Chapter 3 (The Molecular Diversity of Life) Carbon, Dehydration and Hydrolysis.

Chapter 3(The Molecular Diversity of Life)

Carbon, Dehydration and Hydrolysis

You Must Know

• The properties of carbon that make it so important.

• The role of dehydration reactions in the

formation of organic compounds and hydrolysis in the digestion of organic compounds.

Importance of Carbon

You don’t need to memorize these carbon skeletons.

Valences of the major elements of organic molecules

Hydrogen(valence 1)

Carbon(valence 4)

Nitrogen(valence 3)

Oxygen(valence 2)

• Critically important molecules of all living things fall into four main classes– Carbohydrates– Nucleic acids– Proteins– Lipids

• The first three of these can form huge molecules called macromolecules

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Hydrocarbons can undergo reactions that release a large amount of energy.

Hydrocarbons

Concept 3.2: Macromolecules are polymers, built from monomers

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• A dehydration reaction occurs when two monomers bond together through the loss of a water molecule

The Synthesis and Breakdown of Polymers

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Figure 3.6a

Unlinked monomerShort polymer

Longer polymer

(a) Dehydration reaction: synthesizing a polymer

Dehydration removesa water molecule,forming a new bond.

• Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction

The Synthesis and Breakdown of Polymers

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Figure 3.6b

(b) Hydrolysis: breaking down a polymer

Hydrolysis addsa water molecule,breaking a bond.

The Diversity of Polymers

• Each cell has thousands of different macromolecules.

• Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species.

• An immense variety of polymers can be built from a small set of monomers.

HO

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The Chemical Groups Most Important to Life

• Functional groups are the components of organic molecules that are most commonly involved in chemical reactions.

• The number and arrangement of functional groups give each molecule its unique properties.

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Figure 3.5Chemical Group

Hydroxyl group ( OH)

Compound Name Examples

Alcohol

Ketone

Aldehyde

Methylatedcompound

Organicphosphate

Thiol

Amine

Carboxylic acid,or organic acid

Ethanol

Acetone Propanal

Acetic acid

Glycine

Cysteine

Glycerolphosphate

5-Methyl cytosine

Amino group ( NH2)

Carboxyl group ( COOH)

Sulfhydryl group ( SH)

Phosphate group ( OPO32–)

Methyl group ( CH3)

Carbonyl group ( C O)

The seven functional groups that are most important in the chemistry of life:

You need to memorize the chemical groups, but not the compound name or examples.

Figure 3.5aa

Hydroxyl group ( OH)

Alcohol(The specific nameusually ends in -ol.)

(may be written HO )

Figure 3.5ab

Carbonyl group ( C O)

Figure 3.5ac

Carboxyl group ( COOH)

Carboxylic acid, or organic acid

Acetic acid, which givesvinegar its sour taste

Ionized form of COOH(carboxylate ion),found in cells

Figure 3.5ad

Amino group ( NH2)

Amine

Glycine, an amino acid(note its carboxyl group)

Ionized form of NH2

found in cells

Figure 3.5ba

Sulfhydryl group ( SH)

(may be written HS )

Figure 3.5bb

Phosphate group ( OPO32–)

Organic phosphate

Figure 3.5bc

Methyl group ( CH3)

Methylated compound