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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
Suggest how SCFR is destroyed by a lysosome.
Answer
The SCFR (Stem Cell Factor Receptor) is destroyed by lysosomes through the following process: The vesicle containing SCFR fuses with the lysosome, where lysosomal enzymes effectively hydrolyze and digest the receptor, breaking it down into its component parts.
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. This can be due to factors such as the infarcted tissue not being repaired or replaced, weakness in ventricular contraction due to limited cardiomyocytes, or low pressure that led to damage or death of remaining cells.
Step 3
Using all of the information, suggest explanations for the results for the c-KIT- group.
Answer
In the c-KIT- group, the results indicate a higher number of new cardiomyocytes compared to the Control group, suggesting that some stem cells were able to differentiate. However, the increase is less than that of the c-KIT+ group, indicating the possibility of other factors that could activate the differentiation process.
Step 4
Calculate the percentage of infarcted tissue that was made up of new cardiomyocytes in the c-KIT- group.
Answer
To calculate the percentage of new cardiomyocytes in the c-KIT- group, it is derived from the functional relationship with the mean ventricular blood pressure, which is directly proportional to the number of new cardiomyocytes. Given that 68% of the c-KIT+ group was made up of new cardiomyocytes, and no new cardiomyocytes were reported in the Control group, we can estimate the percentage based on proportionality.
Step 5
Suggest how production of Connexin-43 could give the result seen in the c-KIT+ group.
Answer
The production of Connexin-43 facilitates the passage of electrical impulses between cardiomyocytes, which enhances coordinated contraction and successful integration into the heart muscle, leading to improved functional recovery in the c-KIT+ group.
Step 6
Suggest how production of GATA-4 could give the result seen in the c-KIT+ group.
Answer
GATA-4 promotes the expression of genes required for the formation of actin and myosin, essential proteins for cardiac muscle contraction. Therefore, its presence in the c-KIT+ group would support the development of functional cardiomyocytes, contributing to the observed regenerative outcomes.