Slide 1 of 31 Chemistry 24.3. © Copyright Pearson Prentice Hall Slide 2 of 31 24.3 Amino Acids and Their Polymers Many people are lactose intolerant

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Chemistry 24.3

© Copyright Pearson Prentice Hall

Slide 2 of 31

24.3 Amino Acids and Their Polymers

Many people are lactose intolerant. These people cannot digest milk products because their bodies do not produce enough of the enzyme lactase to digest lactose, the sugar found in milk. You will learn what enzymes are and what function they serve in the body.


Amino Acids and Their Polymers >

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24.3 Amino Acids

Amino Acids

What is the general structure of an amino acid?

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24.3 Amino Acids and Their Polymers > Amino Acids

An amino acid is any compound that contains an amino group (—NH2) and a carboxyl group (—COOH) in the same molecule.


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Amino Acids and Their Polymers >24.3 Amino Acids

Amino acids have a skeleton that consists of a carboxyl group and an amino group, both of which are covalently bonded to a central carbon atom. The remaining two groups on the central carbon atom are hydrogen and an R group that constitutes the amino acid side chain.

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24.3 Amino Acids and Their Polymers > Amino Acids



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24.3 Peptides

Peptides

Which functional groups are always involved in amide bonds between amino acids?

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24.3 Amino Acids and Their Polymers > Peptides

A peptide is any combination of amino acids in which the amino group of one amino acid is united with the carboxyl group of another amino acid.

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24.3 Amino Acids and Their Polymers > Peptides

The amide bond between the carboxyl group of one amino acid and the nitrogen in the amino group of the next amino acid in the peptide chain is called a peptide bond.


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Amino Acids and Their Polymers >24.3 Peptides

The amide bonds between amino acids always involve the central amino and central carboxyl groups. The side chains are not involved in the bonding.



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24.3 Proteins

Proteins

What determines the differences in the chemical and physiological properties of peptides and proteins?

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24.3 Amino Acids and Their Polymers > Proteins

A peptide with more than about 100 amino acids is called a protein.

• Your skin, hair, nails, and muscles are made of protein.

• Proteins are needed for almost all chemical reactions that take place in the body.

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Amino Acids in a Peptide Chain

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Sections of a peptide chain may coil into a regular spiral, known as a helix.

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Peptide chains may also be arranged side by side to form a pleated sheet.


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Amino Acids and Their Polymers >24.3 Proteins

Differences in the chemical and physiological properties of peptides and proteins result from differences in the amino acid sequence.

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The Shape of Myoglobin



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24.3 Enzymes

Enzymes

How do enzymes affect the rates of reactions in living things?

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24.3 Amino Acids and Their Polymers > Enzymes

Enzymes are proteins that act as biological catalysts.

Enzymes increase the rates of chemical reactions in living things.

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The enzyme urease hydrolyzes urea, a constituent of urine, into ammonia and carbon dioxide.

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How Enzymes Work

Enzymes catalyze most of the chemical changes that occur in the cell.

• Substrates are the molecules on which an enzyme acts.

• The place on an enzyme where a substrate binds is called the active site.

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In a typical enzymatic reaction, the substrate interacts with side chains of the amino acids on the enzyme. These interactions cause the making and breaking of bonds.

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An HIV particle (red) infects a human white blood cell (orange). The diagram models the enzyme HIV protease.

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The enzyme carbonic anhydrase catalyzes the reversible breakdown of carbonic acid to carbon dioxide and water.

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Coenzymes

Coenzymes are metal ions or small organic molecules that must be present for an enzyme-catalyzed reaction to occur.

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The enzyme catalase includes an iron(III) ion in its structure. Catalase catalyzes the breakdown of hydrogen peroxide to water and oxygen.


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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

24.3 Section Quiz.

24.3.


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24.3 Section Quiz.

1. Choose the correct words for the spaces. An amino acid is a compound having the ________ group and the _________ group bonded to a central carbon atom.

a. carboxyl, amino

b. carbonyl, amide

c. amino, peptide

d. carbohydrate, amide


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24.3 Section Quiz.

2. Choose the correct words for the space. A protein is a peptide with ___________ amino acids linked in a chain.

a. more than about 100

b. less than about 100

c. two

d. zero


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24.3 Section Quiz.

3. Enzymes affect biochemical reactions by

a. changing the equilibrium position of the system.

b. acting as catalysts to speed up the reaction.

c. being consumed as the reaction progresses.

d. decreasing the size of competing substrates.


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24.3 Section Quiz.

4. Some vitamins participate in biological processes as

a. peptides.

b. amino acids.

c. enzymes.

d. coenzymes.

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Slide 1 of 31 Chemistry 24.3. © Copyright Pearson Prentice Hall Slide 2 of 31 24.3 Amino Acids and Their Polymers Many people are lactose intolerant