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SATURATED AND UNSATURATED

There are two kinds of fats, saturated and unsaturated. Unsaturated fats have at least one double bond in one of the fatty acids. A double bond happens when two electrons are shared or exchanged in a bond. They are much stronger than single bonds. Saturated fats have no double bonds.
Fats have a lot of energy stored up in their molecular bonds. That's why the human body stores fat as an energy source. When it needs extra fuel, your body breaks down the fat and uses the energy. Where one molecule of sugar only gives a small amount of energy, a fat molecule gives off many times more.

5. THE NUCLEIC ACIDS

The nucleic acids are the building blocks of living organisms. You may have heard of DNA described the same way. Guess what? DNA is just one type of nucleic acid. Some other types are RNA, mRNA, and tRNA. All of these "Na's" work together to help cells replicate and build proteins. NA? Hold on. Might that stand for nucleic acid? It might.

THE BASICS

We already told you about the biggie nucleic acids (DNA, RNA, mRNA, tRNA). They are actually made up chains of base pairs stretching from only a few to millions. When those pairs combine in super long chains (DNA), they make a shape called a double helix. The double helix shape is like a twisty ladder. The base pairs are the rungs. We're very close to talking about the biology of cells here. Back to the chemistry..

FIVE EASY PIECES

There are five easy parts of nucleic acids. All nucleic acids are made up of the same building blocks (monomers). Chemists call the monomers nucleotides. The five pieces are Uracil, Cytosine, Thymine, Adenine, and Guanine. Just as there are twenty (20) amino acids needed by humans to survive, there are five (5) nucleotides.
These nucleotides are made of three parts.
1. A five carbon sugar
2. A base that has a nitrogen (N) atom
3. An ion of phosphoric acid

 

DNA

DNA DETAILS

DNA stands for Deoxyribonucleic Acid. It is special because it holds the code for every cell in your body. That's right, every cell in your body uses DNA for an instruction manual. If you want to take away all of the importance of that statement, you can say that DNA is just a long spiral chain of nucleotides. But it's more. So much more.

So you get all of those nucleotides in two long chains that twist around each other. That twisting shape is called a double-helix. The spiral ladder has the ability to wind and unwind so that the nucleic acid chain can duplicate itself. That duplication process happens every time a cell divides.

DNA DOWN TIME

When a cell is in its normal state, the DNA is not duplicating and it just looks like a blob of white strands. The nucleic acid chains usually sit around uncoiled and as loose strands called chromatin. When it is time for the cell to reproduce, they condense and wrap up very tightly. The tightly wound DNA is called a chromosome. Chromosomes look kind of like long, limp hot dogs. They are also found in pairs.

In most organisms, you will find DNA in the nucleus. Chromosomes work with other nucleic acids in the cell to build proteins and help in duplication. You will most likely find mRNA (messenger-ribonucleic acid) in the nucleus with the DNA. tRNA (transfer-ribonucleic acid) is found outside of the nucleus, floating in the cell. In a few organisms called prokaryotes, there is no defined nucleus and the DNA is found throughout the cell.



DNA = INSTRUCTION BOOK

Just remember that DNA is the instruction manual for an organism. Even though all organisms use the same five base pairs to build DNA (purines and pyrimidines), it is the order that makes us who we are. Every organism on Earth has a different number and order of base pairs. That order determines your physiology. (to determine=to be the cause of or reason for (something)
▪ The demand for a product determines its price. ▪ He believes that one's personality is determined mostly by genetics. ◊A determining factor is a reason to make a particular choice or decision.
▪ Price was the determining factor in their decision).


Date: 2016-01-03; view: 262


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