2.1 Digestion

Question 1

What is a cell?

Answer 1

The basic building block of a living organism

Question 2

What is a tissue?

Answer 2

A group of cells with a similar structure and function working together. For example, muscular tissue contracts to bring about movement.

Question 3

What is an organ?

Answer 3

A collection of tissues working together to perform a specific function. For example, the stomach contains glandular, muscular and epithelial tissues.

Question 4

What is an organ system?

Answer 4

A group of organs working together to perform specific functions. For example, the digestive system contains organs such as the stomach, small intestine and large intestine.

Question 5

What is the main function of the digestive system?

Answer 5

To digest food and absorb nutrients obtained from digestion

Question 6

What is the role of the pancreas and salivary gland in the digestive system?

Answer 6

The pancreas and salivary gland are glands that produce digestive juices containing enzymes

Question 7

What is the role of the stomach in the digestive system?

Answer 7

Produces hydrochloric acid - which kills any bacteria present and provides the optimum acidic pH for the protease enzyme to function

Question 8

What is the role of the small intestine in the digestive system?

Answer 8

The small intestine is the site where soluble food molecules are absorbed into the bloodstream

Question 9

What is the role of the liver in the digestive system?

Answer 9

Produces bile (stored in the gallbladder) which emulsifies lipids and allows the lipase enzyme to work more efficiently

Question 10

What is the role of the large intestine in the digestive system?

Answer 10

Absorbs water from undigested food, producing faeces

Question 11

What is the role of enzymes in the digestive system?

Answer 11

Enzymes act as biological catalysts which speed up the rate of biological reactions (the breakdown of food) without being used up

Question 12

How does the shape of an enzyme affect its function?

Answer 12

Enzymes have a specific active site which is complementary to their substrate

Question 13

What is metabolism?

Answer 13

The sum of all reactions in a cell or an organism

Question 14

What types of metabolic reactions do enzymes catalyse?

Answer 14

● Building larger molecules from smaller molecules e.g. glucose to starch

● Changing one molecule to another e.g. glucose to fructose

● Breaking down larger molecules into smaller molecules e.g. carbohydrates to glucose

Question 15

What is the lock and key hypothesis of enzyme function?

Answer 15

The shape of the enzyme active site and the substrate are complementary, so can bind together to form an enzyme-substrate complex.

Question 16

How does temperature affect enzyme action?

Answer 16

Up to a certain point, increasing temperature increases enzyme action, as molecules have a higher kinetic energy.

Above a certain temperature, the shape of the active site is altered and the enzyme becomes denatured, so it can no longer catalyse the reaction. The optimum temperature is around 37 degrees celsius.

Question 17

How does pH affect enzyme function?

Answer 17

The optimum pH for most enzymes is 7 (apart from proteases in the stomach). If the pH is too extreme, the shape of the active site may be altered and the enzyme may no longer work.

Question 18

Where are carbohydrases, proteases, and lipases produced in the body?

Answer 18

● Carbohydrases: Amylase - salivary gland and pancreas; Maltase - small intestine

● Proteases: Pepsin - stomach; others - pancreas and small intestine

● Lipases: pancreas and small intestine

Question 19

What is the role of carbohydrases in the digestive system?

Answer 19

● Carbohydrases break down carbohydrates into monosaccharides and disaccharides.

● Amylase breaks down starch into maltose, and maltase breaks down maltose into glucose.

Question 20

What is the role of proteases in the digestive system?

Answer 20

Proteases break down proteins into amino acids

Question 21

What is the role of lipases in the digestive system?

Answer 21

Lipases break down lipids into fatty acids and glycerol

Question 22

How are the products of digestion used?

Answer 22

They are used to build bigger molecules such as carbohydrates and proteins. Glucose is used as a substrate in respiration.

Question 23

Where is bile made and stored in the body?

Answer 23

Bile is made by the liver and stored in the gallbladder

Question 24

What is the role of bile in the digestive system?

Answer 24

● Bile is an alkaline substance which neutralises the hydrochloric acid secreted by the stomach.

● Bile emulsifies lipids to form droplets - this increases the surface area for the lipase enzyme to work on.