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Testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens - AQA - A-Level Biology - Question 2 - 2020 - Paper 1
Question 2
Testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens. 1. Steroid hormones are hydrophobic. Explain why steroid hormones ... show full transcript
Worked Solution & Example Answer:Testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens - AQA - A-Level Biology - Question 2 - 2020 - Paper 1
Step 1
Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface membrane.
Answer
Steroid hormones, being hydrophobic, can easily diffuse through the lipid bilayer of the cell's plasma membrane. This structure is primarily composed of phospholipids, which allow lipid-soluble substances to pass through without the need for specific transport mechanisms.
Step 2
Suggest and explain why testosterone binds to a specific AR.
Answer
Testosterone binds to a specific androgen receptor (AR) because the AR has a unique tertiary structure that is complementary to the structure of testosterone. This specific interaction ensures that only testosterone can effectively bind to the AR, allowing for precise biological signaling.
Step 3
Suggest how the AR could stimulate gene expression.
Answer
The AR can stimulate gene expression by functioning as a transcription factor. Once testosterone binds to the AR, the receptor undergoes a conformational change that enables it to bind to specific DNA sequences, thereby activating transcription of target genes involved in male sexual development.
Step 4
What can you conclude from the data in Table 1?
Answer
With 16 or fewer CAG repeats, there is a significant association with prostate cancer risk, as indicated by a probability value (P) of 0.02, which is less than 0.05. Conversely, for 17 or more CAG repeats, the association is not significant at the same threshold, as indicated by higher probability values.
Step 5
What can you conclude from the data in Table 1?
Answer
The data shows that as the number of CAG repeats increases, the probability of a significant cancer association decreases. Specifically, individuals with 16 or fewer CAG repeats have a higher risk, while those with 17 or more show no significant association, with P values rising above 0.05.