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 Cell vs. virus: A battle for health
 이** (jean)



All living things are made of cells. In the human body, these highly efficient units

are protected by layer upon layer of defense against icky invaders like the cold virus.

Shannon Stiles takes a journey into the cell, introducing the microscopic arsenal of 

weapons and warriors that play a role in the battle for your health. 



You're in line at the grocery store when, uh oh, someone sneezes on you. 

The cold virus is sucked inside your lungs and lands on a cell on your airway lining.

Every living thing on Earth is made of cells, from the smallest one-celled bacteria 

to the giant blue whale to you. Each cell in your body is surrounded by a cell 

membrane, a thick flexible layer made of fats and proteins, that surrounds and 

protects the inner components. It's semipermeable, meaning that it lets some

thing pass in and out but blocks others. The cell membrane is covered with tiny 

projections. They all have functions, like helping cells adhere to their neighbors 

or binding to nutrients the cell will need. Animal and plant cells have cell 

membranes.Only plant cells have a cell wall, which is made of rigid cellulose

that gives the plant structure. The virus cell that was sneezed into your lungs

is sneaky. Pretending to be a friend, it attaches to a projection on the cell 

membrane, and the cell brings it through the cell membrane and inside. 

When the virus gets through, the cell recognizes its mistake. An enemy is inside!

Special enzymes arrive at the scene and chop the virus to pieces.

They then send one of the pieces back through the cell membrane, 

where the cell displays it to warn neighboring cells about the invader. 

A nearby cell sees the warning and immediately goes into action.

It needs to make antibodies, proteins that will attack and kill the invading virus. 

This process starts in the nucleus. The nucleus contains our DNA, the blueprint

that tells our cells how to make everything our bodies need to function. 

A certain section of our DNA contains instructions that tell our cells how to make

antibodies. Enzymes in the nucleus find the right section of DNA, then create 

a copy of these instructions, called messenger RNA. The messenger RNA leaves

the nucleus to carry out its orders. The messenger RNA travels to a ribosome. 

There can be as many as 10 million ribosomes in a human cell, all studded along

a ribbon-like structure called the endoplasmic reticulum. This ribosome reads the

instructions from the nucleus. It takes amino acids and links them together one by

one creating an antibody protein that will go fight the virus. But before it can do 

that, the antibody needs to leave the cell. The antibody heads to the golgi 

apparatus. Here, it's packed up for delivery outside the cell. Enclosed in a bubble

made of the same material as the cell membrane, the golgi apparatus also gives

the antibody directions, telling it how to get to the edge of the cell. When it gets

there, the bubble surrounding the antibody fuses to the cell membrane. The cell 

ejects the antibody, and it heads out to track down the virus. The leftover bubble

will be broken down by the cell's lysosomes and its pieces recycled over and over

again. Where did the cell get the energy to do all this? That's the roll of the 

mitochondria. To make energy, the mitochondria takes oxygen, this is the only

reason we breathe it, and adds electrons from the food we eat to make water

molecules. That process also creates a high energy molecule, called ATP which

the cell uses to power all of its parts. Plant cells make energy a different way.

They have chloroplasts that combine carbon dioxide and water with light energy 

from the sun to create oxygen and sugar, a form of chemical energy. All the parts

of a cell have to work together to keep things running smoothly, and all the cells 

of your body have to work together to keep you running smoothly. 

That's a whole lot of cells. Scientists think there are about 37 trillion of them. 



1. What is a cell? 

2. How do cells beat the virus?

3. Cells need energy to perform all of their functions.

    Where in the cell is energy made?

2021-02-17 오후 2:06:46
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