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25 Cards in this Set

  • Front
  • Back

What do the walls of the ileum do?

They fold

What is found on the folds?

Finger-like projections called villi

What adaptations do villi have?

Increased surface area


Thin walls


Muscle


Blood vessels


Microvilli

What do villi do?

They increase the surface area for diffusion

What do thin walls do?

They reduce the diffusion pathway

What does the muscle do?

It allows them to move, helping to maintain the concentration gradient for faster diffusion

What forms microvilli?

The cell surface membrane of epithelial cells

What do microvilli do?

They further increase the surface area for absorption

What does a network of blood vessels mean?

It maintains a concentration gradient for faster diffusion

How is glucose absorbed?

By active transport involving sodium-potassium pumps and co-transporters

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

What is step 2 of glucose absorption?

A lower concentration of Na+ in the cell means Na+ enters the epithelial cell from the lumen of the ileum

What is step 3 of glucose absorption?

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

What is step 4 of glucose absorption?

Glucose moves into the blood stream by facilitated diffusion

What monosachharide also uses this process ?

Galactose

What other molecules use this process?

Amino acids

How is fructose absorbed?

By facilitated diffusion through a different transporter protein

What is a property of monoglycerides and fatty acids?

They're non- polar and lipid soluble.

What do they form?

Along with bile salts, they form micelles

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

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.

What happens at the golgi apparatus?

They associate with cholesterol and lipoproteins to form chylomicrons.

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.

What are the lymphatic capillaries called?

Lacteals

Where are the lacteals found?

In the centre of each villus