Cell physiology Flashcards
Animal cells – 3 compartments
1) cell membrane
2) cytoplasm
3) nucleus
protoplasm = cytoplasm + nucleus
functions of plasma membrane
1) barrier b/w cell & environment
(cells, ISF/plasma)
2) SELECTIVELY PERMEABLE MEMBRANE
3) I.e. UNIQUE internal cell environment
cell membrane structure
75% phospholipids
phospholipids are…
amphipathic
both polar and non-polar components
nonpolar fatty acid tails
polar phosphate head
cell membrane structure (bilayer)
high amounts of phospholipids in aqueous solution
= phospholipid bilayer
= phosphate heads towards water, FA tails away from water (towards each other)
majority of phospholipid bilayer is (hydrophilic? hydrophobic?)
hydrophobic (tails)
consequence of majority hydrophobic bilayer
only hydrophobic (non-polar) molecules can pass through
hydrophilic (polar) molecules need carrier/channel mediation
exception to what can/can’t typically pass through lipid bilayer
Size is important variable
some small polar molecules can pass through – even though polar
some large nonpolar molecules may need transport (?) – even though nonpolar
permeable to…
Non-polar, hydrophobic, uncharged, (small?) – E.G. STEROIDS, O2, CO2
impermeable to…
polar, hydrophilic, charged – E.G. IONS, LARGE PROTEINS
example of exception
H2O – permeable to some degree – even though POLAR, HYDROPHILIC
what happens if lose selective permeability?
cell would no longer be able to maintain homeostasis – would be destroyed
lipid bilayer is composed of which lipids?
75% phospholipids
20% cholesterol
5% glycolipids
cholesterol in the lipid bilayer
carries a (polar) OH group (HYDROXIL GROUP)
attaches to phosphate group (polar head)
function of cholesterol in lipid bilayer
structure @ high temp
fluidity @ low temp
1) maintains structure @ high temperatures
(by keeping phospholipids locked together)
2) maintains fluidity of membrane @ low temperatures
(Non-polar portion prevents phospholipids (tails?) interacting)
GLYCOLIPIDS in the lipid bilayer
sugar attached to lipid
FOUND ON EXTRACELLULAR SIDE
which side are glycolipids?
extracellular side
function of GLYCOLIPIDS in cell membrane
SIGNAL TRANSDUCTION (convert signal type)
CELL TO CELL ADHESION
what is GLYCOCALYX composed of?
“sugary coat”
composed of carbohydrate portion of glycolipids (& glycoproteins)
function of GLYCOCALYX
1) cell recognition/signalling
2) protection
3) regulates cell behaviour
Cell membrane PROTEIN categories
1) Integral proteins
2) Peripheral proteins
integral proteins
crosses bilayer (“embedded”)
contains both polar/nonpolar parts (AMPHIPATHIC?)
complex/large
peripheral proteins
on surface of membrane (external or internal side)
attach to polar head of phospholipid
or attach to integral proteins
less complex/large
membrane proteins functional types
1) Transporters
2) Ion Channels
3) Receptors
4) Enzymes
5) Linkers
6) Markers