Wrap-Up

Summary

Let's take a few moments to go through an overview of the information that has been presented to you in this lesson.

	Proteins are synthesized from twenty common amino acids.
	Some of these can be made in our body and some are derived from our diet.
	They are ingested as proteins which are then digested into amino acids by means of hydrolysis reactions.
	Those amino acids are transported to the cells where they are reassembled by dehydrogenation reactions which involve the acid group of one molecule and the amino group of another molecule. This is achieved using a process that we will study more when we take up the study of nucleic acids.

Structure

	The order in which the amino acids are joined to one another is referred to as the primary structure of the protein.
	The reaction between the amino and acid functional groups causes the formation of the amide or peptide bond which is what holds together the primary structure.
	These amino acids then form a secondary structure. And whether it is alpha or beta or some other form it is the residual carbonyl group from the carboxylic acid group and the residual NH from the ammonia functional group that form hydrogen bonds that secures the secondary structure.
	The side groups of the amino acids then take over and cause the shape of the protein into its particular conformation by dictating the tertiary structure and in some cases even a fourth level, a quaternary structure if there are more than one amino acid or polypeptide chains that are joined together to make the protein.

Properties

	The side groups of the amino acids allow for or determine the properties of the proteins other than just the conformation.
	They also determine the solubility of the protein in the water because those side groups can either be hydrophilic or hydrophobic.
	Also, because of the presence of amino groups and carboxylic acid groups in the side chains of some proteins, it's also possible for proteins to serve as buffers either accepting protons from the solution if it becomes too acidic or donating protons to the solution if it becomes too basic. In this way the side chains allow protein molecules to serve as a pH buffering mechanism for body fluids.

Function

The side groups along with the conformation also determine the function of the proteins.

The functions of proteins are many and we concentrated on just four of those.

	Proteins can serve to provide structure.
	They can serve as enzymes.
	They can serve as carrier molecules, also known as transport proteins.
	They can serve as messengers, for example, hormones.

In addition, proteins can provide energy by being oxidized in the citric acid cycle and respiration pathway.

Problem Set and Self Quiz

To help you review some of the things you need to do with regard to this lesson I recommend that you take some time now to work on the problem set for the lesson. This is also given in Exercise 14 in your workbook. Then also take the self quiz and check your answers for that. If you have any questions with these or need any help, be sure to ask.

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E-mail instructor: Sue Eggling

Clackamas Community College
Š2001, 2003 Clackamas Community College, Hal Bender