1. 1.4 Membrane transport

2. Understandings Applications
Particles move across membranes by simple diffusion, facilitated diffusion, osmosis, & active transport
The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis
Vesicles move materials within cells
Applications
Structure & function of Na-K pumps for active transport and K channels for facilitated diffusion in axons
Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis
Nature of Science
Experimental Design: accurate quantitative measurements in osmosis experiments are essential
Skills
Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions

3. 4 ways particles move across membranes
Simple diffusion
Facilitated diffusion
Osmosis
Active transport

5. SIMPLE DIFFUSION
Diffusion = spreading out of particles (from area of high concentration to area of low concentration)
Molecules are in constant motion
Molecules randomly collide with each other
If more molecules are in one area, there’s more chances for random collisions, so more spreading out takes place
Passive = No energy input is required
Net movement = movement in one direction – movement in the other direction (can be zero even when molecules are still moving)
Molecules are always moving (even in solids, molecules vibrate); movement is driven by heat
Concentration gradient = a difference in the concentration of particles in one area compared to another

6. Concentration gradient
No gradient
Concentration gradient

9. What is the only part of the human body that has no blood supply?

10. So how does the cornea get oxygen?
From the Air!!

13. Let’s look at osmosis on U Tube

14. Osmosis * movement of water across a semi-permeable membrane from area of lower solutes to higher solutes * water movement has to do with the amount of solutes dissolved in it * water moves from HYPO to HYPERtonic

16. Active transport Against concentration gradient Requires ATP
Requires globular proteins called “protein pumps”
Proteins take in particle, change configuration (shape) using ATP, then particle moves to other side

17. Passive vs active transport

18. Application: Structure & function of sodium-potassium pumps for active transport in axons

19. Application: potassium channels for facilitated diffusion in axons

20. Application: Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis
Osmolarity = solute concentration
Hypertonic = higher osmolarity
Hypotonic = lower osmolarity

21. Normal saline 0.9% NaCl = 300 mOsm (milliosmoles) Sterile
IV for replenishing fluids or electrolytes
Rinse wounds & abrasions
Moisten skin before skin grafts
Ingredient in eye drops
Frozen for packing organs for transplant

22. SKILL: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions.
DBQ p41-42
OsmOSIS IS DUE TO SOLUTES THAT FORM BONDS WITH WATER
SOLUTES ARE SAID TO BE “OSMOTICALLY ACTIVE”
E.G. Glucose, Na+, K+, Cl+
Cells contain many osmotically active solutes
Osmolarity = total concentration of osmotically active solutes
Unit = osmoles or milliosmoles (mOsm)
Normal = 300 mosm
Isotonic solution = same osmolarity as human tissue