Topic 6.1: ABSORPTIOn
ABSORPTIOn!!
Purpose of Absorption
Absorption involves the movement of fluids or dissolved substances (such as nutrients) across a cellular membrane
¥ The absorbed components then undergo assimilation within the cell in order to become fluid or solid parts of an organism
Nutrient absorption occurs within the small intestine, while water and mineral ions are absorbed within the large intestine
Membrane Transport Mechanisms
Secondary Active Transport Endocytosis
¥ Glucose and amino acids are co-transported across the ¥ Dissolved materials may be rapidly absorbed en masse via
epithelial membrane with sodium ions (Na+) the process of pinocytosis (cell ÔdrinkingÕ)
Facilitated Diffusion Extracellular Fluid
¥ Certain monosaccharides, vitamins and some minerals
may be transported by epithelial channel proteins
Simple Diffusion
¥ Hydrophobic materials (e.g. lipids) are capable of freely
Cytoplasm Vesicle
diffusing across the epithelial membrane
Small Intestine Structure
Transverse Cross-Section Longitudinal Cross-Section
Villi
Circular muscle
Mucosa
Muscle
layers
Villi Modelling Absorption
Villi are finger-like mucosal projections that Dialysis tubing can be used to model the Sample Experiment:
increase the surface area of epithelium over size-specific permeability of a membrane
which absorption is carried out ¥ Large molecules cannot cross (e.g. starch)
¥ Smaller molecules can cross (e.g. glucose)
Key features of villi include:
If large molecules are digested with enzymes,
¥ Rich blood network the absorption of the smaller subunits can
¥ Single layer epithelium then be measured in a number of ways:
¥ Lacteals (absorb lipids) ¥ Via a change in fluid / meniscus levels Control Digestion
¥ Intestinal crypts (exocrine) ¥ Via the presence of specific materials Starch in Maltose exits
¥ Membrane proteins (identified via treatment with a reagent) Water in Water exits
ABSORPTIOn!!
Purpose of Absorption
Absorption involves the movement of fluids or dissolved substances (such as nutrients) across a cellular membrane
¥ The absorbed components then undergo assimilation within the cell in order to become fluid or solid parts of an organism
Nutrient absorption occurs within the small intestine, while water and mineral ions are absorbed within the large intestine
Membrane Transport Mechanisms
Secondary Active Transport Endocytosis
¥ Glucose and amino acids are co-transported across the ¥ Dissolved materials may be rapidly absorbed en masse via
epithelial membrane with sodium ions (Na+) the process of pinocytosis (cell ÔdrinkingÕ)
Facilitated Diffusion Extracellular Fluid
¥ Certain monosaccharides, vitamins and some minerals
may be transported by epithelial channel proteins
Simple Diffusion
¥ Hydrophobic materials (e.g. lipids) are capable of freely
Cytoplasm Vesicle
diffusing across the epithelial membrane
Small Intestine Structure
Transverse Cross-Section Longitudinal Cross-Section
Villi
Circular muscle
Mucosa
Muscle
layers
Villi Modelling Absorption
Villi are finger-like mucosal projections that Dialysis tubing can be used to model the Sample Experiment:
increase the surface area of epithelium over size-specific permeability of a membrane
which absorption is carried out ¥ Large molecules cannot cross (e.g. starch)
¥ Smaller molecules can cross (e.g. glucose)
Key features of villi include:
If large molecules are digested with enzymes,
¥ Rich blood network the absorption of the smaller subunits can
¥ Single layer epithelium then be measured in a number of ways:
¥ Lacteals (absorb lipids) ¥ Via a change in fluid / meniscus levels Control Digestion
¥ Intestinal crypts (exocrine) ¥ Via the presence of specific materials Starch in Maltose exits
¥ Membrane proteins (identified via treatment with a reagent) Water in Water exits
