The Cell Membrane Phospholipids Phosphate head Phosphate attracted
The Cell Membrane
Phospholipids • Phosphate head Phosphate “attracted to water” – hydrophilic • Fatty acid tails – hydrophobic Fatty acid • Arranged as a bilayer “repelled by water” Aaaah, one of those structure–function examples
What passes the bilayer? sugar polar hydrophilic heads nonpolar hydrophobic tails H 2 O salt impermeable to polar molecules polar hydrophilic heads waste lipids
How do polar molecules cross? inside cell NH 3 salt H 2 O aa sugar outside cell
Why are proteins the perfect molecule for transport?
Classes of amino acids What do these amino acids have in common? nonpolar & hydrophobic
Classes of amino acids What do these amino acids have in common? I like the polar ones the best! polar & hydrophilic
Protein domains anchor molecule Polar areas of protein Nonpolar areas of protein
H+ Examples H+ Retinal chromophore NH 2 aquaporin = water channel in bacteria Porin monomer H 2 O β-pleated sheets Bacterial outer membrane Nonpolar (hydrophobic) α-helices in the cell membrane COOH H+ H + Cytoplasm proton pump channel in photosynthetic bacteria H 2 O function through conformational change = protein changes shape
Membrane Proteins
Cholesterol • What is the function of cholesterol? 11
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
Let’s go to the video 13
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