Transcript Chapter-5 Membrane Dynamics

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
Normally
closed
Normally
open
These are types of “gates”

Chemical gates

Voltage gates

Mechanical gates
Gated channels almost always closed
Cystic Fibrosis Trans-membrane Receptor
CF: autosomal recessive
CFTR mutation
Blocks Cl-
Carrier Proteins
Like a revolving door!
Movement across membranes

I. Passive transport: no ATP


Non-carrier mediated
Carrier mediated
Diffusion: passive
Without membrane
Passive diffusion
Across membrane: no carrier
Passive transport
Passive movement can require a carrier
Specific
Can 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!
NOTICE
Na+ gradient is
potential energy
Figure 5-28 (insert)
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
A
B
Term Used
Particle #
Particle #
300
300
A & B are Isomotic
#>300
300
A Hyperosmotic to B
#<300
300
A Hyposmotic to B
A
A
B
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
But I’m so
tired…

Non-penetrating versus
Penetrating solutes
3 Beakers with various concentrations of nonpenetrating solutes and RBCs
Here’s your experiment:
600 mOsm
You place red blood cells in the three
Beakers and view them later under the
microscope. Now what will you observ
300 mOsm
200 mOsm
Tonicity defines the affect on cell size or shape.
Crenation
No change
Swelling
Hypertonic
600 mOsm
Isotonic
300 mOsm
Hypotonic
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??
Look and penetrating versus non-penetrating
But what eventually happens to H20?
Clinical Application
Physio

A. 0.9% saline
SMC
A. 0.9% saline: is isosmotic and isotonic
0.9% saline is non penetrating= 300 mOsm
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
ICF
K+
mM
150
Na+
mM
15
ECF
5
150
Now let’s now integrate the concept of
cell membranes and a physiological
process…
Cell function and Charge