Plants and animals often use color to attract attention.The substances responsible for these colors belong to a class of chemical called antioxidants(抗氧化物).Plants make antioxidant to protect themselves from the sun’s ultraviolet(UV)(紫外线)light.
Ultraviolet light causes chemicals called free radicals(自由基)to form within plant cells.They can destroy parts of plant.Free radicals also have damaging effects on human beings.Some of these effects like wrinkled skin can be seen.The damage is caused by the free radicals attacking cells in our bodies.Certain cancers and heart disease are linked to free radicals.
Our bodies have natural defences for fighting off free radicals.While we are young,our defences are pretty strong.However,they get weaker as we get older.The body’s built-in defences can only go so far without extra help.
The key to fighting free radicals with fruits and vegetables is to mix and match colors.It’s like sunscreen(防晒霜)for the inside of your body.Go for a range of very bright colors.Colorful foods contain hundreds of healthy chemicals not found anywhere else.
Research into how chemicals in blueberries affect the brain’s function in rats suggests that these chemicals may help our own brains work more efficiently.
Don’t just blame the sun.Ultraviolet light isn’t the only source of free radicals.If you breathe polluted air such as smog,automobile exhaust(废气),or wasted gas from a factory,you take in chemicals that also cause such damage.And,the body itself produces free radicals as it processes food.
【2017届《名师A计划》高考英语新人教版一轮复习配套练习:必修1 Unit 3《Travel journal》(含解析)】相关文章:
★ 【人教版】2014届高考英语一轮复习指导考点针对练:选修6 unit3《A healthy life》
★ (安徽专用)2014届高考英语一轮复习方案 作业手册(24)模块8 《Unit 24 Society》(含解析) 北师大版必修1
★ 【三维设计】2017版(江苏专用)二轮复习练习:必修3 Unit 3《Back to the past》课时跟踪检测A卷(含解析)
★ 【人教版】2014届高考英语一轮复习指导考点针对练:选修6 unit4《Global warming》
★ 【北京专用】2014届高考英语一轮复习方案课时作业:必修5 Unit 2 The United Kingdom
★ 【浙江专用】2014届高考英语一轮复习课时作业(二十二)必修5Unit 2《The United Kingdom》
★ 【北京专用】2014届高考英语一轮复习方案课时作业:必修4 Unit 1 Women of achievement
★ 【北师大版】2014届高考英语一轮复习指导课时作业:Unit 7 B卷 Word版含解析
★ 贵州省贵阳市2014高考英语(新人教版)一轮阅读训练(34)附答案
最新
2017-04-24
2017-04-24
2017-04-24
2017-04-24
2017-04-21
2017-04-21