AB7: Death and Beyond

Question 1

What is necrosis?

Answer 1

Occurs as a result of the uncontrolled release of degradative enzymes, such as proteases from lysosomes, which cause necrosis in other cells
Necrosis tends to spread to neighbouring cells causing harm to the organism- so it is not relied upon eliminate cells
Can be caused by traumatic damage such as extremes in temperature, pH, acute poisoning and many more

Question 2

What are the characteristics of necrotic cells?

Answer 2

• Swollen/exploded appearance
• Disruption to the plasma membrane
• Leakage of the cell contents
• Loss of cell structure

Question 3

What is apoptosis?

Answer 3

Is the controlled, programmed activation of a series of protease enzymes- Caspases
An ordered programme of cellular and molecular events whereby cells are:
1. Dismantled from within without leaking any potential toxic contents
2. Expose molecules on their surface which acts as signals for other cells to remove the apoptotic cells

Question 4

What is efferocytosis?

Answer 4

after apoptosis, molecules appear on the surface of cells, e.g. phosphatidylserine from the inner layer of the plasma membrane flips and is found on the outside facing the outside of the cell and are recognised by phagocytes- digest the apoptotic cell, means that it is hard to spot apoptotic cells

Question 5

What are the characteristics of apoptotic cells?

Answer 5

• Shrunken appearance
• Initially intact plasma membrane- so dangerous enzymes aren’t released
• Contents of the cell are not leaking out
• Discernible cell structure

Question 6

What are viruses?

Answer 6

Viruses: autonomous nucleic/protein complexes which replicate inside prokaryotes or eukaryotes using the host cells replication machinery- are not cells.
They are not entirely independent, they require a host cell in which to replicate
Some viruses have their genetic information in circular or linear and double or single stranded DNA, some have their genetic material in single or double stranded RNA

Question 7

What are retroviruses? How do these replicate? What is an example?

Answer 7

contains RNA and not DNA
replicate as they have an enzyme called reverse transcriptase which makes complimentary from of RNA in form of DNA- can form double stranded DNA that can be incorporated into the hosts genome to be replicated to make more proteins for the virus
e.g. HIV

Question 8

What are prions? How do they replicate?

Answer 8

Prions- infectious agents without cells or nucleic acids- they are infectious proteins which replicate in a host organism by copying an abnormal protein structure
Prions contain no DNA, no RNA, just protein so replicate by turning normal proteins to prion proteins by binding to them

Question 9

How is amyloid formed?

Answer 9

Failure to remove misfolded proteins via the ubiquitin-proteasome pathway can lead accumulation of protein aggregates which leads to Alzheimer’s
One protein aggregate structure that is resistant to proteolysis is cross-beta filament- gives rise to amyloid

Question 10

Why is setting up a positive control experiment important to assess validity of negative experimental results?

Answer 10

If an experiment fails (gives a negative result) is it because there is nothing to discover or is it because your experimental method is inadequate ?
To test this, you set up a positive control experiment- an experiment in which you know that the answer should be positive- can your technique detect a positive result