Digestion + Absorption Flashcards
What is digestion?
Physical digestions occurs before chemical digestions
What are two ways lipids are digested?
Lipids are digested chemically and physically. Chemically through the enzyme lipase. Physically through emulsification and micelles formation
Which digestion process occurs first?
Physical digestions occurs before chemical digestions
Where are bile salts prodcued?
Bile salt are produced in the liver
What are the substrates and products of carbohydrate digestive enzymes?
Amylase = starch into smaller polysaccharides
Maltase = maltose into 2x glucose molecules
Sucrase = sucrose into glucose and fructose
Lactase = lactose into glucose and galactose
Where are lipids digested?
In the small intestine
Where are bile salts stored?
Bile salts are stored in the gall bladder
Where do bile salts go after production?
Bile salts are diffused into the small intestine, specifically the duodenum, through the bile ducts
What needs to happen before lipids can be digested?
Lipids must be emulsified by bile salts produced by the liver. This break down the large fat molecules into smaller, soluble molecules called micelles, increasing surface area
How do bile salts hydrolyse 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 emulsifying lipids into micelles, provides a larger surface area, which enables 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 secretes lipases into the small inetstine leading to the duodenum and the ileum
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
- Monoglycerides 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
- Triglycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells of the blood capillaries from where they diffuse into cells
How does lipase act on triglycerides?
Lipase hydrolyses the ester bond in triglycerides to form monoglycerides and fatty acids
When do micelles start to break down? What do they release?
Micelles break down once they come into contact with 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 recombined to form triglycerides
