Biological membranes Flashcards
(22 cards)
Bulk transport
A way of transporting molecules in or out of cells, when they are too big to pass through the plasma membrane. This process requires ATP.
Partially permeable
Allows some, but not all, substances to pass through.
Plasma membrane
The cell surface membrane.
Plasmolysed
A plant cell where the content have shrunk due to loss of water by osmosis and the plasma membrane has separated from the cell wall.
Fluid mosaic model
A theory of cell membrane structure with proteins embedded in a sea of phospholipids. It is described as a fluid mosaic because it can move (it is fluid) and the embedded proteins make it look like a mosaic from the top.
Glycolipids
A lipid/phospholipid with a chain of carbohydrate molecules attached.
Glycoproteins
A protein with a chain of carbohydrate molecules attached.
Diffusion
The movement of molecules from an area of high concentration of that molecule to an area of low concentration. This can be across a membrane.
Facilitated diffusion
Movement of molecules from an area of high concentration of that molecule to an area of low concentration, across a partially permeable membrane via protein channels or carriers. It does not require ATP.
Osmosis
The passage of water molecules down their water potential gradient, across a partially permeable membrane.
Water potential
A measure of the tendency of water molecules to diffuse from one area to another. High water potential = lots of water molecules.
Cytolysis
The process in animal cells where, if a lot of water molecules enter, the cell will swell and burst as the plasma membrane breaks.
Turgid
A swollen state of plant cells that have taken in water by osmosis and have reached their maximum state of swelling. The cell wall now exerts a pressure and prevents any more water from entering the cell. This is a plant’s normal state.
Crenated
A shrivelled animal cell that has lost water by osmosis.
Flaccid
Plant tissue that is no longer turgid and the tissue is soft.
Active transport
The movement of substances against their concentration gradient (high to low concentration) across a cell membrane using ATP.
Endocytosis
The bulk transport of molecules, too large to pass through a cell membrane (even via channel or carrier proteins) into a cell.
Excocytosis
The bulk transport of molecules, too large to pass through a cell membrane (even via channel or carrier proteins) out of a cell.
Channel proteins
A protein embedded in the phospholipid bilayer that opens and closes to allow substances to diffuse across the plasma membrane.
Carrier proteins
A protein embedded in the phospholipid bilayer that can change shape (depending on the molecule) to allow substances to diffuse across the plasma membrane. The carrier protein allows molecules through as it has a binding site which a specific substance can bind to.
Saturated fatty acid
A fatty acid with only single bonds between the carbon atoms in the hydrocarbon tail.
Unsaturated fatty acid
A fatty acid with one or more double bonds between carbon atoms in the hydrocarbon tail.
