essentials chapter 3 the molecules of life

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Chemical Compounds of Life

Chapter 3

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Biologically important compounds

Organic and Inorganic compounds:

 ± Organic ± contain carbon ± occur naturally in

living things. Also contain H,O, and N

Less frequently ± P,S,Fe,Ca,Na,Cl,Mg and K.

 ± Inorganic do not contain carbon ± except

carbon dioxide, carbon monoxide and calcium

carbonate. Water,carbon dioxide,salts,inorganic bases and

acids commonly found in living things

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Inorganic compounds: Water 

Properties of Water 

 ± Cohesion ± water as a polar molecule - force

of attraction between molecules of the same

substance

 ± Adhesion ± attraction between molecules of 

one substance and molecules of another 

substance ± why water is one of the bestsolvents.

 ± Capillary action

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Organic compounds

Four types:

 ± Carbohydrates

 ± Proteins ± Lipids

 ± Nucleic Acids

 ± Looking at structure and function

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Carbohydrates

Contain C,H,O

H, O always in a 2:1

ratio

Building blocks ±

simple sugars called

monosaccharides

Names end in ³ose´ Importance ± contain

large amounts of 

energy

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Carbohydrates

Simplest sugar = glucose = monosaccharide (mono =one)

Monosaccharide + monosaccharide disaccharide(double sugar)

Polysaccharide (many sugars) = mono + mono + mono+di + disaccharide.

Polymers are large molecules consisting of repeatingsubunits (monomers)

Excess sugar stored as a polysaccharide in

organisms:Plants: store starch ± a polysaccharide (seeds, roots

and stems

animals: store glycogen ± a polysaccharide in theliver and muscles

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How organic compounds are

synthesized and broken down Hydrolysis: Large complex molecules are broken

down into simpler ones. Water must be presentduring the reaction.

 AB

+ water -

 A +B

Complex + water = simple + simple

Dehydration synthesis : small molecules arebonded together to make more complexmolecules

 A + B - AB + water » Simple + simple = complex + water 

Enzymes are organic catalysts ± they must be present for allchemical reactions to occur in living things.

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disaccharides

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Carbohydrates

Function as a source of energy in living

things.

Function in structure: ± Polysaccharides:

 ± Chitin ± exoskeleton of insects

 ± Cellulose ± cell walls of plant cells.

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Lipids

Fats, oils and waxes

Contain C,H,O ± less oxygen in lipids

Function in cell structure ± cellmembranes

Some hormones are lipids

reserve energy supply ± Plants store oils in seeds

 ± Animals store fat under skin for insulation and

reserve energy source in fat cells

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Lipids

Fats and oils are made up of glycerol and

fatty acids.

 ± Glycerol is a 3 carbon compound with an OHbonded to each carbon

 ± Fatty acids are chains of carbon and

hydrogen with a carboxyl group at the end

 ± (COOH) ± Dehydration synthesis of a fat produces a fat

and 3 water molecules

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Lipids

fatty acid

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Lipids

Fats can be saturated or unsaturated

 ± Saturated ± solid at room temperature, single

bonds in carbon chain ± butter, lard, bacon

grease

 ± Unsaturated ± liquid at room temperature,

double bonds in carbon chain - oils

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LE 5-12a

Saturated fat and fatty acid.

Stearic acid

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LE 5-12b

Unsaturated fat and fatty acid.

Oleic acid

cis double bondcauses bending

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Fats made from unsaturated fatty acids are calledunsaturated fats

Plant fats and fish fats are usually unsaturated

Plant fats and fish fats are liquid at room

temperature and are called oils

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Unsaturated fat

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LE 5-11b

Fat molecule (triacylglycerol)

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Steroids

Steroids are lipids characterized by a carbonskeleton consisting of four fused rings

Cholesterol, an important steroid, is a component

in animal cell membranes

Although cholesterol is essential in animals, high

levels in the blood may contribute to

cardiovascular disease

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Saturated fats

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Phospholipids

Phospholipids make up the plasma

membrane all living things. They are made

up of a glycerol molecule and 2 fatty acids

plus a phosphate group.

The cell membrane is called a

phospholipid bilayer 

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LE 5-14

WATERHydrophilichead

Hydrophobic

tailsWATER

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LE 5-13

Structural formula Space-filling model Phospholipid symbol

Hydrophilic

head

Hydrophobictails

Fatty acids

Choline

Phosphate

Glycerol

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Proteins

Contain C,H,O,N (some contain S)

Amino acids are the building blocks ± 20

different amino acids

Structural parts of cells and body tissues Hormones ± chemical messengers

Enzymes ± catalysts for chemical reactions

Antibodies ±protect organisms against disease.

Examples of some proteins ± insulin (regulates

blood sugar levels)- hemoglobin ±in red blood

cells (carries oxygen to body cells)

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Structure of proteins

Made of amino acids bonded together 

forming dipeptides and polypeptides ± the

bond is called a peptide bond

Amino acids have distinct makeup

 ± Amino group

 ± Carboxyl group

 ± R group ± variable group

 ± Central carbon atom

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Formation of a dipeptide

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Protein structure

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Nucleic Acids

Deoxyribonucleic acid - DNA

Ribonucleic acid - RNA

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DNA

Hereditary material Made up of building blocks called

nucleotides

 ± Nucleotides ± sugar, phosphate, nitrogenousbase

Sugar = deoxyribose

Phosphate PO4

Nitrogenous base (4) = adenine, guanine,cytosine, thymine

 ± Purines = adenine and guanine

 ± Pyrimidines = cytosine and thymine

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nucleotide

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Structure of DNA

Adenine bonds to

thymine

Guanine bonds to

cytosine

DNA is a double helix

 ± Double stranded ± a

polymer of nucleotides

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RNA

Ribonucleic Acid

 ± Single strand

 ± Involved in protein

synthesis ± Polymer of nucleotides

Sugar = ribose

Phosphate = PO4

Nitrogenous bases (4)

 ± Adenine

 ± Cytosine

 ± Guanine

 ± Uracil

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From DNA to RNA to Protein