本文为大家带来了2025年8月雅思考试听力备考重点-Test 3Part 4，希望对大家的雅思备考有所帮助。

　　Test 3

　　Part 4

　　PART 4

　　You will hear a talk about new materials based on spider silk.

　　First you have some time to look at questions 31-40. Now listen carefully and answer questions

　　31-40.

　　Well, good morning, everyone, and thanks for inviting us today. As you know, I work as a senior

　　materials researcher for Future Mat. My colleague Frank and I are here today to interest you in getting

　　in at the beginning of an exciting new branch of material science "synthetic spider silk.”

　　You've all seen spider webs and spider thread, or silk as we call it. Now, some of you might not

　　like spiders, but believe me, they all have their own technology which we're only now beginning to

　　understand.

　　Now, you’re here as investors(Q31). Well, we firmly believe that the production processes(Q32) we’re

　　developing, based around the properties of spider silk, have the potential to revolutionize a number

　　of industries. For example, textiles, cosmetics, leisure equipment industries, and even some fields in

　　automotive and aerospace.

　　The interesting thing is that the multinational companies(Q33), even the household names you all

　　know, have invested millions in trying to develop synthetic spider silk into commercial products, but

　　basically have given up on it.

　　So, it's been left to the smaller startup companies like ours to continue the work. We may not have the

　　resources to scale up to commercial products just yet, but we and a couple of our competitors have

　　made some breakthroughs in the production processes and we're sure that will interest the major

　　companies in buying our patents(Q34).

　　So, let’s get to some specifics. People have known for many years that, weight for weight spider silk is

　　incredibly strong and tough, which has led to all this interest by material scientists.

　　Now, "strong" and "tough" are not the same thing because we define strength(Q35) as the weight a

　　material can bear while toughness(Q35) is a measure of the energy it can absorb before it breaks.

　　It may surprise you that some types of spider silk are five times stronger than steel! And you know those

　　bulletproof vests that are worn by riot police(Q36)? They're made of Kevlar, which is a tough, man

　　made fiber. Well, spider silk is lighter, but could be three times as tough!

　　It's important to note that real spider silk is a complex protein, but we now understand a lot about its

　　amino-acid structure. I won't bore you with the details but it mainly consists of repeated glycine and

　　alanine chains.

　　Now, this protein structure gives it other interesting applications which have excited medical companies,

　　particularly producers of external wound dressings and patches and that is because it has antimicrobial

　　properties and is not rejected by human tissue. So, infection rates could be reduced in accident victims.

　　And thinking far ahead, another medical application is in replacements for human tendons or ligaments,

　　you know, as parts within artificial limbs(Q37) where flexibility is crucial. And finally in construction,

　　clearly, there are a lot of uses for lighter, stronger cables linking machine parts, supporting or lifting

　　items.

　　So, you're probably wondering how the silk is produced? You might think it could be taken from wild

　　spiders themselves. So, to give you an idea of how long that can take, a piece of fabric about 3 to 4 meters

　　took 82 people over four years to create!

　　And clearly it won't be from farmed spiders. These creatures are far too aggressive towards each other.

　　They can't be kept in close proximity in large numbers So, the only way is to artificially produce the proteins

　　in a kind of sticky liquid, which can be made into very thin fibers(Q38).

　　One approach to this has been to genetically modify goats which then produce this silk in their milk.

　　The protein content of the milk is about one or two grams per liter of milk, so you need a lot of it to

　　get a quantity of protein, but it has been done, although extracting the protein isn't really such a tricky

　　process(Q39).

　　Erm…, another approach has involved the genetic modification of an obvious candidate, the silkworm,

　　but again, the quantities produced are insufficient(Q39). Hmm...the resultant materials are very suitable

　　for medical applications, though.

　　These days it seems a more reliable and, very importantly, scalable method is to directly modify bacteria,

　　such as the E. coli bacterium to produce the proteins in liquid form. There are a number of companies and

　　this is where we come in, working in this field.

　　So, we've shown you that it is indeed scalable. There are definitely some issues in going from the raw

　　proteins to useable silks, but the quantity is there(Q40).

　　So, now we've got the background. Let's have a look at our proposals in more detail. Frank, could you

　　start the video please...

　　That is the end of part 4. You now have half a minute to check your answers.

　　That is the end of the listening test. You now have 10 minutes to transfer your answers to the

　　answer sheet.

       题目

　　PART 4 Questions 31-40

　　Questions 31-37

　　Complete the notes below.

　　Write NO MORE THAN TWO WORDS for each answer.

　　Questions 38-40

　　Choose THREE problems from the list below and write the correct

　　letter next to questions 38-40.

　　Problems in producing the material

　　A High production costs

　　B Variable quality

　　C Difficult to make into materials

　　D Very slow process

　　E Dangerous to humans

　　F Low output

　　Methods

　　38 Using real spiders

　　39 Using genetically modified animals

　　40 Using genetically modified bacteria

　　答案

　　Part 4, Questions 31-40

　　31 investors

　　32 production processes

　　33 multinational companies

　　34 patents

　　35 strength, toughness

　　36 riot police

　　37 artificial limbs

　　38 D

　　39 F

　　40 C