cell biology 2 Flashcards
what are the functions of the cell membrane
- selectively permeable
- concentration gradient
- structural scaffold
what are the components of the cell membrane
- amphiphilic lipid bilayer - 5mm thick
- membrane proteins - 30% of genome
what does amphiphilic mean
molecule which has a hydrophobic and hydrophilic end
what ways to lipids move
- lateral diffusion - left to right
- flip-flop - membrane flips
- flexion - tails move
- rotation - spinning
what are the properties determining membrane fluidity
- melting temperature - length of fatty acid chain and saturation
- cholesterol - disrupts fatty acid interactions stabilising membrane fluidity
- proteins in the membrane
- cytoskeleton structure
what makes a membrane more rigid
- saturated fatty acid
- long chains
how do proteins move in the bilayer
- lateral diffusion
- rotate in the bilayer
- no flip flop motion - as proteins are asymmetric
- movement can be restricted by polarised cells
what causes HS cytoskeleton cell shape
- hereditary spherocytosis
- molecular defects ankyrin alpha/beta band 3 protein 4.2
- membrane loss
what causes HE and HPP cytoskeleton cell shapes
- hereditary elliptocytosis and hereditary pyropoikilocytosis
- alpha/beta spectrin - protein 4.1 glycophorin C defect
- membrane instability
what causes SAO cytoskeleton cell shape
- southeast asian ovalocytosis
- band 3 defect
- increase membrane rigidity
what happens when there is a loss of membrane integrity
- selective permeability disrupted
- cell death/ malfunction
what is passive transport/ facilitated diffusion
- down a concentration gradient
- via transporter or channel
what is the difference between charged and uncharged molecules via passive transport
uncharged - concentration gradient drives transport
charged - concentration gradient and electrode potential difference drives transport
what are the three times of gated ion channels
- voltage gated
- ligand gated
- mechanical gated
how do voltage gated ion channels work
responds to direct changes in the membrane potential
how to ligand gated ion channels work
respond to a specific chemical stimulus
how do mechanically gated ion channels work
respond to mechanical movement/ vibration
how does ATP stimulate insulin release
1) glucokinase responds to glucose in glycolysis
2) ATP produced in the mitochondria
3) ATP-sensitive potassium channels close
4) change across the membrane potential
5) calcium gated open
6) insulin vesicles fuse with membrane
7) insulin released into blood
what is active transport
- requires metabolic energy
- can generate a concentration gradient
what is primary active transport
- used ATP as energy
- ions transported across the membrane
eg. sodium potassium pump
what is secondary active transport
- concentration gradient of the driving ions used
- ions serve as driving molecules for other molecules to be driven across
eg. NA+/CA2+
what are the three types of primary active transport
- p-type pump - ion transporters
- F and V type pumps - generate ATP
- ABC transporters
what are symporters
- cotransporters
- molecules move in the same direction
what are antiporters
- exchangers
- molecules move in opposite directions
what are ion pumps
- used to stabilise osmolarity
- high cellular concentration of macromolecules, small organic molecules and ions
how does glucose transport work
- [NA+] gradient drives glucose transport into the epithelium
- [glucose] gradient drives export to the extrascapular fluid
