movement of molecules Flashcards
what is active transport?
movement of molecules from a low to high concentration gradient which requires energy in the form of ATP
what is the importance of active transport?
- reabsorption of molecules after kidney infiltration / digestion
- phloem loading
- loading of ions into root hair from soil
summarise the process of active transport
- molecule binds to carrier protein outside cell
- protein changes shape and cell opens
- molecule joins to receptor site on protein
- ATP joins to receptor site inside cell
- protein changes shape
- the molecule passes through and is released
what is passive diffusion?
net movement of a substance from a high to low concentration gradient across a partially permeable membrane
state the three factors affecting diffusion
- concentration gradient
- temperature
- surface area
how does conc gradient affect diffusion?
more molecules on one side increases the gradient which makes for faster diffusion
how does temperature affect diffusion?
molecules have more kinetic energy so move faster which makes for faster diffusion
how does surface area affect diffusion?
more molecules can cross at one time which makes for faster diffusion
how is rate of diffusion calculated?
SA x concentration difference / exchange surface thickness
what is facilitated diffusion?
a form of diffusion which requires proteins to move large or polar molecules across, requires ATP
what is a channel protein?
water filled, gated protein which opens and closes to control exchange of ions
what is a carrier protein?
changes shape and binds to the molecule to move it
what is bulk transport?
transporting large quantities of material
what is endocytosis?
membrane engulfs material
- requires ATP
what is phagocytosis?
a form of endocytosis
- solid
