Digestion and absorption Flashcards
Define digestion
Process of breaking down complex nutrients into simple molecules
Define absorption
Transport of small molecules across intestine wall
List 5 functions of the SI
- Enzymatic digestion (proteins, CHO’s, fats)
- Absorption of digestion products
- Absorption of vitamins, bile salts, electrolytes, water
- Secretion of electrolytes and water
- Mixing and movement of digesta
In terms of the GIT lumen, where are new cells continuously produced?
New cells continuously produced in crypts.. (depressions in the villi)
out of crypt cells and villious cells, which are secretory cells and which are absorptive cells
Crypt cells are secretory
Villous cells are absorptive
Explain the importance of physical breakdown of food (2)
- Reduces particle size so can pass into GIT
2. Increases surface area for faster digestion
Physical breakdown is achieved by.. (2)
Mastication (teeth & tongue)
Grinding of stomach (pepsin and HCl)
define hydrolysis
splitting of a chemical bond by inserting H2O molecule, catalysed by enzymes.
List 3 common sites that hydrolysis occurs:
- CHO @ glycoside linkages
- Proteins @ peptide bonds between adjacent aa’s
- Fats @ ester bonds
There are 2 main types of digestive enzymes. Where are these located?
- Act within lumen of gut (Luminal phase of digestion)
2. Act at membrane surface of epithelium (Membranous phase of digestion)
define absorption
movement of products of digestion across intestinal mucosa & into vascular system
Proteins provide a highly specific regulated transport pathway for:
- Ions
* Organic molecules
The Sodium-Potassium ATPase pump is a part of what type of transport?
Active transport
What does active transport do?
Moves ions or molecules across membranes against either an electrical or chemical gradient
In passive transport, the ion channels are:
Completely passive, responding only to electrochemical gradients
