Macromolecules:
introduction on structural
features and
most important functions
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.
1
Outline
•  Atomic and molecular composition of living matter
•  Carbohydrates
•  Nucleobases, nucleosides, nucleotides
•  Aminoacids
•  Fatty Acids
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.
2
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.
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.
3
Molecules of Life
A few fundamental molecules
•  Water (70% of our body mass)
•  Phosphoric acid, dissolved as phosphate ions and protons:
(H3PO4 ⇔ HPO42- + 2H+)
•  Simple sugars (glucose, ribose, saccarose)
•  Nucleobases (pirimidines and purines)
•  Nucleotides (ATP, dGTP, cAMP, etc.)
•  Fatty acids and phospholipids (POPC, DPPC, etc.)
•  Aminoacids
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.
4
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
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.
5
Monosaccharides
•  (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
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.
6
Monosaccharides
•  Found in nature as mixture of open and cyclic structures.
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.
7
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).
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.
8
Disaccharides
•  Examples are lactose, sucrose, maltose
•  First energy stock
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.
9
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.
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.
10
Oligo/polysaccharides
Amide (starch): polysaccharide of glucose
•  Fundamental stock of energy in plants.
•  Two principal structures:
1. Amylose
•  Linear chain with glycosidic bond α-1,4
(helicoid structure).
•  Constitutes about 20% of amide structure.
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.
11
Oligo/polysaccharides
Amide (starch): polysaccharide of glucose
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.
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.
12
Oligo/polysaccharides
Glycogen: polysaccharide of glucose
•  Primary energy stock in animals.
•  Structure similar to amylopectin, more branching
(ratio of α-1,6 vs. α-1,4 bonds equals 1/10).
•  Synthesized from protein
glycogenin.
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.
13
Oligo/polysaccharides
Cellulose: polysaccharide of glucose
•  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.
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.
14
Oligo/polysaccharides
Difference between α-1,4 and β,1-4 bonds
•  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.
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.
15
Nucleobases, nucleosides, nucleotides
•  Bases of nucleic acids: 5 fundamental types
•  2 classes: purines (2) and pirimidines (3)
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.
16
Nucleobases, nucleosides, nucleotides
DNA: A, G, C, T
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.
17
Nucleobases, nucleosides, nucleotides
RNA: A, G, C, U
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.
18
Nucleobases, nucleosides, nucleotides
•  (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.
5’
3’
1’
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.
19
Nucleobases, nucleosides, nucleotides
•  Nucleotide  nucleoside bound to
one or more phosphate groups.
5’
•  5’ o 3’ depending on where
substitution do occur.
5’
3’
1’
5’
3’
3’
5’-ATP  Adenosine Tri-Phosphate
3’-dGMP  deoxyGuanosine Mono-Phosphate
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.
20
Aminoacids
•  21 different types of α-aminoacids in eukaryotes
•  Same backbone, different side chains R
Amine
(base) Carboxyl
(acid) Side chain 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.
21
Aminoacids
•  21 different types of α-aminoacids in eukaryotes
•  Same backbone, different side chains R
•  Zwitterions in solution (terminal amino e carboxyl groups)
Neutral Zwitterionic Amine
(base) Carboxyl
(acid) Side chain 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.
22
Aminoacids
Chiral molecules (not superimposable to their mirror image)
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...
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.
23
Chirality
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!
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.
24
Chirality
Chirality is an essential parameter for the intermolecular
interactions and for processes such as molecular recognition
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
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.
25
Aminoacids
Most are hydrophobic
•  Aliphatic  A, V, I, L, M
•  Aromatic  F, Y, W
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.
26
Aminoacids
Polar (pH 7.4)  S, T, N, Q
Charged (pH 7.4)
+  R, H, K
-  D, E
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.
27
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)
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.
28
Aminoacids
Several functional groups are attached to different AAs
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.
29
Aminoacids
Nomenclature of carbon atoms of the side chain
In some cases amino group
bound to β or γ carbon

β/γ-aminoacids
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.
30
Fatty acids
Aliphatic chain of C atoms ending with carboxyl group (-COOH)
•  Polar head and hydrophobic tail  amphiphatic molecules
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.
31
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
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.
32
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)
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.
33
Some unsaturated fatty acids
Common
name
Chemical structure
Δx
C:D n−x
Myristoleic acid
CH3 (CH2 )3 CH=CH(CH2 )7 COOH
cis-Δ9
14:1 n−5
Palmitoleic acid
CH3 (CH2 )5 CH=CH(CH2 )7 COOH
cis-Δ9
16:1 n−7
Sapienic acid
CH3 (CH2 )8 CH=CH(CH2 )4 COOH
cis-Δ6
16:1 n−10
Oleic acid
CH3 (CH2 )7 CH=CH(CH2 )7 COOH
cis-Δ9
18:1 n−9
Elaidic acid
CH3 (CH2 )7 CH=CH(CH2 )7 COOH
trans-Δ9
18:1 n−9
Vaccenic acid
CH3 (CH2 )5 CH=CH(CH2 )9 COOH
trans-Δ11
18:1 n−7
Linoleic acid
CH3 (CH2 )4 CH=CHCH2 CH=CH(CH2 )7 COOH
cis,cis-Δ9 ,Δ12
18:2 n−6
Linoelaidic acid
CH3 (CH2 )4 CH=CHCH2 CH=CH(CH2 )7 COOH
trans,trans-Δ9 ,Δ12
18:2 n−6
α-Linolenic acid
CH3 CH2 CH=CHCH2 CH=CHCH2 CH=CH(CH2 )7 COOH
cis,cis,cis-Δ9 ,Δ12 ,Δ15
18:3 n−3
Arachidonic acid
CH3 (CH2 )4 CH=CHCH2 CH=CHCH2 CH=CHCH2 CH=CH(CH2 )3 COOH
Eicosapentaenoic
acid
CH3 CH2 CH=CHCH2 CH=CHCH2 CH=CHCH2 CH=CHCH2 CH=CH(CH2 )3 COOH
cis,cis,cis,cis,cisΔ5 ,Δ8 ,Δ11 ,Δ14 ,Δ17
20:5 n−3
Erucic acid
CH3 (CH2 )7 CH=CH(CH2 )11 COOH
cis-Δ13
22:1 n−9
Docosahexaenoic
acid
CH3 CH2 CH=CHCH2 CH=CHCH2 CH=CHCH2 CH=CHCH2 CH=CHCH2 CH=CH(CH2 )2 COOH
cis,cis,cis,cis,cis,cisΔ4 ,Δ7 ,Δ10 ,Δ13 ,Δ16 ,Δ19
22:6 n−3
!
cis,cis,cis,cis-Δ5 Δ8 ,Δ11 ,Δ14 20:4 n−6
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.
34
Some saturated fatty acids
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.
35
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.
α-linolenic acid (ω-3) Linoleic acid (ω-6) 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.
36
Most common fatty acids
•  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)
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.
37
Most common fatty acids
•  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.
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.
38
Glycerides
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
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.
39
Glycerides
•  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.
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.
40
Phospholipids
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
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.
41
Glycerophospholipids
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.
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.
42
Glycerophospholipids
Principal components of membranes of all living organisms
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.
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.
43
Glycerophospholipids
Principal components of membranes of all living organisms
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.
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.
44
Glycerophospholipids
Principal components of membranes of all living organisms
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.
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.
45
Glycerophospholipids
Principal components of membranes of all living organisms
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.
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.
46
Sphingolipids
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
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.
47
Glycolipids
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
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.
48
Sterols
Derivatives of sterol  polycyclic compound bearing four
condensed rings (three exa- and one penta-ring).
17
C
3
A
D
B
•  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)
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.
49
Cholesterol
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.
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.
50