Absorption of the products of digestion Flashcards
What is the main function of the ileum?
To absorb the products of digestion
What structures in the ileum increase the surface area for absorption?
Villi and microvilli
What is the function of the villi?
They increase the surface area and accelerate absorption
Why are villi thin - walled?
To reduce the diffusion distance and speed up absorption
How do villi maintain a diffusion gradient?
- Movement - the villi contains muscle that mixes the ileum contents, ensuring fresh nutrients replace absorbed ones’s
- Rich blood supply - the blood will carry away absorbed molecules, maintaining a concentration gradient
What are microvilli, and where are they found?
Finger - like projections f the epithelial cell membrane that increase surface area for absorption
What are the products of protein digestion?
What are the products of carbohydrate digestion?
Protein = amino acids
Carbohydrate = monosaccharides (glucose, fructose and galactose)
What are the two main methods of absorbing amino acids and monosaccharides?
Diffusion and co - transport
What is co - transport?
A form of active transport where substances are absorbed along with sodium ions through carrier proteins
What structures do monoglycerides and fatty acids form after digestion?
Micelles, which are small lipid droplets associated with bile salts
How do micelles aid in lipid absorption?
They transport monoglycerides and fatty acids to the epithelial cells of the ileum, where they break down and release these molecules
How do monoglycerides and fatty acids enter the epithelial cells?
They diffuse across the cell - surface membrane because they are non polar
Where are monoglycerides and fatty recombined into triglycerides?
In the endoplasmic reticulum of the epithelial cells
What structures are formed when triglycerides associate with cholesterol and lipoproteins?
Chylomicrons
What is the function of chylomicrons?
They are adapted for the transport of lipids in the body
Outline the process of the absorption of triglycerides: ( 8 steps)
1/Bile salts emulsify monoglycerides and fatty acids into tiny droplets called micelles
2/ Through movement within the lumen of the ileum, micelles come into contact with epithelial cells lining villi of ileum
3/ Micelles start breaking down, releasing monoglycerides and fatty acids
4/ Monoglycerides and fatty acids diffuse easily across the cell - surface membrane into the epithelial cells
5/ Once inside, monoglycerides and fatty acids are transported to endoplasmic reticulum where they are recombined and form triglycerides
6/ They continue into the golgi apparatus, where the triglycerides associate with cholesterol and lipoproteins to form chylomicrons
7/ The chylomicrons pass through the lymphatic vessels into the blood system
8/ Triglycerides in chylomicrons are hydrolysed by enzymes in endothelial cells of blood capillaries from where they diffuse into cells
How do chylomicrons leave the epithelial cells?
By exocytosis
How are triglycerides in chylomicrons made available to cells?
They are hydrolysed by enzymes in the endothelial cells of capillaries and then diffuse into cells
Where do chylomicrons go after leaving the epithelial cells?
They enter lacteals (lymphatic capillaries in the villi) and then pass into the blood system
What structure do monoglycerides and fatty acids form after digestion?
Micelles, which are small lipid droplets associated with bile salts
How do micelles aid in lipid absorption?
They transport monoglycerides and fatty acids to the epithelial cells of the ileum, where they break down and release these molecules
How do monoglycerides and fatty acids enter epithelial cells?
They diffuse across the cell - surface membrane because they are non - polar
Where are monoglycerides and fatty acids recombined into triglycerides?
In the endoplasmic reticulum of the epithelial cells
What structures are formed when triglycerides associate with cholesterol and lipoproteins?
What is the function of this structure?
Chylomicrons, which are adapted for the transport of lipids in the body
