Achademic Tutorials

Question 1

What is the structure of acyclovir?

Answer 1

Similar to deoxyguanosine, with only one -OH group rather than two. It is a nucleoside.

Question 2

How does acyclovir work?

Answer 2

Thymidine kinase adds a phosphate group to the acyclovir so it can bind to DNA polymerase. It is added to the viral DNA by viral DNA polymerase once it has been activated.

Question 3

How is acyclovir specific to viral DNA?

Answer 3

It has a high affinity to viral DNA polymerase and cannot bind to human DNA polymerase. It is only activated by thymidine kinase, which is only produced by bacteria.

Question 4

What is the active compound in acyclovir?

Answer 4

The -OH group which forms a phosphodiester bond with exposed nucleotides.

Question 5

What is the spectrum of activity of acyclovir?

Answer 5

Acyclovir May be used for different strains of virus, eg. Zorovax to treat herpes and treatment of chicken pox.

Question 6

In what tissues is creatine kinase present at high levels, and what isoform is present?

Answer 6

• Present in skeletal muscle as MM
• Present in the brain as BB
• Present in the heart as MB
• Present in all cells at low levels

Question 7

Why is creatine kinase described as a dimer isoform?

Answer 7

As there are two subunits, meaning there are different forms of creatine kinase which perform different functions?

Question 8

Why are different forms of creatine kinase made in different tissue types?

Answer 8

As different genes are expressed in different tissues.

Question 9

Why is creatine kinase sometimes found in the blood?

Answer 9

Creatine kinase is found in the blood if the muscle is damaged, for example in muscular dystrophy or myocardial infarction.

Question 10

When might the plasma membrane of the myocardial cells become leaky?

Answer 10

When cells have less oxygen, less ATP is produced. This results in the cell membrane breaking down, and cell contents will be released as the cell dies.

Question 11

How can creatine kinase activity be determined?

Answer 11

• Spectrophotometers are used to detect the absorbance of the blood sample.
• This test identifies NADPH levels
• Then electrophoresis is used to identify the type of CK Present in the sample.

Question 12

How can creatine kinase result in production of NADPH?

Answer 12

NADPH is produced when creatine phosphate and ADP react to make ATP. ATP then reacts with glucose to make glucose 6-phosphate, which reacts with NADP to make 6-phosphoglycerate using G6P dehydrogenase

Question 13

Why are the isoenzymes separated by gel electrophoresis?

Answer 13

This separates the proteins based on charge, as they all have the same mass.

Question 14

How is a diagnosis of myocardial damaged established?

Answer 14

If NADPH levels are higher than normal, gel electrophoresis is performed to look at the presence of the BM subtype.

Question 15

Does an increase in serum CK activity related to the size of myocardial damage?

Answer 15

Yes - the levels of CK BM are proportional to the amount of cell death as myocytes are the same volume.

Question 16

What is the time course of serum CK after a myocardial infarction?

Answer 16

Peaks after 1 day, raises above normal after an hour.

Question 17

What other markers of myocardial damage could be used?

Answer 17

• Serum glutamate oxaloacetate transaminase
• Lactate dehydrogenase
• Cardiac troponin

Question 18

What makes a good marker?

Answer 18

• Easily detectable
• Last a long time
• Specific to the cardiac muscle
• Specific function in the cell, allowing cause of the issue to be detected

Question 19

Why is the rate of respiration in the presence of succinate and ADP greater than with glutamate plus malate and ADP?

Answer 19

• Malate aspartate shuttle produces NADH, which results in production of 3ATP.
• Succinate produces FADH2, which only makes 2ATP, so a higher rate of respiration is needed for the same amount of ATP production

Question 20

How does DNOC affect respiration?

Answer 20

It is a weak acid, so dissociates to make protons which dissipates the proton gradient in the mitochondria.

Question 21

What are the post mortem findings following poisoning by DNOC?

Answer 21

• Absence of body fat (lipids used in respiration)
• Tissue hypoxia (large amount of oxygen consumption)
• High levels of red bone marrow as erythropoiesis increases
• Advanced rigor mortis as ATP is required for muscles to relax and none is present.

Question 22

What is a common mission that occurs in brittle bone disease?

Answer 22

A substitution of glycine to cysteine. This leads to the protein structure being disrupted, as cystine is too large to fit in the triple helix.

Question 23

How is the electrophoresis pattern affected by a mutation resulting in introduction of cystine?

Answer 23

Disulphide bridges would form, meaning that the subunits stay together and so the fragment travels a shorter distance.

Question 24

What antibody subtype activates mast cells?

Answer 24

IgE subtype, as they bid to surface receptors.

Question 25

Why may adrenaline be used in treatment of inflammation?

Answer 25

As adrenaline causes blood cells to constrict, which redirects the blood to the organs.

Question 26

Why may patients feel faint during inflammation?

Answer 26

• There is low blood pressure so there is a lack of oxygen being delivered to cells.
• This is called shock if it affects organs
• Constriction of bronchi elevates this by causing difficulty breathing