Cell Membranes Flashcards
cell membrane
controls what goes in and out of the cell
phospholipid
phosphate head- negatively charged, polar, hydrophilic
glycerol molecule
2 fatty acid chains - no charge, non polar, hydrophobic
phospholipid bilayer
arranged with hydrophilic head on the outside and hydrophobic tails on the inside
water
polar molecule
partially positive- hydrogen
partially negative- oxygen
polar molecules
polar (charged) molecules like PL are attracted to water
they are soluble in water as they form h bonds with water
hydrophobic group together in water as they are non polar
non polar
hydrophobic - not charged
are not soluble in water because they are not attracted to water molecules + clump together
are soluble in non polar liquid eg oil will mix with more oil
PL bilayer functions
allows lipid soluble (non polar) molecules in and out of the cell
prevents water soluble (polar) molecules in and out of cell
makes membrane flexible
proteins
interspersed throughout membrane
span the membrane from one side to the other- transmembrane
on the inside (intrinsic) or the outside (extrinsic)
transmembrane protein
facilitated diffusion uses carrier and channel proteins
protein channels- have a hole/ channel all the way through to allow polar molecules (water soluble)
carrier proteins- span membrane and help transport ions or larger substances eg glucose + amino acids by changing shape
carrier proteins
some are involved in diffusion and do not require ATP to change shape
some are involved in active transport and require ATP to move molecules against conc gradient from low to high
glycoproteins and glycolipids
proteins/ lipids with branches of sugars attached
carbohydrate (sugar) portion extends to the outside of the cell
both- act as recognition sites
help cells attach/adhere together to form tissue
GP- acts as receptors to receive chemicals eg NT and hormones
cholesterol
found within PLB of eukaryotic cells, in cell surface membrane
provides stability to cell membrane as it prevents too much lateral movement of other molecules in membrane
permeability of PL
only small non polar molecules can diffuse through easily
they are soluble in non polar fatty acid tails
charged ions and polar molecules do not diffuse through easily as they are not soluble in fatty acid tails
polar molecules are only soluble in polar substances eg water
-transported using protein channels and carrier molecules
fluid mosaic model
fluid- individual phospholipid molecules can move so it is flexible
mosaic- proteins and phospholipids interspersed in the membrane vary in shape and size
active transport
requires ATP from aerobic respiration- mitochondria
uses carrier proteins- molecule attaches, protein changes shape, moves molecule across membrane and releases it on other side