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Following a body injury, bone marrow stem cells move to the site of damage and undergo cell differentiation - AQA - A-Level Biology - Question 4 - 2023 - Paper 3
Question 4
Following a body injury, bone marrow stem cells move to the site of damage and undergo cell differentiation. Figure 5 shows how this differentiation occurs. 1. Sug... show full transcript
Worked Solution & Example Answer:Following a body injury, bone marrow stem cells move to the site of damage and undergo cell differentiation - AQA - A-Level Biology - Question 4 - 2023 - Paper 3
Step 1
Step 2
Using all of the information, suggest explanations for the results for the Control group.
Answer
In the Control group, cardiomyocytes (cardiac muscle) cells have not been replaced. The infarcted tissue is not repaired or replaced, likely due to inadequate stem cell differentiation or availability. This means there is a small number of cardiomyocytes, leading to poor heart function.
Step 3
Using all of the information, suggest explanations for the results for the c-KIT– group.
Answer
For the c-KIT– group, the results show that some stem cells have managed to differentiate into new cardiomyocytes. However, the increase in cardiomyocytes is less than that observed in the c-KIT+ group, indicating that while some differentiation has occurred, it is not sufficient to significantly repair the myocardial damage.
Step 4
Calculate the percentage of infarcted tissue that was made up of new cardiomyocytes in the c-KIT– group.
Answer
Given that the c-KIT+ group showed that 68% of infarcted tissue was made up of new cardiomyocytes, the c-KIT– group's percentage can be calculated based on how many cardiomyocytes could potentially differentiate, which is influenced by both SCFR presence and the efficiency of the differentiation process.
Step 5
Suggest how production of Connexin-43 could give the result seen in the c-KIT+ group.
Answer
Connexin-43 facilitates the electrical impulse transmission between cardiomyocytes, which ensures coordinated heart contractions. Its presence in new cardiomyocytes enhances the electrical connectivity of the heart, essential for effective cardiac function post-infarction.
Step 6
Suggest how production of GATA-4 could give the result seen in the c-KIT+ group.
Answer
GATA-4 acts as a transcriptional factor that promotes the expression of genes important for cardiomyocyte function, specifically those associated with actin and myosin. Increased levels of GATA-4 would foster the development and maturation of new functional cardiac cells, contributing positively to the repair of infarcted tissue.