点的方法,原理是:如果结合是特异性的话,只有信号分子能够同受体结 合,而与信号分子无关的分子则不能同受体结合。例如,放射性标记的胰岛 素与受体的结合不会受葡萄糖或ACTH(促肾上腺皮质激素)的抑制,但是能 够被非放射性标记的胰岛素或胰岛素衍生物所抑制(图E5-2)。 图5-17证明激素与受体结合特异性的实验 实验中,将放射性标记的胰岛素与分离的膜一起温育,同时加入各种 不同浓度的葡萄糖或ACTH。与胰岛素无关的激素不会与放射性标记的胰 岛素竞争质膜受体。通过检测放射性即可证明 六、分析、计算与思考(20分) 1.“解铃还需系铃人″这句谚语在细胞活动中能找到对应的故事吗?请 说明。(5分) 答:IP3的钙的释放和对钙浓度的消减。 2.计算题(5分) a The average molecular weight of proteins in the cell is about 30,000 daltons. A few proteins, however, are very much larger. The largest known polypeptide chain made by any cell is a protein called titin(made by muscle cells), and it has a molecular weight of 3,000,000 daltons Estimate how long it will take a muscle cell to translate an mRNAcoding for titin(assume the average molecular weight of an amino acid to be 120 and a translation rate of two amino acids per second for eucaryotic cells 2 Transcription occurs at a rate of about 30 nucleotides per second. Is it possible to calculate the time required to synthesize a titin mRNA from the information given here? 2.A A titin molecule is made of 25,000 amino acids. It therefore takes about 3.5 hours to synthesize a single molecule of titin in muscle cells To calculate the time it takes to transcribe a titin mRNA, you would need to know the size of its gene, which is likely to contain many introns Transcription of the exons alone requires about 42 minutes. Because introns can be quite large, the time required to transcribe the entire gene is likely to be considerably longer 2.综合思考(10分,按答题最多者计算每题得分)12 点的方法，原理是: 如果结合是特异性的话,只有信号分子能够同受体结 合,而与信号分子无关的分子则不能同受体结合。例如,放射性标记的胰岛 素与受体的结合不会受葡萄糖或ACTH(促肾上腺皮质激素)的抑制,但是能 够被非放射性标记的胰岛素或胰岛素衍生物所抑制(图 E5-2)。 图 5-17 证明激素与受体结合特异性的实验 实验中,将放射性标记的胰岛素与分离的膜一起温育,同时加入各种 不同浓度的葡萄糖或 ACTH。与胰岛素无关的激素不会与放射性标记的胰 岛素竞争质膜受体。通过检测放射性即可证明。 六、分析、计算与思考(20 分) 1. “解铃还需系铃人”这句谚语在细胞活动中能找到对应的故事吗？请 说明。（5 分） 答：IP3的钙的释放和对钙浓度的消减。 2. 计算题（5 分） ① The average molecular weight of proteins in the cell is about 30,000 daltons. A few proteins, however, are very much larger. The largest known polypeptide chain made by any cell is a protein called titin (made by muscle cells), and it has a molecular weight of 3,000,000 daltons. Estimate how long it will take a muscle cell to translate an mRNA coding for titin (assume the average molecular weight of an amino acid to be 120, and a translation rate of two amino acids per second for eucaryotic cells). ② Transcription occurs at a rate of about 30 nucleotides per second. Is it possible to calculate the time required to synthesize a titin mRNA from the information given here? 2. Answer: ① A titin molecule is made of 25,000 amino acids. It therefore takes about 3.5 hours to synthesize a single molecule of titin in muscle cells. ② To calculate the time it takes to transcribe a titin mRNA, you would need to know the size of its gene, which is likely to contain many introns. Transcription of the exons alone requires about 42 minutes. Because introns can be quite large, the time required to transcribe the entire gene is likely to be considerably longer. 2. 综合思考(10 分, 按答题最多者计算每题得分)