Section 2 Molecules of LifeChapter 3

Objectives

• Distinguish between monosaccharides, disaccharides,and polysaccharides.

• Explain the relationship between amino acids and protein structure.

• Describe the induced fit model of enzyme action.

• Compare the structure and function of each of the different types of lipids.

• Compare the nucleic acids DNA and RNA.

Section 2 Molecules of LifeChapter 3

Carbohydrates

• Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen in a ratio of about one carbon to two hydrogen atoms to one oxygen atom (1C:2H:1O)

• Carbohydrates are a source of energy and are used as structural materials in organisms.

Chapter 3

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Carbohydrates

Section 2 Molecules of Life

Section 2 Molecules of LifeChapter 3

Carbohydrates, continued

• Monosaccharides – Carbohydrates are made up of monomers called

monosaccharides (or simple sugars). – Contains carbon, hydrogen, and oxygen in a ratio

of 1:2:1

– General formula is (CH20)n

Monosaccharides

• The most common monosaccharides:– Glucose – the main source of energy for cells– Fructose – found in fruits and is the sweetest

monosaccharide– Galactose – found in milk

Monosaccharides

• Glucose, fructose, and galactose have the same molecular formula (C6H1206), but differing structures

• The different structures determine the slightly different properties of the three compounds

• Isomers are compounds with the same chemical formula but different structural forms

Section 2 Molecules of LifeChapter 3

Carbohydrates, continued

• Disaccharides and Polysaccharides– Two monosaccharides join in a condensation

reaction to form a double sugar called a disaccharide.

– A complex sugar, or polysaccharide, is made of three or more monosaccharides.

Polysaccharides

• Animals store glucose as the polysaccharide glycogen

• Plants store glucose as the polysaccharide starch

• Plants also make the polysaccharide cellulose (gives strength and rigidity to plant cells)

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Disaccharides

Section 2 Molecules of Life

Section 2 Molecules of LifeChapter 3

Proteins

• Proteins are organic compounds composed mainly of carbon, hydrogen, oxygen, and nitrogen.

• Proteins have many functions including structural, defensive, and catalytic roles.

Section 2 Molecules of LifeChapter 3

Proteins, continued

• Amino Acids– Proteins are made up of monomers called amino

acids. The sequence of amino acids determines a protein’s shape and function.

Amino Acids

• There are 20 amino acids that all share a basic structure

• Each amino acid contains a central carbon atom covalently bonded to four other atoms or functional groups– A single hydrogen atom– A carboxyl group– An amino group– R group

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Amino Acids

Section 2 Molecules of Life

Section 2 Molecules of LifeChapter 3

Proteins, continued

• Dipeptides and Polypeptides– Two amino acids are joined by peptide bonds

through a condensation reaction to form a dipeptide.

– A long chain of amino acids is called a polypeptide.

Chapter 3

Structure of Proteins

Section 2 Molecules of Life

Section 2 Molecules of LifeChapter 3

Proteins, continued

• Enzymes– Enzymes speed up chemical reactions and bind

to specific substrates. – The binding of a substrate with an enzyme causes

a change in the enzyme’s shape and reduces the activation energy of the reaction.

Chapter 3

Enzyme Activity

Section 2 Molecules of Life

Enzymes

• To learn more about the function of enzymes, you are going to do a virtual experiment

• PHSchool.com• cbp-1024

Section 2 Molecules of LifeChapter 3

Lipids

• Lipids are nonpolar molecules that store energy and are an important part of cell membranes.

Section 2 Molecules of LifeChapter 3

Lipids, continued

• Fatty Acids– Most lipids contain fatty acids, unbranched

carbon molecules that have a hydrophilic end and a hydrophobic end.

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Fatty Acids

Section 2 Molecules of Life

Section 2 Molecules of LifeChapter 3

Lipids, continued

• Triglycerides– Triglycerides consist of three fatty acids and one

molecule of glycerol.

Section 2 Molecules of LifeChapter 3

Lipids, continued

• Phospholipids– Phospholipids, which make up cell membranes,

consist of two fatty acids and one glycerol molecule.

Section 2 Molecules of LifeChapter 3

Lipids, continued

• Waxes– A wax is made of one long fatty acid chain joined

to one long alcohol.

• Steroids– A steroid is composed of four fused carbon rings.

Section 2 Molecules of LifeChapter 3

Nucleic Acids

• A nucleic acid is a large and complex organic molecule that stores and transports information.

Chapter 3

Structure of Nucleic Acids

Section 2 Molecules of Life

Chapter 3

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Nucleic Acids

Section 2 Molecules of Life

Section 2 Molecules of LifeChapter 3

Nucleic Acids, continued

• The nucleic acid deoxyribonucleic acid (DNA) contains genetic information for cell activities.

• Ribonucleic acid (RNA) molecules play many key roles in building of proteins and can act as enzymes.