Lipid Digestion Flashcards
What are the 4 most predominant dietary lipids?
TAG’s, Phospholipids, Cholesterol and Fat-soluble Vitamins.
Where does digestion begin?
In the oral cavity, where lipids are exposed to lingual lipases.
What secretes lingual lipases?
Serous glands.
Serous glands.
Salivary glands located on both sides of oral cavity towards back of tongue.
Lingual Lipases
Generate non-esterfied FA from dietary fats through lipolysis.
Esterfication
Formation of esters from reactions between acids and alcohols.
Esters
Organic compounds that react with water to produce alcohols/in/organic acids.
Alcohol
An organic compond containing hydroxyl groups.
Acids
Chemicals that form hydrogen ions in solutions.
Where are ester bonds fond in lipids?
Between FA and glycerol.
What are non-esterfied FA?
Molecules isolated from glycerol, released by lipase action.
What does lipase convert TAGS to after ester hydrolysis?
Diacylglycerols or Monoacylglycerols with free FA
What does phospholipid ester hydrolysis yield?
FFA and lysophospholipids.
What does cholesterol ester hydrolysis yield?
Cholesterol and FFA.
Cholesterol Ester
A cholesterol with a fatty acid bound by ester bonds.
What two ways do Enterocytes use to uptake MAG and FFA?
Diffusion and Protein-mediated transport.
When does enterocyte diffusion occur?
When luminal FFA concentration exceeds intracellular.
What happens to FFA when they enter enterocytes?
Processing in various organelles via FA binding proteins.
What protein is used for cholesterol uptake into enterocytes?
Niemann-Pick C1-like 1.
What do Niemann-Pick C1-like 1. form in the PM?
Lipid rafts.
Process of cholesterol enterocyte uptake by Niemann-Pick C1-like 1….
Cholesterol binds NTD binding site, exposing CTD, with interacts with proteins facilitating clathrin recruitment.
What happens after cholesterol interaction with Niemann-Pick C1-like 1.?
Internalised, transporting to endocytic compartments, releasing and transporting to other organelles.
What happens to MAG in the ER?
Esterfied with FFA by enzymes, forming DAGS that can be used to synthesize phospholipids.
What happens to cholesterol in the ER?
They are esterfied.
Why are MAG and CHOL esterfied in the ER after enterocyte absorption?
Favours entry of more hydrolysed intraluminal products, due to reduced intracellular concentraitons.
What happens to newly synthesised ER lipids?
Form cytosolic lipid droplets which can be either stored or secreted.
Lipid Droplets
Intracellular organelles specialise in energy storage in the form of TAGS and sterol esters.
General structure of Lipid Droplets?
They have a phospholipid monolayer, with a core of triglycerides and cholesterol esters.
What happens to lipid droplets in fasting states?
Mobilised and secreted from enterocytes.
What does lipid droplet mobilisation require?
TAG hydrolysis with FA mobilisation to ER for TAG re-synthesis, followed by secretion with lipoproteins.
What happens to ER synthesised lipids proceeding lipid droplet mobilisation?
Packaged into chylomicrons.
Structure of CM?
Phospholipid monolayer, surrounded by ALP B48, with a TAG and cholesteryl ester core.
What happens to CM after their assembly?
Released from basolateral side, entering general circulation at the thoracic duct.
