Chapter 5
Membrane Dynamics
Outline
Cell Membranes
Movement across membranes
Distribution of water and solutes in the body
Osmosis Lab
Proteins: role in communication
Proteins act as “passageways”
Channel Proteins Open Gated*
Carrier Proteins
Open and Gated Channels
Norm
ally
clo
sed
Norm
ally
op
en
These are types of “gates”
Chemical gates
Voltage gates
Mechanical gates
Gated channels almost always closed
Cystic Fibrosis Trans-membrane Receptor
CFTR mutationBlocks Cl-
CF: autosomal recessive
Carrier Proteins
Like a revolving door!
Movement across membranes
I. Passive transport: no ATP Non-carrier mediated Carrier mediated
Diffusion: passive
Without membrane Across membrane: no carrier
Passive transportPassive diffusion
Passive movement can require a carrier
SpecificCan saturate
II. Active Transport
Active Transport
Requires a TRANSPORTER
AND
Requires ENERGY
Primary Active Transport
Is this a symport or antiport?
Let’s look at both primary and secondary together!
Figure 5-28 (insert)
Na+ gradient is potential energy
NOTICE
Distribution of water and solutes in the body
Osmosis
Movement of water across a semi-permeable membrane
Compare osmolarity of one solution to another solution.
Isosmotic
Hyperosmotic
Hyposmotic
Number of particles are
ABA
Particle #
BParticle #
Term Used
300 300 A & B are Isomotic
#>300 300 A Hyperosmotic to B
#<300 300 A Hyposmotic to B
A B
Now, look at the following terms
Isotonic
Hypotonic
Hypertonic
Tonicity defines what a solution would do to the cell volume (size).
To cell size and tonicity: You must understand the terms
Non-penetrating versus Penetrating solutes
But I’m so tired…
3 Beakers with various concentrations of non-penetrating solutes and RBCs
Here’s your experiment: You place red blood cells in the threeBeakers and view them later under themicroscope. Now what will you observe?
200 mOsm600 mOsm 300 mOsm
Tonicity defines the affect on cell size or shape.
Crenation SwellingNo change
Hypertonic Isotonic Hypotonic600 mOsm 300 mOsm 200 mOsm
Non Penetrating
What if…
A cell of 6 Osm is placed in a solution also of 6 Osm then what is the tonicity?
Oops, that’s tricky! There is no way to know the tonicity with the information given! Why??
But what eventually happens to H20?
Look and penetrating versus non-penetrating
Clinical Application
A. 0.9% saline
SMC
Physio
0.9% saline is non penetrating= 300 mOsm
A. 0.9% saline: is isosmotic and isotonic
Transport of Macromolecules
Transport of Macromolecules White blood cells
Phagocytosis
Receptor-Mediated Endocytosis
all cells can carry out endocytosis
Transport errors…
Membrane Potential
Cell charge and cell function are related
The cell membrane separates charges
Measurement of this charge
What ions may cause this charge?
Nernst Equation: You can calculate this answer.
Eion= 61/z log [ion]out/[ion]in
61 is a constant Z is charge of ion
Ion K+mM
Na+mM
ICF 150 15
ECF 5 150
Now let’s now integrate the concept of cell membranes and a physiological process…
Cell function and Charge