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.