The Cell Membrane

Phospholipids

Fatty acid

Phosphate

• Phosphate head – hydrophilic

• Fatty acid tails– hydrophobic

• Arranged as a bilayer

Aaaah, one of those

structure–functionexamples

“repelled by water”

“attracted to water”

What passes the bilayer?

polarhydrophilic

heads

nonpolarhydrophobic

tails

polarhydrophilic

heads

H2Osugar

lipids

salt

waste

impermeable to polar molecules

How do polar molecules cross?

inside cellinside cell

outside celloutside cell

sugaraaH2O

saltNH3

Why areproteins the perfect

molecule for transport?

Classes of amino acids

What do these amino acids have in common?What do these amino acids have in common?

nonpolar & hydrophobic

Classes of amino acids

What do these amino acids have in common?What do these amino acids have in common?

polar & hydrophilic

I like thepolar onesthe best!

Protein domains anchor moleculePolar areasof protein

Nonpolar areas of protein

NH2

H+

COOH

Cytoplasm

Retinalchromophore

Nonpolar(hydrophobic)α-helices in thecell membrane H+

Porin monomer

β-pleated sheets

Bacterialoutermembrane

proton pump channel in photosynthetic bacteria

aquaporin = water channel in bacteria

function through conformational change = protein changes shape

Examples

H2O

H2O

H+

H+

10

Membrane Proteins

11

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

1313

Let’s go to the video

Any Questions??