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First Aid: Biochemistry > Principles: Cellular > Flashcards

Principles: Cellular Flashcards

1
Q

What tumor suppressors regulate G1 to S progression?

A

p53 and hypophosphorylated Rb

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2
Q

How does the synthesis and activity of cyclins and CDKs differ?

A

Cyclins are constitutively around and active.

Cyclins are phase-specific and control cell cycle events by activating CDKs.

Cyclin-CDK complexes must be both activated and inactivated for cell cycle to progress.

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3
Q

What are permanent cell types, and how is their cell cycle phase characterized?

A

Remain in G0, can only regenerate from stem cells.

Neurons, skeletal and cardiac muscle, RBCs.

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4
Q

What are stable cell types, and how is their cell cycle phase characterized?

A

Capable of entering G1 from G0 when stimulated.

Hepatocytes, lymphocytes.

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5
Q

What are labile cell types, and how is their cell cycle phase characterized?

A

Never go to G0, divide rapidly with a short G1.

Most affected by chemotherapy.

Bone marrow, gut epithelium, skin, hair follicles, germ cells.

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6
Q

What is rough endoplasmic reticulum responsible for?

A

Synthesis of secreted (exported) proteins and N-linked oligosaccharide addition to many proteins.

Mucus-secreting goblet cells of small intestine and plasma cells rich in RER.

Nissl bodies (RER in neurons) synthesize peptide neurotransmitters for secretion.

Free ribosomes - unattached to any membrane; site of synthesis of cytosolic and organellar proteins.

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7
Q

What is smooth endoplasmic reticulum responsible for?

A

Site of steroid synthesis and detoxification of drugs and proteins.

Lacks surface ribosomes.

Liver hepatocytes and steroid hormone-producing cells of the adrenal cortex and gonads are rich in SER.

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8
Q

What is the function of the golgi?

A

Distribution of proteins and lipids from ER to vesicles and plasma membrane.

Modofies N-oligosaccharides on asparagine

Adds O-oligosaccharides on serine and threonine.

Adds mannose-6-phosphate to proteins for trafficking to lysosomes.

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9
Q

What is I-cell disease?

A

AKA Inclusion cell disease.

Delivery from golgi to lysosomes is disrupted by defect in phosphotransferase. Proteins secreted instead, less mannose-6-phosphate.

Clinical features: Coarse facial features, clouded corneas, restricted joint movement, high plasma levels of lysosomal enzymes.

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10
Q

What is a signal recognition particle (SRP)?

A

Abundant cytosolic ribonucleoprotein that traffics proteins from ribosome to RER.

If absent or deficient, proteins accumulate in cytosol.

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11
Q

What kind of transport is COPI involved in?

A

Golgi -> Golgi (retrograde);

Golgi -> ER

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12
Q

What kind of transport is COPII involved in?

A

Golgi -> Golgi (anterograde

ER -> Golgi

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13
Q

What kind of transport is Clathrin involved in?

A

Trans golgi -> lysosomes;

Plasma membrane -> Endosomes (receptor mediated endocytosis, e.g., LDL receptor activity)

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14
Q

What is the function of peroxisomes?

A

Membrane-enclosed organelle involved in catabolism of very-long-chain fatty acids, brancehd-chain fatty acids, and amino acids.

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15
Q

What is the function of proteasomes?

A

Barrel-shaped protein complex that degrades damaged or ubiquitin-tagged proteins.

Defects in ubiquitin-proteasome system implicated in parkinsons.

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16
Q

What is the structure of microtubules?

A

Helical array of polymerized heterodimers of α and β-tubulin. Each dimer has 2GTP bound. Used in flagella, cilia, mitotic spindles. Grows slowly, collapses quickly.

Involved in slow axonal transport.

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17
Q

What are the microtubule molecular motors?

A

Dynein = retrograde to microtubule (+ -> - end)

Kinesin = anterograde to microtubule (- -> + end)

The polymer builds from negative end to positive end (the + end is growing).

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18
Q

What are some drugs that act on microtubules?

A

Microtubules Get Constructed Very Poorly

Mebendazole (anti-helminthic)

Griseofulvin (anti-fungal)

Colchicine (anti-gout)

Vincristine/Vinblastine (anti-cancer)

Paclitaxel (anti-cancer)

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19
Q

What is the structure of cilia?

A

9+2 arrangement of microtubules.

Axonemal dynein - ATPase that links peripheral 9 doublets and causes bending of cilium by differential sliding of doublets.

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20
Q

What is Kartagener syndrome?

A

AKA primary ciliary dyskinesia.

Immotile cilia due to a dynein arm defect. Results in male and female infertility (immotile sperm, fallopian tube cilia dysfunctional).

Increased risk of ectopic pregnancy.

Can cause bronchiectasis, recurrent sinusitis, and sinus inversus (dextrocardia on CXR).

21
Q

What structures have actin and myosin incorporation?

A

Muscle contraction, microvilli, cytokinesis, adherens junctions.

Actins = long, structural polymers

Myosins: Dimeric, ATP-driven motor proteins that move along actins

22
Q

What structures have microtubule incorporation?

A

Movement. Cilia, flagella, mitotic spindle, axonal trafficking, centrioles.

23
Q

What structures have intermediate filament incorporation?

A

Structural protein.

Vimentin, desmin, cytokeratin, lamins, glial fibrillary acid proteins (GFAP), neurofilaments.

24
Q

What are some components of the plasma membrane?

A

Asymmetric lipid bilayer.

Cholesterol, phospholipids, sphingolipid, glycolipids, proteins.

25
Q

What is a unique structural component of fungal membranes?

A

Ergosterol

26
Q

An immunohistochemical stain for vimentin suggests what type of cell?

A

Connective tissue

27
Q

An immunohistochemical stain for desmin suggests what type of cell?

A

DesMin = Muscle

28
Q

An immunohistochemical stain for cytokeratin suggests what type of cell?

A

Epithelial cells

29
Q

An immunohistochemical stain for GFAP suggests what type of cell?

A

GFAP = NeuroGlia

30
Q

An immunohistochemical stain for neurofilaments suggests what type of cell?

A

Neurons

31
Q

What is the precise ion exchange performed by the Na+/K+ ATPase?

A

For each ATP consumed

3 Na+ out

2 K+ in

32
Q

What drugs inhibit the Na+/K+ ATPase?

A

Ouabain: Inhibits by binding to K+ site.

Cardiag glycosides (digoxin and digitoxin) directly inhibit the Na+/K+ ATPase, which leads to direct inhibition of Na+/Ca2+ exchange, which increases intracellular calcium and cardiac contractility.

33
Q

What is the acronym for remembering what types of collagen compose different tissues?

A

Be (So Totally) Cool, Read Books

Type I Collagen: Bone, Skin, Tendon

Type II Collagen: Cartilage

Type III Collagen: Reticulin

Type IV collagen: Basement membrane

34
Q

What are some special properties of type I collagen, and what does it compose?

Any diseases?

A

Most common.

Bone (made by osteoblasts, reduced production in osteogenesis imperfecta type I)

Skin

Tendons

Dentin, fascia, cornea, late wound repair.

35
Q

What are some special properties of type II collagen, and what does it compose?

A

Type II: Cartwolage

Cartilage (including hyaline), vitreous body, nucleus pulposus

36
Q

What are some special properties of type III collagen, and what does it compose?

Any diseases?

A

Composes Reticulin – skin, blood vessels, uterus, fetal tissue, granulation tissue.

Type III Deficient in the uncommon, vascular type of Ehlers-Danlos syndrome

(ThreE D).

37
Q

What are some special properties of type IV collagen, and what does it compose?

Any diseases?

A

Basement membrane, basal lamina, lens.

Type IV: Under the floor (basement membrane).

Defective in alport syndrome, targeted by autoantibodies in Goodpasture syndrome.

38
Q

What are the steps of collagen synthesis?

A

Inside fibroblasts:

  1. Synthesis (RER)
  2. Hydroxylation (RER)
  3. Glycosylation (RER)
  4. Exocytosis

Outside fibroblasts:

  1. Proteolytic processing
  2. Cross-linking
39
Q

What occurs during synthesis of collagen?

A

Occurs in RER.

Translation of collagen α chains (preprocollagen) - usually Gly-X-Y. (X and Y are proline or lysine). Glycine content best reflects collagen synthesis (collagen is 1/3rd glycine).

40
Q

What occurs during the hydroxylation step of collagen synthesis?

What is required?

A

Hydroxylation of specific proline and lysine residues.

Requires vitamin C; deficiency is scurvy.

41
Q

What occurs during the glycosylation step of collagen synthesis?

Diseases?

A

Glycosylation of α-chain hydroxylysine residues and formation of procollagen via hydrogen and disulfide bonds (triple helix of 3 collagen α chains).

Problems forming the triple helix -> osteogenesis imperfecta

42
Q

What occurs during the proteolytic processing step of collagen synthesis?

Diseases?

A

First, procollagen must have left cell by exocytosis.

Cleavage of disulfide-rich terminal regions of procollagen tranform it into insoluble tropocollagen.

43
Q

What occurs during the cross-linking step of collagen synthesis?

Diseases?

A

Extracellular.

Reinforcement of many staggered tropocollagen molecules by covalent lysine-hydroxylysine cros-linkage (by Cu2+ containing lysyl oxidase) to make collagen fibrils.

Problems with cross linking -> Ehlers-Danlos

44
Q

What is the problem in osteogenesis imperfecta?

What is the clinical presentation?

A

Most common autosomal dominant with reduced production of otherwise normal type I collagen. (Glycosylation issue forming triple helix).

Fractures with minimal trauma, blue sclerae, hearing loss, dental imperfections due to lack of dentin.

45
Q

What is Ehlers-Danlos syndrome?
Clinical presentation?

A

Faulty collagen synthesis causing hyperextensible skin, tendency to bleed (easy bruising), and hypermobile joints.

Can be autosomal dominant or recessive, associated with joint dislocation, berry and aortic aneurysms, organ rupture.

Hypermobility type most common

Classic type (joint and skin) caused by mutations in type V collagen

Vascular type (vascular and organ rupture) due to deficient type III collagen.

46
Q

What is Menkes disease?

A

Connective tissue disease caused by impaired copper absorption and transport.

Reduced activity of lysyl oxidase (copper is necessary cofactor), which cross-links collagen with lysine-hydroxylysine covalent bonds.

Brittle “kinky” hair, growth retardation, and hypotonia.

47
Q

What is elastin?

A

Stretchy protein within skin, lungs,m large arteries, elastic ligaments, vocal cords, ligamenta flava (connect vertebrae, relaxed and stretched conformations).

Rich in proline and glycine, nonhydroxylated forms.

Tropoelastin with fibrillin scaffolding.

Cross-linking extracellular, gives elastin its elastic properties.

Broken down by elastase, which is inhibited by alpha-1 antitrypsin.

48
Q

What is Marfan syndrome?

A

Caused by defect in fibrillin, a glycoprotein that forms a sheath around elastin.

49
Q

What is emphysema?

A

Can be caused by alpha-1 antitrypsin deficiency, resulting in excess elastase activity. Wrinkles of aging due to reduced collagen and elastin production.

First Aid: Biochemistry (7 decks)

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