General ---------Biology----------------------------------------------------- ------------------Online----------------------------------- Ch. 5 Macromolecules: carbohydrates, fats, proteins, nucleic acids

Table 5.1 in your text lists the types of proteins and their functions.  Read these and be prepared to discuss your three favorite functions of proteins.  Figure 5.15 illustrates the structural formula of the 20 commonly found amino acids.  Study these and be prepared to explain why some amino acids are polar and others are not.

Amino acid monomers are hooked together by condensation synthesis reactions to form proteins;  this was covered as an example, in the section on polymers.  Figure 5.16 further illustrates the synthesis of a protein (polypeptide) from amino acid monomers.  Study this figure and be prepared to locate the peptide bonds in a short protein.

The conformation or shape of proteins is the key to their function.  Proteins that function as enzymes, have active sites that accept reactant molecules that are exactly the right shape (like a lock and a key).  For an example, recall from Ch. 2 that
the endorphin molecule, and morphine molecule, both fit the protein endorphin receptor like a lock and key. Another examples is the enzyme you have in your salava that brakes down sucrose, a disaccharide sugar; the enzyme sucrase has an active site that the sucrose molecule must fit exactly to be browken down into two monosaccharides. 

The conformation of a protein is determined by:
its primary structure
its secondary structure
its tertiary structure, and sometimes
its quaternary structure.

Figures 5.17, 18, 19, 20, 23 and 24 describe these structural features.

A protein can be denatured by heat.  This is the reason you must store certain medicines in the refrigerator.  Figure 5.25 illustrates how heat increases the vibrational kinetic energy of the atoms in the molecule and causes hydrogen bonds to break.  As these hydrogen bonds break, the proteins shape changes, and it looses its ability to function.  This is an important process in the production of vaccines and the pasteurization of milk; it is also fundamental to the process of cooking foods.

The production of a protein in a cell, is shown in Figure 5.28. This is a central mechanism to all cell and organism functions and it underlies all topics in this course.  Read the Figure and associated text in your book, and complete the following assignment.

Assignment:  Print out Fig. 5.28 and label.