Biochemistry: Cellular Flashcards
What are the phases of cell growth?
G0 phase = arrest phase
G1 phase = growth/proliferation phase
- this is where tumor suppressor genes help checkpoint cells and prevent cancer normally
S phase = DNA synthesis phase
G2 phase = preparation for mitosis
M phase = mitosis occurs
- “IPPMAT”
- interphase
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
Cytokinesis phase
What cells have the most Rough endoplasmic reticulum?
Mucus secreting goblet cells
What cells have the most Smooth endoplasmic reticulum
Hepatocytes and adrenal cortex cells
I-cell disease
A, autosomal recessive, mucolipidosis type 2 disorder
Causes failure of the golgi to phosphorylate mannose residues on glycoproteins, which causes dysfunctional proteins to be secreted extracellular instead of sent to lysosomes for breakdown.
Symptoms:
- course facial features
- gingival hyperplasia
- cataracts
- restricted joint movements and ROM
- claw hand
- increased kyphosis and scoliosis
is often fatal in adolescence years
What are signal recognition particles (SRPs)?
Cytosolic ribonucleoproteins that aid in trafficking polypeptide complexes from cytosol to the RER to be packaged out.
If absent = accumulation of proteins in the cytosol
What are the types of vesicular trafficking proteins?
COP1: Golgi -> ER (retrograde delivery)
COP2: ER -> golgi (anterograde delivery)
“ two steps forward, one step back”
What is clathrin?
A vesicular trafficking protein that marks defective proteins in golgi -> lysosomes
Zellweger syndrome
Autosomal recessive disorder that disables peroxisome biogenesis via mutated PEX genes
- normal function, just little numbers
Symptoms:
- chronic seizures
- hepatomegaly
- early death
Refsum disease
Autosomal recessive disorder which prevents a-oxidation in peroxisomes.
- there is a normal number of them, just disabled function
- causes build up of pristanic acid
Symptoms:
- scaly skin
- ataxia
- cataracts
- shortening of 4th toe
Treatment:
- plasmapheresis
Adrenoleukodystrophy
X-linked recessive disorder which prevents B-oxidation of peroxisomes due to mutations in the ABCD1 gene
- normal numbers, just dysfunctional
- causes build up of VLCFA in adrenal glands, white matter and testes
What os the function of proteasomes?
Protein complexes that degrade damaged or ubiquinated proteins
there are some linked to dysfunctional proteasomes and Parkinson’s disease
Types of cellular filaments
Microfilaments:
- includes actin and microvilli
- function is to aid in muscle contraction and cytokinesis during anaphase
Intermediate filaments
- includes desmin, lamina, glial cells, I mention and GFAP proteins
- function is to maintain cell structure
Microtubules
- includes cillia, flagella, mitotic spindles and centrioles
- function is cell division and movement
Microtubules and molecular motor proteins
Microtubules
- composed of a/b- tubulin w/ 2 GTP bound per dimer.
- also aid in slow axoplasmic transport of materials in neurons
Molecular motor proteins
- used as carrier proteins to transport cellular cargo toward ends of microtubules
- includes dynein and kinesin proteins
Dynein vs kinesin functions
Dynein = retrograde transport to microtubule (moves (+) charge -> (-) charge)
Kinesin = anterograde transport to microtubule (moves (-) charge -> (+) charge)
- positive end is towards the periphery, negative end is towards the nucleus*
“REaDY to AttacK”
What are some examples of microorganisms that use dynein to infect neuronal cell bodies?
Clostridium tetani
Herpes
Poliovirus
Rabies virus
What are common medications that affect microtubule production?
Mebendazole (antihelminthic)
Griseofluvin (antifungal)
Colchicine (antigout)
Vincristine/blastine (anticancer)
Paclitaxel (anticancer)
Kartagener syndrome
Primary ciliary dyskinesia
Autosomal recessive disorder which causes Immobile cilia due to defective dynein production
- diagnosed via testing for nasal nitric oxide levels (will be low)
Symptoms:
- increased sterility
- increased chance of ectopic pregnancy
- (+/-) bronchiectasis
- (+/-) recurrent sinusitis
- (+/-) chronic ear infections
- conductive hearing loss
- sinus inversus
- no cure*
What cardiac glycosides directly inhibit NA/K pumps?
Ouabain
- binds directly to the K site
Digoxin/digitoxin
- binds to the ATPase protein directly
- also used in heart fill auer since by blocking NA/K pump, indirectly blocks Na/Ca pump and keeps Calcium levels high in cardiac tissue = increased contractility
For every 1 ATP used in NA/K pump, how many molecules of NA and K are moved?
3 and 2 respectively
Types of collagen
Type 1:
- most common type
- found in bone, skin, tendons, fascia, cornea
- seen in late wound repairs
- defects in type 1 collagen = osteogenesis imperfecta type 1
Type 2:
- found in cartilage, vitreous body and nucleus purposes of spinal cord
Type 3:
- found in skin, blood vessels, uterus, fetal tissue
- is seen in early wound repair
- defects in type 3 = vascular Ehlers-Danlos syndrome
Type 4:
- least common
- found in basement membrane and lens
- defect is secondary to Alport and goodpasture syndromes
What is the most common AA found in all collagen types?
Glycine
Steps of collagen synthesis
1) synthesis
- translation of collagen a-chains - > glycine-X-Y peptides
( X-Y = combination of proline or lysine residues)
2) Hydroxylation
- hydroxylation of proline and lysine residues
- * requires vitamin C, hence scurvy limits this step
3) glycosylation
- glycosylation of hydroxylysine residues and forms procollagen via hydrogen and disulfide bonds.
- forms triple helix structure
- * osteogenesis imperfecta limits this step
4) Exocytosis
- exocytosis of procollagen into extracellular spaces
5) proteolytic processing
- cleavage of disulfide -rich terminals of procollagen -> tropocollagen
- this occurs in extracellular matrix
6) cross-linking
- covalent founding of lysine- hydroxylysine residues in staggered tropocollagen molecules
- forms mature collagen fibrils
- *uses the copper enzyme Lysyl oxidase to do this step (menkes disease affects this enzyme)
Osteogenesis imperfecta
Autosomal dominant (most common form type 1) disorder that causes mutated COLIA1/2 genes and ends up producing defective type 1 collagen - produces defective type 1 collagen due to inability to properly form triple helix structure in glycosylation
Symptoms: “patients cant BITE”
Bones: multiple fractures
Iye: blue sclera
Teeth: dental imperfections due to dentin loss
Ear: conductive hearing loss due to middle ear bone osteoporosis
- often is mistaken for child abuse
Treatment: Not curable
- calcium and bisphosphonates
Ehlers Danlos syndrome
Autosomal dominant or recessive (recessive is worse) disorder that causes faulty type 3 collagen production (reticulin)
Symptoms:
- hyperextendable skin (2)
- hypermobile joints (1/2)
- in ability to clot properly (3)
- increased risk of berry and aortic aneurysms (3)
- increased risk of joint dislocations (1/2)
- increased chances of muscle and tendon ruptures (3)
Types:
1) hypermobility: most common type and shows joint instability as the most prominent feature
2) classical type: defective type 5 collagen due to gene mutations in COL5A1/2
3) vascular type: most deadly. Defective type 3 collagen due to gene mutations on COL3A1.
Menkes disease
X-linked recessive disorder that produces impaired copper absorption and transport due to mutations in ATP7A gene
- low copper levels decrease Lysyl oxidase activity and prevent maturation fo collagen fibrils
Symptoms:
- brittle “kinky” hair
- growth retardation
- hypotonia of muscles
- increased risk of cerebral aneurysms
Elastin
Subtype of collagen found in skin/lungs/arteries/vocal cords/ligamenta flava
Rich in nonhydroxylated proline, glycine and lysine residues
- normal collagen is hydroxylated
Is broken down by elastase enzymes
- this is countered by a-antitrypsin proteins until needed
- a-antitrypsin deficency syndrome affects this and can cause COPD
Marfan syndrome
Autosomal dominant disorder that poor dudes a gene mutation in FBN1 on chromosome 15.
- results in defective fibrilin (glycoprotein that shealths elastin molecules and keeps them from overstretching)
Symptoms:
- tall with really long extremities
- pectus carinatum (can be excavatum also but usually isnt)
- hypermobile joints
- arachnodactyly (really long fingers and toes)
- *increased chances of aortic aneurysms/ruptures (leading cause of death)
- increases chances of MVP and subluxation of lenses.
