Carbon & The Molecular Diversity of Life. Carbon: The Backbone of Life Living organisms consist...

Carbon & The Molecular Diversity of Life

Carbon: The Backbone of Life

• Living organisms consist mostly of carbon-based compounds

• Carbon is unparalleled in its ability to form large, complex, and diverse molecules

• Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds

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Carbon: Organic Chemistry

• Carbon is important enough to have it’s own branch of chemistry called Organic chemistry

• Organic compounds range from simple molecules to colossal ones

• Most organic compounds contain hydrogen atoms in addition to carbon atoms with O, N and P among others thrown in from time to time.

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Experimental Design: The origin of life on this planet

• The Miller-Urey experiment demonstrated the abiotic synthesis of organic compounds.

• Water (H2O), methane (CH4), ammonia (NH3), and hydrogen

(H2) were all sealed inside a sterile array of glass tubes and flasks connected in a loop, with one flask half-full of liquid water and another flask containing a pair of electrodes.

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• The liquid water was heated to induce evaporation, sparks were fired between the electrodes to simulate lightning through the atmosphere and water vapor, and then the atmosphere was cooled again so that the water could condense and trickle back into the first flask in a continuous cycle.

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• Within a day, the mixture had turned pink in color, and at the end of two weeks of continuous operation, Miller and Urey observed that as much as 10–15% of the carbon within the system was now in the form of organic compounds.

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• Two percent of the carbon had formed amino acids that are used to make proteins in living cells, with glycine as the most abundant. Nucleic acids were not formed within the reaction. But the common 20 amino acids were formed, in various concentrations.

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Carbon has 4 valence electrons, thus makes 4 bonds

• With four valence electrons, carbon can form four covalent bonds with a variety of atoms

• This ability makes large, complex molecules possible

• In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape

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“CNOPS” can combine together to make double and triple covalent bonds

• 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

• Why is this important? Because the shape of a molecule dictates its reactivity, thus its function!

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No need to memorize these!

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Carbon Skeletons Vary

• Carbon chains form the skeletons of most organic molecules• Carbon chains vary in length and shape

Hydrocarbons

• Hydrocarbons are organic molecules consisting of only carbon and hydrogen

• Many organic molecules, such as fats, have hydrocarbon components

• Hydrocarbons can undergo reactions that release a large amount of energy

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Nucleus

Fat droplets

(b) A fat molecule(a) Part of a human adipose cell

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Fats

Isomers

• Isomers are compounds with the same molecular formula but different structures, thus different properties.

– Structural isomers have different covalent arrangements of their atoms

– Cis-trans isomers have the same covalent bonds but differ in spatial arrangements

– Enantiomers are isomers that are mirror images of each other & rotate light differently

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More detail than you need, but cool none the less!

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• Enantiomers are important in the pharmaceutical industry

• Two enantiomers of a drug may have different effects

• Usually only one isomer is biologically active• Differing effects of enantiomers demonstrate that

organisms are sensitive to even subtle variations in molecules

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Drug

Ibuprofen

Albuterol

ConditionEffective

EnantiomerIneffectiveEnantiomer

Pain;inflammation

Asthma

S-Ibuprofen R-Ibuprofen

R-Albuterol S-Albuterol

Note the mirror imaging

Functional Groups

A few chemical groups are key to the functioning of molecules• Distinctive properties of organic molecules depend on

the carbon skeleton and on the molecular components attached to it

• A number of characteristic groups can replace the hydrogens attached to skeletons of organic molecules

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• Functional groups are the components of organic molecules that are most commonly involved in chemical reactions

• The number and arrangement of functional groups give each molecule its unique properties

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Functional Groups

STRUCTURE

EXAMPLE

Alcohols(Their specificnames usuallyend in -ol.)

NAME OFCOMPOUND

FUNCTIONALPROPERTIES

(may be written HO—)

Ethanol

• Is polar as a resultof the electronsspending moretime near theelectronegativeoxygen atom.

• Can form hydrogenbonds with watermolecules, helpingdissolve organiccompounds suchas sugars.

Hydroxyl

Carbonyl

STRUCTURE

EXAMPLE

Ketones if the carbonylgroup is within acarbon skeleton

NAME OFCOMPOUND


Aldehydes if the carbonylgroup is at the end of thecarbon skeleton

• A ketone and analdehyde may bestructural isomerswith different properties,as is the case foracetone and propanal.

Acetone

Propanal

• Ketone and aldehydegroups are also foundin sugars, giving riseto two major groupsof sugars: ketoses(containing ketonegroups) and aldoses(containing aldehydegroups).

Carboxyl

STRUCTURE

EXAMPLE

Carboxylic acids, or organicacids

NAME OFCOMPOUND


Acetic acid

• Acts as an acid; candonate an H+ because thecovalent bond betweenoxygen and hydrogen is sopolar:

• Found in cells in the ionizedform with a charge of 1– andcalled a carboxylate ion.

Nonionized Ionized

Amino

Amines

Glycine

STRUCTURE

EXAMPLE • Acts as a base; canpick up an H+ from thesurrounding solution(water, in livingorganisms):

NAME OFCOMPOUND


• Found in cells in theionized form with acharge of 1.

Nonionized Ionized

Sulfhydryl

Thiols

(may bewritten HS—)

STRUCTURE

EXAMPLE • Two sulfhydryl groups canreact, forming a covalentbond. This “cross-linking”helps stabilize proteinstructure.

NAME OFCOMPOUND


• Cross-linking of cysteinesin hair proteins maintainsthe curliness or straightnessof hair. Straight hair can be“permanently” curled byshaping it around curlersand then breaking andre-forming the cross-linkingbonds.

Cysteine

Phosphate

STRUCTURE

EXAMPLE

NAME OFCOMPOUND


Organic phosphates

Glycerol phosphate

• Contributes negativecharge to the moleculeof which it is a part(2– when at the end ofa molecule, as at left;1– when locatedinternally in a chain ofphosphates).

• Molecules containingphosphate groups havethe potential to reactwith water, releasingenergy.

Methyl

STRUCTURE

EXAMPLE

NAME OFCOMPOUND


Methylated compounds

5-Methyl cytidine

• Addition of a methyl groupto DNA, or to moleculesbound to DNA, affects theexpression of genes.

• Arrangement of methylgroups in male and femalesex hormones affects theirshape and function.

• One phosphate molecule, adenosine triphosphate (ATP), is the primary energy-transferring molecule in the cell

• ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups

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ATP: An Important Source of Energy for Cellular Processes

• The versatility of carbon makes possible the great diversity of organic molecules

• Variation at the molecular level lies at the foundation of all biological diversity

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Final Thoughts

Created by:

René McCormickNational Math and Science Dallas, TX

Carbon & The Molecular Diversity of Life. Carbon: The Backbone of Life Living organisms consist...

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