3.3.3.2 Absorption of the Products of Digestion Flashcards
What does the diagram show?
Active transport of molecules by a carrier protein against a concentration gradient.
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)
Identify the label on the diagram and the type of transport that take place.
Glucose carrier protein
Facilitated diffusion
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.
Identify the label on the diagram.
A capillary within a villus
What does the diagram show?
The path taken by glucose/amino acids through the epithelial cells of the ileum and into the blood.
Identify the label on the diagram and the type of transport that take place.
Sodium-Glucose co-transport carrier protein
Facillitated diffusion
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.
What is happening at stage 3 in the diagram?
Glucose is moving into the blood stream via facilitated diffusion through a carrier protein.
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 happening at stage 2 in the diagram?
- Sodium ions are moving into the epithelial cell through a cotransport carrier protein via facilitated diffusion.
- A glucose molecule is carried through the cotransport carrier protein by the sodium ion (still facilitated diffusion)
- The sodium ion moves down a concentration gradient
- Glucose moves against its concentration gradient.