Transport Across Membranes Flashcards
(17 cards)
What is the membrane described as?
Selectively permeable
Why the membrane described as a fluid mosaic model?
Fluid = phospholipids forming the bilayer are constantly moving
Mosaic = different proteins unevenly distrubted throughout the membrane
How do phospholipids form the fluid mosaic model?
Phospholipids consist of fatty acids which are non polar and hydrophobic so face inwards and phosphate groups which are polar and hydrophilic so face outwards
Role of phospholipids in the membrane
They allow small, lipid soluble, non polar molecules to pass through simple diffusion by passing through non polar fatty acids and prevent large polar molecules which reqiure a protien.
Role of cholesterol in membrane
More chlorestral means less fluidity so membrane os mote stable
Role of Channel proteins on membrane
They allow polar, small molecules to pass through via their protein by facilitated diffusion. They have a specific tertiary structure which means they can only transport complementary molecules thrift the membrane.
Role of Carrier protien in membrane
They allow large, polar molecules to pass through via facilitated diffusion or active transport using ATP. Phosphate group of ATP molecule bonds to the binding site of protein exposing its binding site to allow the complementary molecule to pass through.
Role of receptor protiens in the membrane
Specific cells have specific receptor protiens. Only specific molecules can bind to specific receptor protiens such as insulin
Role of enzymes in membrane
They are embedded within the membrane eg maltase . The active site is complementary to the substrate and forms enzyme substrate complexes.
Role of glycoproteins in the membrane
They are composed of carbohydrates and protiens and are on the outer surface membrane and important in cell recognition. They are produced in the golgi body.
Role of aquaporins in the membrane
They are channel proteins specific to water molecule make the cell more permeable and carry out osmosis easily
Simple diffusion definition
Net movement of lipid soluble, non polar, small molecules from an area of high to low concentration down a concentration gradient through a partially permeable membrane. Passive process as no ATP
Facilitated diffusion definition
Net movement of large polar molecules from an area of high to low concentration down a concentration gradient through a partially permeable membrane using a carrier or Chanel protein. Passive process as no ATP
Active transport definition
Net movement of larhe polar molecules from an area of low to high concentration against a concentration gradient through a partially permeable membrane using ATP and a carrier protein
Two other types which are exocytosis and endocytosis
Osmosis definition
Net movement of water molecules from an area of high to low water potential down a water potential gradient through a partially permeable membrane using aquaporin protein.
Low water potential means more solute dissolved so -10kpa vice versa for high
Ficks law
Surface area x concentration gradient/ diffusion distance
Factors affecting rate of diffusion
High Temperature
Large Surface area
Big Concentration gradient
Small diffusion distance
