Digestion and Absorption of Lipids Flashcards
What are the two way lipids are digested?
Lipids are digested physically and chemically. Physically through emulsification and michelle formation. Chemically through the enzyme lipase.
Which digestion process occurs first?
Physical digestion occurs before chemical digestions
Where are bile salts produced?
Bile salts are produced in the liver
Where are bile salts stored?
Bile salts are stored in the gall bladder
Where do bile salts go to after production?
Bile salts are delivered to the small intestine (specifically the duodenum) through the bile ducts
How do the bile salts breakdown the lipids?
Bile salts emulsify lipids to form tiny droplets called micelles
What is an advantage of bile salts emulsifying lipids before the chemical breakdown process?
Bile salts form micelles which provide a larger surface area, which enable faster hydrolysis action from lipase
Where is lipase produced?
Lipase is produced in the pancreas
After the pancreas produces lipase, what does it do?
The pancreas will secrete lipase into the small intestine leading to the duodenum and the ileum
What does the lipase do to the micelles?
Lipase hydrolyses the ester bond in triglycerides to form the monoglycerides and fatty acids
How are triglycerides absorbed?
- Micelles come into contact with the epithelial cells through the movement within the lumen of the ileum
- Micelles break down and release monoglycerides and fatty acids
- Monogylcerides and fatty acids easily diffuse across a cell surface membrane into epithelial cells (non -polar molecules)
- Monoglycerides and fatty acids are transported to the endoplasmic reticulum and are recombined to form triglycerides
- From the endoplasmic reticulum, to the Golgi apparatus the triglycerides associate with cholesterol and lipoproteins to form chylomicrons
- Chylomicrons move out the epithelial cells by exocytosis
- The chylomicrons enter lymphatic capillaries called lacteals in the centre of each villus
- From here, chylomicrons pass into the blood system through lymphatic vessels
- Tryglycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells of the blood capillaries from where they diffuse into cells
When do micelles start to break down? What do they release?
Micelles break down once they come into contact with the epithelial cells. They release monoglycerides and fatty acids
Why do monoglycerides and fatty acids easily diffuse across the cell surface membrane?
Monoglycerides and fatty acids are non polar molecules
What happens once monoglycerides and fatty acids are inside the epithelial cells?
The monoglycerides and fatty acids are transported to the endoplasmic reticulum and are recombined to form triglycerides
What happens with triglycerides as they move from the endoplasmic reticulum to the golgi apparatus?
The triglycerides associated with with cholesterol and lipoproteins to form structures called chylomicrons
