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Chemistry of Life

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Water• About 60-90 percent of an organism is

water• Water is used in most reactions in the

body• Water is called the universal solvent• Water properties:

– Polarity– Cohesivness– Adhesivness– Surface Tension

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Organic Compounds

• Compounds that contain CARBON are called organic.

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Carbon (C)• Carbon has 4 electrons in

it’s outer shell.• Carbon can form covalent

bonds with as many as 4 other atoms (elements).

• Usually with C, H, O or N.

• Example: CH4(methane)

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Macromolecules• Large organic molecules.• Also called POLYMERS.• Made up of smaller “building

blocks” called MONOMERS.• Examples:

1. Carbohydrates2. Lipids3. Proteins4. Nucleic acids (DNA and

RNA)

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Question:How Are

Macromolecules

Formed?

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Answer: Dehydration Synthesis

• Also called “condensation reaction”

• Forms polymers by combining monomers by “removing water”.

HO H

HO HO HH

H2O

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Question: How are

Macromolecules separated or digested?

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Answer: Hydrolysis

• Separates monomers by “adding water”

HO HO HH

HO H

H2O

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Carbohydrates

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Carbohydrates• Small sugar molecules to large

sugar molecules.• Americans consume an average of

140 pounds of sugar per person per year

• Examples:A. monosaccharideB. disaccharideC. polysaccharide

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CarbohydratesMonosaccharide: one sugar

unit

Examples: glucose (C6H12O6)

deoxyriboseriboseFructoseGalactose

glucose

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CarbohydratesDisaccharide: two sugar

unitExamples:

–Sucrose (glucose+fructose)

–Lactose (glucose+galactose)

–Maltose (glucose+glucose)glucoseglucose

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CarbohydratesPolysaccharide: many sugar

unitsExamples: starch (bread,

potatoes)glycogen (beef

muscle)cellulose

(lettuce, corn)

glucoseglucose

glucoseglucose

glucoseglucose

glucoseglucose

cellulose

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Cellulose• Cellulose is not a nutrient for humans,

but it is an important part of a healthful diet

• Most fresh fruits, vegetables, and whole grains are rich in cellulose

• Some microbes can break down cellulose into glucose monomers

• Cellulose, found in plant cell walls, is the most abundant organic compound on Earth

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• Cows harbor cellulose-digesting bacteria in their stomach to hydrolyze the cellulose of hay and grass to convert the glucose to other nutrients that nourish the cow• Termites also have cellulose digesting microbes within their gut because they are unable to digest it by themselves.

• Some fungi can also digest cellulose, helping recycle chemical elements within the Earth’s ecosystem

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Lipids

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Lipids• General term for compounds

which are not soluble in water.• Lipids are soluble in hydrophobic

solvents.• Remember: “stores the most

energy”• Examples: 1. Fats

2. Phospholipids3. Oils4. Waxes5. Steroid hormones6. Triglycerides

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LipidsSix functions of lipids:

1. Long term energy storage2. Protection against heat loss (insulation)3. Protection against physical shock4. Protection against water loss5. Chemical messengers (hormones)6. Major component of membranes (phospholipids)

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LipidsTriglycerides:

composed of 1 glycerol and 3 fatty acids.

HH-C----O

H-C----O

H-C----O

H

glycerol

OC-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

=

fatty acids

OC-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

=

OC-CH2-CH2-CH2-CH =CH-CH

2 -CH2-CH

2 -CH2-CH

3

=

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Fatty AcidsThere are two kinds of fatty acids you may

see on food labels:1. Saturated fatty acids: no double bonds (bad)

2. Unsaturated fatty acids: double bonds (good)

OC-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

=

saturated

OC-CH2-CH2-CH2-CH=CH-CH

2 -CH2 -CH

2 -CH2 -CH

3

=

unsaturated

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Proteins

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Proteins (Polypeptides)• Amino acids (20 different kinds of aa)

are bonded together by peptide bonds (polypeptides).

• Six functions of proteins:1. Storage: albumin (egg white)2. Transport: hemoglobin3. Regulatory: hormones4. Movement: muscles5. Structural: membranes, hair, nails6. Enzymes: cellular reactions

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Proteins (Polypeptides)

Four levels of protein structure:A. Primary StructureB. Secondary Structure C. Tertiary Structure D. Quaternary Structure

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Primary StructureAmino acids bonded

together by peptide bonds (straight chains)

aa1 aa2 aa3 aa4 aa5 aa6

Peptide Bonds

Amino Acids (aa)

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Secondary Structure• 3-dimensional folding

arrangement of a primary structure into coils and pleats held together by hydrogen bonds.

• Two examples:

Alpha Helix

Beta Pleated Sheet

Hydrogen Bonds

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Tertiary Structure• Secondary structure is bent and

folded into a more complex 3-D arrangement of linked polypeptides

• Bonds: H-bonds, ionic, disulfide bridges (S-S)

• Call a “subunit”.Alpha Helix

Beta Pleated Sheet

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Quaternary Structure

• Composed of 2 or more “subunits”

• Globular in shape• Form in Aqueous

environments• Example: enzymes

(hemoglobin)subunits

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Nucleic Acids

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Nucleic acids• Two types:

a. Deoxyribonucleic acid (DNA- double helix)

b. Ribonucleic acid (RNA-single strand)

• Nucleic acids are composed of long chains of nucleotides linked by dehydration synthesis.

• A typical cell in your body has about 2 meters of DNA

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Nucleic acids• Nucleotides include:

phosphate grouppentose sugar (5-carbon)nitrogenous bases:

adenine (A)thymine (T) DNA

onlyuracil (U) RNA onlycytosine (C)guanine (G)

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Nucleotide

OO=P-O O

Phosphate Group

NNitrogenous base (A, G, C, or T)

CH2

O

C1C4

C3 C2

5

Sugar(deoxyribose)

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DNA - double helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A