问题 问答题 简答题

简述熔点与油脂结构的关系,举植物油、动物油、深海动物油各一例。

答案

参考答案:

油脂没有敏锐的熔点,而仅有一段熔化的温度的范围。游离脂肪酸,一酰基甘油、二酰基甘油、三酰基甘油的熔点依次降低。这是因为它们的极性依次降低,分子之间的作用力依次减小的缘故。三酰基甘油中脂肪酸的碳链越长,饱和度越高,则熔点越高;反式结构的熔点高于顺式结构,共轭双键结构的熔点高于非共轭双键结构,可可脂及陆产动物油脂相对于植物油而言,饱和脂肪酸含量较高,在室温下常呈固态;植物油在室温下呈液态。一般油脂的熔点低于人体温度37℃时,消化率达96%以上;熔点高于37℃越多,越不易消化。植物油如花生油;动物油如猪油;深海动物油如海狗油。

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Last spring, I was fortunate to be chosen to participate in an exchange study program. In my application letter, I was careful to ____ how much I wanted to see France; evidently, my excitement really came through in my words. Once I ____ that I was going, all I could think about was the fun of foreign travel and making all sorts of new and ____ friends. While traveling was inspiring and meeting people was ____, nothing about my term in France was what I ____.
The moment I arrived in Paris, I was ____ by a nice French couple who would become my host parents. My entire experience was joyous and exciting ____ I received some shocking news from my program coordinator(协调人): there had been a death in my host parents' extended family. They had to travel outside France for several weeks. That afternoon, I had to ____ out of one family's house and into another. The exchange coordinator told me I'd have a ____ this time and asked whether I could share a bedroom with an English speaker. To avoid the temptation(诱惑) to ____ my native language, I asked not to be ____ with an English­speaking roommate. When I got to my new room, I ____ myself to my new roommate Paolo, a Brazilian(巴西人) the same age as I, whom I was surprised to find playing one of my favorite CDs! In just a few hours, we knew we'd be good friends for the rest of the ____.
I left France with many ____, so when people ask me what my favorite part of the trip was, they are always ____ to hear me talk about my Brazilian friend Paolo and the scores of weekdays in class, weeknights on the town, and weekends ____ France we enjoyed together. I love how people ____ seem so different, but end up being so ____. The most valuable lesson I gained from studying in France wasn't just to respect the French people ____ to respect all people,for your next best friend could be just a continent away. I would recommend an exchange program to anyone who wants to experience foreign cultures and gain meaningful ____.
小题1:
A.discussB.expressC.announceD.argue
小题2:
A.approvedB.knewC.warnedD.denied
小题3:
A.stubbornB.anxiousC.universalD.interesting
小题4:
A.boringB.upsettingC.excitingD.promising
小题5:
A.expectedB.likedC.doubtedD.feared
小题6:
A.sponsoredB.witnessedC.greetedD.supported
小题7:
A.untilB.whenC.sinceD.while
小题8:
A.moveB.travelC.walkD.rush
小题9:
A.housekeeperB.leader
C.roommateD.colleague
小题10:
A.learnB.appreciateC.speakD.master
小题11:
A.combinedB.fittedC.involvedD.placed
小题12:
A.addedB.introducedC.devotedD.adapted
小题13:
A.termB.weekC.monthD.vacation
小题14:
A.presentsB.suitcasesC.storiesD.dreams
小题15:
A.surprisedB.disturbed
C.embarrassedD.concerned
小题16:
A.analyzingB.exploring
C.describingD.investigating
小题17:
A.needB.shallC.mustD.can
小题18:
A.generousB.independent
C.similarD.distant
小题19:
A.andB.butC.orD.so
小题20:
A.instructionsB.friendships
C.factsD.data