B1 中級 其他腔 959 分類 收藏
What is a protein? We often think about
protein as a nutritional requirement. You
eat meat because it has a lot of protein.
But proteins are far more than just food.
Proteins are made of a string of smaller
building blocks called amino acids. Amino
acids are kind of like Legos that can be
used to build proteins with different
structures. When we eat our food, we break
down the proteins that we ate into amino
acids and then we stick them back
together again to make lots of different
types of proteins to do jobs in the cell.
Here are some things that proteins can
do: detect light, form hair, and fight
disease. Let's look more closely at three
examples. One: proteins move you. The
reason that meat has a lot of protein is
that meat is muscle. Muscle has to
contract to move our body, so it's full
of a type of protein that moves stuff
around. Let's see how that works: here are
some proteins in the muscle fiber. This
protein, called myosin, can change its
shape. When it changes shape, it moves
these fibers relative to one another.
Millions of these tiny movements cause
the whole muscle to contract.
Two: proteins can kill you. Botox is a protein
that cuts up molecules in nerve cells
that control your muscles. This means
that Botox makes your muscles relax. This
can be handy to reduce wrinkles for
Hollywood actors, but it's not so great
with the muscles controlling your lungs
stop working after you eat food
contaminated with botulism.
Three: proteins speed things up. Enzymes are
proteins that make reactions go more
quickly. For example, the enzyme amylase
helps break down starch into sugar. You
have amylase in your saliva. Try
chewing a piece of bread for a really
long time. Keep chewing! What do you notice?


什麼是蛋白質 (What is a protein?)

959 分類 收藏
葉紫含 發佈於 2018 年 1 月 9 日
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