DIGESTION OF LIPIDS

Question 1

Why are some enzymes membrane bound

Answer 1

Being fixed to the membrane of the gut epithelium is more efficient since the enzyme is not removed and can be reused
Even when the epithelial cell is rubbed odd, the enzyme can still function

Question 2

What is lipid digestion hydrolysed by

Answer 2

Lipases produced in the pancreas and absorbed in the small intestine

Question 3

What is the problem with lipid digestion

Answer 3

Lipids are insoluble
Enzymes are soluble
Enzyme action only on the surface of each droplet

Question 4

Bile production

Answer 4

Produced in the liver and stored in the gall bladdee nefore being injected into the duodenum

Question 5

Describe emulsification

Answer 5

A process in which large lipid globules are broken down into several small lipid globules
These small globules are widely distributed in the chyme rather than forming large aggregates
Lipids are hydrophobic
Bile contains bile salts which have hydrophobic and hydrophilic sides

Question 6

Role of bile

Answer 6

Lipids are first split into tiny droplets called micelles by bile salts which emulsify fats

Question 7

Benefit of emulsification

Answer 7

Smaller droplets increases surface area of lipids so a faster rate of reaction for lipases

Question 8

What are micelles

Answer 8

Micelles allow both fatty acids and monoglycerides to pass through the epithelial membrane
Complicated process which is summarised as diffusion

Question 9

Describe the digestion of lipids

Answer 9

Bile salts emulsify the lipid to form smaller droplets called micelles
Micelles carry fatty acids and monoglycerides to membrane via diffusion
Golgi apparatus modifies and processes triglycerides
Triglycerides associated with cholestrol and proteins
Packaged for release exocytosis as chylomicrons
Lacteal (lymphatic system) takes the chylomicrons to the blood system
Chylomicrons hydrolysed by an enzyme in the endothelial cells of capillaries and then diffuse into cells

Question 10

Lipid digestion

Answer 10

1. Emulsification of lipids into smaller droplets increases sa of lipids and lipases break it down faster
2. Lipases hydrolyse ester bonds in triglycerides forming fatty acids and monoglycerides
3. Formation of micelles
4. Micelles transport the fatty acids and monoglycerides to epithelial cells
5. Fatty acids and monoglycerides cross the cell surface membrane by diffusion

Question 11

Lipid absorption

Answer 11

Inside the epithelial cell
1. Fatty acids and monoglycerides form triglycerides at the endoplasmic reticulum
2. The triglyceride then combine with lipoproteins and cholestrol in the golgi body, forming chylomicrons
3. Vesicles pinching off the end of the golgi body containign chylomicrons, travel to the bottom surface of the epithelial cell and fuse to it
4. This releases the chylomicrons out of the cell (exocytosis)
5. Chylomicrons enter the lacteal (lymph vessel) where they are carried to the blood system
6. Chylomicrons and triglycerides are hydrolysed by enzymes in the endothelial cells of blood capillaries