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25 Cards in this Set
- Front
- Back
What do the walls of the ileum do? |
They fold |
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What is found on the folds? |
Finger-like projections called villi |
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What adaptations do villi have? |
Increased surface area Thin walls Muscle Blood vessels Microvilli |
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What do villi do? |
They increase the surface area for diffusion |
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What do thin walls do? |
They reduce the diffusion pathway |
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What does the muscle do? |
It allows them to move, helping to maintain the concentration gradient for faster diffusion |
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What forms microvilli? |
The cell surface membrane of epithelial cells |
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What do microvilli do? |
They further increase the surface area for absorption |
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What does a network of blood vessels mean? |
It maintains a concentration gradient for faster diffusion |
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How is glucose absorbed? |
By active transport involving sodium-potassium pumps and co-transporters |
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What is step 1 of glucose absorption? |
The Na+/K+ pump actively pumps Na+ out of the epithelial cell, into the blood stream and K+ into the cell, producing a concentration gradient |
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What is step 2 of glucose absorption?
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A lower concentration of Na+ in the cell means Na+ enters the epithelial cell from the lumen of the ileum |
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What is step 3 of glucose absorption?
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As Na+ enters it also brings glucose using a co-transporter protein in the membrane of the epithelial cell by facilitated diffusion. It also establishes a concentration gradient |
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What is step 4 of glucose absorption?
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Glucose moves into the blood stream by facilitated diffusion |
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What monosachharide also uses this process ? |
Galactose |
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What other molecules use this process? |
Amino acids |
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How is fructose absorbed? |
By facilitated diffusion through a different transporter protein |
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What is a property of monoglycerides and fatty acids? |
They're non- polar and lipid soluble. |
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What do they form? |
Along with bile salts, they form micelles |
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What then happens to the micelles? |
They break down and release the monoglycerides and fatty acids which can easily diffuse through the cell surface membrane |
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What happens when they get inside the cell? |
They move to the ER and reform triglycerides. The triglycerides are then taken to the golgi apparatus. |
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What happens at the golgi apparatus? |
They associate with cholesterol and lipoproteins to form chylomicrons. |
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What then happens to the chylomicrons? |
They move out of the epithelial cell by exocytosis and enter the lymphatic capillaries, from here, they pass through the lymphatic vessels and into the blood. |
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What are the lymphatic capillaries called? |
Lacteals |
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Where are the lacteals found? |
In the centre of each villus |