lecture 25 - absorption of carbohydrates and protein

Question 1

are sugars soluble and can they diffuse across the cell membrane

Answer 1

sugars are highly water soluble and can not simply diffuse across the cell membrane

Question 2

how are sugars transported across the membrane

Answer 2

require specific transporter proteins anchored in the membrane that form ‘pores’ in the membrane

Question 3

what are the two glucose transporters needed across the intestinal epithelia

Answer 3

SGLT 1 = secondary active transporter

GLUT 2 = facilitative transporter

Question 4

what does SGLT 1 do to transport glucose into an epithelial cell

Answer 4

uses symport of glucose and Na+ into the cell

Question 5

how is the symport of glucose by SGLT 1 facilitated

Answer 5

by the sodium gradient that is created by Na+/K+ ATPase = keeping Na+ low in the cell

• this is why SGLT 1 is considered to be an active transport

Question 6

what does elevated glucose in the epithelial cell facilitate

Answer 6

the transport of glucose into the blood capillaries by GLUT 2

Question 7

how does Na+/K+ ATPase work

Answer 7

for every 3 Na+ transported out of the cell, 2 K+ are transported into the cell

Question 8

what allows conformational change of the Na+/K+ATPase

Answer 8

hydrolysis of ATP and phosphorylation of the

transporter leads to conformational change, enabling the transport of the Na+ followed by K+

Question 9

how are di and tri peptides absorbed in the small intestine

Answer 9

by co transport with H+ ions via membrane transporter PepT1

Question 10

what is the transport system of amino acid absorption in the GI tract

Answer 10

semi specific Na+ dependent transport system - not amino acid specific, amino acid class specific

• neutral amino acid
• proline and hydroxyproline
• acidic amino acid
• basic amino acid

Question 11

what is pancreatitis

Answer 11

leads to inappropriate activation of zymogens, resulting in self digestion

Question 12

what are stomach ulcers caused by

Answer 12

breakdown of mucus which normally protects against protease action

Question 13

what does cystic fibrosis cause

Answer 13

thick mucus secretions which block the pancreatic duct and secretion of pancreatic enzymes

Question 14

what is the digestion of dietary nucleic acid polymers

Answer 14

intestinal endonuclease enzymes hydrolyse the phosphodiester bonds linking individual nucleotides