Transport 2: Across the alimentary tract Flashcards
What does the alimentary tract absorb?
Absorb nutrients, salts and water
How is absorption in the alimentary tract achieved?
Absorption is achieved by transport of food components, ions, e.g. Na+
and water follows by osmosis
How much water is absorbed from the colon once it arrives?
Colon absorbs 90% of the water from the contents that arrive at it
What gives the small intestine a large surface area?
epithelial folds, villi, and microvilli (large surface area -
an internal surface area of 200 m2)
Where are all dietary nutrients, water and electrolytes absorbed?
All dietary nutrients, water and electrolytes that enter the upper small
intestine are absorbed
What is transcellular transport across the enterocyte?
Transport through the cell like glucose transport
What is paracellular transport across the enterocyte?
Passive but selective variable and regulated, through a tight junction between epithelial cells
What form can carbohydrates only be absorbed in?
Can only be absorbed in the form of monosaccharides
What are complex carbohydrates reduced to disaccharides by?
Complex carbohydrates are reduced to disaccharides by amylases
What converts disaccharides to monosaccharides?
Specific brush border enzymes convert disaccharides to monosaccharides
Where does digestion of carbohydrates occur?
In the intestinal lumen and at the brush border
What does sucrase, at the brush border, convert sucrose into?
Sucrose –> Glucose and fructose
What does glucoamylase, at the brush border, convert glucose oligomers into?
Glucose oligomers –> Glucose
What does lactase convert lactose into at the brush border?
Lactose –> Glucose and galactose
What is glucose and galactose absorbed by and how fast?
Glucose and galactose are rapidly absorbed by a secondary active transport process
What is fructose absorbed by and how fast?
Fructose is slowly absorbed by passive transport on a GLUT 5 carrier
