Nutrient Digestion 2 Flashcards Preview

07. Year 2: Alimentary System > Nutrient Digestion 2 > Flashcards

Flashcards in Nutrient Digestion 2 Deck (58)
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1

What form is almost all ingested fat?

Tricylglycerol

2

Where is all fat digested?

Small intestine

3

What enzyme digests fat?

Pancreatic lipase

4

What is a lipase?

Water-soluble enzyme that digests fat

5

Why is digestion of triacylglycerols without modifications very slowly?

They present as large lipid droplets and digestion can only take place at the surface of the droplet

6

What makes triacylglycerol?

Glycerol molecule and 3 stearic acids

7

What does lipase break triacylglycerol down into?

Monoglyceride and 2 fatty acids

8

What is emulsification?

Dividing large lipid droplets into smaller droplets (about 1mm in diameter) to increase surface area and accessibility to lipase action

9

Why does emulsification occur?

Dividing large droplets into smaller ones increases surface area so can be broken down by lipase faster

10

What does emulsification require?

Mechanical disruption of large lipid droplet into small droplets

Emulsifying agent (prevents small droplets reforming into large droplets)

11

What provides mechanical disruption of large lipid droplets into small droplets?

Smooth muscle contraction grinds and mixes luminal content

12

What is the function of an emulsifying agent?

Prevents small droplets reforming into large droplets

13

What is an example of an emulsifying agent?

Bile salts and phospholipids in bile

14

What can be said about the charge of emulsifying agents?

Amphipathic molecules (polar charged and non-polar charged portions

15

What does the polar and non-polar portion of emulsifying agents bind to?

Non-polar associated to non-polar lipid interior of fat, leaving polar portion exposed at water surface

16

How do emulsifying agents prevent droplets reforming into large ones?

Polar portion of emulsifying agent surrounds the outside of the fat which prevents them reforming into large droplets

17

Why are micelles required to be formed after emulsification?

Absorption is still slow after emulsification, micelles speed this up

18

How is absorption of fat enhanced?

By forming micelles

19

What are micelles formed from?

Bile salt

Monoglycerides

Fatty acids

Phospholipids

20

What are the charges of micelles?

Polar surface, non-polar core

21

What size are micelles?

4-7 um (much smaller than emulsion droplets)

22

What do micelles release when they are broken down?

Free fatty acids and monoglycerides which diffuse across plasma membrane of absorbing cells

23

Explain the equilbrium between fatty acids and monoglycerides in solution and in micelles?

Dynamic equilbrium exists, so micelles retains most of fat digestion products in solution while constantly replenishing supply of free molecules for absorption

24

What is not absorbed once micceles reach the epithelial surface of lumen cells?

The micelles themselves are not absorbed, whilst their breakdown products are

25

Summarise the process of fat absorption prior to the fat being inside of the epithelial cells?

1) Emulsification

2) Formation of micelles

3) Travel to surface of cells and release fatty acids

4) Fatty acids enter epithelial cells

26

Summarise the process of fat absorption after entering epithelial cells?

1) Fatty acids and monoglycerides enter smooth endoplasmic reticulum (SER) where they are reformed into triaclyglycerols

2) Coated with amphiphatic protein (emulsification)

3) Transported though cell in vesicles formed from SER membrane, processed though golgi apparatus

4) Exocytosed into ECF at serosal membrane

5) Chylomicrones pass into lacteals between endothelial cells (cannot pass through capillary basement membrane)

27

Where are fatty acids and monoglycerides reformed into triaglyerols once they enter epithelial cells after the gut lumen?

Smooth endoplasmic reticulum (SER)

28

Where do chylomicrons enter to be transported around the body?

Lacteals between endothelial cells (cannot pass through capillary basement membrane)

29

What are chylomicrones?

Extracellular faty droplets

30

What do chylomicrons contain?

Fat droplets

Phospholipids

Cholesterol

Fat soluble vitamins