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diffusion and active/co transport (strand 2) - Coggle Diagram
diffusion and active/co transport (strand 2)
simple diffusion ~ the net movement of particles down a concentration gradient from a high concentration to an area of lower concentration
factors affecting diffusion across a membrane: concentration gradient, temperature, thickness of membrane
facilitated diffusion
passive process
occurs down a concentration gradient
occurs at specific points on the plasma membrane
protein molecules help move molecules across the membrane if they're too big or polar
types of proteins involved: channel proteins, carrier proteins
protein channels
form water filled hydrophilic channels across membranes
allow specific water soluble ions to pass through
some channels only open in the presence of a specific ion so therefore they're specific
ions bind to the protein, causing it to change shape so that it opens on one side of the membrane and closes on the other
carrier proteins
specific molecules bind with these proteins, causing the proteins to change shape, they open on one side and close on the other
active transport ~ process by which a cell takes up a substance against the concentration gradient
it uses protein carrier molecules but also requires energy, this comes in the form of a molecule called ATP, produced during respiration
cells in which lots of active transport occurs, such as the epithelial cells of the small intestine have many mitochondria which produce ATP for this process
protein pumps
differ from those in facilitated diffusion because they carry specific molecules one way across the membrane
use ATP
carry molecules in the opposite direction to the concentration gradient
carry molecules at a faster rate
molecules can be accumulated either inside cells or organelles, or outside cells
co - transport
process in which two substances are simultaneously transported across a membrane by one protein or protein complex
the energy required to move a substance against a concentration gradient is provided by the movement of another substance along its concentration gradient