Lab 1: Enzyme Metabolism

Question 1

Enzymes are an example of what kind of interaction%

Answer 1

Protein-protein interaction

Question 2

How do enzymes speed up the rate of a reaction?

Answer 2

By lowering the activation energy

Question 3

Enzymes can catalyze reactions at rates up to ________ billion times higher than comparable non-catalyzed reactions

Answer 3

10 billion times

Question 4

How do enzymes lower the energy of activation? (2)

Answer 4

By their specific configuration, they can:

1) Hold the reactant molecules in close proximity
2) Hold the reactant molecules in the correct orientation

Question 5

Where do substrates and enzymes combine?

Answer 5

Active site

Question 6

The specificity of an enzyme is due to what?

Answer 6

Their structure

Question 7

What happens when an enzyme is subjected to high temperatures?

Answer 7

The enzyme ceases to function

Question 8

What happens when an enzyme is subjected to low temperatures?

Answer 8

The enzyme is inactive, but not permanently denatured

Question 9

What is lactose composed of?

Answer 9

Glucose and galactose

Question 10

Lactose has been shown to aid in the absorption of several minerals, such as what?

Answer 10

• Calcium
• Magnesium
• Zinc

Question 11

What is the cause of lactose intolerance?

Answer 11

Due to little or no activity of lactase, which prevents lactose from being broken down into glucose and galactose

Question 12

What happens if there is low lactase activity in the small intestine?

Answer 12

Undigested lactose is passed into the colon where bacteria ferment the sugar to hydrogen gas and organic acids

Question 13

An inadequate intake of calcium can lead to which kinds of diseases?

Answer 13

• Rickets
• Osteoporosis
• Hypertension

Question 14

Where is the gene for the production of lactase located on?

Answer 14

Chromosome 2

Question 15

What is the difference in DNA in individuals with lactase activity and without?

Answer 15

There isn’t any

Question 16

What does the difference in mRNA in individuals with lactase activity and without indicate?

Answer 16

Indicates that the primary regulation of the enzyme occurs during translation

Question 17

What type of sugars are located in cow, soy, and rice milks?

Answer 17

• Cow: lactose
• Soy: sucrose
• Rice: glucose

Question 18

What was the glucose composition of soy milk before lactase was added? What about after?

Answer 18

• Before: negative

- After: negative

Question 19

What was the glucose composition of cow’s milk before lactase was added? What about after?

Answer 19

• Before: negative

- After: positive (1/4)

Question 20

What was the glucose composition of rice milk before lactase was added? What about after?

Answer 20

• Before: positive (2)

- After: positive (2)

Question 21

How did the relative amount of glucose change depending on the pH of lactase?

Answer 21

2: negative
5: 1/10
7: 1/4
9: 1/4
12: negative

Question 22

At which pH is lactase optimally active?

Answer 22

7-9

Question 23

What is sucrose composed of?

Answer 23

Glucose and fructose

Question 24

Why did lactase not function on sucrose?

Answer 24

Since the enzyme is specific to lactose

Question 25

How do monosaccharides join to form the disaccharide lactose? What kind of bond is formed?

Answer 25

• Glucose and galactose undergo condensation to form lactose.
• An OH group from one monosaccharide and an H from the other combine to form water, which prompts the formation of the disaccharide
• β-1→4 glycosidic bond

Question 26

Where is lactase produced? What is its role?

Answer 26

• Produced in the brush border of the small intestine

- Hydrolyzes the β-1→4 glycosidic bond in lactose into glucose and galactose

Question 27

How does a hydrolase enzyme function?

Answer 27

• Through the addition of water, hydrolase enzymes cleave bonds
• One end receives an OH group, and another end receives the H+

Question 28

How does pH affect enzymatic activity?

Answer 28

• pH may affect the charge/shape of the substrates

- If so, they cannot bind to the active site and cannot undergo catalysis

Question 29

How does cold temperature affect enzymatic activity?

Answer 29

• Cold temperatures slow molecular movement

- Decreases enzyme activity due to less enzyme-substrate collisions

Question 30

At what temperature is lactase optimally functional? What was the optimal temperature in this experiment?

Answer 30

• 37oC

- 25oC in this experiment (room temperature)