Absorption of Ions and Water

Question 1

What does absorption of water in the GIT depend on

Answer 1

• Absorption of Na+ and Cl- ions

Question 2

What are the 4 different ways that Na+ is absorbed in the intestine

Answer 2

• Na/Glucose transport or Na/Amino acid transport
• Na-H exchanger
• Parallel Na-H and Cl-HCO3 exchange
• Epithelial Na+ Channels

Question 3

What are the 4 categories of secretagogues

Answer 3

• Bacterial enterotoxins
• Hormone neurotransmitters
• Products of cells of the immune system
• Laxatives

Question 4

What effect do bacterial enterotoxins have and how do they do this

Answer 4

• They induce secretary diarrhoeas
• They induce intracellular concentrations of cAMP which increases Cl and K secretion inhibiting electroneutral NaCl absorption

Question 5

What are the roles of Iron in the human body

Answer 5

• O2 transportation and storage (via haemoglobin)
• Cofactor in enzyme controlled reactions

Question 6

What are the types of iron gained from a diet

Answer 6

• Inorganic iron (greens)
• Haem iron (red meats)

Question 7

Why is inorganic iron not as useful as haem iron

Answer 7

• Fe3+ - needs to be reduced to Fe 2+ to be useful
• Bound to antioxidants - makes the iron inaccessible and inert

Question 8

What regulates iron absorption and where is this made

Answer 8

• Hepcidin
• Made in the liver

Question 9

What are the 3 proteins in hepatocytes that sense high iron levels

Answer 9

• TfR2
• HFE
• HJV