biochem: cellular Flashcards
CDKs
constitutive and inactive
cyclins
regulatory proteins that control cell cycle events; phase specific; activate CDKs
cyclin-CDK complexes
phosphorylate other proteins to coordinate cell cycle progression; must be activvated and inactivated at appropriate times for cell cycle to progress
tumor suppressors
p53 and hypophosphorylated Rb normally inhibit G1-to-S progression; mutations in these genes result in unrestrained cell division (e.g. li-fraumeni syndrome)
phases of cell cycle
G0G1->S->G2->M->G1
permanent cells
remain in G0, regenerate from stem cells. e.g. neuron,s skeletal and cardiac muscle, RBCs
stable (quiescent) cells
enter G1 from G0 when stimulated. e.g. hepatocytes, lymphocytes
labile cells
never go to G0, divide rapidly with a short G1. most affected by chemotherapy. e.g. bone marrow, gut epithelium, skin, hair follicles, germ cells
rough ER
site of synthesis of secretory (exported) proteins and of N-linked oligosaccharide additions to proteins.
Nissl bodies
= RER in neurons. synthesize peptide neurotransmitters for secretion
free ribosomes
= unattached to any membrane; site of synthesis of cytosolic and organellar proteins
goblet cells and plasma cells are rich in:
RER. they’re secreting mucus/antibodies! so lots of export
smooth ER
site of steroid synthesis and detoxification of drugs and poisons. lacks surface ribosomes
hepatocytes, adrenal cortex, and gonads are rich in:
SER! they have to detoxify stuff/make steroids
golgi
= distribution center for proteins and lipids from ER to vesicles and plasma membrane. also modifies N-oligosaccharides on arparagine and adds O-oligosaccharides on serine and threonine. Adds mannose-6-phosphate to proteins for trafficking to lysosomes
endosomes
= sorting centers for material from outside the cell or from the golgi, sending it to lysosomes for destruction or back to the membrane/golgi for further use
I-cell dz
= inherited lysosomal storage disorder. defect in N-acetylglucosaminyl-1-phosphotransferase -> failure of the golgi to phosphorylate mannose residues, so proteins are secreted extracellularly rather than delivered to lysosomes. -> coarse facial features, clouded corneas, restricted joint movement, and high plasma levels of lysosomal enzymes. often fatal in childhood.
signal recognition particle (SRP)
abundant, cytosolic ribonucleoprotein that traffics proteins from the ribosome to the RER. absent or dysfunctional SRP -> protein accumulation in cytosol
vesicular trafficking proteins
COPI: golgi->cis-golgi -> ER, retrograde. COPII: ER -> cis-golgi, anterograde. clathrin: trans-golgi -> lysosomes; plasma membraine -> endosomes (receptor-mediated endocytosis)
peroxisome
membrane-enclosed organelle involved in catabolism of very-long-chain fatty acids, branched-chain fatty acids, and AAs
proteasome
barrel-shaped protein complex that degrades damaged or ubiquitin-tagged proteins. defects in the ubiquitin-proteasome system have been implicated in some cases of PD
microfilaments
usually fxn for muscle contraction, cytokinesis. e.g. actin
intermediate filaments
maintain cell structure. e.g. vimentin, desmin, cytokeratin, lamins, GFAP, neurofilaments
microtubules
usually fxn for movement, cell division. e.g. cilia, flagella, mitotic spindle, axonal trafficking, centrioles. made of alpha and beta tubulin dimers. grows slowly, collapses quickly.
drugs that act on microtubules
Microtubules Get Constructed Very Poorly: mebendazole (antihelminthic), Griseofulvin (antifungal), colchicine (antigout), vincristine/vinblastine (anticancer), paclitaxel (anticancer)
molecular motor proteins
transport cellular cargo toward opposite ends of microtubule tracks. dynein = retrograde (+ -> -), kinesin = anterograde (- -> +)
kartagener syndrome
= primary ciliary dyskinesia. immotile cilia due to dynein arm defect. causes infertility, bronchiectasis, recurrent sinusitis, and situs inversus
ouabain
inhibits Na-K-ATPase by binding to K site
cardiac glycosides
= digoxin. directly inhibit Na-K-ATPase, indirectly inhibiting Na/Ca exchange -> increased [Ca] -> inc. cardiac contractility
collagen type mnemonic
Be (So Totally) Cool, Read Books: I: bone, skin, tendon; II: cartwolage; III: reticulin (in skin, blood vessels, uterus, fetal tissue, granulation tissue); IV: basement membrane, basal lamina (type IV, under the floor)
type I collagen defect
OI type I. problem forming triple helix during glycosylation step
type IV collagen defect
alport syndrome, targeted by Abs in goodpasture syndrome
steps of collagen synthesis
inside fibroblasts: 1. synthesis (RER). 2. hydroxylation (RER). 3. glycosylation (RER). 4. exosytosis. outside fibroblasts: 5. proteolytic processing. 6. cross-linking
scurvy
caused by vit. C deficiency: hydroxylation of collagen requires it
ehlers-danlos syndrome
faulty collagen, classically type V but can be type III in vascular type. causes hyperextensible skin, easy bruising, and hypermobile joints. variable genetics
menke’s dz
x-linked recessive dz caused by impaired copper absorption and transport -> dec. activity of lysyl oxidase (part of collagen/elastin synthesis) (Cu = cofactor), -> brittle kinky hair, growth retardation, and hypotonia
marfan syndrome
caused by defect in fibrillin = glycoprotein that forms a sheath around elastin
alpha-1-antitrypsin
inhibits elastase. deficiency can cause emphysema because elastase breaks down elastin in the lungs.
