Tutorials 1-3 Flashcards
What is latency?
The ability to induce a lifelong infection in a host cell.
How do viruses differ from normal host cells? (4)
- No functional ribosomes
- No cellular organelles
- Produce very few of the enzymes needed for viral replication
- Can encode genetic information into RNA
What is acyclovir?
A nucleoside analogue, used as a lifelong medication for immunosuppression and reduction of viral load of the HSV virus.
What are the six variants of the Herpes virus?
1) HSV1
2) HSV2
3) Epstein-Barr virus (EBV)
4) Cytomegalovirus (CMV)
5) Human herpes virus 5 (HHV6)
6) Varicella zoster virus (VZV)
What are the three major components of the herpes virus?
1) Herpes simplex virus (HSV)
2) Cytomegalovirus (CMV)
3) Epstein-Barr virus (EBV)
What is selective toxicity?
Ability of a drug to selectively target specific sites relative to the microorganism that is causing the infection without harming host cell. Basis for chemotherapy.
What is a nucleoside?
A base and a sugar bonded together.
What OTC medications is acyclovir incorporated into?
Cold sore medication (and prescriptions to treat Chickenpox)
How does acyclovir stop viral replication of HSV?
- Acyclovir is taken up by cell and phosphorylated a number of times by thymidine kinase (and other cellular enzymes) to produce acyclovir triphosphate.
- Acyclovir triphosphate competitively inhibits viral DNA polymerase.
- If incorporated, acyclovir is missing 3’ end of carbon, meaning elongation is impossible and chain termination occurs.
What are the steps of the viral life cycle?
1) Attachment to cell
2) Penetration of cell by endocytosis
3) Uncoating of viral contents
4) Biosynthesis
5) Assembly of new phage particles
6) Release
Where is creatine kinase at its highest concentrations?
Highly metabolically active tissues such as the muscle and brain.
How can creatine be ingested?
In red meat and fish.
Where is creatine endogenously produced in the body?
Pancreas, liver and kidneys.
What is creatine kinase used for?
Phosphorylation of creatine into creatine phosphate (energy store).
What can CK in the blood indicate?
Cell death as it leaks from cells upon death.
What is an isoenzyme?
Has the same function but different structures.
How many isoforms of CK are present in the body?
3
What are the different isoforms and where are they found?
MM - skeletal muscle tissue (85%)
MB - myocardium (15%)
BB - brain (mainly)
What is a myocardial infarction?
A heart attack caused by a blockage in the coronary arteries, preventing blood flow to the heart and resulting in cell death.
What are the molecular weights of both monomers?
Roughly the same (43kDa)
What are the isoelectric points of both monomers?
B is 5.2 whilst M is 6.7.
How can CK-MB levels show cell damage in the heart?
CK-MB levels in the blood are directly proportional to the amount of cell death in the heart as each myocyte is of equal volume and will release equal volume of CK into the blood upon death.
How can the isoforms of CK be separated?
Gel electrophoresis or column chromatography.
How is cell death caused in MIs?
- ATP is needed to maintain ion gradients in between the outside and inside of cells
- If blood flow is occluded, ATP is not delivered to cells and ion gradients are unregulated
- The unregulated ion gradients can lead the cell membrane to be compromised.
- Lysozyme can then leak out of the cell, causing self-digestion
- CK is then able to also leak out of the cell into the bloodstream where it is detected
Why is measuring CK levels not that useful?
It does not differentiate between the different isoforms of CK and therefore does not tell you where the damage is.
What is the only product that can be detected/measured?
A couple reaction is used and NADPH is measured by absorption of UV light.
What is a more clinically-relevant way of testing isoforms of CK than electrophoresis?
Antibody testing
How does antibody testing work?
- Antibodies have high specificity so can be used to recognise the MB subunit after an MI.
- When the antibodies bind to the MB subunit, a signal is given off.
- The stronger the signal, the more of the MB subunit there is
- This test is often used in conjunction with others
What can antibody testing show you?
How long ago the MI happened and how big it was.
What can lactate dehydrogenase tell you?
LDH. Used as a measure of anaerobic respiration (oxygen deprivation). Allows measurement over a longer period of time as it can persist for up to 10 days after an MI.
What does SGOT stand for?
Serum glutamic oxaloacetic transaminase
What can SGOT tell you?
It is released by myocardium after MI and can persist for around 5 days after an MI.
What other proteins are specific to cardiac tissue?
Cardiac troponin I and troponin T
What can troponin I and T tell you?
Specific to cardiac tissue so presence in the blood is a specific marker for myocardial infarction. Typically appear 48 hours after MI and persist for 5 days.
Where does malate enter ETC?
When NADH is transferred to first electron acceptor.
When does succinate enter the ETC?
When FAD is transferred to the second electron acceptor.
Why does succinate need more oxygen than malate?
As succinate enters the ETC later than malate, it is reduced at fewer acceptor so fewer protons are given by FAD, therefore more oxygen is needed to compensate for this.
What does cyanide block?
Cytochrome oxidase (complex 4)
How does cyanide work?
Binds to the Fe3+ molecule in the electron acceptor and acts as a non-competitive inhibitor, preventing further electrons from passing down ETC.
What does oligomycin block?
ATP synthase
How does oligomycin work?
Binds to ATP synthase, causing the same effect as cyanide. No ADP is phosphorylated so protons and electrons back up and concentration gradient dissipates.
What is DNOC?
Its a lipid-soluble weak acid that uncouples ATP synthase in the inner mitochondrial membrane and acts as an alternative shuttle.
What does DNP stand for?
Dinitrophenol
What is DNP?
Used as a weight loss medication but can be toxic in very small doses. Long biological half life and lipid solubility makes it hard to filter out of body. Once toxic dose is taken, there is no cure.
How does DNOC work?
- Uncouples ATP synthase so ETC and acceptors are working at maximum rate so breathing rate increases as oxygen demand increases
- Protons move across the membrane freely from high to low concentration
- Energy that would be stored in ATP is released at heat
- No ATP so no muscle contraction so advanced stages of rigorous mortis in deceased body
- Aromatic compound so can cause yellow discolouration of skin
- Causes increased erythrocyte production due to oxygen demand
