Nutrient digestion

Question 1

What are the membranes of the small intestine?

Answer 1

Apical membrane

basolateral membrane

Question 2

What are paracellular pathways?

Answer 2

Pathways between the cell to allow water to enter the cell

Question 3

What are the principle dietary nutrients?

Answer 3

Carbohydrates
Protein
Fats

Question 4

What are the forms of polysaccharides?

Answer 4

Starch
Cellulose
Glycogen

Question 5

What is starch?

Answer 5

Plant storage form of glucose

Question 6

What are the types of starch?

Answer 6

⍺ amylase

amylopectin

Question 7

What is the difference between ⍺ amylase and amylopectin?

Answer 7

⍺amylase has glucose linked in straight chains while amylopectin has highly branched glucose chains

Question 8

What is the structural makeup of starch?

Answer 8

Glucose monomers linked by ⍺-1,4 glycosidic bonds

Question 9

How is starch broken down?

Answer 9

Amylase

Question 10

What is cellulose?

Answer 10

Constituent of plant cell walls, dietary fibre

Question 11

What is the structure of cellulose?

Answer 11

Unbranched linear chains of glucose monomers lined by β-1,4 glycosidic bonds

Question 12

Why is cellulose a dietary fibre?

Answer 12

No enzymatic digestion in vertebrates

Question 13

What is glycogen?

Answer 13

Animal storage form of glucose

Question 14

What is the structure of glycogen?

Answer 14

Glucose monomers linked by ⍺-1,4 glycosidic bonds

Question 15

How is starch and glycogen broken down?

Answer 15

by amylase

Question 16

How are glucose and galactose absorbed into the cells of the small intestine?

Answer 16

Via SGLT1 accompanied by Na

Question 17

How are glucose and galactose transported out of the small intestinal cells and into the bloodstream?

Answer 17

Via GLUT2

Question 18

Why are glucose and galactose accompanied by Na?

Answer 18

Create a gradient to allow for passive absorption of water

Question 19

How is water absorbed into the bloodstream?

Answer 19

Na/K pump created a gradient that allows water to passively pass through the paracellular pathway

Question 20

How is fructose absorbed into the cells of the small intestine??

Answer 20

Via GLUT5 accompanied by Na

Question 21

How is fructose transported out of the cells of the small intestine and into the bloodstream?

Answer 21

Via GLUT2

Question 22

What are the transporter proteins of glucose and galactose?

Answer 22

Into cell= SGLT1

Out= GLUT2

Question 23

What are the transporter proteins of fructose?

Answer 23

in= GLUT5
out= GLUT2

Question 24

What are proteins?

Answer 24

Polymers of amino acids linked together by peptide bonds of varying length

Question 25

What are peptides?

Answer 25

Small proteins constituting of 3-10 amino acids

Question 26

What breaks down proteins and peptides?

Answer 26

Proteases and peptides

Question 27

How are amino acids absorbed into the bloodstream?

Answer 27

Via SAAT1 accompanied by Na then cross over into the bloodstream

Question 28

How are dipeptides absorbed into the bloodstream?

Answer 28

Taken into the cells via Pep1 accompanied by H Na is taken into the cell by NHE3 as H is transported out Dipeptides cross into the bloodstream

Question 29

Why is NHE3 essential?

Answer 29

maintains the Na gradient to allow water to enter the bloodstream via the paracellular pathway

Question 30

What is the most common form of ingested fat?

Answer 30

Triacylglycerol

Question 31

Where does fat digestion take place?

Answer 31

Small intestine

Question 32

What enzyme is involved in fat digestion?

Answer 32

Pancreatic lipase

Question 33

What does lipase break triacylglycerol down into?

Answer 33

Monoglyceride and 2 fat acids

Question 34

What makes lipase inefficient on triacylglycerol?

Answer 34

Triacylglycerol is insoluble in water while lipase is, so lipase can only work on the surface of lipid droplets

Question 35

What is done to make digestion of fats more efficient?

Answer 35

Emulsification

Question 36

What are the requirements of emulsification?

Answer 36

Mechanical disruption | Emulsifying agent

Question 37

What mechanical disruption is used in emulsification of fats?

Answer 37

Smooth muscle contraction of the stomach | Grinds and mixes lumenal contents

Question 38

What is the purpose of an emulsifying agent?

Answer 38

Prevents small droplets reforming into large droplets

Question 39

What emulsifying agent is used for fats?

Answer 39

Bile salts and phospholipids

Question 40

How do emulsifying agents work?

Answer 40

Have a polar and a non polar end | Non polar end associated with lipid droplet, leaving polar ends exposed at the water surface to repel each other

Question 41

What can emulsifying agents be classified as?

Answer 41

Amphipathic molecules

Question 42

What are micelles?

Answer 42

Bile salt, monoglyceride, fatty acid and phospholipid

Question 43

What is the structure of a micelle?

Answer 43

Polar portion at surface, non polar core

Question 44

How do micelles break down?

Answer 44

As micelles come into contact with the villi in the acid microclimate, they release the fatty acids and monoglyceride for passive diffusion across the intestinal cell membrane

Question 45

What happens to fatty acids and monoglycerides once they enter the small intestinal cells?

Answer 45

Smooth endoplasmic reticulum

Question 46

What do fatty acids and monoglycerides form into in the small intestinal cells?

Answer 46

Triacylglycerol

Question 47

How are fatty acids and monoglycerides formed into triacylglycerol?

Answer 47

Via enzymes in the smooth endoplasmic reticulum

Question 48

How is triacylglycerol transported in the cell?

Answer 48

In vesicles formed from the smooth endoplasmic reticulum membrane

Question 49

What happens to triacylglycerol in the small intestinal cells?

Answer 49

Processed through the Golgi apparatus and exorcised to the extracellular fluid at the basolateral membrane

Question 50

What are chylomicrons?

Answer 50

Coated extracellular fat droplet containing phospholipids, cholesterol and fat soluble vitamins

Question 51

What happens to chylomicrons in the small intestine?

Answer 51

Pass into lacteals between endothelial cells as they are too large to pass through the capillary basement membrane

Question 52

What are the fat soluble vitamins?

Answer 52

A, D, E, K

Question 53

How are fat soluble vitamins absorbed?

Answer 53

Via the same absorptive path as fat

Question 54

What are the water soluble vitamins?

Answer 54

B group, C, folic acid

Question 55

How are water soluble vitamins absorbed?

Answer 55

Passive diffusion | Carrier mediated transport

Question 56

How is B12 absorbed?

Answer 56

Binds to intrinsic factor in stomach to form a complex which is absorbed via a specific transport system in the distal ileum

Question 57

How much B12 can the body store?

Answer 57

3 years worth stored in liver

Question 58

What does a B12 deficiency cause?

Answer 58

Prenicious anaemia- failure of RBC maturation

Question 59

How is iron absorbed?

Answer 59

Transported across brush border membrane via DMT1 into duodenal enterocytes

Question 60

What are the 2 fates of iron in cells?

Answer 60

Incorporated into ferritin in the cell | Bound to transferrin in the blood for transport

Question 61

Why does iron bind to transferrin in the blood?

Answer 61

Cannot travel alone in the blood due to the charge and dangers of free radical creation

Question 62

How is ferritin expression controlled?

Answer 62

Depending on the body's iron status