Macromolecules: introduction on structural features and ... · Macromolecules: introduction on...
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Macromolecules: introduction on structural
features and most important functions
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Outline
• Atomic and molecular composition of living matter
• Carbohydrates
• Nucleobases, nucleosides, nucleotides
• Aminoacids
• Fatty Acids
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Atoms in biological matter
Fundamental atoms
• Only a few are traceable in human body: O, N, C, H, P, S.
• H+, Na+, K+, Cl-, Ca2+ most frequent ions.
• Others (Fe, Ni, Cu) present only in limited quantities.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Molecules of Life A few fundamental molecules
• Water (70% of our body mass)
• Phosphoric acid, dissolved as phosphate ions and protons: (H3PO4 ⇔ HPO4
2- + 2H+)
• Simple sugars (glucose, ribose, saccarose)
• Nucleobases (pirimidines and purines)
• Nucleotides (ATP, dGTP, cAMP, etc.)
• Fatty acids and phospholipids (POPC, DPPC, etc.)
• Aminoacids
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Carbohydrates • Molecules made of C, H and O, with general formula
Cm(H2O)n H:O ratio generally equal to 2:1.
– Exceptions do exist, ominous one is deoxyribose in DNA, having formula C5H10O4.
• Very important energy source of metabolism.
• More structurally complex than other macromolecules.
• In biochemistry they are synonymous of saccharides:
– Mono-, di-, oligo- and poly-saccharides
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Monosaccharides
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• (CH2O)n n≥3 (glucose, fructose, ribose).
• Important source of energy (synthesis of ATP) and constituents of nucleic acids.
• 5 or 6-atoms ring structures with 1 oxygen.
• Stereochemistry: α or β.
α-D-Glucopyranose
β-D-Glucopyranose
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Monosaccharides
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• Found in nature as mixture of open and cyclic structures.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Disaccharides • Dimers of monosaccharides linked by a glycosidic bond of type α or β.
• Glycosidic bond: between a carboydrate and a functional group (e.g. alcohol).
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Disaccharides • Examples are lactose, sucrose, maltose
• First energy stock
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Oligo/polysaccharides • Oligosaccharides have formula [Cm(H2O)n]x, x between 3 and 9.
– Can covalently bind to amino acids glycoproteins (lying on both membrane and cytosol)
and to lipids glycolipids.
– Play a role in inter-cellular interactions.
• Polysaccharides have formula Cm(H2O)n with m≥200.
– Cellulose, amides, glycogen, pectin, chitin, etc.
– Capsules secerned by some bacteria composed of thick layers of polysaccharides enveloping antigenes.
Hinder immunity response of host organism.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Oligo/polysaccharides Amide (starch): polysaccharide of glucose
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1. Amylose
• Linear chain with glycosidic bond α-1,4 (helicoid structure).
• Constitutes about 20% of amide structure.
• Fundamental stock of energy in plants.
• Two principal structures:
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Oligo/polysaccharides
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2. Amylopectin
• Features branches through glycosidic bond α-1,6.
• Ratios of 1,6 vs. 1,4 bonds in range 1/24-1/30.
• Constitutes about 80% of amide structure.
Amide (starch): polysaccharide of glucose
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Oligo/polysaccharides Glycogen: polysaccharide of glucose
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• Structure similar to amylopectin, more branching (ratio of α-1,6 vs. α-1,4 bonds equals 1/10).
• Primary energy stock in animals.
• Synthesized from protein glycogenin.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Oligo/polysaccharides
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• Fundamental structure in vegetal kingdom.
• ~1015 Kg of cellulose synthesized and degraded
per year.
• Planar structure due to β-1,4 glycosidic bond, functional to build highly resistant fibers
such as those found in plants.
Cellulose: polysaccharide of glucose
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Oligo/polysaccharides Difference between α-1,4 and β,1-4 bonds
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• Structures built through α-1,4 bonds are willing to assume
helicoidal structure.
• Structures built through β-1,4 bonds tend to form linear
structures and to self-assemble into planar sheets linked
through H-bonds.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Nucleobases, nucleosides, nucleotides • Bases of nucleic acids: 5 fundamental types
• 2 classes: purines (2) and pirimidines (3)
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and pirimidines (3)
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Nucleobases, nucleosides, nucleotides DNA: A, G, C, T
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Nucleobases, nucleosides, nucleotides RNA: A, G, C, U
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Nucleobases, nucleosides, nucleotides
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• (deoxy)nucleoside base covalently bound (glycosidic bond) to a molecule of (deoxy)ribose.
• Glycosilation always occurs between atom C1’ of sugar and atoms N9 (purines) or N1 (pirimidines) of nucleobases.
1’ 3’
5’
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Nucleobases, nucleosides, nucleotides • Nucleotide nucleoside bound to one or more phosphate groups.
• 5’ o 3’ depending on where substitution do occur.
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1’ 3’
5’
3’
5’
3’
5’
5’-ATP Adenosine Tri-Phosphate
3’-dGMP deoxyGuanosine Mono-Phosphate
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Aminoacids
• 21 different types of α-aminoacids in eukaryotes
• Same backbone, different side chains R
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Carboxyl (acid)
Amine (base)
Side chain
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Aminoacids
• 21 different types of α-aminoacids in eukaryotes
• Same backbone, different side chains R
• Zwitterions in solution (terminal amino e carboxyl groups)
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Zwitterionic Neutral
Carboxyl (acid)
Amine (base)
Side chain
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Aminoacids Chiral molecules (not superimposable to their mirror image)
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Enantiomers
• Enantiomers (optical isomers) D and L
• All aminoacids exist in L form during translation
• D enantiomers generated by post-translation processes, occur in peptidoglycan, are used as neurotransmitters...
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Chirality
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Chirality is an essential parameter for the intermolecular interactions and for processes such as molecular recognition
L carvon (smells like mint)
R carvon (smells like cumin)
Odorant receptors contain chiral groups!
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Chirality
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L methorphan (analgesic)
R methorphan (cough sedative)
Molecules with different chirality interact in a different way (with high or low affinity) with the same receptors
Chirality is an essential parameter for the intermolecular interactions and for processes such as molecular recognition
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Aminoacids Most are hydrophobic
• Aliphatic A, V, I, L, M
• Aromatic F, Y, W
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Aminoacids
Polar (pH 7.4) S, T, N, Q
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Charged (pH 7.4)
+ R, H, K
- D, E
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Aminoacids “Special”
• C: contains the thiol group (SH), is polar and used to form disuphilde bonds
• G: hydrogen as side chain (only achiral AA)
• P: side chain include a C-N bond (hydrophobic)
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Aminoacids Several functional groups are attached to different AAs
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Aminoacids Nomenclature of carbon atoms of the side chain
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In some cases amino group bound to β or γ carbon
β/γ-aminoacids
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Fatty acids Aliphatic chain of C atoms ending with carboxyl group (-COOH)
• Polar head and hydrophobic tail amphiphatic molecules
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Fatty acids Aliphatic chain of C atoms ending with carboxyl group (-COOH)
• Polar head and hydrophobic tail amphiphatic molecules
• Aliphatic chain can be saturated (linear) or contain one or more double bonds (unsaturated carbons) conformations cis and trans
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Fatty acids
A few ways of naming fatty acids – Common names (e.g. palmitoleic, oleic, arachidic,… acid)
– Regular nomenclature by IUPAC: counting starts from carboxylic acid carbon, and cis-/trans- or E-/Z- notation is used when double bond encountered
(e.g (9Z,12Z,15Z,18Z)-octadecatetraenoic acid)
– Δx: double bonds indicated by Δx where x is number of C atom counting from carboxylic acid. Every double bond must be specified as cis or trans
(e.g. cis, cis, cis, cis-Δ9,Δ12,Δ15,Δ18-octadecatetraenoic acid)
– n-x or ω-x nomenclature: based on biosynthetic properties of molecules in animals. First double bond counting from methyl terminal identifies class (e.g. n-3 or ω-3).
However, no further details are given, so this nomenclature is ambiguous
– Lipid numbers: has form C:D, where C and D are total numbers of C atoms and double bonds, respectively. Ambiguous, often comes with n-x o Δx
(e.g. 18:3, 18:3ω6, 18:3, cis,cis,cis-Δ9,Δ12,Δ15)
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Some unsaturated fatty acids
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Common name Chemical structure Δx C:D n−x
Myristoleic acid CH3(CH2)3CH=CH(CH2)7COOH cis-Δ9 14:1 n−5
Palmitoleic acid CH3(CH2)5CH=CH(CH2)7COOH cis-Δ9 16:1 n−7
Sapienic acid CH3(CH2)8CH=CH(CH2)4COOH cis-Δ6 16:1 n−10
Oleic acid CH3(CH2)7CH=CH(CH2)7COOH cis-Δ9 18:1 n−9
Elaidic acid CH3(CH2)7CH=CH(CH2)7COOH trans-Δ9 18:1 n−9
Vaccenic acid CH3(CH2)5CH=CH(CH2)9COOH trans-Δ11 18:1 n−7
Linoleic acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH cis,cis-Δ9,Δ12 18:2 n−6
Linoelaidic acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH trans,trans-Δ9,Δ12 18:2 n−6
α-Linolenic acid CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH cis,cis,cis-Δ9,Δ12,Δ15 18:3 n−3
Arachidonic acid CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH cis,cis,cis,cis-Δ5Δ8,Δ11,Δ14 20:4 n−6
Eicosapentaenoic acid CH3CH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH cis,cis,cis,cis,cis-
Δ5,Δ8,Δ11,Δ14,Δ17 20:5 n−3
Erucic acid CH3(CH2)7CH=CH(CH2)11COOH cis-Δ13 22:1 n−9
Docosahexaenoic acid CH3CH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)2COOH cis,cis,cis,cis,cis,cis-
Δ4,Δ7,Δ10,Δ13,Δ16,Δ19 22:6 n−3
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Some saturated fatty acids
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Fatty acids • Fundamental for energy storage.
• Components of multi-glycerides and phospholipids.
• Natural fatty acids generally have even number of C atoms (4-28).
• Essential fatty acids: animals must assume them from external sources (food) since not able to synthetize them. Examples are ω-3 and ω-6.
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α-linolenic acid (ω-3) Linoleic acid (ω-6)
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Most common fatty acids
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• Short chain (C:D 4:0/6:0) • Fatty acids from cow milk and derivatives
• Butyric acid • Esanoic acid
• Medium chain (C:D 8:0/14:0)
• Tropical oils (coconut, palm) • Lauric acid (C12:0) (industrial word: vegetal oil) • Myristic acid (C14:0)
• Long chain (C:D ≥ C16)
• Animal and vegetal fatty acids • Palmitic acid (C16:0) • Stearic acid (C18:0)
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Most common fatty acids
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• Long chain (C:D ≥ C16)
• Oleic acid and cis-9-octadecenoic acid (18:Δ9) • Most abundant fatty acid in animal and
vegetal fat. • Typical of olive oil (where constitutes
about 80% of all fatty acids).
• Essential fatty acids: linoleic, α-linolenic • Precursors of long chain poly-unsaturated
acids of classes n-6 (ω6) and n-3 (ω3) respectively.
• E.g. eicosapentaenoic acid (ω3) in fish oil.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycerides
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Also called acyl-glyceroles, they are esters formed by glycerol and one to three fatty acids (mono-, di-, tri-glicerides)
Glycerol (alchool)
Monoglyceride Diglyceride Triglyceride
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycerides
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• Mono and di-glyceride are said partial since not all of hydroxyl groups are esterified.
• Short partial glycerides are strongly polar.
– Used as excipients to increase solubility of drugs.
– Used as emulsion enhancers in food industry.
• Triglycerides are contained in both animal and vegetal fats.
– Components of skin oils.
– Present in blood, help bidirectional transfer of adipose fat and glucose from liver.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Phospholipids
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Subclass of lipids, generally formed by a 1,2-diglyceride (glycerophospholipids or phosphoglycerides), a phosphate group (at 3) and a alcohol (e.g. choline)
• Polar head • Negative group • Hydrophobic tail
Amphiphatic
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycerophospholipids
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Principal components of membranes of all living organisms
Phosphatidic Acid (PA)
• -1 net charge. • Precursor of biosynthesis of
several other lipids. • Influences curvature of phospholipid membrane.
• Transmitter of signals that drive recruitment of cytosolic proteins towards appropriate cellular
membrane.
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycerophospholipids
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Phosphatidil Ethanolamine (PE)
• Principal component of bacterial membranes.
• 25% of all phospholipids in cellular membranes.
• Generally coupled to a saturated and an unsaturated fatty acid
(e.g. 1-Palmitoyl-2-oleoyl-sn-glycero -3-phosphoethanolamine, POPE). • Mainly found in inner leaflet. • Modulates membrane curvature.
Principal components of membranes of all living organisms
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycerophospholipids
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Phosphatidil Choline (PC)
• Principal component of membranes in animals.
• Generally coupled to a saturated and a unsaturated fatty acid (e.g. 1-Palmitoyl-2-oleoyl-sn-glycero
-3-phosphocholine, POPC). • Mainly present in outer leaflet of
membrane. • Absent in almost all bacteria.
Principal components of membranes of all living organisms
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycerophospholipids
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Phosphatidil Serine (PS)
• Anionic at physioligical pH. • Role in cell-signaling:
- In normal conditions kept within inner leaflet by flippases
(other phospholipids free to change their orientation).
- During cellular apoptosis flippase stops its activity, and PS is found
also on outer leaflet, which is a signal to macrophages.
Principal components of membranes of all living organisms
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycerophospholipids
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Phosphatidil Glycerol (PG)
• Anionic at physiological pH. • Found in almost all bacteria (e.g.
20% of membranes in E. coli). • Building block of cardiolipin, constitutive molecule of inner
mitochondrial membrane.
Principal components of membranes of all living organisms
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Sphingolipids
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A.k.a. glycosilceramides: second most important class of lipids Contain sphingoids, an ensemble of amino-alcohol bases among which the
most frequent is sphingosin
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Glycolipids
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Lipids bound to a carbohydrate. Depending on intermediate group classified as glyco (H),
glycero-glyco (glycerol) and sphingo-glyco (sphingosin) lipids
• Energy source • Signaling (carbohydrates on outer membranes in eukaryotes) • Involved in inter-cellular adhesion and building of tissues
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Sterols
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Derivatives of sterol polycyclic compound bearing four condensed rings (three exa- and one penta-ring).
A B
C D
3
17
• Alcoholic group bound to 3 in A, remaining aromatic amphiphatic lipids
• Aliphatic chain branching off from C17 of ring D (precursors of steroids)
• Subclass of steroids (also called alcohol-steroids)
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Biophysics Course held at Physics Department, University of Cagliari, Italy. Academic Year: 2016/2017. Dr. Attilio Vittorio Vargiu PLEASE NOTE! This material is meant just as a guide, it does not substitute the books suggested for the Course.
Cholesterol
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Most important sterol synthetized by animals
• Structural block of all animal membranes, where inserts between two
layers of phospholipids with–OH group close to polar heads. • Key to structural integrity and fluidity of membrane.
• Contributes to reduce permeability of small hydro-soluble molecules. • Key component of cellular (synaptic) vesicles (many synaptic proteins bind to it). • Precursor of steroids hormones (e.g. cortisone and testosterone) and vitamin D.