Summary 5.4

Proteins execute most of the functions in cells. A protein is a polymer that is built up from a set of 20 kinds of monomers called amino acids. Furthermore, proteins play an important role in many of our daily functions; such as proteins that form hair, make up muscle, etc.

Amino Acid:
-monomer that consists of a central carbon atom, bonded to four other partners
-three of these four partners are common to all amino acids (amino group, carboxyl group, and hydrogen atom)
-the last group is the side group (AKA the "R-group), which determines the particular chemical properties of an amino acid

Long chains of amino acids linked together are called a polypeptide. Each link between the amino acids is connected through the process of dehydration. Proteins are created from one or more polypeptide chains. By arranging different amino acids into different orders, the body can compose an enormous variety of proteins. Every protein has a unique amino acid sequence.

Every protein is a series of precisely coiled, twisted, and folded polypeptides. The answer to how the proteins fold in the exact way is not fully understood. Certain side groups bond with others, which helps to fold polypeptides and to keep them folded. A protein is also affected by its environment, which in usual circumstances is aqueous. Thus, the hydrophillic amino acids tend to move to the edges of the protein, while the hydrophobic amino acids cluster in the middle.

When a protein undergoes unfavorable changes in temperature, pH, and other qualities, it could cause the protein to unravel and lose its shape; this process is called denaturation. Heating causes proteins to unfold because it breaks apart the weak bonds between side groups, and between side groups and water. After a protein goes through denaturation, it loses its power to function properly.

Concept Check

1.Give at least two examples of proteins you can "see" in the world around you. What are their functions? Two proteins that I can see are the proteins that make up fur, hair, and muscles. The function of fur is to keep animals warm, and muscles are used to perform daily things, such as moving and eating.

2.Relate amino acids, polypeptides, and proteins. Polypeptides (polymers) are longs chains of amino acids (monomers), and these polypeptides form in specific folds creating proteins.

3.Explain how heat can destroy a protein. Heat can destroy a protein by overcoming the weak bonds that are between the side groups, and between the side groups and water. Once this occurs, it changes the shape of the protein, and causes it not to function well.

4.Which parts of an amino acid's structure are the same in all amino acids? Which part is unique? The parts of an amino acid's structure that are the same in all amino acids are the carboxyl group, the amino group, and the hydrogen atom. The unique part is the side group, which determines the particular chemical properties of the amino acid.