Biology for Kids
Proteins and Amino Acids
What are amino acids?
Amino acids are special organic molecules used by living organisms to make proteins. The main elements in amino acids are carbon, hydrogen, oxygen, and nitrogen. There are twenty different kinds of amino acids that combine to make proteins in our bodies. Our bodies can actually make some amino acids, but the rest we must get from our food.
What are proteins?
Proteins are long chains of amino acids. There are thousands of different proteins in the human body. They provide all sorts of functions to help us survive.
Structure of a protein
Why are they important?
Proteins are essential for life. Around 20% of our body is made up of proteins. Every cell in our body uses proteins to perform functions.
How are they made?
Proteins are made inside cells. When a cell makes a protein it is called protein synthesis. The instructions for how to make a protein are held inside the DNA molecule. The two major stages in making a protein are called transcription and translation.
The first step in making a protein is called transcription. This is when the cell makes a copy (or "transcript") of the DNA. The copy of DNA is called RNA because it uses a different type of nucleic acid called ribonucleic acid. The RNA is used in the next step, which is called translation.
The next step in making a protein is called translation. This is when the RNA is converted (or "translated") into a sequence of amino acids that makes up the protein.
The translation process of making the new protein from the RNA instructions takes place in a complex machine in the cell called the ribosome. The following steps take place in the ribosome.
- The RNA moves to the ribosome. This type of RNA is called the "messenger" RNA. It is abbreviated as mRNA where the "m" is for messenger.
- The mRNA attaches itself to the ribosome.
- The ribosome figures out where to start on the mRNA by finding a special three letter "begin" sequence called a codon.
- The ribosome then moves down the strand of mRNA. Every three letters represents another amino acid molecule. The ribosome builds a string of amino acids based on the codes in the mRNA.
- When the ribosome sees the "stop" code, it ends the translation and the protein is complete.
How a ribosome makes a protein
Different Types of Proteins
There are literally thousands of different types of proteins in our bodies. Here are a few of the major groups and functions of proteins:
- Structural - Many proteins provide structure for our bodies. This includes collagen which is found in cartilage and tendons.
- Defensive - Proteins help protect us from diseases. They make up antibodies that fight off foreign invaders such as bacteria and other toxic substances.
- Transport - Proteins can help to carry essential nutrients around our bodies. One example is hemoglobin which carries oxygen in our red blood cells.
- Catalysts - Some proteins, such as enzymes, act as catalysts to assist in chemical reactions. They help us to break up and digest our food so it can be used by our cells.
- We get amino acids from basic foods such as chicken, bread, milk, nuts, fish, and eggs.
- Hair is made up of a protein called keratin.
- A special kind of RNA called transfer RNA moves the amino acids to the ribosome. It is abbreviated as tRNA where the "t" stands for transfer.
- The bonds that link the amino acids in a protein together are called peptide bonds.
- The arrangement and type of different amino acids along the protein strand determines the function of the protein.
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