Lecture 3 Class Activities
Membrane Transport
Facilitated diffusion in contrast to _____________________________ :
A. requires ATP
B. moves water across the plasma membrane
C. can move molecules UP their concentration gradient
D. transports hydrophobic molecules across the membrane
Sample Study table:
Passive Transport
Diffusion across
Diffusion through
membrane
channels
Energy used
Up or down
concentration
gradient?
Common molecule
types
Insert figure
Examples
Active Transport
Pumps and
Exocytosis and
cotransporters
Endocytosis
Water diffuses through aquaporins
Application: Salt and water in the gut
Cells lining the gut are called enterocytes.
(http://www.sciencedirect.com/science/article/pii/S0140673668905916)
The transport of molecules in the gut
Solute transport causes water transport
Absorption of cholesterol uses receptor-mediated endocytosis
Which is the correct orientation of an endocytosed LDL receptor that is bound to its ligand
(represented by the star shape) in the newly formed vesicle shown below?
For Online Discussion:
Glucose is transported from the gut into epithelial cells using a sodium glucose co-transporters
called SGLT1. The sodium gradient used is created by a Na/K pump. A rare disorder called
“glucose-galactose malabsorption” is caused by a non-functional SGLT1. This results in water
accumulation in the gut and severe diarrhea in newborns because::
A. continued Na/K pumping makes the epithelial cells ______________
to the gut lumen
B. high solutes in the gut makes epithelial cells ___________________
to the gut lumen
C. water cannot cross a non-functional ________________________
and it remains in the gut.