6b. DIGESTION

Question 1

Name the organs associated with digestion.

Answer 1

Mouth (teeth and salivary gland), oesophagus, stomach, ileum, large intestine, rectum, pancreas, liver, gall bladder

Question 2

Describe the function of stomach acid

Answer 2

Kills pathogens

Question 3

Describe what villi are

Answer 3

Folds of the epithelial tissue of the ileum

Question 4

Describe what microvilli are

Answer 4

Folds of the cell surface membrane of the epithelial cells of the ileum

Question 5

Describe the function of villi and microvilli

Answer 5

Increase the surface area for absorption of small biological molecules

Question 6

Define digestion

Answer 6

The breakdown of large biological molecules into smaller biological molecules

Question 7

Name the two types of digestion

Answer 7

Physical digestion and chemical digestion

Question 8

What is physical digestion?

Answer 8

The mechanical breakdown of food using physical movement

Question 9

Give two examples of physical digestion

Answer 9

Chewing (mastication), and muscle contraction causing churning of food in the stomach

Question 10

Explain the function of physical digestion

Answer 10

To increase the surface area for chemical digestion

Question 10

What is chemical digestion?

Answer 10

The hydrolysis of bonds by enzymes to break large food molecules into smaller ones.

Question 11

Name the 6 digestive enzymes

Answer 11

Amylase, maltase, lipase, endopeptidases, exopeptidases, dipeptidases

Question 12

Why are digestive enzymes specific?

Answer 12

Because their active sites have a specific tertiary shape, which is only complementary to the substrate

Question 13

Why is it advantageous for digestive enzymes to be embedded in the plasma membranes of the epithelial cells of the ileum, rather than be secreted into the ileum lumen?

Answer 13

Because they are not lost with the gut contents

Question 14

Where is amylase produced?

Answer 14

The pancreas

Question 15

Where does amylase act?

Answer 15

The mouth (secreted from the salivary gland) and the plasma membranes of the epithelial cells of the ileum

Question 16

What is the function of amylase?

Answer 16

To hydrolyse starch to maltose

Question 17

Where is maltase produced?

Answer 17

The ileum

Question 18

Where does maltase act?

Answer 18

In the plasma membranes of the epithelial cells of the ileum

Question 19

What is the function of maltase?

Answer 19

To hydrolyse maltose to glucose

Question 20

How is glucose transported from the ileum lumen to the blood?

Answer 20

By co-transport

Question 21

Once monosaccharides are in the bloodstream, what happens to them?

Answer 21

Transported to cells to be used in respiration, or transported to liver and muscle cells to be stored as glycogen

Question 22

Recall the five stages of lipid digestion and absorption

Answer 22

Emulsification, Hydrolysis, Micelle formation, Chylomicron formation and Chylomicron transport.

Question 23

Name the chemicals that are used to emulsify lipids

Answer 23

Bile salts

Question 24

Where are bile salts produced, stored and secreted into?

Answer 24

Produced in the liver, stored in the gall bladder and secreted into the ileum lumen.

Question 25

Where does emulsification occur?

Answer 25

Ileum lumen

Question 26

What is emulsification?

Answer 26

Breaking lipids down into many smaller droplets

Question 27

Explain the function of emulsification

Answer 27

Smaller droplets have a higher SA:Volume, which increases surface area for lipase action, which allows faster hydrolysis of lipids

Question 28

Where are lipases produced?

Answer 28

Pancreas.

Question 29

Where do lipases act?

Answer 29

In the plasma membranes of the epithelial cells of the ileum

Question 30

What is the function of lipases?

Answer 30

To hydrolyse ester bonds in triglycerides, forming a monoglyceride and two fatty acids

Question 31

What is a monoglyceride?

Answer 31

A molecule containing a glycerol and a fatty acid

Question 32

Where does micelle formation occur?

Answer 32

In the ileum lumen

Question 33

What is a micelle?

Answer 33

An association of monoglycerides, fatty acids and bile salts

Question 34

Describe the function of micelles

Answer 34

To transport monoglycerides and fatty acids across the cell surface membrane of the ileum epithelial cells.

Question 35

By which type of molecular transport do glycerol and fatty acid molecules cross the cell surface membrane of the epithelial cells of the ileum?

Answer 35

Diffusion

Question 36

Where does chylomicron formation occur?

Answer 36

In the epithelial cells of the ileum

Question 37

Which two cell organelles are involved in chylomicron formation?

Answer 37

SER and Golgi apparatus

Question 38

Describe the role of the SER in chylomicron formation

Answer 38

Here the monoglycerides and fatty acids are reformed into triglycerides

Question 39

Describe the role of the Golgi apparatus in chylomicron formation

Answer 39

Here triglycerides are combined with proteins and formed into chylomicrons

Question 40

What are chylomicrons?

Answer 40

Lipoprotein vesicles used to transport lipids from the ileum lumen around the body

Question 41

How do chylomicrons travel out of the ileum epitheliel cells?

Answer 41

Exocytosis

Question 42

Where do chylomicrons travel to when they leave the ileum epithelial cells?

Answer 42

Lacteals

Question 43

What are lacteals?

Answer 43

Lymphatic capillaries

Question 44

Where are lacteals found in the digestive system?

Answer 44

At the centre of each villus

Question 45

Where are peptidases (proteases) produced?

Answer 45

Pancreas

Question 46

Where do peptidases (proteases) act?

Answer 46

Stomach and the plasma membranes of the epithelial cells of the ileum

Question 47

Why are peptidases (proteases) produced in the pancreas in an inactive form?

Answer 47

So they don't hydrolyse the pancreas tissue

Question 48

How is Trypsin transported from the pancreas to the ileum?

Answer 48

Through pancreatic ducts

Question 49

What is the function of endopeptidases?

Answer 49

They break polypeptides into smaller peptide chains by hydrolysing internal peptide bonds. This increases the surface area for exopeptidases.

Question 50

What is the function of exopeptidases?

Answer 50

They remove terminal amino acids by hydrolysing the terminal peptide bonds

Question 51

What is the function of dipeptidases?

Answer 51

Hydrolyse dipeptides into amino acids

Question 52

How are amino acids transported from the ileum lumen to the blood?

Answer 52

By co-transport

Question 53

Once amino acids are in the bloodstream, what happens to them?

Answer 53

Transported to cells to be used in protein synthesis.

Question 54

Which two monosaccharides make up the disaccharide lactose?

Answer 54

Glucose and galactose

Question 55

Which enzyme hydrolyses lactose to its monosaccharides?

Answer 55

Lactase

Question 56

Where is lactase found in the digestive system?

Answer 56

In the plasma membranes of the epithelial cells of the ileum

Question 57

What is 'lactose intolerance?'

Answer 57

An inability to digest lactose

Question 58

What is the cause of lactose intolerance?

Answer 58

Lactase deficiency

Question 59

What are the two advantages of using immobilised lactase in experiments to study lactose intolerance?

Answer 59

No lactase in the milk, and the enzymes can be reused

Question 60

Which biochemical test could you use to ascertain whether the immobilised lactase has hydrolysed lactose?

Answer 60

Benedict's solution

Question 61

If the immobilised lactase hasn't hydrolysed the lactose, what would the result of the Benedict's test be?

Answer 61

Blue - negative

Question 62

If the immobilised lactase has hydrolysed the lactose, what would the result of the Benedict's test be?

Answer 62

Brick red precipitate - positive

Question 63

What is the function of an experimental control?

Answer 63

Experimental controls are needed to eliminate alternate explanations of experimental results