fat cell

[baikuza]

have you heard about hidrophobic and hidrophilic as the properties of compounds?

lipid (e.g. oil, fat) are hidrophobic. so that it float to water.

am i right, moderator?

[Poison]

If you put a stone in water it will sink. Right? Means Stone's density > water's density.

And about the hydrophilic compounds: Hydrophilic side is turned to the water and hydrophobic side is turned to each other. If I shold give an example from cell membrane- as it is easy to draw here- ( you know, it is made of two lipid bilayers)

O: hydrophilic head
ll : hydrophobic tails

Outside the cell

OOOOOOOOOO
ll ll ll ll ll ll ll ll ll ll
ll ll ll ll ll ll ll ll ll ll
OOOOOOOOOO

Inside the cell

[victor]

Can you also explain why oils float on water? I guess waxes can float too.

a little bit correction my friends, lets see:
water consist of 2 H atom and one O atom forming H2O with a tetrahedron geometry molecule. There are still some free electron pairs that makes H2O become polar molecules that only can soluble other polar molecules.
While fats are the unpolar one so, fats don't soluble in the water.
The floating thing can be explained by the presence of Hydrogen bond in the water..it's the same like a cube of ice float in the water. ice has a bigger density than water but water has more freely hydrogen bond compared to ice cube...
For more information, read your organic chemistry book...

[Poison]

ice has a bigger density than water

No. density of ice is less than density of water. Think that ice expands when it freezes.

[victor]

Oops...sorry, got it upside down...

[Mjhavok]

i know the bits and pieces that go to form the lipid bilayer of a cell membrane. But what is the names of the bits and pieces ?of the bilayer? that keeps the cell membrane from dissolving into a heap of goo within and without? Cn't be phosphate and metal cations only.

Bits and pieces of the bilayer? Do you mean phospholipids, sphingolipids, glycoproteins, glycolipids, cholesterol etc.

[victor]

Seems to be likely...because the bits at the bilayer are integrins, proteoglycane, glicoprotein, etc....