Biochem: cellular Flashcards
Where do Rb and p53 regulate the cell cycle?
G1/S phase checkpoint
therefore, mutations lead to unrestrained cell division
What cell types are permanent? What does permanent mean?
remain in G0, regenerate from stem cells
neurones, skeletal and cardiac muscle, RBCs
What cell types are stable? What does stable mean?
hepatocytes, lymphocytes
enter G1 from G0 when stimulated
What cell types are labile? What does labile mean?
never go to G0, divide rapidly with a short G1
bone marrow, gut epithelium, skin, hair follicles, germ cells
What takes place in the RER?
synthesis of secretroy proteins
N-linked oligosaccharide addition to many proteins
What does the SER do?
synthesize steroids
detoxify drugs and poisons
(prominant in hepatocytes and steroid hormone producing cells of the adrenal cortex)
What does golgi apparatus do?
distribution center for proteins and lipids from the ER to the vesicles and plasma membrain
modified N oligosaccharides on asparagine
adds O oligosaccharides on serine nad threonine
adds mannose 6 phosphate to proeteins for trafficking to lysosomes
glycosylates core proteins to form proglycans
adds sulfate groups to sugar and tyrosine
What is I cell disease caused by?
failure of addition of mannose 6 phosphate to lysosome proteins (enzymes sent to outside of cell instead of lysosome)
What are the sx of I cell disease?
coarse facial features, clouded corneas, restricted joint movement, high plasma level of lysosomal enzymes
often fatal in childhood
Which protein traffics from golgi to golgi (retro) or golgi to ER?
COPI
Which protein traffics from golgi to golgi (antero) or ER to golgi?
COPII
What does clathrin do?
traffics from trans golgi to lysosomes or from plasma membrane to endosomes
What do peroxisomes do?
catabolize very long fatty acids and amino acids
What are the 3 methods of proteolysis?
- lysosomal degradation
- proteasomal degradation
- Ca 2+ dependent enzymes
What does the proteasome do?
degrade damaged or unnecessary proteins tagged for destruction with ubiquitin
What does dynein do?
retrograde microtubule transport (+ —> - )
Waht does kinesin do?
anterograde microtubule transport ( - —> + )
What drugs act on microtubules?
mebendazole/thiabendazole griseofulvin vincristine/vinblastine paclitaxel colchicine
What casues chediak higashi syndrome?
mutation in lysosomal trafficking regulator gene LYST, whose product is required for microtubule dependent sorting of endosomal proteins into late multivesicular endosomes
What are the sx of Chediak higashi syndrome?
recurrent pyogenic infections, partial albinism, peripheral neuropathy
(lysosomes of phagocytes are neffective and there is abnormal storage of melanin)
Where is a 9 + 2 arrangement of microtubules found?
cilia
What coordinates cilia movement?
gap junctions between cells
What causes Kartagener’s syndrome? Sx?
immotile cilia due to a dynein arm defect
infertility (M & F) , bronchiectasis, recurrent sinusitis, assoc w/situs inversus
What cell type is vimentin found in? what type of ccancer does it denote?
connective tissue
sarcoma
What cell type is desmin found in? What type of cancer does it denote?
desmin
myosarcoma
What cell type is cytokeratin found in? What type of cancer does it denote?
epithelial cells
carcinoma
What cell type is GFAP found in? What type of cancer does it denote?
neuroglia
astrocytomas/glioblastoma
What cell type is neurofilaments found in? What type of cancer does it denote?
neurons
neuroblastoma, etc
any primitive neuroectoderm tumor
What drugs inhibit the sodium potassium pump?
digoxin & ouabain
Where is type I collagen found?
bone, skin, tendon, late wound repair
When is defective type I collagen found?
in osteogenesis imperfecta
Where is type II collagen found?
cartilage, vitreous body, nucleus pulposis
Wher is type III collagen found?
reticulin-skin, blood vessels, uterus, fetal tissue, granulation tissue
When is defectivetype III collagen found?
Ehlers-Danlos
Where is type IV collagen found?
Basement membrane/basal lamina
When is defective type IV collagen found?
Alport s/o
What steps of collagen synthesis occur inside the fibroblast?
synthesis (RER)
hydroxylation (ER)
Glycosylation (ER) {osteogenesis imperfecta (problems forming triple helix)}
Exocytosis
What steps of collagen synthesis occur outside the fibroblast?
Proteolytic processing (cleavae of terminal regions of procollagen [procollagen ---> tropocollagen])
Cross Linking to make collagen fibrils {ehlers danlos}How is osteogenesis imperfecta inherited?
AD (most common)
AR (OI II, perinathal lethal type)
What are sx of OI?
blue sclera
mutliple fractures
hearing loss
dental imperfections (lack of dentin)
What are the sx of Ehlers danlos?
2 types
1. hyperextensible skin, hypermobile joints
2. tendency to bleed (vascular ED)
may be associaed with join dislocation, berry aneurysms and organ rupture
What causes a keloid?
too much collagen in the scar, inject with glucocorticoid to try and help
What are the sx of alport s/o? Inheritance?
XR
progressive hereditary nephritis and deafness
may get occular disturbances
“can’t see, can’t ee, can’t hear high C”
What breaks down elastin? What inhibits elastin breakdown?
elastase
a1 antitrypsin
Where is elastin commonly found?
skin, lungs, large arteries, ligaments, vocal cords, ligamenta flava
What AAs is elastin rich in?
proline & glycine (non hydroxylated)
What serves as scaffolding for elastin? When is it defective?
fibrillin
Marfan’s
When a patient has panacinar emphysema, young onset, with liver disease, what is likely deficient?
a1 Antitrypsin
What causes wrinkles?
reduced collagen and elastin production
