biological membranes Flashcards
what are 3 functions of the plasma membranes?
cell communication
recognition by other cells
barrier between cell and its environment (partially permeable)
what are 3 functions of membranes within cells?
form vesicles to transport substances between different areas of the cell
site of chemical reactions
control which substance can enter and leave the organelle eg RNA in nucleus via nuclear membrane
what do channel proteins allow into the phospholipid bilayer?
they allow small or charged particles through by forming pores
different channel proteins facilitate the diffusion of different charged particles
what do carrier proteins do?
they transport large molecules and ions across the membrane by active transport and facilitated diffusion
different carrier proteins facilitate the diffusion of different molecules
what do proteins act as?
receptors for molecules in cell signalling
what is the role of glycoproteins and glycolipids?
they stabilise the membrane by forming hydrogen bonds with surrounding water molecules
where drugs, hormones and antibodies binds
act as receptors for cell signalling
they are antigens
how is a messenger molecule detected?
it binds to the receptor on the cells cell membrane
why can messenger molecules only bind to specific receptor proteins?
its because the receptor proteins have a specific shape and only messenger molecules with a complementary shape can bind to them
what 2 factors affect membrane permeability?
temperature and the solvent
define diffusion
is the net movement of particles from an area of high concentration to an area of lower concentration down a conc gradient
passive process
which molecules can diffuse through cell membranes?
small,non polar molecules such as oxygen and carbon dioxide and water as even though its polar it is small enough to fit between phospholipids
which 4 factors does the rate of diffusion depend on?
the conc gradient-higher-faster rate of diffusion
thickness of exchange surface-thinner (shorter distance)
surface area-larger
temperature-warmer, the faster it is
define active transport
uses energy to move molecules and ions across plasma membranes against a conc gradient, this process involves carrier proteins
describe endocytosis
a cell surrounds a substance with a section of its plasma membrane
the membrane then pinches off to form a vesicle inside the cell containing the ingested substance
requires ATP
describe exocytosis
vesicles containing substances such as hormones, digestive enzymes etc pinch off from the sacs of golgi apparatus and moves towards the plasma membrane
the vesicles fuse with the plasma membrane and release their contents outside the cell.
ATP IS USED