The digestive system

Question 1

What does the digestive system consist of?

Answer 1

the gut/alimentary canal
associated glands

Question 2

What is the gut?

Answer 2

a long muscular tube that stretches from the mouth to anus

Question 3

Are the contents of the gut inside the body?

Answer 3

NO

Question 4

What is digestion?
(KEY DEFINITION)

Answer 4

the process in which large biological molecules are hydrolysed by enzymes to produce smaller molecules that can be absorbed across cell membranes and assimilated

Question 5

What are endopeptidases?

Answer 5

hydrolyse internal peptide bonds to form smaller polypeptide chains

Question 6

What are exopeptidases?

Answer 6

hydrolyse terminal peptide bonds to form single amino acids or dipeptides

Question 7

What is dipeptidases?

Answer 7

hydrolyse dipeptides into amino acids

Question 8

Describe the basic breakdown of carbohydrate/starch in the gut

Answer 8

starch is hydrolysed by amylase, leaving maltose
maltose is then hydrolysed by maltase, leaving glucose

Question 9

What is broken during the digestion of carbohydrates?

Answer 9

glycosidic bonds

Question 10

What enzymes are embedded in the cell membrane?

Answer 10

maltase
dipeptidase

Question 11

What are the organs involved in the digestive system?

Answer 11

-oesophagus
-stomach
-small intestine/duodenum
-small intestine/ileum
-large intestine
-rectum

Question 12

What are the glands involved in the digestive system?

Answer 12

-salivary gland
-pancreas

Question 13

What are the four stages to digestion?

Answer 13

-ingestion
-digestion
-absorption
-egestion

Question 14

What is ingestion?

Answer 14

food is taken into the mouth

Question 15

What is digestion?
(stage description)

Answer 15

enzymes break large insoluble molecules into small insoluble ones

Question 16

What is absorption?

Answer 16

the products of digestion are absorbed through the lining of the intestine

Question 17

What is egestion?

Answer 17

the removal of faeces containing:
-undigested food
-bacteria
-cells from the intestine lining
-enzymes

Question 18

Explain the advantages of endopeptidases hydrolysing proteins before exopeptidases?

Answer 18

the endopeptidases will break down the polypeptide chain into smaller chains, leaving more terminal peptide bonds exposed for the exopeptidases to hydrolyse

Question 19

Why is the lining of the stomach covered in thick mucus?

Answer 19

to protect the stomach lining from being digested by the protein enzymes

Question 20

List the similarities and differences between carbohydrate and protein digestion

Answer 20

similarities:
-both have enzymes which are embedded in the cell membrane

differences:
-both have different enzymes (dipeptidase/amylase)
-protein digestion is in the stomach + small intestine
-carbohydrate digestion is in the small intestine only

Question 21

Describe the digestion of lipids

Answer 21

lipids are emulsified by bile into emulsified lipids/small fat droplets, which are hydrolysed into fatty acids and glycerol

Question 22

Explain lipid absorption

Answer 22

lipids are hydrolysed into glycerol, fatty acids, and monoglycerides; then monoglycerides and fatty acids associate with bile salts to form micelles

Question 23

What are micelles?

Answer 23

droplets that are about 200 times smaller than the small fat droplets in the emulsified lipids

Question 24

What do micelles do and how?

Answer 24

they transport the poorly soluble monoglycerides and fatty acids to the surface of the epithelial cells where they can be absorbed- the micelles constantly break up and reform which allows them to release the monoglycerides and fatty acids so they can be absorbed (whole micelles are not absorbed)