digestion n absorption

Question 1

process of absorption and transport of digested lipid molecules from ileum into lymph vessels

Answer 1

micelles contain bile salts and fatty acids and monoglycerides
they make monoglycerides and fatty acids more soluble in water and they are absorbed by diffusion
triglycerides reform and vesicles move to cell membrane

Question 2

movement of na out of cell allows absorption of glucose into the cell lining the ileum how

Answer 2

maintains a conc gradient for na
so na move in by FD bringing glucose with it

Question 3

role of micelles in absorption of fats into cells lining ileum

Answer 3

micelles - fatty acids and bile salts
make fatty acids more soluble in water and carry them to cell lining of ileum
maintaining a higher conc of fatty acids to cell lining ileum
fatty acids absorbed by diffusion

Question 4

benefits of rabbit eating on caecal droppings for digestion and absorption

Answer 4

remaining undigested protein broken down
so more AA absorbed as protein passes through stomach again

Question 5

advantage of lipid droplet and micelle formation

Answer 5

droplets increase surface area for enzyme action so faster hydrolysis
micelles carry fatty acids an glycerol through membrane to epithelial cell

Question 6

Golgi vesicle role in absorption of lipids

Answer 6

modifies triglycerides
combines triglycerides with protiens
packaged for release and form vesicles

Question 7

cells lining ileum absorb glucose by cotransport with sodium - how

Answer 7

sodium actively transported from ileum cell to blood
= diffusion gradient for sodium to enter cells from gut bring glucose with it
glucose enters by FD with na ions

Question 8

glucose rise in blood slower for starch than sucrose - why

Answer 8

starch - maltose by amylase - maltose to glucose by maltase
sucrase - digestion one step by sucrase

Question 9

starch digestion

Answer 9

Amylase hydrolyses starch to maltose
Membrane-bound maltase hydrolyses maltose to glucose
Hydrolysis of glycosidic bond

Question 10

Describe the digestion of disaccharides in mammals

Answer 10

Membrane-bound disaccharidases hydrolyse disaccharides to 2 monosaccharides:
○ Maltase - maltose → glucose + glucose
○ Sucrase - sucrose → fructose + glucose
○ Lactase - lactose → galactose + glucose
● Hydrolysis of glycosidic bond

Question 11

Describe the digestion of lipids in mammals, including action of bile salts

Answer 11

Bile salts emulsify lipids causing them to form smaller lipid droplets
increases surface area of lipids for increased / faster lipase activity
● Lipase (made in pancreas) hydrolyses lipids → monoglycerides + fatty acids
● Hydrolysis of ester bond

Question 12

Suggest why membrane-bound enzymes are important in digestion

Answer 12

● Membrane-bound enzymes are located on cell membranes of epithelial cells lining ileum
● maintain concentration gradients for absorption

Question 13

Describe the pathway for absorption of products of digestion in mammals

Answer 13

Lumen of ileum → cells lining ileum → blood

Question 14

Describe the absorption of lipids by a mammal, including the role of micelles

Answer 14

● Micelles contain bile salts, monoglycerides and fatty acids
○ Make monoglycerides and fatty acids (more) soluble in water
○ release fatty acids and monoglycerides to lining of ileum
○ Maintain high concentration of fatty acids to lining
● Monoglycerides / fatty acids absorbed by diffusion
● Triglycerides reformed in (epithelial) cells and aggregate into globules
● Globules coated with proteins forming chylomicrons which are then packaged into vesicles
● Vesicles move to cell membrane and leave via exocytosis
○ Enter lymphatic vessels and eventually return to blood circulation