The Chemistry of Life:The Chemistry of Life:Organic CompoundsOrganic Compounds

Chapter 3

Learning Objective 1Learning Objective 1

• What properties make carbon the central component of organic compounds?

Carbon Atoms Carbon Atoms

• form four covalent bonds• single, double, or triple• straight or branched chains• rings

• bond with many different elements

Organic MoleculesOrganic Molecules

• Chains

Organic MoleculesOrganic Molecules

• Double bonds

Organic MoleculesOrganic Molecules

• Branched chains

Organic MoleculesOrganic Molecules

• Rings

KEY CONCEPTSKEY CONCEPTS

• Carbon atoms join with one another or other atoms to form large molecules with a wide variety of shapes

Learning Objective 2Learning Objective 2

• What is an isomer?

• What are the 3 principal isomer types?

IsomersIsomers

• Structural isomers• different covalent arrangements

IsomersIsomers

• Geometric isomers (cis–trans isomers)• different spatial arrangements

IsomersIsomers

• Enantiomers• mirror images

Learning Objective 3Learning Objective 3

• What are the major functional groups present in organic compounds, and their properties?

HydrocarbonsHydrocarbons

• Organic compounds• carbon and hydrogen only• nonpolar• hydrophobic

• Methyl group

Polar and Ionic Polar and Ionic Functional Groups Functional Groups

• Partial charges on atoms• at opposite ends of a bond• interact with one another• hydrophilic

• Hydroxyl and carbonyl groups

Acidic and Basic GroupsAcidic and Basic Groups

• Acidic• release hydrogen ions • become negatively charged• carboxyl and phosphate groups

• Basic• accepts a hydrogen ion• become positively charged• amino group

Functional GroupsFunctional Groups

• Polar (hydroxyl)

• Acidic (carboxyl)

• Basic (amino)

Table 3-1a, p. 49

Table 3-1b, p. 49

KEY CONCEPTSKEY CONCEPTS

• Hydrocarbons• nonpolar and hydrophobic

• Properties depend on functional groups: • hydroxyl and carbonyl groups (polar)• carboxyl and phosphate groups (acidic)• amino groups (basic)

Learning Objective 4Learning Objective 4

• What is the relationship between polymers and macromolecules?

Polymers and MacromoleculesPolymers and Macromolecules

• Polymers • long chains of monomers • linked through condensation reactions

• Macromolecules • large polymers• polysaccharides, proteins, and DNA• broken down by hydrolysis reactions

Condensation and HydrolysisCondensation and Hydrolysis

Fig. 3-5, p. 50

H2O

Condensation

Enzyme A

Hydrolysis

Enzyme BMonomerMonomer Dimer

HO OH HO OH HO O OH +

Learning Objective 5Learning Objective 5

• Distinguish among monosaccharides, disaccharides, and polysaccharides

• What is the difference between storage polysaccharides and structural polysaccharides?

CarbohydratesCarbohydrates

• Ratio• 1carbon: 2 hydrogen: 1 oxygen

• Monosaccharide• simple sugar• glucose, fructose, ribose

• Disaccharide• 2 monosaccharides• joined by glycosidic linkage • maltose, sucrose

Fig. 3-6, p. 51

Fig. 3-6, p. 51

Dihydroxyacetone (C3H6O3)(a ketone)

(a) Triose sugars (3-carbon sugars)

Glyceraldehyde (C3H6O3)(an aldehyde)

Fig. 3-6, p. 51

Ribose (C5H10O5)(the sugar component of RNA)

(b) Pentose sugars (5-carbon sugars)

Deoxyribose (C5H10O4)(the sugar component of DNA)

Fig. 3-6, p. 51

Glucose (C6H12O6)(an aldehyde)

(c) Hexose sugars (6-carbon sugars)

Galactose (C6H12O6)(an aldehyde)

Fructose (C6H12O6)(a ketone)

PolysaccharidesPolysaccharides

• Long chains• repeating units of simple sugar

• Storage polysaccharides• starch in plants • glycogen in animals

• Structural polysaccharide• cellulose, cell walls of plants

PolysaccharidesPolysaccharides

• Starch

KEY CONCEPTSKEY CONCEPTS

• Carbohydrates are composed of sugar subunits (monosaccharides), which can be joined to form disaccharides, storage polysaccharides, and structural polysaccharides

Learning Objective 6Learning Objective 6

• What are the characteristics, composition, and biological functions of fats, phospholipids, and steroids?

LipidsLipids

• Mainly hydrocarbon-containing regions• few oxygens (polar or ionic groups)

• Greasy or oily consistency• relatively insoluble in water

FatsFats

• Triacylglycerol• main storage fat• glycerol + 3 fatty acids

• Monoacylglycerols & diacylglycerols• 1 or 2 fatty acids

• saturated or unsaturated fatty acid• hydrogens

TriacylglycerolTriacylglycerol

Fig. 3-12b, p. 56

Ester linkage

A triacylglycerol

PhospholipidsPhospholipids

• Structure• glycerol • 2 fatty acids• phosphate group

• Function• cell membrane component

PhospholipidPhospholipid

Fig. 3-13, p. 58

Fatty acidsCholine

PhosphategroupGlycerol

Hydrophilichead

Hydrophobictail

Water

SteroidsSteroids

• Carbon atoms arranged in 4 rings • cholesterol, bile salts, some hormones

Fig. 3-15a, p. 59

Cholesterol

(a) Cholesterol is an essential component of animalcell membranes.

Indicatesdouble bond

KEY CONCEPTSKEY CONCEPTS

• Lipids store energy (triacylglycerol) and are the main structural components of cell membranes (phospholipids)

Learning Objective 7Learning Objective 7

• What are the structures and functions of proteins?

ProteinsProteins

• Polypeptides• long, linear polymers • 20 amino acids (monomers)• joined by peptide bonds

• Many functions• enzymes• structural components• cell regulators

Peptide BondsPeptide Bonds

Fig. 3-18, p. 63

Glycylalanine (a dipeptide)

R groupCarboxyl

groupAminogroup R group Peptide bond

Glycine Alanine

Learning Objective 8Learning Objective 8

• What features are shared by all amino acids?

• How are amino acids grouped into classes based on their side chains?

Amino AcidsAmino Acids

• Amino group and carboxyl group

• Side chains• determine chemical properties• nonpolar, polar, acidic, or basic

• Dipolar ions at cell pH• important biological buffers

Dipolar IonsDipolar Ions

Learning Objective 9Learning Objective 9

• What are the four levels of organization of protein molecules?

Primary StructurePrimary Structure

• Linear sequence of amino acids in polypeptide chain

Secondary StructureSecondary Structure

• Regular conformation• α-helix or β-pleated sheet• hydrogen bonds between amino acids

Fig. 3-20a, p. 64

(a) In an α-helix the R groups project out from the sides. (TheR groups have been omitted in the simplified diagram at left.)

Hydrogen bondshold helix coilsin shape

KEY:

Carbon atom

Oxygen atom

Nitrogen atom

Hydrogen atom

R group

Tertiary StructureTertiary Structure

• Overall shape of polypeptide chain• chemical interactions of side chains

Fig. 3-21a, p. 65

Hydrophobicinteraction

Hydrogenbond

Ionic bond

Disulfide bond

(a) Hydrogen bonds, ionic bonds, hydrophobic interactions,and disulfide bridges between R groups hold the parts ofthe molecule in the designated shape.

Quaternary StructureQuaternary Structure

• 2 or more polypeptide chains

Fig. 3-22a, p. 66

Alpha chain(α-globin)

Heme Alpha chain(α-globin)

Beta chain(β-globin)

(a) Hemoglobin, a globular protein, consistsof four polypeptide chains, each joined to aniron-containing molecule, a heme.

Beta chain(β-globin)

Alpha chain(α-globin)

Alpha chain(α-globin)

Stepped Art

Fig. 3-22a, p. 66

Heme

Beta chain(β-globin)

Beta chain(β-globin)

KEY CONCEPTSKEY CONCEPTS

• Proteins have multiple levels of structure and are composed of amino acid subunits joined by peptide bonds

Learning Objective 10Learning Objective 10

• What are the components of a nucleotide?

• Name some nucleic acids and nucleotides, and discuss their importance in living organisms

NucleotidesNucleotides

• Nitrogenous base• 2-ring purine or 1-ring pyrimidine

• Five-carbon sugar• ribose or deoxyribose

• One or more phosphate groups

Purines and PyrimidinesPurines and Pyrimidines

Fig. 3-23a, p. 68

(a) Pyrimidines. The three major pyrimidine bases found innucleotides are cytosine, thymine (in DNA only), and uracil(in RNA only).

Cytosine (C) Uracil (U)Thymine (T)

Fig. 3-23b, p. 68

(b) Purines. The two major purine bases found in nucleotidesare adenine and guanine.

Adenine (A) Guanine (G)

Nucleic AcidsNucleic Acids

• DNA and RNA• long chains of nucleotides

• Store and transfer information• sequence of amino acids in proteins• structure and function of the organism

Nucleic AcidNucleic Acid

• RNA

Fig. 3-24, p. 68

Phosphodiesterlinkage

Nucleotide

Guanine

Uracil

Adenine

Cytosine

Ribose

Ribose

Ribose

Ribose

NucleotidesNucleotides

• ATP (adenosine triphosphate)• essential in energy metabolism

• NAD+ • electron acceptor in biological oxidation

and reduction reactions

NucleotidesNucleotides

• cAMP

KEY CONCEPTSKEY CONCEPTS

• Nucleic acids (DNA and RNA) are informational molecules composed of long chains of nucleotide subunits. ATP and some other nucleotides have a central role in energy metabolism

Learning Objective 11Learning Objective 11

• Review the functions and chemical compositions of the 4 major groups of organic compounds: carbohydrates, lipids, proteins, and nucleic acids

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Structure of a PhospholipidStructure of a Phospholipid

Condensation and HydrolysisCondensation and Hydrolysis

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Secondary and Tertiary Secondary and Tertiary StructureStructure

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Structure of Starch and Structure of Starch and CelluloseCellulose

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Triglyceride FormationTriglyceride Formation

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