Chapter 3Carbon and

the Molecular Diversity of Life

You Must Know

• The cellular functions of lipids.

• How the sequence and subcomponents of lipids determine their properties.

• The basic structure of a nucleic acid.

• How changes in organic molecules would affect their function.

Concept 3.4: Lipids are a diverse group of molecules

• What do these molecules have in common?

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Fats

OH

OH

OH

Glycerol

Hydroxyl

HO

HO

HO

Fatty Acid

carboxyl

triglyceride

Ester linkage

• Fatty acids vary in length (number of carbons) and in the number and locations of double bonds

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(a) Saturated fat

Structuralformula of asaturated fatmolecule

Space-fillingmodel ofstearic acid,a saturatedfatty acid

Saturated fatty acids have the maximum number of hydrogen atoms possible and no carbon carbon double bonds.

(b) Unsaturated fat

Structuralformula of anunsaturated fat molecule

Space-fillingmodel of oleic acid, an unsaturatedfatty acid Double bond

causes bending.

Unsaturated fatty acids have one or more carbon carbon double bonds.

• The major function of fats is energy storage• Fat is a compact way for animals to carry their

energy stores with them

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Figure 3.14ab

(a) Structural formula (b) Space-filling model

Choline

Phosphate

Glycerol

Fatty acids

Hyd

rop

hili

c h

ead

Hyd

rop

ho

bic

tai

ls

Phospholipids

Figure 3.14cd

Hydrophilichead

(d) Phospholipid bilayer

(c) Phospholipid symbol

Hydrophobictails

Steroids

Concept 3.6: Nucleic acids store, transmit, and help express hereditary information

• The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene

• Genes are made of DNA, a nucleic acid made of monomers called nucleotides

• There are two types of nucleic acids– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)

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Figure 3.26aSugar-phosphate backbone(on blue background)

(a) Polynucleotide, or nucleic acid

(b) Nucleotide

5 end

3 end

5C

5C

3C

3C

Phosphategroup Sugar

(pentose)

Nitrogenousbase

Nucleoside