Molecules of Life
Molecules of Life• Carbohydrates
– Monomer-monosaccharides– energy supply
• Proteins– Monomer-amino acids– structural components
• Lipids– Monomer-fatty acids– structural components, energy, hormones
• Nucleic acids– Monomer-nucleotides– DNA-genetic material
Composition of Molecules of Life• most are carbon based• organic compounds • unique to living systems
– with exception of CO2 & carbides
• carbon is necessary for life
• electroneutral– never loses or gains
electrons
– always shares or forms covalent bonds
Covalent Bonding• carbon can form 4
covalent bonds with other elements or with itself– has 4 electrons in
outermost shell• makes each carbon
atom a connecting point from which another molecule can branch in four directions
H |
H--C--H | H
Covalent Bonding• since carbon can bind
to itself• has capacity to
construct endless numbers of carbon skeletons varying in size & branching patterns
Organic Compounds• chain of carbons in organic
molecule-carbon skeleton• branched or unbranched• double or single bonds• straight or arranged in ring
form• each has unique 3-D shape• properties depend on carbon
skeleton & atoms attached to skeleton
• groups of atoms participating in chemical reactions- functional groups
H | C ||| C | H
Functional Groups• OH- (hydroxyl)• C=O (carbonyl)• COOH (carboxyl)• NH2 (amino)• SH-sulfhydryl
group• PO3 (phosphate) Phosphate group
Classes of Molecules & Functional Groups
• COOH & NH2- amino acids
• hydroxyl groups-alcohols• carboxyl groups-
carboxylic acids-acetic acid
• sugars contain both-carbonyl group & several hydroxyl groups
• phosphate groups-found on nucleic acids
Macromolecules• 4 main classes
– macromolecules or polymers• consist of many identical or
similar molecular units strung together– monomers
• monomers are linked in anabolic reactions– dehydration synthesis– chemical reaction which
removes water• broken down into constituent
monomers by adding water– catabolic reactions-
hydrolysis
Carbohydrates• composed of C, H & O• 1:2:1 ratio• Formula: (CH2O)n
• may contain nitrogen, phosphate and/or sulfur
• Monomers-monosaccharides– simple sugars– building blocks for all other
carbohydrates• 2-10 monosaccharides-
oligosaccharide• hundreds-polysaccharide.• hydrophilic
– water loving• larger molecules are less soluble
in water
Glucose
Monosaccharides• simple sugars• single chain or ring of 3-7 carbons• named for number of carbons • 5 -pentoses• 6 -hexoses• glucose contains 6 carbons-hexose• formula-C6H1206
– most important metabolic fuel in body
– broken downATP + CO2
• fructose-6 carbon monosaccharide• same formula as glucose • fructose & glucose are isomers
– chemical compounds with same molecular formula but with elements arranged in different configurations
• Galactose-isomer of glucose & fructose
Glucose
Galactose
Fructose
Disaccharides• double sugars• covalent bond- between hydroxyl
groups of two simple sugars• Sucrose
– Glucose + fructosesucrose + H2O
• Lactose-found in milk of mammals– disaccharide of galactose &
glucose• Maltose
– major degradation product of starch
– composed of 2 glucose monomers
• too large to pass through cell membranes
• must be broken down into constituent parts by hydrolysis
• Sucrose + H20 glucose + fructose
Polysaccharides• complex carbohydrates• dehydration synthesis reactions add more
monosaccharides polysaccharides• most in nature are in this form• fairly insoluble
– make perfect storage molecules• Glycogen
– major stored carbohydrate in animal liver & muscle cells
– highly branched at about every 8-10 residues
• Starch– major form of stored carbohydrate in
plants– Structure-identical to glycogen-less
branching at every 20-30 residues• Cellulose
– found in plants– most abundant compound on earth– cannot be digested by humans
Lipids• contain mostly C & H• 1:2 ratio• also contain oxygen
but less than carbohydrates
• often have N, S & phosphorous
• hydrophobic– do not dissolve in
water• include neutral fats,
phospholipids & steroids
Lipid Functions• structural components of
biological membranes– cholesterol, phospholipids &
glycolipids help form & maintain intracellular structures
• energy reserves– provide 2X as much energy as
carbohydrates• compose some hormones &
vitamins-steroids• lipophilic bile acids
– important for lipid solubilization
Lipids• composed of fatty acids & glycerol • fatty acids-long-chain hydrocarbon
molecules• hydrocarbon chains make lipids nonpolar
and therefore insoluble in water• fat synthesis involves attaching 3 fatty acid
chains to one glycerol by dehydration synthesis-producing triglycerides
• glycerol is always the same; fatty acid composition varies
• length of neutral fat’s fatty acid chains & degree of saturation determine how solid a fat is at room temperature
• saturated– fatty acids with no carbon to carbon
double bonds• unsaturated
– have double bonds• monounsaturated fats have one
unsaturated bond• polyunsaturated fats have multiple
unsaturated bonds• double bonds make for lower melting points• presence of unsaturated fatty acids makes
fat liquid at room temperature
Hydrolysis of Triglycerides
• Hydrolysis breaks triglycerides
• fatty acid + glycerol
Proteins• C, H, O, N & small
amounts of S & sometimes phosphorous
• monomer-amino acids• 1-7-peptide• up to 100- polypeptide• more than 100- protein
Proteins• most abundant organic compounds in
human body• provide support for cells, tissues & organs
and create a 3-D framework for body• contractile proteins allow for movement via
muscle contractions• transport proteins carry insoluble lipids,
respiratory gases & minerals in blood• serve as buffers; help to prevent dangerous
pH changes• enzymes are proteins important in
metabolic regulation– needed to speed rate of chemical
reactions• protein hormones coordinate, control &
influence metabolic activities of nearly every cell
• important for defense• skin, hair, & nails protect underlying tissues
from environment• antibodies protect us from disease• clotting proteins protect from us from
bleeding out
Amino Acids• 20 in nature• (excluding proline) contain carboxylic acid-
COOH & amino-NH2 or amine group
• functional groups are attached to same carbon atom
• R group attaches to same carbon • amino acid is distinguished by its particular
R-group• 2 broad classes based upon whether R-
group is hydrophobic or hydrophilic • hydrophobic repel aqueous environments
– reside predominantly in interior of proteins
• hydrophilic amino acids interact with aqueous environments & often form H-bonds– found predominantly on exterior of
proteins
Protein Structure• Primary
• Secondary
• Tertiary
• Quaternary
Structure & Function• structure determines function• shape of protein allows it to carry
out specific duties• proteins whose job is to fill in a
space (active site) on another molecule-globular in shape
• those that make up something like muscles or tendons-fibrous
• shapes depend on environmental characteristics– ionic composition, pH &
temperature• non homeostatic change in any of
these will denature protein• denaturation causes protein to
lose shape• loss of shapecannot function
properly
Nucleic Acids• largest, organic molecules• C, H, O, N, & phosphorous• nucleotides
– monomer for nucleic acids
• provide directions for building proteins
• 2 main types• RNA
– translates DNA code• DNA
– contains genetic information that is inherited from our parents
Nucleic Acids• RNA
–single polynucleotide chain
• DNA–double helix form–two polynucleotide
chains wrapped around one another
Nucleic Acids• mono-, di-, & tri-
phosphorylated forms• often abbreviated• mono, di- & tri-phosphorylated
forms of adenosine are abbreviated AMP, ADP & ATP
• phosphate bonds are high energy bonds– contain energy– when broken yield 7kcals
• ATP ADP + Pi + energy• ATP-energy currency of all
cells