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More Organic Chemistry
• Functional Groups and Enzymes
The seven functional groups that are most important in the chemistry of life:
Hydroxyl groupCarbonyl groupCarboxyl groupAmino groupSulfhydryl groupPhosphate groupMethyl group
HydroxylCHEMICALGROUP
STRUCTURE
NAME OF COMPOUND
EXAMPLE
FUNCTIONALPROPERTIES
Carbonyl Carboxyl
(may be written HO—)
In a hydroxyl group (—OH), ahydrogen atom is bonded to anoxygen atom, which in turn isbonded to the carbon skeleton ofthe organic molecule. (Do notconfuse this functional groupwith the hydroxide ion, OH–.)
When an oxygen atom isdouble-bonded to a carbonatom that is also bonded toan —OH group, the entireassembly of atoms is calleda carboxyl group (—COOH).
Carboxylic acids, or organicacids
Ketones if the carbonyl group iswithin a carbon skeleton
Aldehydes if the carbonyl groupis at the end of the carbonskeleton
Alcohols (their specific namesusually end in -ol)
Ethanol, the alcohol present inalcoholic beverages
Acetone, the simplest ketone Acetic acid, which gives vinegarits sour taste
Propanal, an aldehyde
Has acidic propertiesbecause the covalent bondbetween oxygen and hydrogenis so polar; for example,
Found in cells in the ionizedform with a charge of 1– andcalled a carboxylate ion (here,specifically, the acetate ion).
Acetic acid Acetate ion
A ketone and an aldehyde maybe structural isomers withdifferent properties, as is thecase for acetone and propanal.
These two groups are alsofound in sugars, giving rise totwo major groups of sugars:aldoses (containing analdehyde) and ketoses(containing a ketone).
Is polar as a result of theelectrons spending more timenear the electronegative oxygen atom.
Can form hydrogen bonds withwater molecules, helpingdissolve organic compoundssuch as sugars.
The carbonyl group ( CO)consists of a carbon atomjoined to an oxygen atom by adouble bond.
CHEMICALGROUP
STRUCTURE
NAME OFCOMPOUND
EXAMPLE
FUNCTIONALPROPERTIES
Amino Sulfhydryl Phosphate Methyl
A methyl group consists of acarbon bonded to threehydrogen atoms. The methylgroup may be attached to acarbon or to a different atom.
In a phosphate group, aphosphorus atom is bonded tofour oxygen atoms; one oxygenis bonded to the carbon skeleton;two oxygens carry negativecharges. The phosphate group(—OPO3
2–, abbreviated ) is anionized form of a phosphoric acidgroup (—OPO3H2; note the twohydrogens).
P
The sulfhydryl groupconsists of a sulfur atombonded to an atom ofhydrogen; resembles ahydroxyl group in shape.
(may bewritten HS—)
The amino group(—NH2) consists of anitrogen atom bondedto two hydrogen atomsand to the carbon skeleton.
Amines Thiols Organic phosphates Methylated compounds
5-Methyl cytidine
5-Methyl cytidine is acomponent of DNA that hasbeen modified by addition ofthe methyl group.
In addition to taking part inmany important chemicalreactions in cells, glycerolphosphate provides thebackbone for phospholipids,the most prevalent molecules incell membranes.
Glycerol phosphate
Cysteine
Cysteine is an importantsulfur-containing aminoacid.
Glycine
Because it also has acarboxyl group, glycineis both an amine anda carboxylic acid;compounds with bothgroups are called amino acids.
Addition of a methyl groupto DNA, or to moleculesbound to DNA, affectsexpression of genes.
Arrangement of methylgroups in male and femalesex hormones affectstheir shape and function.
Contributes negative chargeto the molecule of which it isa part (2– when at the end ofa molecule; 1– when locatedinternally in a chain ofphosphates).Has the potential to reactwith water, releasing energy.
Two sulfhydryl groupscan react, forming acovalent bond. This“cross-linking” helpsstabilize proteinstructure.
Cross-linking ofcysteines in hairproteins maintains thecurliness or straightnessof hair. Straight hair canbe “permanently” curledby shaping it aroundcurlers, then breakingand re-forming thecross-linking bonds.
Acts as a base; canpick up an H+ fromthe surroundingsolution (water, in living organisms).
Ionized, with acharge of 1+, undercellular conditions.
(nonionized) (ionized)
Fig. 4-10c
STRUCTURE
EXAMPLE
NAME OFCOMPOUND
FUNCTIONALPROPERTIES
Carboxyl
Acetic acid, which gives vinegar its sour taste
Carboxylic acids, or organic acids
Has acidic propertiesbecause 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
Fig. 4-10d
STRUCTURE
EXAMPLE
NAME OFCOMPOUND
FUNCTIONALPROPERTIES
Amino
Because it also has a carboxyl group, glycine is both an amine anda 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 OFCOMPOUND
FUNCTIONALPROPERTIES
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 ofcysteines in hairproteins maintains the curliness or straightness of hair. Straight hair can be “permanently” curled by shaping it around curlers, then breakingand re-forming thecross-linking bonds.
STRUCTURE
EXAMPLE
NAME OFCOMPOUND
FUNCTIONALPROPERTIES
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.
STRUCTURE
EXAMPLE
NAME OFCOMPOUND
FUNCTIONALPROPERTIES
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 affectstheir shape and function.
• ATP: An Important Source of Energy for Cellular Processes
• 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
The Chemical Elements of Life: A Review
• 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
Fig. 4-UN3
Adenosine
Fig. 4-UN4
P P P P i P PAdenosine Adenosine Energy
ADPATP Inorganic phosphate
Reacts with H2O
Enzymes
• Enzymes are a type of protein that acts as a catalyst to speed up chemical reactions
• Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life
Fig. 5-16
Enzyme(sucrase)
Substrate(sucrose)
Fructose
Glucose
OH
HO
H2O
Properties of Enzymes• They are all proteins, which is one reason why we need
protein in our diet. • They are all biological catalysts.They speed up a
reaction without being used up; this means they can be used over and over again.
• A small amount of enzyme can effect the change of a large amount of chemical.
• The way enzymes work is affected by temperature, pH and pressure. They can be denatured (destroyed) by excessive heat.
• The reactions are reversible. Enzymes are specific that is they control only one reaction. So maltase only acts on maltose, sucrase on sucrose etc.
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