• List the function of proteins.Section Objectives:

• Describe the structure of amino acids and proteins.

• Explain how enzymes affect activation energy.

• Describe how an enzymes shape relates to its function.

• A protein is a polymer composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

Proteins

• The protein polymer is called a polypeptide.

• The protein monomer is called an amino acid.

The Function of Proteins • Structural proteins (e.g., hair & muscle).

• Disease fighting.

• Cell-to-cell signaling.• Transport.

• Control chemical reactions.

Amino Acids • Each amino acid consists of a central carbon

atom bonded to:– Hydrogen– Carboxyl group– Amino group– Side group (R Group)

• Dehydration reaction between the amino end of one amino acid to the carboxyl group of another.

Building a Protein

• Protein shape determines protein function.

Protein Shape

• Shape determined by side group and surrounding environment.– Primary (1°), Secondary (2°)

• Denaturation occurs when protein looses shape therefor function (e.g., temp. & pH).

• Hydrophilic or hydrophobic.

Enzymes • An enzyme is a

protein that changes the rate of a chemical reaction.

• Enzymes lower the activation energy of chemical reactions by acting as a catalyst.

How Enzymes Work • A specific reactant (substrate) fits into the

active site of the enzyme.• Active site positions

reactant molecules to facilitate chemical reaction.

• Enzymes themselves are unaffected by the reaction.

1. How is the enzyme’s active site important to the reaction?The active site holds the substrate while the reaction takes place.

2. Does this enzyme get used up after one reaction? Explain.No, the enzyme is recyclable. After the products are released, the active site becomes available again.

• What are the functions of proteins?Reconnect to Objectives:

• What is the protein monomer?

• What is an enzyme and how does it affect chemical reactions?

• How is an enzymes shape related to its function?

• What is the protein polymer?

End of Chapter 5!!