1. Chapter 16 - - - - Proteins and Enzymes
Proteins are probably the most important of the Biological Compounds because even though they carry out different functions in the body, they all have one important function in common:
THEY PROMOTE GROWTH.
Any living thing that cannot grow will die.

2. Proteins are classified according to their function in the body:
See Page 558
The 4 most important classes of proteins are:
Examples:
Structural They provide structure to the body
Collagen, Keratin
Transport They carry substances throughout the body
Hemoglobin
Hormonal They regulate body metabolism
Insulin
Enzymes They make chemical reactions happen in the body
Sucrase
Collagen is the most abundant and most important protein in the human body

3. Functions of Proteins [See Page 558]

4. Like all biological compounds, Proteins are long chain molecules.
The basic unit (or building block) that forms long chains of proteins is an “Amino acid”

5. A base
An acid

6. Amino Acids Amino acids
1 - are the molecular building blocks of proteins
2 - contain a carboxylic acid group and an amino group on the alpha () carbon
3 - each contain a different side group (R)
(or side chain)
side chain R │
H2N—C —COOH H

7. Examples of Amino AcidsH
+ │
H3N—C—COO− │
H Glycine
CH3 │
H Alanine

8. by Pearson Education, Inc.
Nonpolar Amino Acids
See page 561 – Table 16.2
The essential non-polar amino acids
Copyright © 2009
by Pearson Education, Inc.

9. Copyright © 2009 by Pearson Education, Inc.
Amino Acids
Some polar amino acids
Copyright © by Pearson Education, Inc.

10. Acidic and Basic Amino Acids
An amino acid is
acidic when the R group is a carboxylic acid.
basic when the R group is an amine.

11. Amino acids will link together to form chains called “Peptides”
The linkage occurs by the bonding of the N-terminal of one amino acid with the C-terminal of another. This forms a train-like chain, and the chain can be any number of units in lenghth
Two amino acids linked together is called a DIPEPTIDE.
Three amino acids linked together is called a TRIPEPTIDE.
More than 3 amino acids linked together is a POLYPEPTIDE.
A protein is defined as a polypeptide containing 50 or more amino acids linked together.

12. The Peptide Bond A peptide bond is an amide bond.
forms between the carboxyl group of one amino acid and the amino group of the next amino acid.
O CH3 O
|| | ||
H3N—CH2—C—O– H3N—CH—C—O–
O H CH3 O
|| | | ||
H3N—CH2—C—N—CH—C—O–
peptide bond

13. The primary structure of a protein can be shown as:
An example of a polypeptide containing 4 amino acids linked.
The blue boxes surround individual amino acids. The red text shows the position of the peptide bonds (peptide or amide linkages) joining the amino acids together.

14. Write the dipeptide Ser-Thr. OH CH3 | | CH2 O HCOH O + | ║ + | ║
| |
CH2 O HCOH O
+ | ║ | ║
H3N─CH─C─O– H3N─CH─C─O–
OH CH3
| |
CH2O H HCOH O
+ | ║ | | ║
NH3─CH─C─N ─CH─ C─O– + H2O
Ser-Thr
The PEPTIDE bond

15. See Pages
A typical tripeptide
N Terminal C Terminal

16. A peptide chain will always contain a “C-terminal” at one end and an “N-terminal” at the other end.
Both ends are open to extend the chain by adding more amino-acids