Transport Across Membranes/Diffusion/Osmosis/Gradients

Question 1

Apoplastic pathway

Answer 1

Faster, along cellulose cell walls via diffusion

Water from root hair cells passes through the root cortex into the xylem through the adjoining cell walls
Fast movement since less resistance to water due to larger gaps between cellulose molecules
Water moves by diffusion
From an area of higher water potential to and area of lower water potential
Reaches the endodermis which has a waterproof strip called the casparian strip
Preventing movement of water in endodermis cell walls
So it is forced into the cytoplasm then to the xylem

Question 2

Symplastic pathway

Answer 2

Slower, through cytoplasm’s and across cell membranes via osmosis

Water from root hair cells passes through the root cortex into the xylem through the cytoplasm of cells
And across cell membranes through the plasmodesmata from one cell to the next
Moves via osmosis down a water potential gradient
Relatively slow as there is resistance to the movement of water due to cell membranes, solutes and vacuoles

Question 3

GLUT1

Answer 3

Prevelant glucose transporter in nearly all adult tissue and all fetal tissue
Very high affinity for glucose
Concentrated in the endothelial cells of blood tissue barriers
Transporting glucose between blood and organs that have limited access to small solutes via passive diffusion
In insulin sensitive tissues (like adipose tissue and muscle) it is present along with GLUT4