GI: Digestion and Absorption 2

Question 1

How is carbohydrate digested?

Answer 1

Mouth- salivary alpha amylase
Stomach- salivary alpha amylase trapped in the bolus
Small intestine- pancreatic alpha amylase and oligosaccharidases (isomaltose, maltose, sucrase, lactase, maltase)

Question 2

What bond does amylase break?

Answer 2

Internal alpha 1. 4 glycosidic bond
Cannot break aplha 1, 6 or beta 1, 4 bonds as in cellulose
ENDOENZYME
produces ogliosaccarhides

Question 3

What are the final products of carbohydrate digestion?

Answer 3

Glucose
Galactose
Fructose

Question 4

How is glucose and galactose absorbed?

Answer 4

Secondary active transport

Question 5

How is fructose reabsorbed?

Answer 5

facilitated diffusion

Question 6

How is fructose transported from the lumen into the enterocyte?

Answer 6

GLUT 5

Question 7

How is glucose or galactose transported from the lumen?

Answer 7

SGLT1

Question 8

How are glucose, galactose and fructose transported into the blood?

Answer 8

GLUT 2

Question 9

How are amino acids absorbed?

Answer 9

Passive diffusion- hydrophobic amino acids
Active transport and facilitates transport
At brush border- five sodium dependant, 2 indepentandt
At basolateral border- Sodium dependant

Question 10

How are di and tripeptides absorbed?

Answer 10

proton dependant mechanism at brush border (co-transport)

Question 11

What happens to peptides within the enterocyte?

Answer 11

Hydrolysed furthur to amino acids

Question 12

How do the amino acids then leave the enterocyte and enter the lumen?

Answer 12

Sodium independent systems at basolateral border

facilitatd transport

Question 13

How are lipids digested?

Answer 13

Lingual lipase
Gastric lipase
Bile emulsifies
Pancreatic lipase

Question 14

What is the products of fat digestion?

Answer 14

Fatty acids and monglycerides

Question 15

What is the role of bile salts?

Answer 15

Deteregents to emulsify large lipid droplets

Question 16

Decribe the structure of a bile salt.

Answer 16

Amphipathic
Hydrophilic outer surface
Hydrophobic inner

Question 17

What can result from failure to secrete bile salts?

Answer 17

Lipid malabsoption and thus steatorrheoa

Secondary vitamen deficiency

Question 18

What is colipase?

Answer 18

An amphipathetic polypeptide secreted with lipase by the pancreas - binds to bile salts and lipase allowing access of the lipase to tri and di-glycerides which are trapped in the core of lipid droplets

Question 19

What are the products of digestion of a triglyceride by pancreatic lipase?

Answer 19

2-monoglyceride

Free fatty acids

Question 20

How are the products of lipid digestion stored in the duodenum?

Answer 20

Micelles

Question 21

How are free fatty acids and monoglyceride absopbed?

Answer 21

Transfer between mixed micelles and the apical mebrane of enterocytes enterying by passive diffusion

Question 22

What happens to long chain fatty acids?

Answer 22

They are resynthesized back into triglycerides and stores as chylomicrons

Question 23

What happens to chylomicrons after leaving the entericyte

Answer 23

Transported to subclavan vein via the thoracic duct

Question 24

What enzyme metabolises chylomicrons in the capillaries?

Answer 24

Lipoprotein lipase

Question 25

What happens to the free fatty acis and glycerol release from the chylomicrons?

Answer 25

Binds to albumen and taken up into tissues

Question 26

What happens tot he chylomicron remenant

Answer 26

Endocytosed by hepatocytes to be stored, secreted or oxidised to bile salts

Question 27

How is cholesterol absopbed from the blood into hepatocytes?

Answer 27

Niemann -Pick C1 like 1 protein

Question 28

What does ezetimibe do?

Answer 28

Binds to PPC1L1 and prevents internalisation and cholesterol absorption
Used in hypercholesterolaemia along with statins