Lipid Digestion, Absorption & Transport

Flashcards for Lipid Digestion, Absorption & Transport

What is the typical daily intake of lipids?

120-150 g

What percentage of lipids are generally absorbed in each meal?

95-100%

What organs are involved in the minimal digestion of triglycerides (TG)?

Mouth and Stomach

Which organ is essential for removing long chain fatty acid digestion from triglycerides?

Pancreas

Which organ releases bile which acts as an emulsifier?

Gallbladder

In what location are phospholipids and cholesterol digested?

Small Intestine

Where is lingual lipase released?

Mouth

What type of fatty acids does lingual lipase act on?

Short or medium chain fatty acids

What are the products of lingual lipase digestion?

DG (diacylglycerol) & FA (fatty acids)

Why do lipids need to be emulsified in the stomach?

Lipids are nonpolar

What percentage of triglycerides do lingual lipase and gastric lipase digest together?

~20%

What are the products of gastric lipase digestion?

DG & FA

What is released when chyme enters the small intestine??

CCK and Secretin

From what is bile made?

Cholesterol

Where is bile stored?

Gallbladder

Where are bile salts from?

Gallbladder

What do Pancreatic lipases digest?

~80% of TG

What activates trypsin?

Enteropeptidase

What enzyme removes sn-1 & sn-3 fatty acids on TG & DG?

Active pancreatic lipase

What are the products of pancreatic lipase digestion?

MG & 2 FA

Which enzyme removes sn-2 FA on phospholipid (mostly lecithin)?

Phospholipase A2

What are the products of phospholipase A2 digestion?

FA & lysophospholipid

What does esterase remove?

FA on cholesterol, Vitamins A & E

What are the products of esterase digestion?

FA & free compounds (cholesterol, Vit. A, Vit. E)

What are lipids digested into?

Free fatty acids, sn-2 monoglycerides, cholesterol & lysophospholipids

What do lipids coalesce with in micelles?

Bile acids

What do micelles contain?

Fat-soluble vitamins (ADEK)

Does lipid digestion occur in the large intestine?

No

What are the products of lingual and gastric lipase digestion?

DG & FA

What are the products of pancreatic lipase digestion?

MG & FA

Where will digestion of a triglyceride begin?

SI due to pancreatic enzymes

Where are micelles absorbed?

By passive diffusion in the duodenum & jejunum (SI)

What are lipids reesterified into?

TAGs, phospholipids & cholesterol esters in smooth endoplasmic reticulum of enterocyte

Where are lipids packaged into chylomicrons?

Golgi complex

What is the exception to the packaging of lipids into chylomicrons?

Short & medium chain FA pass directly into portal blood & taken to liver

What are micelles composed of?

Fatty acids, monoglycerides, fat-soluble vitamins, cholesterol & bile salts

How are micelles absorbed?

Passive diffusion

How is bile absorbed?

Facilitated diffusion in Ileum

What causes lipid malabsorption?

Impaired digestion or absorption

What are the signs of lipid malabsorption?

Steatorrhea (fatty stools)

How is lipid malabsorption diagnosed?

Fecal fat content

How can lipid malabsorption be treated?

Limit fat intake or Supplement with pancreatic lipase and/or bile salts

What is the function of Orlistat (Xenical/Alli)?

Pancreatic lipase inhibitor

Why do lipids need a special carrier?

Lipids do not like water

What are the examples of lipoproteins?

Chylomicrons, very low-density lipoprotein (VLDL), low-density lipoprotein (LDL) & high-density lipoprotein (HDL)

What is the function of apoA-I?

Activates the LCAT enzyme used to pick up free cholesterol

What is the function of apoA-II?

Inhibits LCAT

What is the function of apoA-IV?

Activates LCAT

What is the function of apoB-48?

Cholesterol transport/clearance

What is the function of apoB-100?

Binds to LDL receptor

What is the function of apoC-II?

Induces lipoprotein lipase

What is the function of apoC-III?

Inhibits lipoprotein lipase

What is the function of apoE?

Triggers clearance of VLDL & chylomicron remnants

Where are chylomicrons synthesized?

Enterocytes from dietary fat

What activates lipoprotein lipase (LPL) in adipose, heart, & skeletal muscle?

ApoC-II

What are VLDLs packaged with?

Dietary lipids (exogenous) + lipids made in the liver (endogenous)

What do VLDS become?

TG-depleted and cholesterol-rich LDL (ApoB-100 is major apoprotein)

What does LDL carry?

Cholesterol to macrophages & extrahepatic cells (muscle, adipose, adrenals) by binding the LDL receptor

Where is nascent HDL made?

Liver & SI

What does nascent HDL contain?

Lecithin-cholesterol acyltransferase (LCAT)

What converts cholesterol & phosphatidylcholine into cholesterol esters?

LCAT

What does mature HDL carry?

Cholesterol esters (CE) back to the liver

What are the major sources of lipids in the liver?

Chylomicron remnants, Cholesterol from extrahepatic tissues, HDL, and De novo synthesis in the liver from carbs, lipids & proteins

What are the major routes by which lipids leave the liver?

Secretion of VLDL and Bile

What type of lipoprotein delivers TG from SI to cells?

Chylomicron

What type of lipoprotein delivers TG from liver to cells?

Very low-density lipoprotein (VLDL)

What type of lipoprotein delivers cholesterol to cells?

Low density lipoprotein (LDL)

What type of lipoprotein picks up free cholesterol from cells to take back to liver?

High density lipoprotein (HDL)

Name some exogenous formations of ROS.

Cigarettes, ionizing radiation, UV light, heavy metals, ozone, pollution and viruses.

Name some endogenous formations of ROS.

Electron transport chain in mitochondria, respiratory burst of white blood cells, endoplasmic reticulum and peroxisomes.

Name a few ROS radicals.

Superoxide and Hydroxyl

Name a few ROS Nonradicals

Singlet oxygen and Hydrogen peroxide

Name a RNS Radical.

Nitric Oxide

What two things can react to form a Hydroxyl Radical?

Superoxide and Hydrogen Peroxide.

What 3 things do inductors of ROS lead to?

Lipid Peroxidation, Protein Damage and DNA Damage

What are three nonenzymatic AOX H donors?

Fat-soluble Vit E, carotenoids, and CoQ10

Fill in the blank: Found in high concentrations in fruits, veggies, whole grains & legumes that are water-soluble is __.

Polyphenols