Chapter 4

2Figure 4.1

AIM: How does carbon lead to the diversity of life?

Chapter 4 – Carbon and the Molecular Diversity of Life

3



4

Carbon has four valence electrons and may form single, double, triple, or quadruple bonds

Carbon compounds range from simple molecules to complex ones



5

(a) Methane

(b) Ethane

(c) Ethene (ethylene)

Molecular Formula

Structural Formula

Ball-and-Stick Model

Space-Filling Model

H

H

H

H

H

H

H

H

H

H

H H

HH

C

C C

C C

CH4

C2H

6

C2H4

Name and Comments

Figure 4.3 A-C



6

H O N C

Hydrogen

(valence = 1)

Oxygen

(valence = 2)

Nitrogen

(valence = 3)

Carbon

(valence = 4)

Figure 4.4



7

H

HH

H

H

H H H

H

H

H

H H H

H H H

H H

H

H

H

H

H

H

H

H

H

H H H H

H H

H H

H H H H

H H

H H

HH

HH

H

H

H

C C C C C

C C C C C C C

CCCCCCCC

C

C

C

C

C

C

C

CC

C

C

C

H

H

H

HH

H

H

(a) Length

(b) Branching

(c) Double bonds

(d) Rings

Ethane Propane

Butane isobutane

1-Butene 2-Butene

Cyclohexane Benzene

H H H HH



8

(a) A fat molecule (b) Mammalian adipose cells100 µm

Fat droplets (stained red)

Figure 4.6 A, B



AIM: Why Carbon?Chapter 3 - The Molecules of Cells

C4H10

The molecular formula does not necessarily tell you the structural formula…explain.

AIM: Why Carbon?

Chapter 4 – Carbon and the Molecular Diversity of LifeAIM: How does carbon lead to the diversity of life?


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• Molecules with the same molecular formula, but there atoms are connected differently (Different connectivity) • Resulting in different structural formula. • Structure = function, therefore structural isomers function or behave differently

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• Differ in their spatial arrangement about a double bonded carbon

Cis Trans

Cis-2-butene

Trans-2-butene

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This can happen only when there is an asymmetric carbon = a carbon with four DIFFERENT groups attached to it.

Asymmetric carbon



mirror

AIM: Why Carbon?Chapter 3 - The Molecules of Cells

Thalidomide, an extreme example of isomers behaving differently

The birth defects caused by thalidomide, which was inadvertently taken with R-thalidomide to treat morning sickness symptoms

ConclusionJust because two molecules have the same molecular formula and may even have the same connectivity, if they can’t be overlaid on top of each other, they aren’t the same.

AIM: Why Carbon?AIM: How does carbon lead to the diversity of life?


15

L-Dopa

(effective against Parkinson’s disease)

D-Dopa

(biologically inactive)Figure 4.8



16

CH3

OH

HO

O

CH3

CH3

OH

Estradiol

Testosterone

Female lion

Male lionFigure 4.9

AIM: What is the function of functional groups?


17

•There are six functional groups that concern us in biology:

•Hydroxyl group (-OH)

•Carbonyl group (>C=O)

•Carboxyl group (-COOH)

•Amino group (-NH2)

•Sulfhydryl group (-SH)

•Phosphate group (-OPO32-)

•These functional groups are hydrophilic and increase the solubility of organic compounds in water.



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•Structure – a hydrogen atom bonded to an oxygen atom which is then bonded to the carbon skeleton of the organic molecule (-OH). (This is not the same thing as an hydroxide ion (OH-)).

•Name of Compounds – alcohols (names usually end in –ol).

•Example – ethanol – the alcohol found in beer and wine.

•Properties:

•Polar as a result of the electronegative oxygen drawing electrons toward itself.

•Attracts water molecules

•Helps dissolve organic compounds such as sugars.

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1. It is composed of a ribose sugar, three negative phosphates, and an adenine base2. It’s an RNA nucleotide3. Primary energy carrying molecule of the cell – fuel for proteins to do work / accelerate matter

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FUNCTIONALGROUP

STRUCTURE

(may be written HO )

HYDROXYL CARBONYL CARBOXYL

OH

In a hydroxyl group (—OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH–.)

When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (—COOH).

C

O O

C

OH

Figure 4.10

The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond.

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Acetic acid, which gives

vinegar its sour tatste

NAME OF

COMPOUNDS

Alcohols (their

specific names usually

end in -ol)

Ketones if the carbonyl

group is within a carbon

skeleton

Aldehydes if the carbonyl

group is at the end of the

carbon skeleton

Carboxylic acids, or

organic acids

EXAMPLE

Propanal, an aldehyde

Acetone, the simplest ketone

Ethanol, the

alcohol present in

alcoholic

beverages

H

H

H

H H

C C OH

H

H

H

HH

H

HC C H

C

C C

C C C

O

H OH

O

H

H

H H

H O

H

Figure 4.10

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The amino group (—NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton.

AMINO SULFHYDRYL PHOSPHATE

(may be written HS )

The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape.

In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P . The phosphate group (—OPO3

2–) is an ionized form of a phosphoric acid group (—OPO3H2; note the two hydrogens).

NH

H

SH

O P

O

OH

OH

Figure 4.10

Chapter 4

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