Creatine Kinase Flashcards Preview

Mcd Tutorials > Creatine Kinase > Flashcards

Flashcards in Creatine Kinase Deck (11)
Loading flashcards...
1
Q

What does creatine kinase do

A

Creatine Kinase is responsible for catalysing the conversion of:
CREATINE PHOSPHATE ——> CREATINE
One molecule of ATP is generated in this reaction

2
Q

What is the difference between necrosis and apoptosis

A
Necrosis = Death of many cells in an organ or tissue due to external physical damage (e.g. disease, injury or failure of blood supply).
Apoptosis = Programmed cell death - a normal and controlled part of the organisms development.
3
Q

In what tissues is CK present in high levels?

A

Muscle and the brain use a huge amount of ATP so needs high levels of creatine kinase.
CK is made of 2 subunits or monomers that are coded for by 2 different genes. Muscle only express the M gene so only makes CK of the MM form; the brain only expresses the B gene; the heart muscle cells are the only cells that express both genes and hence make dimers of the BM form.
There are different types of CK:
Muscle = MM
Brain = BB
Myocardium = BM

4
Q

When and why is CK found in the blood?

A

Damage to the cell membrane allows leakage of CK into the blood stream.

5
Q

What causes the plasma membrane of myocardial cells to become leaky?

A

Active transport membrane proteins (pumps) stop working because they require ATP to function. High concentrations of everything inside the cells leaks out.

6
Q

How is CK activity detected

A

Creatine and Creatine Phosphate is not easily detectable so COUPLED ASSAYS are used.
Coupled Assay = Use 2 or more reactions to find something detectable. (i.e. the product of the first reaction becomes a substrate of the next and it goes on until an easily detectable product is formed.)
In the case of Creatine Kinase:
1. Creatine Phosphate + ADP ——————-> Creatine + ATP (Enzyme = Creatine Kinase)
2. ATP + D-glucose ———————-> ADP + Glucose-6-Phosphate (Enzyme = Hexokinase)
3. Glucose-6-Phosphate + NADP+ —————> 6-PG + NADPH + H+ (Enzyme = G6P dehydrogenase)
NADPH IS DETECTABLE! It absorbs UV light.

7
Q

How can the isoenzymes be separated by electrophoresis

A

They have very similar molecular weights so they must be separated based on their charges. They each have different charges.
A quicker way of doing it is isoelectric focussing. You place the isoenzymes in the gel with a positive charge on one side and a negative charge on the other side; the isoenzyme will move to where it has a net charge of zero hence its ISOELECTRIC POINT (pI).

8
Q

How might one establish a diagnosis of myocardial damage?

A

Elevated levels of MB creatine kinase in the serum.

9
Q

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

A

Yes - levels of CK BM isoform in the serum are directly proportional to the amount of cell death in the heart. Each myocyte has a set amount of CK so when more cells are damaged, there is more CK.

10
Q

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

A

30 mins to 2.5 days

11
Q

What other markers can be used for diagnosis of myocardial damage?

A

Lactate Dehydrogenase (LDH) - leaks out when cells are damaged. It is not particularly specific and only peaks after 6 days.
Troponin - there is a specific myocardium version - look for elevated levels of Troponin I and Troponin T, which are specific to cardiac muscle (appears after 48 hours and lasts 5 days).
Serum Glutamate Oxaloacetate Transaminase (SGOT) - starts being released from cells. Peaks as CK goes down.
Use antibodies which attach to the protein