考满分 toefl

1 .Listen to part of a lecture in a biology class.

请听一段生物学课堂讲座的节选。

1 .I'm sure most of you know that we've been able to extract certain compounds from plants for use in medicine, um compounds like proteins. Proteins from some plants can be used in medicines as antibodies and vaccines. And we can even cause some plants to produce certain proteins by incorporating DNA into the plant cells, usually in the leaves. We then extract the proteins to use as antibodies. However, we've never been able to produce enough protein to make the process worthwhile. It hasn't been practical until now.

我相信你们大多数人都知道，我们已经能够从植物中提取某些化合物用于医药，比如蛋白质。某些植物的蛋白质可以作为抗体和疫苗用于药物。我们甚至可以通过将DNA植入植物细胞（通常在叶片中）来促使植物产生特定蛋白质，然后提取这些蛋白质作为抗体使用。然而，我们一直无法生产足够数量的蛋白质使这一过程具有价值。直到现在才变得可行。

1 .Now it appears that it is possible to get a large amount of usable protein from plants. Some researchers have recently succeeded in doing this by using plant seeds to produce these proteins, rather than the leaves or the other parts of the plant.

目前看来，从植物中获取大量可用蛋白质已成为可能。一些研究人员最近通过使用植物种子（而非叶片或其他部位）来生产这些蛋白质取得了成功。

1 .Now, there are a number of advantages to getting protein from plant seeds to produce antibodies, but we have to be sure that these proteins are just as effective as human proteins, and so far, the research has shown that they are. That antibodies produced from plant seed proteins are effective in humans, which is great, because typically antibodies for vaccines and medicines too, are produced from microorganisms like yeasts or bacteria, and it's rather complicated process.

从植物种子获取蛋白质生产抗体具有诸多优势，但我们必须确认这些蛋白质与人类蛋白质同样有效。迄今为止研究表明确实如此。植物种子蛋白质产生的抗体对人类有效，这很棒，因为通常疫苗和药物所需的抗体是从酵母或细菌等微生物中生产的，这个过程相当复杂。

1 .OK, so what makes plant seeds good production units? Well, for one thing, there's lots of them, right? One plant can produce a lot of seeds. And then there's the issue of storage. Seeds can be stored for long periods of time, and the protein retains its effectiveness.

那么，为什么植物种子是理想的生产单元？首先，种子数量庞大，一株植物能产生大量种子。其次是储存问题，种子可长期储存且蛋白质能保持有效性。

1 .Now, that's not true with other parts of the plant, leaves, for instance, you can't store them very long, which means that you have to get that protein out right away, as soon as it's produced. But using plant seeds as production units allows you to isolate the protein whenever you need it. And you can transport seeds all over the world, even the places where refrigeration might be a problem, not so for yeasts or bacteria.

而植物其他部位（如叶片）就无法长期储存，这意味着蛋白质一经产生就必须立即提取。但以种子为生产单元可随时提取所需蛋白质。种子还能运输到世界各地，即便是冷藏条件受限的地区，这点酵母或细菌培养物就做不到。

1 .But with seeds, it seems quite possible that will be able to supply vaccines to places that need them. Whereas before, transporting and preserving these products over long distances simply wasn't feasible.

通过种子，我们很可能实现向需要疫苗的地区供货。而此前，长距离运输和保存这些产品根本不可行。

1 .And another major benefit of extracting plant proteins for medical use, it's cost-effective. Unlike the production of proteins for medicinal purposes using yeasts or bacteria like insulin, which is a vital protein used in medications, extracting protein from seeds doesn't require high-tech production labs with all kinds of equipment.

另一个重要优势是成本效益。与使用酵母或细菌生产药用蛋白质（如药物中的重要蛋白质胰岛素）不同，从种子提取蛋白质不需要配备各种设备的高科技实验室。

1 .And since refrigeration is not crucial for maintenance or transport, it's just much less expensive to store and maintain plant seeds than other sources of protein. We estimate the total production cost to be ten to 100 times lower.

且由于储存运输无需严格冷藏，植物种子的保存成本远低于其他蛋白质来源。我们估计总生产成本能降低10到100倍。