionic bonds (and polar and non polar interactions) that hold proteins in their precise shape

Question 14

Optimum pH

Answer 14

Active site is only the right shape at a certain hydrogen ion concentration
Change in pH= structure of enzyme changes and the shape of the active site is altered

Question 15

What is renaturation and until what point can it happen?

Answer 15

If the pH returns back to optimum, the enzyme goes back to its original shape- renaturation
When the pH changes more significantly, the structure of the enzyme is irreversibly altered and the active site changes shape- enzyme is denatured

Question 16

Why can enzymes only function within a narrow pH range?

Answer 16

More hydrogen ions= less R group interactions= bond breaking= shape of active site changes
Less hydrogen ions= more R group interactions- bond breaking= shape of active site changes

Question 17

How does substrate concentration affect enzyme activity?

Answer 17

More substrates= higher collision rate with enzyme= more enzyme substrate complexes are formed
Rate of reaction increases until Vmaxx, where all of the active sites are occupied by substrates and adding more has no effect
Increase ror= add more enzymes/ increase the temperature