Overview Cell membrane separates living cell from
nonliving surroundings Controls traffic in & out of the cell
selectively permeable allows some substances to cross more easily than
others
A. Phospholipids
Fatty acid
Phosphate
1. Tails: Fatty acid chain Hydrophobic (water Fearing)
2. Heads: Phosphate and glycerol Hydrophilic(water loving)
3. Arranged as a bilayer
Hydrophobic/hydrophilic
Phospholipids cont.4. Phospholipids can move laterally and
allow small molecules, such as water, pass in and out of the cell as needed.
Protein Fluidity
Phospholipid bilayerBilayer Animation
polarhydrophilic
heads
nonpolarhydrophobic
tails
polarhydrophilic
heads
B. Glycolipid1. Makes the cell membrane more fluid
Cholesterol Without cholesterol, cell membranes
would be too fluid and too permeable to some molecules.
Cholesterol
D. Membrane Proteins1. Proteins determine membrane’s specific
functions
2. Membrane proteins:
a. peripheral proteins loosely bound to surface of membrane cell surface identity marker (antigens)
b. integral proteins (transmembrane) penetrate lipid bilayer, usually across whole membrane transport proteins
Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer
Extracellular (outside)
Cholesterol
Cytoplasm
Glycolipid
Transmembraneproteins
Filaments ofcytoskeleton
Peripheralprotein
Glycoprotein
Phospholipids
LABEL THE PARTS
Intracellular (inside)
E. Many Functions of Membrane Proteins
Outside
Plasmamembrane
InsideTransporter Cell surface
receptorEnzymeactivity
Cell surface identity marker
Attachment to thecytoskeleton
Cell adhesion
Membrane carbohydrates Play a key role in cell-cell recognition
ability of a cell to distinguish one cell from another antigens
important in organ & tissue development
basis for rejection of foreign cells by immune system
G. 4 Functions of the Plasma Membrane
1. Cell signaling between cells.
2. Selective transport of substances into and out of the cell.
3. Adhesion of a cell to other cells.
4. Enclose the cytoplasm and prevent dispersion of organelles.
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