Enzymes and digestion

Question 1

What is an enzyme?

Answer 1

A biological catalyst that speeds up the rate of reaction without being used up.

Question 2

What is a substrate?

Answer 2

The substance on which an enzyme acts and that is changed in the reaction.

Question 3

What happens to a substrate during a reaction?

Answer 3

It is either broken down or built up, producing a product.

Question 4

What is an enzyme-substrate complex?

Answer 4

The binding of a substrate to the active site of the enzyme.

Question 5

How do enzymes reduce activation energy?

Answer 5

By holding the substrate in the correct position.

Question 6

What are metabolic reactions?

Answer 6

Chemical reactions in the body that can be sped up by enzymes.

Question 7

What are the main properties of enzymes?

Answer 7

• Made of proteins (amino acids)
• Each has an active site
• Specific to one type of substrate
• Unaffected by the reaction they catalyse
• Work best in specific environments (temp and pH)
• Can be denatured by excessive conditions.

Question 8

What is the active site of an enzyme?

Answer 8

A depression used to hold a substrate in place.

Question 9

What does the lock and key theory describe?

Answer 9

The specificity of enzymes, where the enzyme and substrate are complementary.

Question 10

What does it mean for an enzyme to be denatured?

Answer 10

The shape of the active site changes so that it is no longer complementary to the substrate.

Question 11

How does pH affect enzyme activity?

Answer 11

Extreme pH levels interfere with bonds holding the enzyme together, changing the shape of the active site and potentially denaturing the enzyme.

Question 12

What is the optimum pH for most enzymes?

Answer 12

Normally pH 7.

Question 13

How does temperature affect enzyme activity at low temperatures?

Answer 13

Substrate particles move slowly, reducing the chance of collision with the enzyme’s active site.

Question 14

What happens to enzyme activity as temperature increases?

Answer 14

Substrates gain kinetic energy, moving more and increasing the likelihood of successful collisions, but excessive heat can cause denaturation.

Question 15

What enzyme is found in celery that breaks down hydrogen peroxide?

Answer 15

Catalase

Catalase is an enzyme that catalyzes the decomposition of hydrogen peroxide into water and oxygen.

Question 16

What happens when washing up liquid is added to the measuring cylinder containing catalase and hydrogen peroxide?

Answer 16

Oxygen makes bubbles and becomes foam

This foam allows for the measurement of the products produced during the reaction.

Question 17

How can the pH be changed in an experiment involving catalase?

Answer 17

By adding different pH buffer solutions

This allows for the investigation of the effect of changing pH on enzyme activity.

Question 18

What is a more reliable method to collect gas produced in the catalase reaction?

Answer 18

Using a gas cylinder

This method is more reliable than measuring the height of the foam.

Question 19

What does amylase break down starch into?

Answer 19

Maltose

Amylase is an enzyme that catalyzes the hydrolysis of starch into maltose.

Question 20

What color indicates the presence of starch when iodine is added?

Answer 20

Bluey black

If starch is broken down by amylase, the iodine will remain browny orange.

Question 21

What safety procedures should be followed when conducting experiments with iodine?

Answer 21

Wear safety goggles and wash skin with water and soap if contact occurs

Iodine is an irritant, and safety precautions help prevent injuries and reactions.

Question 22

What happens to the rate of reaction as enzyme concentration increases?

Answer 22

The rate of reaction increases

More enzyme molecules increase the chances of successful collisions with substrates.

Question 23

What limits the rate of reaction when substrate concentration increases?

Answer 23

Plateaus occur when there are not enough substrate particles

Eventually, all enzymes may reach full capacity, preventing further increases in reaction rate.

Question 24

What are the main functions of the mouth in digestion?

Answer 24

Chewing, mixing with saliva, and amylase action

Teeth chew the food, the tongue helps mix it, and amylase begins starch digestion.

Question 25

Fill in the blank: The mixture of food, water, and mucus in the mouth is called a _______.

Answer 25

Bolus

A bolus is formed to facilitate swallowing.

Question 26

What is the primary function of the stomach?

Answer 26

Wall muscles contract to churn food, protease enzyme breaks down proteins into amino acids

Hydrochloric acid creates an optimum pH for protease and kills bacteria. Mucus protects stomach walls from acid.

Question 27

What role does hydrochloric acid play in the stomach?

Answer 27

Creates optimum pH for protease and kills bacteria

It also aids in the digestion process.

Question 28

What is the function of mucus in the stomach?

Answer 28

Protects stomach walls from acid

This prevents damage to the stomach lining.

Question 29

What enzymes are found in pancreatic juice and their functions?

Answer 29

Amylase, protease, lipase, maltase

Amylase converts starch to maltose, protease converts proteins to amino acids, lipase converts fats to fatty acids and glycerol, maltase converts maltose to glucose.

Question 30

What are the adaptations of the small intestine for absorption?

Answer 30

Bile neutralizes stomach acid, good blood supply, long folds, villi with microvilli

These adaptations increase the surface area and maintain a concentration gradient for faster diffusion.

Question 31

How does bile assist in digestion?

Answer 31

Neutralizes stomach acid and emulsifies fat

This prepares fats for easier breakdown by lipase.

Question 32

Why is the surface of the small intestine adapted for absorption?

Answer 32

Villi are one cell thick and have microvilli

This reduces the diffusion distance and increases the rate of nutrient absorption.

Question 33

What is the primary function of the large intestine?

Answer 33

Excess water is absorbed

This helps in the formation of solid waste.

Question 34

What is stored in the rectum before egestion?

Answer 34

Faeces made up of roughage, bacteria, and dead cells

This is the final stage before waste is removed from the body.

Question 35

Define ingestion in the context of digestion.

Answer 35

Taking food into the body via the mouth

It is the first step in the digestive process.

Question 36

What is absorption in the digestive system?

Answer 36

Movement of small soluble molecules from the small intestine into the blood

This is a crucial step for nutrient uptake.

Question 37

What does assimilation refer to?

Answer 37

Using small molecules to build large molecules in the body

It involves the conversion of nutrients into usable forms.

Question 38

What is egestion?

Answer 38

Removal of undigested food and faeces from the anus

This is the final step of the digestive process.