Lecture 27: Absorption

Question 1

Why is motility important for digestion

Answer 1

Controls how fast food through the tract

Too fast = not enough time for absorption

Too slow = too much time for absorption

Question 2

What are some driving forces to make things move across the cell

Answer 2

Energy (ATP)
Electrochemical gradient
Osmotic gradient

Question 3

What can be passively absorbed via the paracellular pathway and why

Answer 3

Glucose, Amino acids, Sodium

Because they have a gradient that allows this as the lumen is full of these molecules.

Question 4

What are the two water soluble vitamins

Answer 4

C and most of group B

Question 5

What is an aquaporin

Answer 5

A channel in the cellular membrane specifically for water

Question 6

How is water absorbed in the body

Answer 6

Mostly through osmosis, passive and paracellular

In the SI:
Some absorbed via the transcellular pathway via aquaporins
Mostly absorbed via the paracellular pathway

Large Intestine - Fine tuning:
Tight epithelia with “tight” tight junctions
ALL water re/absorbed via the transcellular pathway (aquaporins)

Question 7

How do fats leave the cell

Answer 7

Reformed TAGs are packaged into chylomicrons and removed from the cell via exocytosis

They go into the lacteals and join the lymph. Our fat soulble vitamins go with them

Question 8

What are the fat soluble vitamins

Answer 8

A D E K

Question 9

How is fat absorbed

Answer 9

Passive absorption
Micelles are fat soluble so they can move into the cell via the phospholipid bilayer