Basic course, CDFD: Molecules of Life, 23-Aug-2007 Molecules of Life Shekhar C. Mande.
Molecules of Life. Molecules of Life Carbohydrates –m–monosaccharides –e–energy supply...
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Transcript of Molecules of Life. Molecules of Life Carbohydrates –m–monosaccharides –e–energy supply...
![Page 1: Molecules of Life. Molecules of Life Carbohydrates –m–monosaccharides –e–energy supply Proteins –a–amino acids –s–structural components Lipids –f–fatty.](https://reader036.fdocuments.us/reader036/viewer/2022062511/5513d08f55034646298b50dc/html5/thumbnails/1.jpg)
Molecules of Life
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Molecules of Life• Carbohydrates
– monosaccharides– energy supply
• Proteins– amino acids– structural components
• Lipids– fatty acids– structural components, energy, hormones
• Nucleic acids– nucleotides– DNA-genetic material
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Composition • Most-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
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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
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Covalent Bonding• since carbon can bind
to itself• has capacity to
construct endless numbers of carbon skeletons varying in size & branching patterns
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Organic Compounds• chain of carbons-carbon
skeleton• branched or unbranched• double or single bonds• straight or arranged in ring
form• each has a unique 3-D shape• properties depend on carbon
skeleton & atoms attached to skeleton
• groups of atoms participating in chemical reactions are functional groups
H | C ||| C | H
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Functional Groups• OH- (hydroxyl)• C=O (carbonyl)• COOH (carboxyl)• NH2 (amino)• SH-sulfhydryl
group• PO3 (phosphate) Phosphate group
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Classes of Molecules Related to 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-nucleic acids
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Macromolecules• 4 main classes• consist of many identical or
similar molecular units strung together– monomers
• cells link monomers in anabolic reactions by dehydration synthesis– chemical reaction which
removes water• broken down into monomers by
adding water– catabolic reactions-
hydrolysis
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Carbohydrates• composed of C, H & O• 1:2:1 ratio• Formula: (CH2O)n gives formula for
any carbohydrate• may contain nitrogen, phosphate
and/or sulfur• Monomers-monosaccharides
– simple sugars– building blocks for all other
carbohydrates• 2-10 monosaccharides form
oligosaccharide• hundreds- polysaccharide.• hydrophilic
– water loving• larger molecules are less soluble
in water
Glucose
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Monosaccharides• simple sugars• single chain or ring of 3-7 carbons• named for number of carbons they
contain• 5 carbons-pentoses• 6 carbons-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
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Disaccharides• double sugars• covalent bond- between hydroxyl
groups of two simple sugars• physiologically important
disaccharides Sucrose– sugar cane & sugar beets– Glucose + fructosesucrose +
H2O• Lactose-found in milk of mammals
– disaccharide of galactose & glucose
• Maltose– major degradation product of
starch– composed of 2 glucose monomers
• Disaccharides-too large to pass through cell membranes
• must be broken down into constituent parts by hydrolysis
• Sucrose + H20 glucose + fructose.
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Polysaccharides• complex carbohydrates• dehydration synthesis reactions add more
monosaccharides polysaccharides• most carbohydrates 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
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Lipids• contain mostly C & H• 1:2 ratio• also contain oxygen
(less than carbohydrates)
• often have N, S & phosphorous
• hydrophobic– do not dissolve in
water• neutral fats,
phospholipids & steroids
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Lipid Functions• structural components of
biological membranes– cholesterol, phospholipids &
glycolipids form & maintain intracellular structures
• energy reserves– provide 2X as much energy
as carbohydrates• hormones & vitamins-steroids• lipophilic bile acids
– important for lipid solubilization
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Lipids• composed of fatty acids & glycerol (an alcohol)• 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
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Hydrolysis of Triglycerides
• Hydrolysis breaks triglycerides
• fatty acid + glycerol
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Steroids• large lipid molecules with carbon
skeleton bent into 4 rings• most important one-cholesterol• obtained by absorption from
animal products in diet– meat, cream & egg yolks
• can also be made by the body• absolutely essential for life• component of cell membranes• raw material for Vitamin D, steroid
hormones & bile salt synthesis• needed to make steroid hormones
such as estrogen & testosterone • corticosteroids-essential for life
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Proteins• C, H, O, N & small
amounts of S & sometimes phosphorous
• monomer-amino acids• 1-7 amino acids-
peptide• up to 100-polypeptide• more than 100- protein
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Proteins• most abundant organic compound 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– 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 from disease• clotting proteins protect from from bleeding
out
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Amino Acids• 20 amino acids
• (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-
groups-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
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Protein Structure• each protein
contains unique sequence of amino acids
• four levels of protein structure
• Primary
• Secondary
• Tertiary
• Quaternary
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Structure & Function• structure determines function• shape of protein allows it to carry
out specific duties• protein whose job is to fill in a
space (active site) on another molecule-globular in shape
• those that make up 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
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Nucleic Acids• largest, organic molecules in
body• C, H, O, N, & phosphorous• long stretches of nucleotides
– monomer for nucleic acids• provide directions for building
proteins• RNA
– translates DNA code• DNA
– contains genetic information that is inherited from our parents
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Nucleic Acids• RNA
–single polynucleotide chain
• DNA–double helix form–two polynucleotide
chains wrapped around one another
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Nucleic Acids• exist in mono-, di-, & tri-
phosphorylated forms• often abbreviated to AMP• Mono, Di- & tri-phosphorylated
forms of adenosine are abbreviated AMP, ADP & ATP
• phosphate bonds are high energy bonds– bonds contain energy– broken-yield 7kcals
• ATP ADP + Pi + energy• ATP is energy currency of all
cells