Digestion and absorption of fat Flashcards
What is the most concentrated store of energy?
Lipids
Where is most of the body fat deposits?
In the subcutaneous adipose tissue layers
What are the two types of fat?
Visceral and subcutaneous
How much fat does a typical 70kg human have?
15kg
How is energy obtained from stored fat?
By beta oxidation
Which vitamins are fat soluble?
A
D
E
K
How are fat soluble vitamins absorbed?
In bile salt micelles
What would a deficiency in vitamin D lead to?
Bone mineralisation
Bone softening
What is vitamin E needed for?
Protection against cardiovascular disease and cancer
Deficiency leads to neurological problems
What is vitamin K needed for?
Gla-residues
Blood coagulation
Bone metabolism
Vascular biology
Why do we need fatty acids in our diet?
Formation of cell membranes
Regulating blood pressure
Immune and inflammatory response
Name some symptoms of essential fatty acid deficiency
Haemorrhagic dermatitis Skin atrophy Scaly dermatitis Dry skin Weakness Impaired vision Tingling sensations Mood swings Edema High blood pressure High triglycerides Haemorrhagic follicullitis Haemotologic disturbances Immune and mental deficiencies Impaired growth
Where may lipids come from other than the diet?
Phospholipds
Unesterified cholesterol
Membrane lipids from desquamated cells
Lipids derived from dead bacteria
Where does lipid hydrolysis take part?
In the aqueous milieu of the intestinal lumen
What catalyses lipid hydrolysis?
Lipases
How are lipid particles stabilised?
As an emulsion
Where does emulsification take place?
Food preparation
Chewing and gastric churning
Squirting contents into the duodenum
Intestinal peristalsis
What prevents lipid particles from coalescing?
Emulsion droplets are coated with membrane lipids, denatured protein, dietary polysaccharides, products of digestion, phospholipids and cholesterol
Hydrophilic groups project into the water
What is at the core of an emulsion particle?
A triglyceride
Containing cholesteryl esters and non-polar lipids
What are the two types of lipase?
Lingual
Gastric
Where is lingual lipase found?
In the mouth and stomach
Where is gastric lipase found?
In the stomach and duodenum
What do lingual and gastric lipases produce?
Release a single fatty acid from triglycerides
Diglyceride remains
Where are medium and short chain fatty acids absorbed?
Across the gastric mucosa into the portal blood
How much fat digestion occurs in the stomach?
15%
What stimulates CCK?
Fatty acids in the duodenum
What does CCK stimulate?
Flow of bile
Secretion of pancreatic enzymes
What four things does pancreatic lipase need to work?
Colipase
Alkaline pH
Bile salts
Fatty acids
What else may hydrolyse lipids?
Bacterial lipases
How do lipolytic products enter cells?
Short/medium chain fatty acids diffuse
Long chain fatty acids are protonated by Na-H brush border membrane
Enter by non-ionic diffusion
Collision and incorporation into membrane
Active carrier mediated processes
What happens once inside the cells?
For long chains
SER forms fat droplets (chylomicron)
Transported to vesicles
Then to lymphatic system
For short chains
Pass directly to blood
Why do long chain fatty acids bind to fatty acid binding proteins?
Prevent leakage out of the cell
Prevent lipid toxicity
Ensure transfer of fatty acids to SER
Where do chylomicrons end up?
In the liver
Transported to either muscle or adipose tissue
