Cell Membrane Structure Flashcards
what are the roles of plasma membrane
- respond to stimuli
- export/import molecules (endo-, exo-cytosis)
- allow for movement during cell growth since it grows itself
describe the plasma membrane’s lipid bilayer
- semi-permeable
- embedded proteins which provide uniqueness
- phospholipids: hydrophilic heads align outside and hydrophobic tails on inside
define amphipathic molecule
those that contain both hydrophilic and hydrophobic groups (EX cholesterol)
phospholipids and glycolipids are distributed ___________ in the membrane
asymmetrically
how is the cell membrane formed
hydrophobic molecules force water molecules to make cage-like arrangement which forces formation of lipid bilayer
the cell membrane is energetically ______________
favourable
why do the properties of phospholipids cause membranes to be spherical
any tear in plasma membrane will expose an edge of tails to water which makes it energetically unfavourable. this is why edges merge and form spherical shape
define fluidity
dynamic cell barrier is able to respond to changing environment
what factors affect fluidity of plasma membrane
- length of hydrocarbon tail
- degree of unsaturation (double bonds)
- dissimilar structures in between (EX cholesterol in between)
what are transporters
membrane proteins that transport nutrients and ions
what are anchor proteins
anchor macromolecules
what are receptor proteins
those that receive information
what do enzymes do
catalyze reactions
how do membrane proteins associate with the membrane in various ways
- transmembrane proteins
- membrane-associated proteins
- lipid-linked proteins
- protein attached proteins
describe transmembrane proteins
hydrophobic regions interact with phospholipid tails, whilst hydrophilic portions interact with cytosol and extracellular environment
describe membrane-associated proteins
protein is entirely cytosolic with alpha-helix associated with inner leaflet of membrane
describe lipid-linked proteins
linked to membrane by covalent bond
describe protein-attached proteins
one protein is held in place with another protein that’s associated with plasma membrane
how can a peptide chain cross the membrane
as alpha-helix, where hydrophobic side chains interact with hydrophobic portion of membrane
how can beta sheets cross the membrane
as beta-barrels, an aqueous channel lining is formed by the hydrophilic portion of beta-sheets and hydrophobic portion interacts with plasma membrane
what is a cortex; what can it do
- protein framework attached by transmembrane proteins
- strengthens cell/plasma membrane
what protein is the human red blood cell cortex made of; what does it do
spectrin; forms meshwork that provides shape
what is the cell surface coated with
carbohydrates
why is cell surface coating beneficial
- prevents cells from sticking together
- cell-cell recognition
- some cells (white-blood) can squeeze between others since it is slimy
- protection from mechanical and chemical damage
- recognize sites of infection (neutrophils)
what are glycolipids
lipids with carbohydrates
what are glycoproteins
membrane proteins with sugars attached (oligosaccharides)
how are carbohydrates on surface of neutrophils beneficial
- oligosaccharides on neutrophils bind to lectin proteins on endothelial cells at infection site
- neutrophils migrate through blood vessel at correct location to site of infection
