6.12 Absorption

Question 1

Purpose of absorption

Answer 1

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.

Question 2

Membrane transport: Secondary Active Transport

Answer 2

Glucose and amino acids are co-transported across the epithelial membrane with sodium ions (Na +)

Question 3

Membrane transport: Facilitated Diffusion

Answer 3

Certain monosaccharides, vitamins and some minerals may be transported by epithelial channel proteins

Question 4

Membrane transport : Simple Diffusion

Answer 4

Hydrophobic materials (e.g lipids) are capable of freely diffusing across the epithelial membrane.

Question 5

Membrane transport: Endocytosis

Answer 5

Dissolved materials may be rapidly absorbed en masse via the process of pinocytosis (cell ‘drinking’)

Question 6

Small Intestine

Answer 6

Serosa
Longitudinal muscle
Circular muscle
Submucosa
Mucosa

Question 7

Longitudinal Cross-Section

Answer 7

Villi
Mucosa
Muscle Layers

Question 8

Villi

Answer 8

Villi are finger-like mucosal projections that increase the surface area of epithelium over which absorption is carried out
Microvilli (Sa Vol)
Rich blood network
Single layer epithelium
Lacteals (absorb lipids)
Intestinal crypts (exocrine)
Membran proteins

Question 9

Modeling absorption

Answer 9

Dialysis tubing can be used to model the size specific permeability of a membrane.
Large molecules cannot cross eg starch
Smaller molecules can cross eg glucose