53 terms

First aid biochem cellular

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Cell cycle phases
m phase (shortest phase of cell cycle) includes mitosis (prophase, prometaphase, metaphase, anaphase, telophase) and cytokinesis

g1 and g0 are of variable duration
cyclin dependent kinases
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 activated and inactivated at appropriate times for cell cycle to progress
tumor suppressors
p53 induces p21, which inhibits CDKs
leads to hypophosphorylation of Rb

leads to inhibition of g1-s progression

mutations in tumor suppressor genes can result in unrestrained cell division
permanent cells
remain in g0 and regenerate from stem cells

include neurons, skeletal and cardiac muscle, RBCs
stable cells
AKA quiescent cells

enter G1 from G0 when stimulated

hepatocytes and lymphocytes
labile cells
never go to g0, divide rapidly with a short g1
most affected by chemotherapy

bone marrow, gut epithelium, skin, hair follicles, germ cells
rough ER
site of synthesis of secretory (exported) proteins and of n linked oligosaccharide addition to many proteins
Nissle bodies
RER in neurons
synthesize peptide neurotransmitters for secretion
free ribosomes
unattached to any membrane
site of synthesis of cytosolic and organellar proteins
smooth er
site of steroid synthesis and detoxification of drugs and poisons

lack surface ribosomes
cells rich in SER
liver hepatocytes and steroid hormone-producing cells of the adrenal cortex and gonads
Golgi
distribution center for proteins and lipids from the ER to the vesicles and plasma membrane

modifies N oligosaccharides on asparagine

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 tot he membrane/Golgi for further use
coarse facial features
clouded corneas
restricted joint movement
high plasma levels of lysosomal enzymes

often fatal in childhood
I cell disease (inclusion cell disease/mucolipidosis type II)

inherited lysosomal storage disorder

defect in N-acetylglucosaminyl-1-phosphotransferase

failure of the Golgi to phosphorylate mannose residues on glycoproteins

proteins are secreted extracellularly rather than delivered to lysosomes
Signal recognition particle (SRP)
abundant cytosolic ribonucleoprotein that traffics proteins from the ribosome to the RER

absent or dysfunctional SRP leads to proteins accumulating in the cytosol
COPI
trafficking protein from Golgi to Golgi (retrograde)

and cis-Golgi back to ER
COP II
ER to cis Golgi (anterograde)
clathrin
trans Golgi to lysosomes
plasma membrane to endosomes (receptor mediated endocytosis) - LDL receptor activity
peroxisome
membrane enclosed organelle
catabolism of very long chain fatty acids, branched chain fatty acids, amino acids, and ethanol
peroxisomal diseases
Zellweger syndrome:
hypotonia, seizures, hepatomegaly, early death

refsum disease
scaly skin, ataxia, cataracts/night blindness, shortening of 4th toe, epiphyseal dysplasia
proteosome
barrel shaped protein complex that degrades damage or ubiquitin tagged proteins

defects implicated in parkinson
microfilaments
muscle contraction and cytokinesis

actin, microvilli
intermediate filaments
maintain cell structure

vimentin, desmin, cytokeratin, lamins, glial fibrillary acid proteins, neurofilaments
microtubules
movement, cell division

cilia, flagella, mitotic spindle, axonal trafficking, centrioles
stains for intermediate filaments

vimentin
mesenchymal tissue - fibroblasts, endothelial cells, macrophages

identifies mesenchymal tumors like sarcomas, but also other tumors like endometrial carcinoma, RCC, meningioma
intermediate filament stains

desmin
muscle

identifies muscle tumors - rhabdomyosarcoma
intermediate filament stains

cytokeratin
epithelial cells

identifies epithelial tumors like squamous cell carcinoma
intermediate filament stains

GFAP
neuroglia - astrocytes, schwann cells, oligodendrocytes

identifies astrocytoma, glioblastoma
intermediate filament stains

neurofilaments
neurons

identifies neuronal tumors like neuroblastoma
microtubule structure
cylindrical outer structure composed of a helical array of polymerized heterodimers of alpha and beta tubulin

each dimer has 2 gtp bound
incorporated into flagella, cilia, mitotic spindles

grows slowly, collapses quickly

also involved in slow axoplasmic transport in neurons
molecular motor proteins
transport cellular cargo toward opposite ends of microtubule

dynein - retrograde to microtubule (+ to -) (negative near nucleus)

kinesin - anterograde to microtubule (- to +) (positive points to periphery)
Cilia structure
9 doublet + 2 singlet arrangement of microtubules

basal body consists of 9 microtubule triplets with no central microtubules
axonemal dynein
ATPase that links peripheral 9 doublets and causes bending of cilium by differential sliding of doublets
bronchiectasis, recurrent sinusitis, chronic ear infections, conductive hearing loss, situs inversus (dextrocardia on CXR)
kartagener syndrome (primary ciliary dyskinesia)

immotile cilia due to a dynein arm defect

results in decreased male and female fertility due to immotile sperm and dysfunction fallopian tube cilia

increased risk of ectopic pregnancyu
Na K ATPase
located in plasma membrane with ATP site on cytosolic side

for each ATP consumed, 2 NA go out of the cell and 2K come into the cell

(PUMPKIN - pump k in)
Ouabain
Na K ATPase pump by binding ot K site
Cardiac glycosides (digoxin and digitoxin)
directly inhibit the Na K ATPase which leads to indirect inhibition of the Na/Ca exchange > increase Ca > increase cardiac contractility
collagen
most abundant protein in the human body

extensively modified by posttranslational modifications

organizes and strengthens extracellular matrix
collagen
Type I
most common (90%)

Bone, Skin, Tendon, dentin, fascia, cornea, late wound repair

decreased production in osteogenesis imperfecta type I
collagen
Type II
Cartilage (including hyaline), vitreous body, nucleus pulposus
collagen
Type III
Reticulin - skin, blood vessels, uterus, fetal tissue, granulation tissue
Type III collagen deficiency
ehlers danlos syndrome vascular type
Type IV Collagen
basement membrane, basal lamina, lens
Type IV collagen deficiency
alport syndrome

targeted by autoantibodies in goodpasture syndrome
Collagen synthesis
synthesis - translation of collagen alpha changes (gly-x-y) (x and y are proline or lysine)

hydroxylation - hydroxylation of specific proline and lysine residues

glycosylation - glycosylation of pro alpha chain hydroxylysine residues and formation of procollagen via hydrogen and disulfide bonds

exocytosis - exocytosis of precollagen into extracellular space

proteolytic processing - cleavage of disulfide-rich terminal regions of procollagen > insoluble tropocollagen

cross-linking - reinforcement of many staggered tropocollagen molecules by covalent lysine-hydroxylysine cross linkage by copper containing lysyl oxidase
multiple fractures with minimal trauma - may occur in birth process

blue sclerae
tooth abnormalities
hearing loss
osteogenesis imperfecta

genetic bone disorder (brittle bone disease) caused by gene defects (COLIA1 and COLIA2)

most commonly autosomal dominant

blue sclera is due to translucent connective tissue over choroidal veins

tooth abnormalities are opalescent teeth that wear easily due to lack of dentin

hearing loss due to abnormal ossicles
Hyperextensible skin, tendency to bleed (easy bruising), and hypermobile joints

maybe joint dislocation, berry and aortic aneurysms, organ rupture
ehlers-danlos

faulty collagen synthesis

inheritance and severity vary
can be autosomal dominant or recessive
brittle kinky hair, growth retardation, hypotonia
menkes disease

x linked recessive

impaired copper absorption and transport due to defective menkes protein (ATP7A)

leads to decreased activity of lysyl oxidase (copper is a necessary cofactor)
elastin
stretch protein within skin, lungs, large arteries, elastic ligaments, vocal cords, ligament flava

rich in nonhydroxylated proline, glycine, lysin eresidues
alpha 1 antitrypsin deficiency
results in excess elastase activity and can cause emphysema
tall with long extremities
pectus carinatum or excavatum
hypermobile joints
long, tapering fingers and toes
cystic medial necrosis of aorta
aortic incompetence
dissecting aortic aneurysms
floppy mitral valve
subluxation of lenses, typically upward and temporally
marfan syndrome

autosomal dominant connective tissue disorder affecting skeleton, heart, and eyes

FBN1 gene mutation on chr 15 results in defective fibrillin, a glycoprotein that forms a sheath around elastin