12.9 Digestion and absorption

Question 1

What enzyme is found in the salivary glands?

Answer 1

Salivary amylase

Question 2

What enzyme is found in the stomach?

Answer 2

Endopeptidase and exopeptidase

Question 3

What enzyme is found in the pancreas?

Answer 3

Pancreatic amylase, lipases and exopeptidase

Question 4

What emzyme is found in the ileum?

Answer 4

Membrane bound dipeptidases and dissacharidases

Question 5

Describe the route of the digestive system

Answer 5

Ingestion
Digestion
Absorption
Ejection

Question 6

Describe the role of the salivary glands

Answer 6

Secretes salivary amylase which hydrolyses starch to maltose

Question 7

Describe the role of the stomach

Answer 7

Food is mixed with gastric juices to kill microorganisms and contains endo and exo peptidases to hydrolyse peptides into dipeptides

Question 8

Describe the role of the pancreas

Answer 8

Secretes pancreatic amylase, endo and eco peptidases and lipases

Question 9

Describe the role of the small intestine (ileum)

Answer 9

Maltase enzymes are embedded within the epithelium cell membrane to hydrolyse maltose to glucose for rapid absorption
It also contains sucrase, lactase and dipeptidase

Question 10

How is the ileum adapted for absorption?

Answer 10

Large surface area for absorption of products of digestion

Question 11

Describe the breakdown of starch

Answer 11

Food enters the mouth and is mixed with saliva and broken down by teeth
Salivary amylase starts to hydrolyse the glycosidic bonds in starch to maltose
The salivary amylase is denatured in the stomach due to high pH
Pancreatic amylase continues ton hydrolyse starch to maltose
Maltose is hydrolysed to glucose by maltase in the membrane of the epithelium cells
Glucose is then absorbed

Question 12

Summarise amylase

Answer 12

Hydrolyses starch to maltose
Synthesised and secreted from salivary glands and pancreas

Question 13

Summarise maltase

Answer 13

Hydrolyses maltose to glucose
Found within the epithelium cell membrane of ileum

Question 14

Describe the co transport of glucose

Answer 14

Sodium ions leave the cell and enter the blood by active transport
Concentration of sodium low in the cell so sodium and glucose enter by facilitated diffusion using co transporter proteins
Sodium diffuses into the cell down the concentration gradient
Glucose moves into the cell against the concentration gradient
Glucose then moves out of the cell, into the blood via facilitated diffusion

Question 15

Describe protein digestion

Answer 15

Proteins hydrolysed b y proteases in the stomach
Endopeptidases hydrolyse peptide bonds within the polypeptide chain
Producing smaller polypeptide chains
Exopeptidases hydrolyse peptide bonds at the terminal ends of the chain

Question 16

What is the role of exopeptidases?

Answer 16

Hydrolyses peptide bonds at the terminal ends of the polypeptide chain, removing one amino acid at a time
Specific to one end of the polypeptide chain - either C or N terminal

Question 17

What is the role of endopeptidases?

Answer 17

Hydrolyses peptide bonds within the polypeptide chain
Increases surface area for faster and more efficient digestion

Question 18

Where is bile produced and stored?

Answer 18

Produced in the liver
Stored in the gall bladder

Question 19

What does bile contain?

Answer 19

Bile salts

Question 20

What do bile salts do?

Answer 20

Emulsify fat droplets and form micelles

Question 21

What is the role of lipase?

Answer 21

Hydrolyse lipids into glycerol, fatty acids and monoglycerides

Question 22

Describe lipid digestion and absorption

Answer 22

Lipids droplets are mixed with bile salts to form smaller droplets
This increases surface area for faster hydrolysis
Triglycerides are hydrolysed into glycerol, fatty acids and monoglycerides
The glycerol and fatty acids form micelles
The micelles make fatty acids soluble in water and bring fatty acids to the surface of the epithelial membrane
Fatty acids enter epithelial membrane by simple diffusion
At the smooth ER, faatty acids ands glycerol recombined to form triglycerides
At the Golgi, triglycerides modified, proteins are added to form lipoproteins called chylomicrons which are transported into lymph vessels by exocytosis