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1112917.  Mon Jan 19, 2015 6:49 pm Reply with quote

1112955.  Tue Jan 20, 2015 4:28 am Reply with quote

1113109.  Tue Jan 20, 2015 12:17 pm Reply with quote

Lecture 4
More on membranes
glycosylation: adding a carbohydrate chain
can change cell properties
can attach to proteins, lipids
post-translationally (protein made first, then modified)
Fluidity of membranes
very important to the cell
If too rigid, some processes can’t happen (proteins can’t move)
If too fluid, membrane might fall apart, not sturdy enough
Has to be fluid enough to allow proteins to “float” around
has one or more double bonds, which causes a kink in the structure. This increases fluidity
every carbon is completely “saturated” with Hydrogen; NO double bonds. Makes a much straighter molecule. This decreases fluidity
Temperature and fluidity
warming increases fluidity: liquid crystal
cooling decreases fluidity: crystalline gel (firmer the liquid)
The transition temperature is the point that it goes from liquid crystal to crystalline gel.
In response to temperature change, the composition of the membrane can change in two ways:
desaturation of lipid
exchange of lipid chains
Some membranes have “ruffles” that allow cells to move and envelop other cells.
As humans, and the same with most other mammals, we have a pretty steady body temperature (37C). However, cold-blooded animals have enzymes that are used to change membrane fluidity to suit the temperature.
Eg. increase when colder by increasing unsaturated chains. Uses desaturase
Biological membranes are dynamic
Lipids are able to move easily laterally (within a layer/leaflet)
Lipid movement to other leaflets is much slower
There are some proteins that are not able to move
Membrane proteins can diffuse within bilayer, although it is restricted, long range is slow
Biochemical modification can dramatically alter protein mobility in the membrane
regulates membrane fluidity
if added to liquid crystal: decreases fluidity
If added to crystalline gel increases fluidity
Is capable of embedding itself in lipid bilayer

Lipid Rafts
Small areas of plasma membrane that are less fluid than the surroundings
Some membrane proteins accumulate in rafts
relatively rigid
Function isn’t completely clear, could be a functional compartment
Movement across cell membranes
The lipid membrane acts as a barrier, does not allow everything through.
Uncharged, small particles can pass through (eg. Oxygen, Water**)
Large, charged particles cannot cross the bilayer easily
There are mechanisms that allow the transport of molecules/particles
**Water goes through aquapori
4 types:
Simple diffusion: Passive, non-mediated, Concentration outside the cell is higher than inside. Naturally goes from high concentrations to low concentrations. Very small, uncharged particles.
Diffusion through a channel: Passive, non-mediated. Think aquapori, substances go through a channel from high to low concentration. Small, charged particles (ions)
Ion channels are selective, and often times gated.
Voltage-gated: responds to change in charge
Ligand-gated: responds to certain molecule that binds with it
Mechano-gated: responds to physical force on membrane
Facilitated diffusion: Passive, mediated. Compound binds to facilitative transporter, an integral membrane.The transporter changes in conformation and allows the substance through to the other side.
Active Transport: Active, mediated. Compound binds to active transporter, which changes in conformation and allows to the other side. This goes against the concentration, so it goes from low concentrations to high concentrations.Requires input of Energy.

Well, looks like you get a portion of my lecture notes for cell biology.

1113206.  Tue Jan 20, 2015 11:26 pm Reply with quote

In the Corpus Juris Canonici the Decretum[5] and the Decretals [6] deal with the subject. The offender whether simoniacus (one who had bought his orders) or simoniace promotus (one who had bought his promotion), was liable to deprivation of his benefice and deposition from orders if a secular priest, or to confinement in a stricter monastery if a regular.

1113208.  Wed Jan 21, 2015 3:02 am Reply with quote

Posital wrote:


(no, really!)

1113236.  Wed Jan 21, 2015 5:40 am Reply with quote

Big Martin
1113313.  Wed Jan 21, 2015 9:01 am Reply with quote

A link to the Aphrodite's Child single I posted under "20 songs".

1113524.  Thu Jan 22, 2015 4:24 am Reply with quote

Marduk - Obedience
The Cramps - Queen of pain
Blitzkid - She Dominates

(again a post under 20 songs featuring)

1114258.  Sun Jan 25, 2015 2:55 am Reply with quote

Dead trees have character,
Dead trees look good.
Out in the fields,
Just old, gray wood

Dead trees once had life,
Roots that stretched down,
With green on the leaves,
And the trunk brown.

How did they die?
‘tis not always known.
Too arid, too dry,
Or too wind blown.

What types of trees?
Most would be gums,
Standing quite tall,
till some wind comes.

But dead trees remain,
Because they are homes,
For animals, birds,
That do the plains roam.

(poem written on my long train trip yesterday)

1114291.  Sun Jan 25, 2015 9:50 am Reply with quote

1114593.  Mon Jan 26, 2015 7:22 pm Reply with quote

for the 20 songs thread

1114594.  Mon Jan 26, 2015 7:23 pm Reply with quote

RGB CH-9000090-NA Black

1114617.  Mon Jan 26, 2015 10:01 pm Reply with quote

1116844.  Fri Feb 06, 2015 3:36 am Reply with quote

1116846.  Fri Feb 06, 2015 3:50 am Reply with quote


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