plasma membranes Flashcards
what does it mean for a membrane to be selectively permeated?
it allows certain molecules through the membrane
what is a plasma membrane?
a membrane which encases any type of cell and organelle
what is a phospholipid?
a lipid molecule with a hydrophillic phosphate head and two hydrophobic fatty acids
what is a monolayer?
a single layer of phospholipids formed at a water/air interference (doesn’t occur within the body)
what is a bilayer?
a double layer of phospholipid with the phosphate heads on the outside, which makes up all plasma membranes
what is a micelle?
a monolayer sphere of lipids to protect non water-soluble molecule (or what bile breaks lipids down into)
what are glycoproteins?
chains of carbohydrates attached to proteins with a receptor (carbon) which make up part of plasma membranes
what is the function of glycoproteins in a plasma membrane?
to act as recognition sites and help cells form tissues
what are glycolipids?
chains of carbohydrates attached to phospholipid heads which make up part of plasma membranes
what is the function of glycolipids in a plasma membrane?
membrane stability and cell recognition
what is the function of cholestrol in a plasma membrane?
prevents membrane distortion and provides strength (very hydrophobic), reduces membrane fluidity at high temperatures
what is a channel in a plasma membrane?
a gap in proteins for small molecules to pass through
what is the difference between an intrinsic and an extrinsic protein?
intrinsic proteins are associated with the bilayer on both sides while extrinsic proteins only touch one side
what components make up the “fluid mosaic” plasma membrane model?
phospholipid bilayer, cholestrol, glycolipids, in/extrinsic proteins and glycoproteins
what does it mean for a process to be passive?
it requires no additional energy
what is diffusion?
the passive net movement of molecules from an area of high concentration to an area of low concentration
what is osmosis?
the passive net movement of solvent molecules from an area of high water potential to an area of low water potential through a selectively permeable membrane
what is simple diffusion?
transport of small, non-polar, lipid soluble molecules through pores in the phospholipid bilayer (eg O2)
what is facilitated diffusion?
the transport of molecules through protein channels or using passive carrier proteins
what is water potential?
pressure exerted by water molecules which determines their movement, measured in kPa
what is a hypotonic solution?
one in which there is more solvent and less solute in the solution than in the cell, results in a lysed/turgid cell
what is a hypertonic solution?
one in which there is more solute and less solvent in the solution than in the cell, results in a crenated/plasmolysed cell
what is a lysed cell?
an animal cell which has shriveled due to being placed in a hypertonic solution
what is a crenated cell?
an animal cell which has swelled (or burst) due to being placed in a hypotonic solution
what is a plasmolysed cell?
a plant cell which has shriveled due to being placed in a hypertonic solution
what is a flaccid cell?
a plant cell which is in an isotonic solution
what is a turgid cell?
a plant cell which has swelled due to being placed in a hypotonic solution (optimum)
