17. Digestion and Absorption of Lipids, Fluids and Electrolytes

Question 1

Bile salts emulsify fats into what?

Answer 1

Colloidal form

Question 2

Bile salts are known as what type of molecules?

Answer 2

Amphipathic

Question 3

What is the function of pancreatic lipase?

Answer 3

Hydrolyse 1 & 3 bonds of TAG’s to yield monoglycerides and 2 FFA

Question 4

What assists the function of pancreatic lipase?

Answer 4

Colipase

Question 5

What molecules digest cholesterol esters and vitamin esters?

Answer 5

Pancreatic esterases

Question 6

What is a micelle?

Answer 6

An aggregate of surfactant in a colloidal solution

Question 7

How are micelle’s formed?

Answer 7

From substrates and products of fat formation and phospholipids

Stabilised by bile salts

Question 8

What is the fate of micelles?

Answer 8

Diffuse slowly acrosse unstirred water layer ot enterocyte - present highly concentrated packets of fats to membrane

Question 9

Where does absorption into enterocyte mainly occur?

Answer 9

Jejunum

Question 10

How do lipid soluble contents of micelle cross membrane into cytosol?

Answer 10

Passive diffusion

Question 11

What is the fate of bile salts after absorption of micelle contents?

Answer 11

Left outside the cell to form more micelles (95%)

Transport from terminal ileum, recycled to liver, gall bladder, “enterohepatic circulation”

Question 12

How are short chain ionised FA’s absorbed?

Answer 12

Pass direct into bloodstream

Question 13

What is the fate of most FFA’s and MG’s?

Answer 13

Re-esterified into TG’s in smooth ER, coated with phospholipids and protein in the Golgi to form chylomicrons

Question 14

How do chylomicrons leave enterocytes?

Answer 14

Pinocytosis into lacteals to lymph and then eventually the bloodstream

Question 15

Ho are TG’s cleared from the blood?

Answer 15

Lipoprotein on endothelial surface of capillaries; TG’s passively diffuse into cells like adipocytes

Question 16

When are bile salts not absorbed?

Answer 16

Terminal ileum damaged or if resins given

Question 17

What do drugs resemble, molecularly?

Answer 17

Weak acids or bases

Question 18

What does the ratio of ionised and non ionised forms of drugs depend on?

Answer 18

pK and pH of environment

Henderson Hasselbach equation

Question 19

How are non-ionised drugs absorbed?

Answer 19

Passive diffusion

Route for most drugs

Question 20

How can water cross epithelial barriers? Where is this greatest?

Answer 20

Diffusion via transcellular and paracellular routes

Wherever villi biggest and epithelia leakiest (duodenum and upper jejunum)

Question 21

Net flux = ?

Answer 21

Absorption - Secretion

Question 22

How is sodium absorbed?

Answer 22

Passive diffusion (paracellular)

Cotransport with glucose and AA

Active transport

Question 23

What are some common causes of diarrhoea?

Answer 23

Drugs

Toxins

Infectious agents

Foods/IBS

Anxiety

Question 24

Explain osmotic factors role in in fluid accumulation of intestinal lumen

Answer 24

Faulty nutrient digestion and absorption

Cause increase in osmotic pressure and subsequent osmotic movement into lumen