cell biology: plasma membrane

Question 1

contents of plasma membrane

Answer 1

phospholipids (very abundant)
sphingolipids (sphingomyelin)
glycolipids
glycoproteins
proteins (very abundant, transport proteins, tyrosine kinase receptor, G-protein linked receptor)
cholesterol (↑rigidity, ↑ melting temp)
ergosterol (if fungal membrane)

Question 2

what are these:
phosphatidylCHOLINE
phosphatidylSERINE
phosphatidylINOSITOL (precursor of arachidonic acid)

Answer 2

phospholipids

Question 3

location of following receptor types:
tyrosine kinase receptor
G-protein coupled receptor
steroid receptor

Answer 3

plasma membrane:
tyrosine kinase receptor (transmembrane)
G-protein coupled receptor (transmembrane)
cytoplasm:
steroid receptor: estrogen/testosterone enter cell

Question 4

these are examples of what receptor type?
insulin receptor, IGF-1 R (2ß subunits have TK activity, 2α subunits bind extracellular ligand, bound by disulfide bonds= STRONG)
PDGF-R, GF R (SINGLE-pass transmembrane receptor)

Answer 4

tyrosine kinase receptor

Question 5

mechanism of tyrosine kinase receptor

Answer 5

bind extracellular ligand → induces conformation change → induces autophosphorylation of tyrosine kinase (first step in signaling cascade) → can transfer phosphate form ATP to tyrosine side chains too

Question 6

mechanism of Na-K ATPase

Answer 6

For each ATP consumed (on cytosol side) →3 Na+ OUT, 2 K+ IN
K+ inside cell maintains resting potential at -55 mV (need for neurotransmission, muscle contraction)
Na+ will slowly go down its natural gradient (out→in) → releases energy which drives molecules AGAINST their concentration gradient

Question 7

drugs that inhibit Na-K ATPase →↑ Na+ in → heart beats harder

Answer 7

digoxin

digitoxin

Question 8

drug that inhibits Na-K ATPase by binding to K+ site

Answer 8

ouabain

Question 9

enzyme adds phosphate group to substrate using ATP

Answer 9

kinase

Question 10

enzyme adds inorganic phosphate to substrate WITHOUT ATP

Answer 10

phosphorylase

Question 11

enzyme removes phosphate from substrate

Answer 11

phosphatase

Question 12

enzyme oxidizes substrate using electron acceptor

Answer 12

dehydrogenase

Question 13

enzyme transfers carbon group with help of biotin (co-factor)

Answer 13

carboxylase

Question 14

enzyme adds hydroxyl group to substrate

Answer 14

hydroxylase

Question 15

enzyme relocates a functional group in a molecule

Answer 15

mutase

Question 16

inherited disorder which causes mutated LDL receptor which can’t bind adaptin + clathrin for receptor mediated endocytosis (no cholesterol stored in cells)

Answer 16

familial hypercholesterolemia

↑ risk MI