An Introduction to Molecular Biology/Protein synthesis

An is a protein used to speed up the rate of a chemical reaction. Because they regulate the rate of chemical reactions, they also are called . There are many, many, many different types of enzymes, because for each chemical reaction that occurs, an enzyme specific to that reaction must be made.

Control of protein synthesis ..

Enzymes are able to catalyze reaction after reaction millions of times before they start to wear out. Then, the body creates more enzymes by synthesizing the proper protein chains from the correct amino acids.

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This lesson provides an overview of the process of protein synthesis and the ..

This is accomplished when the double spiral of DNA unwinds and unzips at the point where the instructions for the given protein are located.

This section of the DNA molecule is called a . While it is unzipped, the gene acts as a pattern or template for another kind of nucleic acid called (). . The other bases, G, T, and C attract the same partners as they do in DNA replication, G attracts C, C attracts G, and T attracts A

The newly formed, single stranded mRNA carries an accurate reproduction of the information that was recorded in the DNA. The formation of messenger RNA is called .

interacts with molecules involved in protein synthesis.

The molecules of messenger RNA (mRNA) leave the nucleus through small pores in the nuclear membrane carrying with them the instructions (encoded in the sequence of their nucleotides) that they picked up from the DNA molecule. In the cytoplasm, the mRNA molecule attaches to a small granular appearing organelle called a ribosome.

From the ribosome, mRNA molecules attract a second kind of smaller RNA molecule called .

One end of a tRNA molecule has a special site which can only bind to one specific kind of amino acid. There are many different types of transfer RNA molecules. In fact, there are more than one for each of 18 of the 20 different amino acids found in proteins (methionine and tryptophan being the exceptions).

The other end of each tRNA molecule carries a unique "tag." The tag is written in the usual code of a nucleic acid--a sequence of bases. Each amino acid carrying molecule has its own three letter tag or code. For example, the valine tRNA is tagged AAC, the alanine-transfer RNA is tagged GGC, the phenylalanine -tRNA is tagged AAA and so on.

The three base pairs of the tRNA tags are attracted to their complementary partners on the mRNA that is lined up on the ribosome. The three letter sequences of the mRNA are called a . The three letter tRNA tags are called . Guided by the mRNA, each transfer RNA donates its amino acid, in the proper order, to a growing chain of amino acids that will be joined by peptide bonds to form a new polypeptide (protein).

Describe initiation of protein synthesis at the ribosome

All proteins are made up of . Think of amino acids as train cars that make up an entire train called a protein. Proteins are formed by amino acids, which are produced based on the genetic information in a cell. Then, the amino acids that are created in the cell are linked together in a certain order. Each protein is made up of a unique number and order of amino acids. The protein that is created has a specific job to do or a specific tissue (such as muscle tissue) to create.

Animations for translation in protein synthesis

One of the most important activities of a cell is the production of proteins that fulfill major roles in the cell--structural, enzymatic, hormonal, and more. Chromosomes never leave the nucleus of the cell. However, protein synthesis is carried out by the , small structures which either float freely in the cytoplasm or are attached to membrane networks that snake their way through the cell—both outside the nucleus.

This section will explain briefly and superficially the way the instructions reach the ribosomes and how they are translated into the language of proteins. This information is not critical for understanding the use of DNA for genealogy but does form a foundation for understanding the way genetic mutations are expressed and a basis for understanding genetic differences.

A protein is a chainlike molecule built of subunits of smaller molecules called amino acids. We obtain most of our amino acids by digesting proteins taken in with our food. The digestive process breaks the protein chains down into individual amino acid molecules which are then absorbed by the blood and transported to the individual body cells. Human cells can also manufacture some amino acids. However, eight of the amino acids that are essential to building human proteins must be acquired from food. They eight essential amino acids are phenylalanine, valine, leucine, isoleucine, lysine, threonine, tryptophan and methionine. Histidine is essential for infants but not for adults.