Transport Across Membranes Flashcards
Simply describe the phospholipid bilayer and describe what kind of molecules can pass through it
Hydrophilic phosphate heads and hydrophobic tails orientate them selves in aqueous conditions, flexibleand self sealing
Small Lipid soluble molecules can pass through
Describe the role of cholesterol in the phospholipid bilayer
Add strength to membranes
Brings fatty acid chains closer together
V hydrophobic so prevents water loss
Describe glycolipids and glycoproteins in terms of the cell surface membrane
Moleucles on the cell surface membrane that act as receptors
Glycoprotein - hormones and neurotransmitters
Glycolipid - cell recognition by lymphocytes
What types of molecule will not get through a phospholipid bilayer
Non lipid soluble molecules
Large molecules
Charged molecules
Define diffusion
The NET movement of molecules from an area of high concentration to an area of low concentration
Describe facilitated diffusion and the two types of protein it can occur in
The diffusion through a protein channel or carrier protein passively down a concentration gradient
Protein channels - water filled hydrophilic channels, allow water soluble ions in selectively permable i.e. Let in when bind to it and change its shape. always passive
Carrier protein - molecule binds opens the protein and goes straight through (no water) can occur in active transport
Why isn’t osmosis quite just “diffusion but with water” ?
Because it occurs across a partially permeable membrane, any solutes within the water will not get through
Describe what happens to plant cells when they are put in water samples of greater water potential and of lesser
Greater water potential and water will pass in via osmosis, this makes the cell turgid
Lesser water potential and water flows out by osmosis makes the cell plasmolysed
What binds to an active transport molecule to change its shape?
The inorganic phosphate from the hydrolysis of ATP
