structures, functions and interactions of biological
TRANSCRIPT
Outline
• Biomolecules (carbohydrates, lipids,
proteins, nucleic acids): structures
and functions
• Chemical bonding & Molecular
interactions
• Stereochemistry
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http://ssds-science.weebly.com/cells-tissue-organ-organ-system.html 3
Four major classes of biomolecules: Proteins, Nucleic
acids,Carbohydrates, and
Lipids
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Biomolecules - an overviewProteins
Nucleic acids
Lipids
Carbohydrates
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Proteins
Amino group
Carboxylic group
Side chain (variable)
Ca
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Example:
Tyrosine-Glycine-Proline-Phenylalamine-Leucine
Tyr-Gly-Pro-Phe-Leu
YGPFL
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Structures, names, abbreviations and isoelectric points (pI)
The pI, is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean
UV absorption spectra of the
aromatic amino acids and bovine serum albumin
Medical Biochemistry, 4th Edition , Ed. John Baynes, Marek Dominiczak, 2014, Elsevier limited.
Trp
Try
Side chain
Phe
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Levels of structure in a protein
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a b
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Primary structures
Tyr Gly Pro Phe Leu
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Secondary structures
a-helix b-pleated sheet
11Medical Biochemistry, 4th Edition , Ed. John Baynes, Marek Dominiczak, 2014, Elsevier limited.
Tertiary structures
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Quaternary structures
a2b2 tetramer of Hb60 copies of each 4 subunitsof rhinovirus coat proteins
Several subunits held together by non-covalent bonds
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Nucleic acids
DNA RNA
Nucleotide: A nucleobase, a sugar (deoxyribose/ribose) and a phosphate group
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• Nucleic acids: DNA and RNA
• A nucleotide comprises three parts: i) ribose or deoxyribose; ii) a nitrogenous
bases/nucleobase (purines or pyrimidines) and a phosphate group
• DNA has deoxyribose and adenine (A), guanine (G), cytosine (C) and thymine (T)
• RNA contains ribose and A, G, C and uracil (U)
• Positions on the base are numbered 1, 2, 3, etc; on the sugar: 1’, 2’, 3’, 4’, 5’.
5 end
3 end
Nucleotide
Nucleoside
DNA RNA
Watson-Crick base pairs and double helix
≡
Strands are anti-parallel
Deoxyribose-phosphate backbone
10 base pairs / turn
of helix
Medical biochemistry at a glance, 3rd ed., J.G. Salway, John Wiley & Sons, Ltd., 2012 16
Organization of DNA in eukaryotes
Medical biochemistry at a glance, 3rd ed., J.G. Salway, John Wiley & Sons, Ltd., 201217
DNA double helix DNA wrapped around histones
Nucleosomes Nucleosomes coiled into chromatin fibers further condensation of chromatin Chromosome
DNA DNA RNA Protein
ribosomeDNA
polymerase
Glycoprotein
glycosylation
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• Describes the flow of genetic information from DNA to proteins
• DNA is transcribed in the nucleus to make a complementary RNA strand
• RNA is exported from the nucleus into the cytoplasm where it is translated to make a protein.
• The protein may then be modified further, for example by glycosylation (attaching sugars) to give a glycoprotein.
• DNA is used for information storage – carries the genetic information
• RNA, Proteins and Glycoproteins are used for information transfer and catalysis
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Structures of the D-AldosesAldehyde
Structures of the D-Ketoses
Ketone
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Aldehyde Aldose
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Ketone
Ketose
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α α β
a b
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Long chain of sugar units
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o
o
o
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Phosphatidylcholine
Glycosphingolipid
Cholesterol
Palmitic acid
Oleic acid
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Linoleic acid
Linolenic acid29
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18
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9121518
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3
a
b
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G
l
y
c
e
r
o
l
Fatty acid
Fatty acid
Fatty acid
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G
l
y
c
e
r
o
l
Fatty acid
Phosphate
Fatty acid
Amino
alcohol
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• Covalent bonds: The strongest types of bonds Formed by sharing electrons between
adjacent atoms (ex. C-C, H-O, S-S, peptide bonds, glycosidic bonds)
• Non-covalent bonds: Electrostatic interactions (Charge-charge/Ionic interactions)
Hydrogen bonding Van der Waals forces Hydrophobic interactions
Weak
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DNA
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Various weak forces stabilize the double helix• Hydrogen bonds: between base pairs
• Stacking interactions (or also known as Van der Waals interactions): between bases as they sit on top of one another
• Hydrophobic effects: by burying the bases in the interior of the helix increases its stability; having the hydrophobic bases clustered in the interior of the helix keeps it away from the surrounding water
• Charge-charge interactions: electrostatic repulsion of negative charged phosphate groups is decreased by cations (e.g. Mg2+ )
Molecular Biology: Principles and Practice, Michael M. Cox, Jennifer Doudna, Michael O'Donnell, 1st Ed. 2012, W.H. Freeman and Company
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Stereochemistry
Molecular Biology: Principles and Practice, Michael M. Cox, Jennifer Doudna, Michael O'Donnell, 1st Ed. 2012, W.H. Freeman and Company
https://cdn.kastatic.org/ka-perseus-images/5029538d3c43e936668b6b7410ea7ea9b7627b16.png
Chiral molecules
Achiral molecules
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• a a
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The L and D isomers (enantiomers) of
amino acids
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Chiral compounds (Enantiomers) are optically active:Capable of rotating the plane of polarized light
Enantiomers rotate the plane of polarized light in the opposite of direction
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The L and D isomers (enantiomers) of
monosaccharides
D-glucose L-glucose
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Carbohydrates Lipids Proteins Nucleic acids
Building blocks Monosaccharides(D-form)
Non-polymers Amino acids(L-form)
Nucleotides(sugars, bases, P)
Intra-/intermolecular
interactions
Glycosidiclinkages/H-bonds (ex in cellulose)
Covalent bonds/hydrophobic interactions (C-H)
Peptide bonds/H-bonds, hydrophobic
interactions, etc.
Phosphodiesterbonds/H-bonds,
hydrophobic interactionsStructure Mono-, di-, oligo-,
polysaccharidesDiverse 1°, 2°, 3°, 4° str. Nucleosides,
nucleotides, polynucleotides
Examples Glucose, lactose, starch, cellulose,
G-6-P
Fatty acids, triacyglycerols, phospholipids
Peptide chains, myoglobin, hemoglobin
DNAs/RNAs
Biological functions
Energy storage, structural
components, cell-cell
communication
Energy storage, structural
components, cell membrane components
Catalysts, transport of vitamins,
minerals, oxygen and fuels, receptors,
cytoskeleton
Genetic information storage (DNA) and transmission (RNA)
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