Factors affecting enzyme action

Question 1

What are the two factors that affect enzyme action?

Answer 1

Temperature and pH

Question 2

What are the factors that affect the rate of reaction?

Answer 2

Temperature, pH, substrate concentration, enzyme concentration and surface area

Question 3

If the temperature is increased how does this affect the rate of reaction?

Answer 3

When the temperature is increased the enzymes and substrates gain more kinetic energy. It is this increase in energy which results in more frequent successful collisions between the substrate and the enzymes active site; thus increasing the rate of reaction.

Question 4

What is the temperature coefficient, Q10, of a reaction measuring?

Answer 4

How much the rate of reaction increases with a 10ºc rise in temperature.

Question 5

How much does the rate of an enzyme reaction usually increase after the rise of 10c?

Answer 5

The rate of reaction usually doubles.

Question 6

Explain how temperature denatures enzymes

Answer 6

At high temperatures the bonds holding the protein together vibrate more as they gain kinetic energy. As the intensity of the vibrations increase the bonds begin to strain and then break. When the bonds break the tertiary structure of the protein is changed.

Question 7

Why does the substrate no longer fit into the active site of the enzyme after it has been denatured?

Answer 7

The tertiary structure of the active site has been changed and so is no longer complimentary of the substrate.

Question 8

What is meant by the optimum temperature?

Answer 8

It is the temperature in which the enzyme has the highest rate of activity.

Question 9

What is the most common optimum temperature of the enzymes found in the human body?

Answer 9

40ºc

Question 10

What is the optimum temperature of thermophilic enzymes?

Answer 10

70ºc

Question 11

What is the optimum temperature of psychrophilic enzymes?

Answer 11

5ºc

Question 12

Sketch the graph that describes the difference between the temperature and rate of a reaction

Answer 12

Question 13

When during a reaction does the temperature, Q10, not apply anymore?

Answer 13

After the enzymes have denatured.

Question 14

How are enzymes adapted for organisms in extreme cold environments?

Answer 14

The enzymes have flexible structures, especially at the active site

Question 15

What is the disadvantage of the flexible structure of an enzyme in a cold environment?

Answer 15

They are less stable and easily denature by even slight changes in temperature `

Question 16

What are thermophiles?

Answer 16

Organisms that are adapted to living in extremely hot environments.

Question 17

How are enzymes adapted for organisms in extreme hot environments?

Answer 17

The enzymes are more stable due to the increased number of bonds (particularly hydrogen bonds and sulfur bridges).

Question 18

What actually happens when the pH levels change?

Answer 18

There is a change in the hydrogen ion concentration

Question 19

When more hydrogen ions are presents what pH level is it?

Answer 19

Low (acid)

Question 20

When less hydrogen ions are presents what pH level is it?

Answer 20

High (alkaline)

Question 21

What is meant by the optimum pH?

Answer 21

It is the level of pH where the active sight is in the right shape (optimum hydrogen ion concentration)

Question 22

What is meant by renaturation?

Answer 22

When the pH strays from the optimum pH and becomes either too alkaline or acidic the enzymes active site becomes altered and the substrate no longer fits. However, if the pH returns to normal then the protein will resume its normal shape.

Question 23

Sketch the graph for the relationship between pH and the rate of enzyme activity.

Answer 23

Question 24

What happens to the enzyme when the pH significantly shifts away from the optimum?

Answer 24

The enzyme denatures and so is irreversible

Question 25

All about interaction

How does the change in pH actually affect the enzyme?

Answer 25

The hydrogen ions interact with the R-groups in the protein, and so by increasing the concentration of the hydrogen ions less interaction occurs between the R-groups inside the protein.

Question 26

All about interaction

How does very low pH denature an enzyme?

Answer 26

There is a larger concentration of hydrogen ions which means that the R-groups interact with each other less. Due to this the bonds between the R-groups break and change the shape of the enzyme.

Question 27

+ interaction

How does very high pH denature an enzyme?

Answer 27

There is a low concentration of hydrogen ions which means that there is more interaction between the R-groups. There are more bonds present and so the shape of the enzyme changes.

Question 28

Where is saliva found?

Answer 28

in the mouth

Question 29

Where is gastric juices found?

Answer 29

In the stomach

Question 30

Where are pancreatic juices found?

Answer 30

In the small intestine

Question 31

What is the name of the enzyme found in the mouth?

Answer 31

amylase

Question 32

What is the name of the enzyme found in the stomach?

Answer 32

Pepsin

Question 33

What is the name of the enzymes found in the small intestine?

Answer 33

• Trypsin
• Lipase
• Amylase
• Maltase

Question 34

What is the optimum pH for the enzymes in the mouth?

Answer 34

Neutral (pH 7)

Question 35

What is the optimum pH for the enzymes in the stomach?

Answer 35

Acidic (pH 1-2)

Question 36

What is the optimum pH for the enzymes in the small intestine?

Answer 36

slightly alkaline (pH 8)

Question 37

What is the function of amylase?

Answer 37

Starch → maltose

Question 38

What is the function of pepsin?

Answer 38

proteins → polypeptides

Question 39

What is the function of trypsin?

Answer 39

proteins → polypeptides

Question 40

What is the function of lipase?

Answer 40

triglycerides → glycerol + fatty acids

Question 41

What is the function of maltase?

Answer 41

maltose → glucose

Question 42

The rate of reaction increases up to a maximum point. What is the symbol for this point?

Answer 42

V max

Question 43

Sketch a graph to show the relationship between the concentration of subrates and the rate of the reaction (include the V max)

Answer 43