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Chapter 5:

Molecules of Life

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Organic vs. InorganicAll compounds may be classified into two broad categories: 1.organic compounds - carbon based

molecules2. inorganic compounds - almost all are

non-carbon based molecules

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Carbon (C)• Carbon has 4 electrons in Carbon has 4 electrons in

outer shell.outer shell.• Carbon can form covalent Carbon can form covalent

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

• Usually with C, H, O or N.Usually with C, H, O or N.

• Example:Example: CHCH44(methane)(methane)

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Carbon Bonding• Carbon can also bond with other

carbon atoms• Forms three types of structures:

– Straight chains– Branched chains– Rings

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Carbon bonding• Carbon can share one, two or three

electrons with another atom– single bond - one electron shared– double bond - two electrons

shared – triple bond - three electrons

shared

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Macromolecules

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

MONOMERS.MONOMERS.

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How Are Macromolecules

Formed?

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Answer:Answer: Dehydration SynthesisDehydration Synthesis

• Also called “condensation reaction”“condensation reaction”• Forms polymerspolymers by combining

monomersmonomers by ““removing water””.

HO H

HO HO HH

H2O

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How are Macromolecules

separated or digested?

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Answer: Answer: HydrolysisHydrolysis

• Separates monomers by “adding water”

HO HO HH

HO H

H2O

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Macromolecules

• FOUR MAIN CATEGORIES: 1) carbohydrates: fuel & building material 2) lipids: fats & oils 3) proteins: perform most cell functions 4) nucleic acids: information storage

(Chap. 11)– Made up of nucleotides– DNA & RNA– Forms the genetic code

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Carbohydrates

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Carbohydrates

• Carbohydrates are made of sugar molecules

• Sugars contain carbon, hydrogen, and oxygen in the following ratio:– 1 carbon : 2 hydrogen : 1 oxygen

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3 main types of carbohydrates:3 main types of carbohydrates:

– Monosaccharide: one sugar unit • Ex: glucose, fructose, lactose

– Disaccharide: two sugar units• Ex: Sucrose (glucose + fructose)• Ex: Galactose (glucose + lactose)

– Polysaccharide: many sugar units; • Ex: Starch: found in plants (bread, tomatoes)• Ex: Glycogen: found in animal cells • Ex: Cellulose: found in cell wall of plants

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Carbohydrates

• Most carbohydrates are polar and hydrophilic

• Hydrophilic: attracted to water molecules• Monosaccharides and disaccharides easily

dissolve in water to form sugar solutions

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Lipids

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Lipids• Lipids are not soluble in water.• They are nonpolar and hydrophobic do

not mix with water• Lipids “store the most energy”• Examples:

– Fats, oils – Phospholipids– Steroid hormones– Triglycerides

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LipidsSix functions of lipids:Six functions of lipids:

1.1. Long term energy storageLong term energy storage2.2. Protection against heat loss Protection against heat loss (insulation)(insulation)3.3. Protection against physical shockProtection against physical shock4.4. Protection against water lossProtection against water loss5.5. Chemical messengers (hormones)Chemical messengers (hormones)6.6. Major component of membranes Major component of membranes

(phospholipids)(phospholipids)

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Simplest FatsTriglycerides:Triglycerides:

composed of composed of 1 glycerol1 glycerol and and 3 fatty acids3 fatty acids.

H

H-C----O

H-C----O

H-C----O

H

glycerol

O

C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

=

fatty acids

O

C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

=

O

C-CH2-CH2-CH2-CH =CH-CH2 -CH

2 -CH2 -CH

2 -CH3

=

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Fatty AcidsThere are two kinds of fatty acids:

1. 1. Saturated fatty acids:Saturated fatty acids: no double bonds (bad) no double bonds (bad)

solid at room temperature, Ex: buttersolid at room temperature, Ex: butter

2. Unsaturated fatty acids:Unsaturated fatty acids: at least 1 double bonds (good) at least 1 double bonds (good)

liquid at room temperature, Ex: Fruits, olive oil

O

C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

=

saturatedsaturated

O

C-CH2-CH2-CH2-CH=CH-CH2 -CH

2 -CH2 -CH

2 -CH3

=

unsaturated

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Steroids

• Classified as lipids are hydrophobic• Differ from fats in structure & function• Some act as chemical signals or

hormones estrogen and testosterone

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Proteins

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Functions of Proteins• Form structures—hair, fur, muscles• Provide long-term nutrient storage• Circulate and defend the body against

microorganisms (antibodies) • Act as chemical signals—hormones• Help control chemical reactions in cells—

enzymes

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Protein Structure• Proteins are polymers formed from Proteins are polymers formed from

monomers called monomers called amino acids.amino acids.• Amino acids bonded together by peptide Amino acids bonded together by peptide

bonds (polypeptides).bonds (polypeptides).• There are 20 different kinds of amino There are 20 different kinds of amino

acids.acids.

aa1 aa2 aa3 aa4 aa5 aa6

Peptide Bonds

Amino Acids (aa)

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Amino Acid Structure• Three of central carbon’s partners

are the same in all of the 20 different amino acids

1. hydrogen atom 2. carboxyl group 3. amino group

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• Differences between one amino acid and another are due to the unique “R group” or side group that each one has

• Each “R group” is responsible for a different chemical property for each amino acid

Amino Acid Structure

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Protein Shape• Functional proteins consist of precisely

twisted, coiled, and shaped polypeptides• Proteins cannot function correctly if shape

is altered • Denaturation: loss of normal protein shape• Unfavorable changes in temperature, pH,

or other environmental conditions may cause proteins to become denatured

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Enzymes are proteins that speed up specific reactions

in cells

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Activation Energy

• Activation energy: minimum energy required to start chemical reaction

• Catalysts: compounds that speed up chemical reactions

• Enzymes: proteins that act as catalysts for chemical reactions in organisms

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How Enzymes WorkACTIVE SITE MODEL

• Substrate: specific reactant acted on by an enzyme

• Active site: specific region of the enzyme that the substrate fits into

• Substrate binds to enzyme’s active site where the substrate undergoes a change