Structure of Cell Membranes (Insane in the membrane)

Structure of Cell Membranes
(Insane in the membrane)
The Cell Membrane
The membrane is
selectively
permeable (or semipermeable)
meaning that
certain molecules
can cross the
membrane and
others cannot.
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Phospholipids!
Why hydrophobic tails? Why hydrophilic
heads?
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Arrangement of Phospholipids in
Membranes
The cell membrane has two layers of phospholipids as shown
below. The hydrophilic heads are facing an aqueous
environment and the hydrophobic tails are facing one
another. If no phosphate group, hydration shell would form!
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Movement of Phospholipids
Phospholipids have the ability to move
laterally but only upon a rare occasion are
able to flip with the opposite.
Cholesterol and Phospholipids
Prevents extremes in fluidity in the membrane.
Acts like a “joint”.
Proteins in the Membrane
Function of Membrane Proteins
1. Transport proteins, or permeases, transport
molecules across the membrane. Aquaporins
are special protein channels used to move water
across the membrane.
Functions of Other
Membrane Proteins
2. Enzyme-Some proteins in the
membrane may expose their
active site to speed up a
chemical reaction.
3. Receptor site-Ex. Insulin never
goes into a cell but binds to a
receptor site on the cell
membrane
4. Cell to cell recognition.
5. Intercellular joining
6. Attachment to the cytoskeleton and extracellular matrix
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(ECM only in animal cells)
Surface Area to Volume
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The Plasma Membrane
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