Introduction to
Biochemistry
Chemistry 301
Course
Outline
- Course Home Page
- Course Objectives
- Course Outline
- Unit 1
- Unit 2
- Unit 3
- Unit 4
- Unit 5
- Unit 6
- Unit 7
- Unit 8
- Unit 9
- Unit 10
- Unit 11
- Unit 12
- Unit 13
- Study Schedule
- Student Evaluation
- Resources
- Digital Reading Room
- Tutor-marked Exercise 2
DNA Sequence for Question 8
Unit 2
Amino Acids and Proteins
Overview
Amino acids are the building blocks that make up proteins. There are twenty common amino acids, and they can be joined together, much like beads on a string, to form proteins. Proteins are the “workers” in the cell. There are thousands of proteins, because amino acids can join together in various combinations and to almost any length. In this unit, you will learn what the amino acids look like, and about their ionic behaviour. You will also learn about the structures and functions of proteins. If you find, while reading the textbook or doing the study problems, that you are getting swamped by too much detail (a common problem in biochemistry), read the summary at the end of the relevant chapter.
Unit 2 is divided into six lessons:
- Amino Acids
- Proteins—Primary Structure
- 3-D Structure of Proteins I—Secondary Structure
- 3-D Structure of Proteins II—Tertiary and Quaternary Structures
- Protein Folding and Protein Dynamics
- What Do Proteins Do?
Objectives
After completing this unit, you should be able to
- identify the twenty common amino acids.
- explain how amino acids are joined to form a protein.
- describe how the physicochemical properties of the amino acids determine the three-dimensional structure of a protein.
- define the terms “primary structure,” “secondary structure,” “tertiary structure,” and “quaternary structure,” as applied to proteins.
- list the diverse roles proteins play in biological systems.
- explain what is meant by “variant” and “invariant” regions in the evolution of proteins.
- use examples to explain how the structural design of a protein is directly related to its biological function.
Glossary
| amino acid | an amino group and a carboxylic acid group attached to an “alpha” carbon (α-C); a hydrogen and a small organic group (e.g., —H, —CH3, —CH2OH), called an R-group, are also attached to the α-C |
| amphoteric | organic substance that acts as both an acid and a base |
| C-terminus (of a protein) |
free carboxyl end |
| chiral compound | molecule that cannot be superimposed on its mirror image |
| conservative substitution | existence of residues with similar but not identical properties in the side chains of particular amino acid positions |
| disulphide bond (in proteins) |
covalent bond between two cysteine R-groups |
| enantiomers | two organic compounds that are not superposable, but that are mirror images; these compounds contain one or more chiral carbons |
| homologous proteins | proteins that are related through evolution (e.g., cytochrome c proteins) |
| invariant residue | same amino acid found at the same position in related proteins |
| L-amino acid | stereoisomeric form of amino acids found in proteins (stereochemistry is reviewed on pages 86-89) |
| N-terminus (of a protein) |
the free amino end |
| peptide bond | linkage between the amino group of one amino acid and the carboxyl group of another amino acid |
| peptide or polypeptide | a polymer chain of three or more amino acids |
| point mutation | amino acid substitution in a homologous protein |
| protein | molecule consisting of one or more polypeptide chains |
| R-group (of an amino acid) |
one of twenty (or more) different organic groups bonded to the alpha carbon |
| reverse turn (or β bond) |
stretches of polypeptide (within proteins) that change direction abruptly |
| stereoisomers | molecules with the same chemical formulae; they differ only in the way the different attached groups are oriented in space |
| zwitterion | ion with a positive and a negative charge |
