Nutrient Digestion II (Fats, Vitamins and Minerals)

Question 1

Where does all fat digestion occur and what enzyme does so?

Answer 1

Small Intestine

Lipase - Made in the pancreas

Question 2

How do triacylglycerols present?

Answer 2

Large lipid droplets

Question 3

What is special about the lipid droplet and lipase relationship?

Answer 3

Lipid droplets and insoluble in water but lipase is a water soluble enzyme so digestion only occurs at the droplet surface

Question 4

What does lipase cleave triacylglycerols into?

Answer 4

Monoglyceride + Fatty Acids x2

Question 5

What is emulsification?

Answer 5

The dividing of large lipid droplets into smaller droplets resulting in an increased surface area and accessibility to lipase action

Question 6

How are droplets made smaller?

Answer 6

Mechanical disruption - Smooth muscle grinding and mixing luminal contents

Question 7

How are smaller droplets prevented from reforming into largers ones?

Answer 7

Emulsifying agent (Comes from bile)
Biles salts and phospholipids emulsify smaller fat globules
Phospholipids are amphipathic so they repel other small lipid droplets

Question 8

How is lipase digestion enhanced?

Answer 8

By the use of micelles

Question 9

What are micelles?

Answer 9

Similar to emulsion droplets but much smaller

Bile salt + Monoglycerides + Fatty Acids + Phospholipids

Question 10

What happens to micelles?

Answer 10

They are not absorbed but instead release small amounts of Fatty Acids and Monoglycerides to diffuse across the plasma membrane

Question 11

When does the micelle destabilise?

Answer 11

When it enters the microclimate outside the cell

Question 12

Triacylglycerol droplets coated with amphipathic protein are transported where, how and what happens to them there?

Answer 12

To Golgi Apparatus via vesicles from RER

Exocytosed into the ECF at the serosal membrane

Question 13

What is a chylomicron?

Answer 13

Extracellular far droplet containing phospholipids, cholesterol and fat-soluble vitamins
A lipoprotein that is present in the blood after digested fat has been absorbed from the small intestine

Question 14

Where do Chylomicrons go?

Answer 14

Into lacteals between endothelial cells

Question 15

What can chylomicrons not pass through?

Answer 15

Tight junctions between capillaries to prevent fat entering the blood

Question 16

What are the fat-soluble vitamins?

Answer 16

A, D, E & K

Question 17

What are the water-soluble vitamins?

Answer 17

B, C & Folic acid - Either absorbed by passive diffusion or carrier-mediated transport

Question 18

What is special about Vitamin B12?

Answer 18

It must bind to intrinsic factor in the stomach and travel to the ileum where a specific transport mechanism recognises the complex itself - not the B12

Question 19

What does B12 have an affect on?

Answer 19

Red blood cell maturation - Can give functional anaemia

Question 20

Why can a sign of gut specific deficiency be delayed?

Answer 20

There is 3 years worth of B12 in the liver

Question 21

What effect can bowel resection have on B12?

Answer 21

B12 transport mechanism is removed and anaemia will ensue 3 years down the line

Question 22

What is iron absorbed across into the blood?

Answer 22

Brush border membrane via DMT1 - 10% a day is ingested across the intestine into blood

Question 23

What does DMT1 transport and where to?

Answer 23

Mainly Iron but also Lead and Cadmium into duodenal enterocytes

Question 24

What are enterocytes?

Answer 24

Simple columnar epithelial cells found in the small intestine

Question 25

What are iron ions incorporated into?

Answer 25

Ferritin

Question 26

What happens to unbound iron?

Answer 26

Transported across the serosal membrane into the blood

Question 27

What does iron in blood bind to?

Answer 27

Transferrin

Question 28

What does transferrin do?

Answer 28

Stops iron becoming free radicals and transports it to the liver

Question 29

How often does the small intestine lining renew itself?

Answer 29

Every 5 days

Question 30

What is the regulator of iron stasis?

Answer 30

The gut

Question 31

What does hyperaemia lead to?

Answer 31

Increased ferritin levels

More iron bound in enterocytes

Question 32

What does anaemia lead to?

Answer 32

Decreased ferritin levels and more iron released into the blood

Question 33

What three glands secrete saliva?

Answer 33

Parotid
Submandibular
Sublingual

Question 34

What is the main component of saliva?

Answer 34

Water - 99% to soften, moisten and dilute particles

Question 35

What are mucins and what is their function?

Answer 35

Mucus + Water

Lubricant function

Question 36

Is amylase found in saliva?

Answer 36

Yes

Question 37

What is a Lysozyme(Natural bacteria)?

Answer 37

Bacteriocidal that cleaves the polysaccharide component of the bacterial cell wall

Question 38

Where does α-amylase come from?

Answer 38

Serous alveolus

Question 39

What effect does the parasympathetic nervous system have on salivary secretion?

Answer 39

Creates a profuse watery salivna

*Cranial nerves VII (Facial) & IX (Glossopharyngeal)

Question 40

What effect does the sympathetic nervous system have on salivary secretion?

Answer 40

Creates a small viscous amount of saliva that is high in protein
If separated a β-2 adrenoreceptor agonist will give you a high amylase content and a α-1 adrenoreceptor agonist will make the saliva gloopy