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Biology AS > Enzymes > Flashcards

Flashcards in Enzymes Deck (30):
1

What are enzymes?

They are globular tertiary proteins with a 3D structure. They are biological catalysts and lower the activation energy nor reactions both intracellular and extracellular.

2

What is activation energy?

The energy needed (that must be overcome) to activate a reaction

3

What are active sites?

A specific region of the enzymes is functional, this is the active site, substrates fit into these active site and they are very specific. The substrate molecules must have a complementary shape to the a active site.

4

What are active sites made up of?

Amino acids.

5

What happens what a substrate and enzyme join?

When a substrate molecule forms with the enzyme it forms an enzyme-substrate complex, this occurs by the induced fit theory.

6

What's the induced fit theory?

This theory suggests that the active sites form as the enzyme and substrate interact. The enzyme is flexible and can mould around the substrate. The enzyme has a general shape which alters in the presence of the specific substrate. As the shape changes it puts strain on the substrate molecule. This strain distorts a particular bond or multiple bonds in the substrate which lowers the activation energy needed to break the bond.

7

What are changes in the enzymes environment likely to do?

Change its shape.

8

How is the dipeptide formed?

Two amino acids join in a condensation reaction to make a dipeptide, a water molecule is lost in this.

9

What's the primary structure of enzymes?

The order of the amino acids, this order determines the function of the protein, the type and position of bonds do this.

10

What's the secondary structure of enzymes?

Where the polypeptide chain folds or coils into an alpha helix or beta pleated sheet, these are made by hydrogen bonds.

11

What's the tertiary structure of enzymes?

Further folding or coiling and these are held together by hydrogen bonds, ionic bonds, disulphide bridges and hydrophobic interactions.

12

What effects the rate of reaction?

Temperature
pH
Substrate concentration
Enzyme concentration
Competitive inhibitors
Non-competitive inhibitors

13

How is the rate of reaction effected at a low temperature?

At a low temperature the rate of reaction is low, there is not much kinetic energy so the molecules are moving slowly causing few successful collisions.

14

How is the rate of reaction effected at the optimum temperature?

At the optimum temperature the rate of reaction is high. There is more kinetic energy so the molecules are moving fast causing many successful collisions.

15

How is the rate of reaction effected at a high temperature?

At a high temperature the rate of reaction is low. There is too much kinetic energy increasing the vibrations in the molecule, this cause the hydrogen bonds in the molecule to break, changing its structure and denaturing it.

16

The effect of temperature on the rate of reaction?

Rate of reaction generally doubles for every 10*C increase in temperature. The optimum temperature for most enzymes in 40*C.

17

The effect of pH on the rate of reaction?

The rate of reaction will vary with changes to the pH, small changes in the pH will affect rate of reaction but not the structure. The charges in the amino acid chain of the enzymes active site are affected by free hydroxyl ions (alkaline) and free hydrogen ions (acidic).

18

How is the rate of reaction effected at a low pH?

At a low pH the rate of reaction is low. Acidity breaks the ionic bonds in the enzyme which maintains its tertiary structure, changing the structure of the active site which causes the enzyme to become denatured.

19

How is the rate of reaction effected at the optimum pH?

At the optimum pH the rate of reaction is high. There are many collisions between working enzymes and substrates which mean a high rate of reaction as many enzyme-substrate complexes are formed.

20

How is the rate of reaction effected at a high pH?

At a high pH the rate of reaction is low, the alkalinity breaks its ionic bonds in the enzyme which maintains its tertiary structure, changing the structure of the active site which causes the enzyme to become denatured.

21

How is the rate of reaction effected at a low substrate concentration?

At a low substrate concentration the rate of reaction is low, there are few substrate molecules so less chance of successful collisions occurring.

22

How is the rate of reaction effected at the optimum substrate concentration?

At the optimum substrate concentration the rate of reaction is high. There more substrate molecules which increases the chance of successful collisions.

23

How is the rate of reaction effected at a high substrate concentration?

At a high substrate concentration the rate of reaction is high as there are even more substrate molecules to form enzyme-substrate complexes with. It doesn't keep increasing as there soon would be no more active sites available at the time to create an enzyme-substrate complex, due to lack of enzymes. This will not be changed by increasing the substrate concentration as it has reached its point of saturation. It could keep increasing if the enzyme concentration was also increase.

24

How is the rate of reaction effected at a low enzyme concentration?

At a low enzyme concentration the rate of reaction is low as there are few enzyme molecules so a lower chance of a successful collision.

25

How is the rate of reaction effected at the optimum enzyme concentration?

At the optimum enzyme concentration the rate of reaction is high, there are more enzyme molecules so a higher chance of a successful collision.

26

How is the rate of reaction effected at a high enzyme concentration?

At a high enzyme concentration the rate of reaction is high, there are even more enzyme molecules so more active site able to form enzyme-substrate molecules with. It does not keep increasing as there will be no more substrates available to form more complexes with, this will not be changed by increasing the enzyme concentration as it has reached its point of saturation. It could keep increasing if the substrate concentration was also increased.

27

What is competitive inhibition?

The inhibitor has a similar shape to the substrate, it temporarily occupies the active site so that the substrate can't form the enzyme-substrate complex. It is reversible.

28

How does competitive inhibition effect the rate of reaction?

The rate of reaction is slower to create the same amount of product.

29

What is non-competitive inhibition?

The inhibitor binds to the enzyme at a point other than the active site which changes the shape of the enzymes active site. It is usually not reversible.

30

How does non-competitive inhibition effect the rate of reaction?

It denatures the enzyme so reduces the rate of reaction causing it to plateau out.