The Nature of Molecules

Chapter 2

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Properties of Water

Water is a key inorganic molecule, involved in biological processes for several reasons:

1. Water is a good solvent.

- Water dissolves polar molecules and ions.

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Properties of Water

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Properties of Water

2. Water organizes nonpolar molecules.- hydrophilic: “water-loving”-hydrophobic: “water-fearing”- Water causes hydrophobic molecules to aggregate or assume specific shapes.

3. Water can form ions.

H2O OH-1 + H+1

hydroxide ion hydrogen ion

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Lipids

The Chemical BuildingBlocks of Life

Chapter 3

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Biological Molecules

Biological molecules consist primarily of-carbon bonded to carbon, or-carbon bonded to other molecules.

Carbon can form up to 4 covalent bonds.

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Isomers: molecules with same chem. formula.

but a different arrangement(Shape)

Biological molecules are typically large molecules constructed from smaller subunits.

Monomer: single subunit

Polymer: many units

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dehydration synthesis: formation of large molecules by the removal of water

-monomers polymers

hydrolysis: breakdown of large molecules by the addition of water

-polymers monomers

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Biological Molecules

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Carbohydrates

Molecules with a 1:2:1 ratio of C, H, O

-empirical formula: (CH2O)n

-examples: sugars, starch, glucose

C – H covalent bonds hold much energy

Carbohydrates are good energy storage molecules.

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Carbohydrates

Glucose

-a monosaccharide – single sugar

-contains 6 carbons

-very important in energy storage

-fructose & galactose are isomers

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Carbohydrates

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Carbohydrates

Disaccharides

-2 monosaccharides linked together by dehydration synthesis

-used for sugar transport or energy storage

-examples: sucrose, lactose, maltose

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Carbohydrates

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Carbohydrates

Polysaccharides

-long chains of sugars

-used for energy storage

(plants use starch; animals use glycogen)

-used for structural support

(plants use cellulose; animals use chitin)

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Carbohydrates - starch

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Carbohydrates - glycogen

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Carbohydrates - cellulose

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Carbohydrates - chitin

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Nucleic Acids

Two types: DNA and RNA

Functions: specialized for the storage, transmission, and use of genetic information

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Nucleic acids are polymers of nucleotides.-nucleotide: (Monomer) sugar + phosphate + nitrogenous

base

Nucleotide

DNAmolecule

-Nitrogenous bases include-purines: adenine and guanine-pyrimidines: thymine, cytosine, uracil

• A pairs with T (or U in RNA)

• C pairs with G

• Order of the bases determines genetics

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Nucleotide

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Segment of DNA

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DNA

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Nucleic Acids

RNA

-contains ribose instead of deoxyribose

-contains uracil instead of thymine

-single polynucleotide strand

-functions:

-read the genetic information in DNA

-direct the synthesis of proteins

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Nucleic Acids

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Proteins

Protein functions include:1. enzyme catalysts2. defense3. transport4. support5. motion6. regulation7. storage

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Proteins

Monomer: Amino acid

-central carbon atom surrounded by

-amino group

-carboxyl group

-single hydrogen

-variable R group (dictates the chemical properties of the amino acid)

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Proteins

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ProteinsThe structure of a protein determines its

function

1) order of amino acids

2) folding and final shape

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Proteins

Denaturation is a change in the shape of a protein, usually causing loss of function.

-can be caused by changes in:

-pH

-temperature

-salt concentration

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Proteins

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LipidsLipids are a group of molecules that are

insoluble in water (hydrophobic)

Two main categories:

-fats (triglycerides)

-phospholipids

Monomers: Fatty acids hydrocarbon chains containing a carboxyl group (COOH)

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Lipids

Triglycerides (fats)-composed of 1 glycerol + 3 fatty acids

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Lipids

Triglycerides

-composed of 1 glycerol + 3 fatty acids

-store twice as much energy as carbohydrates

-saturated fats (animals) solid at room T

-unsaturated fats (plant oils) liquid at room T

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Lipids – saturated (each C bonded to 4 other atoms)

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Lipids – unsaturated(double bonds on some C)

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Lipids

Phospholipids -composed of:

-1 glycerol

-2 fatty acids

-a phosphate group

Phospholipids contain polar “heads” and nonpolar “tails”.

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Lipids

Phospholipids spontaneously form micelles or lipid bilayers cell membranes!

hydrophobic regions toward the inside and leave the hydrophilic regions exposed to the water environment.

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Lipids

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Lipids

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Lipids