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Carbon & the Molecular

Diversity of Life

Chapter 4

Graphite & Diamond

You should be able to:

1. Explain how carbons electron configuration explains its ability to form

large, complex, diverse organic molecules

2. Describe how carbon skeletons may vary

and explain how this variation contributes

to the diversity and complexity of organic

molecules

3. Distinguish among the three types of

isomers: structural, geometric, and

enantiomer

4. Name the major functional groups found in

organic molecules; describe the basic

structure of each functional group and

outline the chemical properties of the

organic molecules in which they occur

5. Explain how ATP functions as the primary

energy transfer molecule in living cells

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Carbon: The Backbone of Life

o Although cells are 7095% water, the rest is mostly carbon-based compounds

o Carbon is unparalleled in its ability to form

large, complex, and diverse molecules

o Proteins, DNA, carbohydrates, and other

molecules that distinguish living matter are

all composed of carbon compounds

o Organic compounds range from simple molecules to colossal ones

oMethane-1 C, 4 Hs

oDNA-100,000s of atoms

o Most organic compounds contain hydrogen atoms, too

Organic chemistry is the study of

carbon compounds

Carbon atoms can form diverse

molecules by bonding to 4 other atoms

o Electron configuration determines the kinds

and number of bonds an atom will form with

other atoms

o With 4 valence electrons, carbon can form 4

covalent bonds with a variety of atoms

o This tetravalence makes large, complex

molecules possible

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The Formation of Bonds with

Carbon o In molecules with multiple carbons, each

carbon bonded to four other atoms has a tetrahedral shape

o However, when two carbon atoms are joined by a double bond, the atoms joined to the carbons are in the same plane as the carbons

Figure 4.3

Name and

Comment

Molecular

Formula

(a) Methane

(b) Ethane

CH4

Ball-and-

Stick Model

Space-Filling

Model

(c) Ethene

(ethylene)

C2H6

C2H4

Structural

Formula

o The electron configuration of carbon gives it

covalent compatibility with many different elements

o The valences of carbon & its most frequent partners

(hydrogen, oxygen, & nitrogen) are the building code that governs the architecture of living molecules

Hydrogen (valence = 1)

Oxygen (valence = 2)

Nitrogen (valence = 3)

Carbon (valence = 4)

H O N C

The Most Common Elements in Life

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o Carbon atoms can partner with atoms other than

hydrogen; for example:

o Carbon dioxide: CO2

o Urea: CO(NH2)2

Ethane Propane 1-Butene 2-Butene

(c) Double bonds

(d) Rings

Cyclohexane Benzene

Butane 2-Methylpropane (commonly called isobutane)

(b) Branching

(a) Length

Carbon Skeletons Allow Tremendous Molecular Diversity

o Chains of connected carbon atoms form the

skeletons of most organic molecules

o Carbon chains vary in length and shape

Animation: Carbon Skeletons

Are these cmpds polar or nonpolar?

Do nonpolar substances readily dissolve in polar solvents?

Hydrocarbons

o Hydrocarbons are organic molecules consisting

of only carbon & hydrogen

o Many organic molecules (ex. Fats) have

hydrocarbon components

o Hydrocarbons can undergo reactions that release

a large amount of energy o H & C have ~same electronegativity, so electrons ~equidistant from

both nuclei

o Energetic Hydrocarbons we use:

o Fat: high in calories

o Fossil Fuels: Gasoline, Coal, Natural Gas, Propane

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Fig. 4-6

(a) Mammalian adipose cells (b) A fat molecule

Fat droplets (stained red)

100 m

Hydrocarbon component

Isomers

o Structural isomers have

different covalent

arrangements of their

atoms

o Geometric isomers

have the same covalent

arrangements but differ in

spatial arrangements

around a double bond

o Enantiomers are

isomers that are mirror

images of each other

Animation: Isomers

Isomers are compounds with the same molecular

formula but different structures and properties:

What Type of Isomer?

http://course1.winona.edu/sberg/ChemStructures/Isomer3.gif

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What Type of Isomer?

http://course1.winona.edu/sberg/ChemStructures/Isomer3.gif

Geometric Isomers

cis isomer the 2 Xs (Br) are on the same

side

trans isomer the 2 Xs (Br) are on

opposite sides

What Type of Isomer?

http://course1.winona.edu/sberg/ChemStructures/Isomers1.gif

What Type of Isomer?

Structural Isomer http://course1.winona.edu/sberg/ChemStructures/Isomers1.gif

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What Type of Isomer?

http://chemwiki.ucdavis.edu/@api/deki/files/7169/=enantiomers.gif

What Type of Isomer?

http://chemwiki.ucdavis.edu/@api/deki/files/7169/=enantiomers.gif

Enantiomers mirror images

o Enantiomers are important in the

pharmaceutical industry

o Two enantiomers of a drug may have different

effects

o Usually only one isomer is biologically active

o Differing effects of enantiomers demonstrate

that organisms are sensitive to even subtle

variations in molecules

Animation: L-Dopa

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Figure 4.8

Drug

Ibuprofen

Albuterol

Condition Effective

Enantiomer Ineffective Enantiomer

Pain; inflammation

Asthma

S-Ibuprofen R-Ibuprofen

R-Albuterol S-Albuterol

L-dopa D-dopa

Enantiomers in large, complex molecules

C9H11NO4 Parkinson's Disease Drug

C9H11NO4 Doesnt Work

Concept 4.3: A few chemical groups are

key to the functioning of biological

molecules

o Distinctive properties of organic molecules

depend on the carbon skeleton and on the

molecular components attached to it

o A number of characteristic groups can

replace the hydrogens attached to skeletons

of organic molecules

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The Chemical Groups Most Important

in the Processes of Life

o Functional groups are the components of

organic molecules that are most commonly

involved in chemical reactions

o Compounds attached to the carbon skeleton

o Like little Sub-Compounds that are part of the Larger

Organic Compound

o The number and arrangement of functional groups

give each molecule its unique properties

Fig. 4-9

Estradiol

Testosterone

Same Basic Carbon Skeleton, Different Functional Group

The 7 functional groups that are most

important in the chemistry of life:

Hydroxyl group

Carbonyl group

Carboxyl group

Amino group

Sulfhydryl group

Phosphate group

Methyl group See Pages 64-65 in Book

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Name of

Compound

Functional

Properties

Fig. 4-10c

STRUCTURE

EXAMPLE

NAME OF COMPOUND

FUNCTIONAL PROPERTIES

Carboxyl

Acetic acid, which gives vinegar its sour taste

Carboxylic acids, or organic acids

Has acidic properties because the covalent bond between oxygen and hydrogen is so polar; for example,

Found in cells in the ionized form with a charge of 1 and called a carboxylate ion (here, specifically, the acetate ion).

Acetic acid Acetate ion

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Fig. 4-10d

STRUCTURE

EXAMPLE

NAME OF COMPOUND

FUNCTIONAL PROPERTIES

Amino

Because it also has a

carboxyl group, glycine

is both an amine and

a carboxylic acid;

compounds with both

groups are called

amino acids.

Amines

Acts as a base; can

pick up an H+ from

the surrounding

solution (water, in

living organisms).

Ionized, with a

charge of 1+, under

cellular conditions.

(ionized) (nonionized)

Glycine

Fig. 4-10e

STRUCTURE

EXAMPLE

NAME OF COMPOUND

FUNCTIONAL PROPERTIES

Sulfhydryl

(may be written HS)

Cysteine

Cysteine is an important sulfur-containing amino acid.

Thiols

Two sulfhydryl groups

can react, forming a

covalent bond. This

cross-linking helps stabilize protein

structure.

Cross-linking of

cysteines in hair

proteins maintains the

curliness or straightness

of hair. Straight hair can

be permanently curled by shaping it around

curlers, then breaking

and re-forming the

cross-linking bonds.

Fig. 4-10g

STRUCTURE

EXAMPLE

NAME OF COMPOUND

FUNCTIONAL PROPERTIES

Methyl

5-Methyl cytidine is a

component of DNA that has

been modified by addition of

the methyl group.

5-Methyl cytidine

Methylated compounds

Addition of a methyl group

to DNA, or to molecules

bound to DNA, affects

expression of genes.

Arrangement of methyl

groups in male and female

sex hormones affects

their shape and function.

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Fig. 4-10f

STRUCTURE

EXAMPLE

NAME OF COMPOUND

FUNCTIONAL PROPERTIES

Phosphate

In addition to taking part in

many important chemical

reactions in cells, glycerol

phosphate provides the

backbone for phospholipids,

the most prevalent molecules in

cell membranes.

Glycerol phosphate

Organic phosphates

Contributes negative charge

to the molecule of which it is

a part (2 when at the end of a molecule; 1 when located internally in a chain of

phosphates).

Has the potential to react

with water, releasing energy.

How many functional groups

and what are the names?

How many functional groups

and what are the names?

Carboxyl

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How many functional groups

and what are the names?

Carboxyl Carboxyl

How many functional groups

and what are the names?

Carboxyl Carboxyl

Carbonyl

(Ketone)

How many functional groups

and what are the names?

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How many functional groups

and what are the names?

Hydroxyl

How many functional groups

and what are the names?

Hydroxyl

Amine

How many functional groups

and what are the names?

Hydroxyl

Amine

Carboxyl

What am I?

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How many functional groups

and what are the names?

Hydroxyl

Amine

Carboxyl

What am I?

Amino Acid

How many functional groups

and what are the names?

How many functional groups

and what are the names?

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ATP: An Important Source of Energy

for Cellular Processes

o One phosphate molecule, adenosine triphosphate (ATP),

is the primary energy-transferring molecule in the cell

o ATP consists of an organic molecule called adenosine

attached to a string of three phosphate groups

Adenosine

P P P P i P P Adenosine Adenosine

ADP ATP Inorganic phosphate

Reacts with H2O

Energy

oLike-charges repel each other.

oKeeping those (-) charges this close

is like rolling a ball up a hill:

oLots of potential energy is stored &

can be released when the bonds are

broken