cell structure and composition Flashcards
membrane proteins and transport: recall the functions of membrane proteins, and distinguish between simple diffusion, facilitated diffusion and active transport of ions and molecules across cell membranes, recall specific examples of each
two forms of movement of molecules through membranes (energy)
active and passive
what does active transport use
ATP-coupled proteins
3 examples of passive transport
osmosis, simple and facilitated diffusion
feature of simple diffusion
down conc. gradient
features of facilitated diffusion
down conc. gradient, through protein channels (with water as charged)
define symporter
protein channel which moves two or more molecule types across the membrane in the same direction
define antiporter
protein channel which moves two or more molecule types across the membrane in the opposite direction
3 examples of active transport
phagocytosis, pinocytosis, exocytosis
define phagocytosis
engulfment by membrane of EC objects such as bacteria, cell debris, which end up in IC vesicles
define pinocytosis
engulfment by membrane of EC solute which ends up in IC vesicles
define exocytosis
movement of proteins and other molecules, such as hormones and blood clotting factors, from IC vesicles towards EC space by fusion with cell membrane
what is the process which provides evidence for the fluid mosaic model
freeze-fracturing
why do some transmembrane proteins have low mobility
membrane skeleton, actin containing ‘fences’
proportion of transmembrane proteins in plasma membrane, inner mitochondria membrane and myelin sheath by increasing %
myelin sheath < plasma membrane < inner mitochondria membrane
why are the proportions of proteins in different organelles or cells different
different functions
