chapter 4 *molecules are important for biological function
DESCRIPTION
The Main Molecules of Life Carbon Hydrogen Oxygen Nitrogen Sulfur PhosphorusTRANSCRIPT
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Chapter 4
*Molecules are important for biological function*Carbon is the molecular backbone of life
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The Main Molecules of Life
Carbon Hydrogen Oxygen Nitrogen Sulfur Phosphorus
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Carbon
• Organic – means that it contains carbon
• Although cells are 70–95% water, the rest consists mostly of carbon-based compounds
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Why is carbon so versatile?
Tetravalence – can bind to four other molecules
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Fig. 4-5
Ethane Propane1-Butene 2-Butene
(c) Double bonds
(d) RingsCyclohexane Benzene
Butane 2-Methylpropane(commonly called isobutane)
(b) Branching
(a) Length
Hydrocarbons – organic molecules consisting of only C and H
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Draw C5H12 on your notes
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Isomers are compounds with the same molecular formula but different structures and properties: Structural isomers have different covalent
arrangements of their atoms Geometric isomers have the same covalent
arrangements but differ in spatial arrangements
Enantiomers are isomers that are mirror images of each other
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Fig. 4-7a
(a) Structural isomers
2-methyl butanePentane
–Structural isomers have different covalent arrangements of their atoms
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Fig. 4-7b
(b) Geometric isomers
cis isomer: The two Xs areon the same side.
trans isomer: The two Xs areon opposite sides.
Geometric isomers have the same covalent arrangements but differ in spatial arrangements
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Fig. 4-7c
(c) EnantiomersL isomer D isomer
Enantiomers are isomers that are mirror images of each other
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Fig. 4-8
Drug
Ibuprofen
Albuterol
Condition
Pain;inflammation
Asthma
EffectiveEnantiomer
S-Ibuprofen
R-Albuterol
R-Ibuprofen
S-Albuterol
IneffectiveEnantiomer
Zyrtec (cetirizine) is both enantiomers and xyzal (levocetirizine) is only the left handed enantiomer
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Functional Groups
The groups (molecules) off of the carbon skeleton that give that molecule its properties
Read/look over the functional groups on page 64 and draw them in your notes. Then we will play the white board game.
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Fig. 4-10aHydroxylCHEMICAL
GROUP
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.
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Fig. 4-10bCHEMICALGROUP
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)
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Fig. 4-UN3
Adenosine
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Fig. 4-UN4
P P P P i P PAdenosine Adenosine Energy
ADPATP Inorganic phosphate
Reacts with H2O
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Macromolecules
Large molecules of life Carbohydrates Proteins Nucleic acids lipids
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Polymers
Polymers (such as carbohydrates, proteins, and nucleic acids) are made up of monomers
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Fig. 5-2
Short polymer
HO 1 2 3 H HO H
Unlinked monomer
Dehydration removes a watermolecule, forming a new bond
HO
H2O
H1 2 3 4
Longer polymer
(a) Dehydration reaction in the synthesis of a polymer
HO 1 2 3 4 H
H2OHydrolysis adds a watermolecule, breaking a bond
HO HH HO1 2 3
(b) Hydrolysis of a polymer