Lecture 1: Cellular Organization

Question 1

Hutchinson-gilford progeria syndrome

Answer 1

• rapid aging

- mutation in lamin A gene

Question 2

Nucleolus

Answer 2

Ribosome production

Zones:
1) fibrillar center - pale staining region, dna loops of 5 chromosomes (fc)

2) fibrillar material - darker bc transcription is taking place, transcription of rRNA genes (f)
3) granular material - initial ribosomal assembly

Question 3

Membrane bound ribosomes

Free ribosomes

Answer 3

Membrane bound:

• bound to ER
• mRNA has ER Signal
• synthesized proteins trans located to
  1) lysosomal proteins
  2) secreted proteins
  3) plasma membrane proteins

Free:

• not attached to ER
• no ER signal
• synthesize proteins to
  1) nuclear proteins
  2) mitochondrial proteins
  3) cystosolic proteins
  4) peroXisomal proteins

Question 4

Tay-Sachs disease

Answer 4

Lysosomal disease

Deficiency of HEXA (B-hexosaminidase A, alpha-subunit)

Results in accumulation of GM2 Ganglias, death of neurons in brain and spinal cord

Autosomal recessive disorder

Jews

Usually fatal

Question 5

Pompe

Answer 5

Accumulated product: glycogen

Affects skeleton and nervous system

Question 6

Pathways to lysosomal digestion

Answer 6

1) phagocytosis
2) endocytosis

3) autophagy
- self eating
1) Intracellular membrane surrounds the organelle
2) Autophagosomes form
3) Fusion of autophagosome with the lysosome
4) Contents degraded recycled and reused

It’s an essential role in starvation, cellular differentiation, cell death and cell aging

Question 7

Proteasomes

Answer 7

Degrade proteins with zero lysosomal involvement

ATP dependent

Proteins targeted for destruction are covalently tagged with ubiquitin

Inhibitors used as anti-cancer agents

Question 8

Mitochondria

Answer 8

Outer membrane- porins, enzymes: phospholipids, acetyl coenzyme A synthese

Inter membrane space- enzymes: creative kinase and adenylated kinase, cytochrome c= important factor in intrinsic apoptosis pathway

Inner membrane- oxidation rx s (electron transport chain), synthesizing ATP, regulates metabolic transport

Matrix- citric acid cycle, oxidation pyruvate, matrix granules

Question 9

Mitochondrial diseases

Answer 9

Myoclonic epilepsy w ragged red fibers (MERRF)
-mutation in tRNA gene MT-TK

Leber hereditary optic neuropathy

• mutations in Mt-ND1, MT-ND4, MT-ND4L, MT-N06 genes
• causes degeneration of retinal ganglion cells (RBGS) and their axins leading to bison loss

MELA

Affect all children of mother affected

Question 10

Peroxisome

Answer 10

Fat metabolism

Synthesized by free ribosomes

Specialized to compartmentalized and degrade toxic reactive oxygen molecules (concerting H2O2 to O2 and H2O)

Disease: zellwegers- mutations in genes required for peroxisome function, causing defective imports of peroXisomal proteins

Question 11

Receptor mediated endocytosis

Answer 11

Uptake is large molecules and particles

• Receptor recycled/ligand degraded = LDL
• Receptor and ligand degraded = Epithelial growth hormone
• Receptor and ligand recycled = iron
• receptor and ligand transcytosis = immunoglobulins (IGA)
• Clarthin dependent
• Cargo specific

Question 12

Phagocytosis

Answer 12

Generally performed by specialized phagocytes

• macrophage
• neutrophil

1) particles bind to plasma membrane receptor
2) extension of pseudopods
3) phagosomes fuses with lysosomes (digestion)
4) residual body

Question 13

Proteasome

Answer 13

• mediated protein degradation without lysosomal
• ATP dependent
• polyubiquitination:
• Proteins targeted for destruction are covalently tagged with the ubquitin proteins