Membrane EXAM 2

• phospholipid bilayer
• Phospholipids are amphipathic molecules (hydrophophic tail hydrophilic head)
• Membranes also contain proteins and carbohydrates

• lipids and proteins can move relative to each other within the membrane
• Not completely rigid

Transmembrane proteins - one or more regions that are physically embedded in the hydrophobic region of the phospholipid bilayer

Lipid-anchored protein - covalent attachment of a lipid to an amino acid side chain within a protein

• Noncovalently bound to regions of
• integral membrane proteins that project out from the membrane, or they are bound to the polar head groups of phospholipids

• Fluidity - individual molecules remain in close association yet have the ability to
• readily move within the membrane

Semifluid- most lipids can rotate freely around their long axes and move laterally within the membrane leaflet

• “Flipflop” of lipids from one leaflet to the opposite leaflet does not occur spontaneously
• -Flippase requires ATP to transport lipids
• from one leaflet to another

• cholesterol
• double chains in tails
• legnth of tails

Process of covalently attaching a carbohydrate to a protein or lipid

-Glycolipid – carbohydrate to lipid

-Glycoprotein – carbohydrate to protein

Serve as recognition signals for other cellular proteins

Play a role in cell surface recognition

protective by coating with glycocalyx

Can provide significant three-dimensional detail about membrane protein form and shape

cytosol and endomembrane system work together to synthesize lipids next to smooth ER

Lipids in ER membrane can diffuse laterally to nuclear envelope

Transported via vessicles to Golgi, lysosomes, vacuoles, or plasma membrane

Lipid exchange proteins – extract lipid from one membrane for insertion in another

• no ATP
• high to low
• no protein

• transport protein/carrier molecule
• no ATP

• needs ATP
• against gradient (low to high)
• primary - pump
• secondary - preexisting pump

Transmembrane gradient - Concentration of a solute is higher on one side of a membrane than the other

Ion electrochemical gradient -Both an electrical gradient and chemical gradient

• hypertonic
• hypertonic
• isotonic

movement of water

provide a passageway for the movement of ions and hydrophilic molecules across membranes

• classes based on manner of movement
• -Channels (gated)
• -Transporters (think wheelbarrow/enzyme active site)

material from inside shipped out via vesicles

• bring things into the cell
• Receptor-mediated endocytosis
• Pinocytosis (fluids)
• Phagocytosis (food)