B2.1.1 Absorption of the Products of Digestion Flashcards
What happens to triglycerides which have been reformed in the endoplasmic reticulum of epithelial cells lining the ileum?
They are associated with cholesterol and lipoproteins to form chylomicrons.
What does the diagram show?
Simple diffusion through a cell membrane from a high to low concentration
Diffusion and facilitated diffusion are both passive processed. What is meant by this?
They do not require ATP (energy)
What is the function of the endoplasmic reticulum in lipid absorption?
- An organelle in the epithelial cells lining the ileum where monoglyerides and fatty acids are recombined to make triglycerides.
- Triglycerides begin to associate with cholesterol and lipoproteins here also.
Why does having many capillaries optimise absorption in the ileum?
Nutrients absorbed in the blood are carried away quickly which maintains the concentration gradient between the ileum and the blood.
Define active transport
the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP (energy) and carrier proteins.
What does the diagram show?
Facilitated diffusion via a carrier protein from a high to low concentration
What happens to the chylomicrons that are produced in the epithelial cells lining the ileum?
They exit the cells via exocytosis and enter the lymphatic system via lacteals.
How are villi adapted to optimise absorption of nutrients?
- They increase the surface area for diffusion
- Very thin walls so less diffusion distance to the blood.
- Many blood capillaries- blood can carry nutrients away and maintain diffusion gradients.
- Epithelial cell lining contains microvilli increasing surface area for absorption further.
- They contain muscle so can move contents of the ileum to maintain concentration gradients.
What is a lacteal?
A lymphatic capillary that is found in the centre of each villus of the small intestine.
Describe the process of active transport.
- Molecule or ion binds to carrier protein.
- ATP binds to carrier protein, gives a phosphate and ADP is released.
- Carrier protein changes shape and moves molecule to opposite side of membrane.
- Phosphate is released from carrier protein and protein reverts back to start position.
Identify the label on the diagram and the type of transport that take place.
Sodium-Potassium Pump (carrier protein)
Active Transport
What is a protein channel?
A protein that spans a cell membrane and will only allow specific molecules to pass through. Involved in facilitated diffusion.
What is facilitated diffusion?
- Diffusion of molecules or ions aided by carrier proteins or protein channels.
- Does NOT use ATP (energy),
Name the products of digestion
Monosaccharides
Amino Acids
Monoglycerides
Fatty Acids
Where are the products of digestion absorbed?
Ileum (small intestine)
How is the ileum adapted to carry out the process of absorption of nutrients?
Its wall contains many villi, which greatly increases the area for nutrient absorption
How does the thin wall of the ileum help to optimise absorption?
Less distance for nutrients to diffuse across before reaching the blood.
What does the diagram show?
Facillitate diffusion via a channel protein from high to low concentration
What happens to monoglycerides and fatty acids after they have entered the epithelial cells lining the ileum?
They are transported to the endoplasmic reticulum where they are recombined into triglycerides.
Micelles are created by an asociation between bile salts and triglycerides. After lipase has acted on micelles of triglyceride we are left with…
Micelles of monoglycerides and fatty acids (still asociated with bile salts)
How do monoglycerides and fatty acids enter the epithelial cells lining the ileum?
Simple diffusion
Bile salts emulsify fatty acids into smaller structures called…
micelles
Define diffusion
the net movement of molecules or ions from a region where they are highly concentrated to a region where they are less concentrated until evenly distributed.
