Seneca

Question 1

Why is bile important?

(Fats)

Answer 1

-Bile breaks up fats into tiny droplets, through a process called emulsification.
-The tiny droplets have a higher surface area than the original fat drop.
-This increases the rate of the lipase-catalysed reactions that break fats down.

Question 2

What does bile do for enzymes?

Answer 2

-Enzymes in the small intestine operate best in alkaline conditions.
-Bile neutralises acid from the stomach to stop these enzymes becoming denatured (lose their activity).

Question 3

How does bile help with digestion?

Answer 3

Bile breaks up fats (like oil) into tiny droplets, through a process called emulsification. The tiny droplets have a higher surface area than the original fat drop, which increases the rate of the reactions (catalysed by lipase) that break fats down.

Question 4

What is Amylase?

Answer 4

Carbohydrase enzymes break carbohydrates down into sugars. Amylase is a type of carbohydrase that can break down starch in our bodies:

Question 5

What does Amylase do?

Answer 5

Amylase breaks down starch into its constituent simple sugars (predominantly maltose).

Question 6

What is starch made of?

Answer 6

Starch → Maltose (+ other sugars).

Question 7

The sites of action of amylase are:

Answer 7

The small intestine.
The mouth.

Question 8

Amylase is produced in:

Answer 8

Pancreas.
Salivary glands.

Question 9

What are proteases?

Answer 9

Proteases are digestive enzymes that can break down proteins into amino acids.

Question 10

The sites of action of proteases are the:

Answer 10

Small intestine.
Stomach.

Question 11

Proteases are produced in the:

Answer 11

Pancreas.
Stomach.

Question 12

What do proteases break proteins into?

Answer 12

Protein → Amino acids.

Question 13

What is lipase?

Answer 13

Lipase is a type of digestive enzyme that breaks down lipids into glycerol and fatty acids.

Question 14

What does lipase break lipids into?

Answer 14

Lipid → glycerol + fatty acids

Question 15

Lipase is produced in the:

Answer 15

Small intestine.
Pancreas.

Question 16

What helps us to test what food substance is present?

Answer 16

Reagents

Question 17

How do you test for food substances?

Answer 17

The first step is to grind up the food and add distilled water to dissolve some of the food. You can then test for the food substances:

Question 18

Describe starch food test

Answer 18

Add iodine solution to test for starch.
It will turn blue-black if starch is present.

Question 19

Describe lipids food test

Answer 19

To test for lipids, add Sudan III (a fat-soluble dye).
If lipids are present, a red-stained oil layer will float on the water surface.
The presence of lipids can also be tested by adding ethanol.
The solution is added to water and shaken. If the solution turns cloudy, lipids are present.

Question 20

What are the two different chemicals for lipids?

Answer 20

• Sudan III
• Ethanol

Question 21

How do you test for proteins?

Answer 21

Add Biuret solution to test for proteins.
It will turn mauve or purple if proteins are present.

Question 22

How do you test for sugar?

Answer 22

Add Benedict’s reagent and heat for about two minutes to test for sugar.
It will turn any of green, yellow or red if sugar is present.
The colour depends on the concentration.

Question 23

When investigating the rate of enzyme activity, what factors need to be kept constant?

Answer 23

pH: Every enzyme has an optimum pH. Extremes of pH will cause the enzyme to denature. pH can be kept constant by using a buffer.
Temperature: Increasing the temperature will initially increase the rate of enzyme activity as the enzymes will have more kinetic energy. Above a certain temperature, enzymes denature as the high temperature breaks the bonds holding together the enzyme.
Enzyme concentration: Increasing the enzyme concentration increases the number of active sites available, which causes the rate of reaction to increase.
Substrate concentration: Increasing the substrate concentration increases the rate of enzyme activity, as there are more substrate molecules to bind to the enzyme active site.

Question 24

What will happen to the rate of enzyme activity if the substrate concentration is continually increased?

Answer 24

Rate will increase and then plateau

Question 25

Pepsin is a digestive enzyme produced in the stomach that breaks down proteins into amino acids.

How would the optimum pH of pepsin likely differ from the optimum pH of amylase?

Answer 25

Amylase breaks down starch into sugars. It is produced in the salivary glands and the small intestine.
Pepsin is produced in the stomach.
The pH of the stomach is a lot lower than the pH of saliva, due to the presence of stomach acid.
This means pepsin likely has a lower (more acidic) optimum pH than amylase.
The pH of the small intestine is also higher (less acidic) than the pH of the stomach. This is due to the presence of bile in the small intestine.

Question 26

What describes an enzyme’s active site? [3 marks]

Answer 26

-Its shape is important
-Only fits one substrate
-Binds to the reacting chemical

Question 27

Name two advantages of using washing powder with enzymes:

Answer 27

Enzymes very effective at removing stains.
Enzymes can be used at low temperatures, saving energy and costs.

Question 28

Name two disadvantages of using washing powder with enzymes:

Answer 28

Enzymes may enter natural water sources, causing pollution.
Enzymes may digest the material of clothing.