Bevington 7 Death & Beyond

Question 1

NECROSIS:

Answer 1

uncontrolled release of protease enzymes
Arising from traumatic damage to cells (e.g. mechanical agitation, extremes of temperature, extremes of pH, acute poisoning etc

Question 2

NECROSIS:

Appearance

Answer 2

• Swollen “exploded” appearance
• Disruption of plasma membrane
• Leakage of cell contents
• Loss of cell structure

Question 3

an informative model system for studying animal development

Answer 3

(C. elegans)
no. of cell divisions = counting nuclei. Generate 1030 somatic cell nuclei. Not all found in a mature C. elegans 131 missing =cell death
This precise and reproducible deletion of cells cannot be necrosis

Question 4

APOPTOSIS:

Answer 4

controlled programmed activation of a series of protease enzymes - Caspases , ordered programme of cellular and molecular events leading to cell death:

a) Dismantled from within without leaking potentially toxic contents
b) Expose molecules on their surface => signals for other cells to remove apoptotic cells

Question 5

Apoptotic Mammalian Cell Morphology

Answer 5

• Shrunken appearance
• Intact plasma membrane (at least initially)
• Contents are not leaking out of the cell
• Discernible cell structure

Question 6

signal to phagocytes

Answer 6

PS “Flips” from inner to outer lipid
monolayer 
Can be triggered by cell stress:
-Procaspase activation by cleavage
- Caspase cascade

Question 7

BACTERIA

apoptosis:

Answer 7

form of programmed cell death occurs in bacterial sporulation and fruiting
-Classical apoptosis involves cell structures only found in eukaryotes

Question 8

VIRUSES

Answer 8

require a host cell to replicate

Question 9

Retroviruses

Answer 9

(e.g. HIV) contain RNA and protein but no DNA

Question 10

Prions :

Answer 10

Infectious agents with NO cells or nucleic acids (DNA or RNA), just protein, replicate in a host organism by copying an abnormal protein structure

Question 11

Failure to remove Prions

Answer 11

remove e.g. because of aging of the organism and/or neuro-degenerative illnesses -Huntington’s Disease or Alzheimer’s Disease => accumulation of protein aggregates

Question 12

Once formed, these aggregates may:

Answer 12

• Be highly resistant to proteolysis

* Ultimately threaten cell viability

Question 13

protein aggregate structure highly resistant to proteolysis is

Answer 13

cross-beta filament

Question 14

amyloid,

Answer 14

aggregates accumulating in tissues give rise to deposits known as amyloid

Question 15

Prion diseases:

Answer 15

Like viral infections, these arise from an infectious agent, NOT cellular
i.e. a misfolded aggregated protein designated the PrP (prion protein)

Question 16

called spongiform …

Answer 16

…characteristic holes in prion-based neurological diseases

Question 17

Smallest “cell”?

Answer 17

Conventional answer – Smallest bacteria - Mycoplasma
Alternative answer – (Highly controversial) – Nanobacteria: too small to be scientifically credible independent living cells. Evidence for alleged existence = structural not biochemical