Lipid (TAG) digestion in the non-ruminants, enzyme notes, 2 FFA & MAG absorption, + TAG in the enterocyte

What level of TAG digestion occurs in the mouth?

minimal digestion of TAG

What enzyme is in the mouth and at what position does it hydrolyze?

lingual lipase (LL) & they act @ the Sn3 position

What is something that happens in the mouth & how does it help?

physical emulsification results in decrease of feed particle size with an increase in surface area

All the result of chewing

When TAG is put with lingual lipase + water, what does it result in?

DAG + a FFA

What are the levels of TAG, DAG, & FFA in the stomach?

lots of TAG, little DAG, & little FFA

What is the enzyme that hydrolyzes TAG to DAG + FFA in the stomach & @ what position?

gastric lipase and acts @ the Sn3 position

What is the physical emulsification that occurs in the stomach?

muscle contraction + physical mixing

What are the relative levels of TAG, DAG, & FFA in the small intestine?

lots of TAG, little DAG, & little FFA

Where is the primary site of digestion?

the small intestine

Where is the only site of absorption?

the small intestine

What are the 3 phases of lipid digestion + absorption?

1. emulsification

2. enzymatic digestion

3. absorption

What is the goal of emulsification?

to increase surface area of the fat droplets

What is something that emulsification does?

makes & maintains small fat droplets

What are the 2 types of emulsification?

Physical + chemical

What is considered physical emulsification and where does it occur?

physical emulsification is the mixing, chewing + movement of digesta

occurs in the mouth, stomach, & duodenum

What does the chemical emulsification do and what specifically is used for this?

maintains the small fat droplets

bile is specifically used for this

In enzymatic digestion what is the enzyme from the pancreas & what positions are hydrolyzed?

pancreatic lipase (PL) + acts on the Sn1 & Sn3 positions

T/F Can pancreatic lipase turn MAG into DAG then TAG?

False, pancreatic lipase turns TAG into DAG & then MAG + 2 FFA

Where does procolipase come from?

the pancreas

When procolipase is put with it turns into ?

trypsin + colipase

What are fat droplets surroundedd by?

bile

What is absorbed how is it abosorbed?

MAG + 2FFA

absorbed by facilitated diffusion

Where does lingual lipase come from?

salivary gland

Where does gastric lipase come from?

chief cells in the stomach

What do lingual lipase and gastric lipase hydrolyze & at what position?

hydrolyzes ester bonds @ Sn3 position

Pancreatic lipase hydrolyzes what & @ what position? What is needed for optimal activity?

hydrolyzes ester bonds @ Sn1 + Sn3

colipase is required for optimal activity

What is trypsin and what does it do?

proteolytic

breaks peptide bonds

Procolipase & colipase? What do they do?

procolipase comes from the pancreas and activated by trypsin into colipase

they interact with fat droplets

What occurs with fatty acids <10 carbon chains?

• diffuse into & through enterocyte into the blood

• in blood they bind to albumin & takes the fatty acid to the liver

What occurs with fatty acids >12 carbon chains?

• intracellular TAG reformation

• adding FFA back with MAG then DAG then TAG

all done by acyl CoA synthetase

What is acyl CoA synthetase?

• makes smaller molecules bigger

• made by the enterocyte

• cannot bind FA<10 carbons

What does the endoplasmic reticulum do?

• accumulates TAG, ADEK, cholesterol = the fat particle

• adds B-48 (apolipoprotein)

What does B-48 do?

1. stabilizes the lipoprotein as it moves through circulation

2. acts as ‘name tag’ to confer specificity (exogenous lipoprotein)

3. stabilizes/enables lipoprotein lipase to hydrolyze TAG to DAG + FFA on the surface of muscle and adipose

What does the Golgi Apparatus (GA) do? What is the result?

• attaches CHO

• result = chylomicron (82% TAG; protein, cholesterol, & ADEK)