Lipids (2) Flashcards
What is facilitated diffusion
Facilitated diffusion is for large and polar molecules to cross the membrane with the aid of channel or carrier proteins
What is a channel protein
A channel protein is a protein that spans the membrane. Channel proteins are shaped to only allow one type of ion through. Pore in membrane
Which proteins are used in facilitated diffusion
Channel and carrier proteins are used in facilitated diffusion
What are carrier proteins
Carrier proteins are proteins that are shaped so that a specific molecule can fit through them at membrane surface. When molecule fits, carrier protein changes shape and as a result the molecule crosses the membrane. This movement occurs in both directions .And molecule cannot go back the way it came due to carrier protein changing shape.
Why can O, CO2 and water diffuse
O2 is a non polar molecule so it diffuses quickly
CO2 is polar, but very small
Water is polar, but small so diffuses quickly.
Why is it harder for polar molecules to diffuse
It is harder for polar molecules to diffuse because they are not soluble in phospholipid tails, unlike non polar molecules. So the hydrophobic tails of phospholipid form a barrier.
What molecules use facilitated diffusion
Very large and polar molecules use facilitated diffusion to move across membrane.
Vesicle
Vesicle is an organelle which has a phospholipid bilayer and contains proteins, like a membrane bound sack.
Endocytosis
Endocytosis is when a vesicle surrounds particles, then the vesicle is taken and put into a cytoplasm of a cell. E.g cholesterol uptake in cells and phagocytosis.
Exocytosis
Exocytosis is when the vesicle fuses with cell membrane, releasing particles. E.g in pancreatic cells when neurotransmitter from nerve endings are absorbed
Aquaporins
Aquaporins are channel proteins which can rapidly transport water into cell
Osmosis definition
Osmosis is the movement of water through a partially permeable membrane from a region with more free water particles to a region with less free water particles down a concentration gradient.
Bulk transport
Bulk transport is when large quantities of a specific molecule need to be transported across a membrane.
What is a gated channel
Gated channel are channels which can be opened or closed, depending on presence or absence of a signal. E.g specific molecule like a hormone, or change in voltage.
