The inside of the barrel-shaped LDL protein consists of hydrophobic amino acids, while its outside portions in contact with the blood fluid consist of hydrophilic amino acids.
LDL is a type of lipoprotein, i.e., it contains protein as well as lipid (cholesterol). The full form of LDL is Low Density Lipid. LDL is considered to be the bad cholesterol for the body. It can cause diseases of the heart like heart attack or stroke. 
Amino acids are the essential molecule that act as a monomer for the formation of proteins inside the body. They contain an amino group and  a carboxylic group attached to the same carbon atom. There are also a hydrogen atom and a variable R group attached to the carbon, also called the alpha carbon. 
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Answer:
Energy is if not the most fundamental unit of everything, along with matter, space and time, thus it is one of the foundations of all science.
Explanation:
Energy in science is like words in a book, you could not read the book without words, similarly, there would be no way to do science without energy. Take this example You can only measure the *speed* of an object if it has energy. 
We could look at biolgy and see how photosynthesis makes use of energy. In photosynthesis we see plant cells converting energy from the sun into usful sugars to help the plant grow.
Now we could look at astronomy and see how energy is used, If you observe stars you can see the different brightnesses and masses, which tells you alot about what type of energy conversion is happening inside the star (nuclear fusion).
 
        
             
        
        
        
I believe it’s B or D sorry I’m not 100% sure
        
             
        
        
        
Answer:
A. keeps you healthy
Explanation:
The immune system protects your body from outside "invaders," such as bacteria, viruses, fungi, and toxins.