Cell Physiology - topic 5 Flashcards
what are the 5 ways that substances can enter or leave the cell?
-simple diffusion
-facilitated diffusion
-active transport
-Cytosis
-osmosis
what does simple diffusion transport and why?
-non polar molecules e.g. oxygen and carbon dioxide, can pass through the membrane unaided, other very small molecules like water can also pass through unaided due to their very small size
-diffusion is not restricted to just membranes
-diffusion is a passive process and does not require energy
what is the definition of simple diffusion?
-diffusion is defined as the net movement of substances from an area of high concentration to an area of low concentration
what are the 5 factors that affect the rate of diffusion?
-the greater the concentration gradient the faster the rate of diffusion
-the smaller the molecule the faster the rate of diffusion compared to larger molecules
-diffusion is greater at high temps as it gives the molecules more kinetic energy
-the thickness of exchange surface effects diffusion, the thinner the membranes helps with faster diffusion
-the grater the surface area the faster the rate of diffusion, in some cells the cell surface membrane is extended to increase the area across which diffusion can take place
what is the definition of facilitated diffusion?
-this is the type of diffusion when diffusion is supported by protein carriers, that have binding sites that match specific molecules which assist the membrane of molecules across the membrane
what are the two types of proteins that are involved in facilitated diffusion?
-carrier proteins which take in molecules, they change shape and release the molecules on the other side of the membrane
-ion channel proteins which allow ions to pass through, come of these are permanently open and some are controlled through a gate
what is active transport?
-some molecules and ions need to be moved against the concentration and so energy is required
what does active transport involve?
-involves protein carrier molecules, the substance being transported binds to the carrier protein
-the carrier changes shape and releases the transported substance on the other side of the membrane
-the carriers are specific to the particular molecule that it carries
why do cells that carry out active transport have many mitochondria?
-they supply the ATP needed for active transport
why do root hair cells carry out active transport?
-root hair cells need to take in nutrients to help them grow, there is a high concentration of nutrients inside the root hair cell, compared to a low concentration outside. Therefore active transport is necessary, active transport will stop in water logged soil as there is no oxygen able to get into the cell
what happens in the process of cytosis?
-the process of cytosis is important in transporting, large molecules that are too big for the carries and transporting the smaller molecules e.g. water in bulk
what are the two types of cytosis?
-endocytosis is the movement of substance into the cell
-exocytosis is the movement of substance out of the cell
what happens during endocytosis?
-the cell surface membrane invaginates around substances entering the cell from the outside, this forms a vesicle which then pinches off inside the cell
-when vesicles are taken in the cell the fluid nature of the cell surface membrane allows it to reform and close the gap
what are the two types of endocytosis?
-phagocytosis involves the transport of solid matter into the cell
-pinocytosis is the transports liquids into the cell
what happens during the process of exocytosis?
-the movement of substances out of the cell
-secretory vesicles move to and fuse with the cell surface membrane, the contents of the vesicles are then released outside the cell, which is then followed by the reforming of the membrane
-exocytosis is important in the secretion of many proteins e.g. digestive enzymes and some hormones