chapter 5 plasma membranes Flashcards
Why do we need cell surface membranes?
they act as barriers (partially permeable/help with compartmentalising), they act as a site of chemical reactions and cell signalling
what is the structure of phospholipids?
a polar phosphate head attached to a glycerol backbone attached to 2 non polar fatty acid tails
what are micelles?
bubbles of lipid which can form via water being shaken with lipids in it
what are the 8 structures in the plasma membrane?
phospholipid bilayer, extrinsic/intrinsic proteins, channel proteins, carrier proteins, glycoproteins, glycolipids, cholesterol
what is the function of extrinsic/intrinsic proteins?
extrinsic are present in one side of bilayer have amino acids with hydrophilic R groups so interact with heads, intrinsic are embedded in the membrane and pass between both layers of the membrane made of amino acids with hydrophobic R groups so they interact with tails
what is the function of glycolipids and glycoproteins?
- lipid with a carbohydrate tail that is involved in cell recognition.
- protein with a carbohydrate tail involved in recognition and signalling, can bind cells together and be receptors.
what is the function of cholesterol?
provides mechanical stability in membranes. water/ions do not pass through it directly and cannot easily get past it
what is the function of carrier proteins?
active movement of substances that requires ATP and moves against concentration gradient.
what is the function of channel proteins?
allow movement of polar molecules and ions to move across concentration gradient, allow movement across membrane, hydrophilic channel.
what is the name of the plasma membrane model?
the fluid mosaic model
what is difference between passive and active movement?
passive moves molecules across cell membranes without energy whereas active requires energy.
what is simple diffusion?
movement of molecules across a partially permeable membrane along the concentration gradient. it works for small non polar molecules
what are factors affecting the rate of diffusion?
concentration gradient, thickness of exchange surface, surface area, stirring/movement, temperature.
what is facilitated diffusion?
diffusion across plasma membrane through protein channels. it works for polar molecules and ions as these substances cannot diffuse through the bilayer, those smaller than 0.8nm can travel through channel proteins
what are the similarities and differences between simple and facilitated diffusion?
both passive. both move from high to low concentration down a concentration gradient. however simple is small/non polar molecules or lipid soluble molecules whereas facilitated is ions/polar molecules/ larger molecules. simple is directly through phospholipids whereas facilitated requires transport proteins.
what is active transport?
movement of particles across plasma membrane from low to high concentration against the concentration gradient and requires energy.
how does active transport happen?
molecules bind to carrier proteins and ATP binds to the membrane protein inside of the cell. ATP releases a phosphate group creating ADP and releasing energy which allows protein to change in shape
what is bulk transport?
method of transport to move molecules too large to move through plasma membrane in/out of cell. requires ATP
what is exocytosis?
bulk transport of molecules out of the cell
what is endocytosis?
bulk transport of molecules into the cell
how does exocytosis work?
secretory vesicle containing substance moves toward cell surface membrane. membrane of vesicle joins the cell surface membrane. it then releases large molecules out of the cell.
how does endocytosis work?
cell surface membrane creates an inwards dip (invagination) for large molecules to fit through. cell surface membrane moves to enclose the gap. large molecules are inside a vesicle (endosome) in the cell.
what is phagocytosis?
movement/bulk transport of solid particles
what is pinocytosis?
movement/bulk transport of liquids
what is osmosis?
movement of water molecules across a partially permeable membrane from a region of high water potential to a region of lower water potential along the water potential gradient.
what is water potential?
measure of the quantity of water water compared to solutes, measured as the pressure created by water molecules in KPa
what is the highest water potential?
0KPa and it is created by pure water
