Download Inorganic compounds in cells

Inorganic compounds in cells
Vladimíra Kvasnicová
Chemical composition of human body
(mass %)
60%
water (2/3 intracellular, 1/3 extracellular)
18%
proteins, peptides, amino acids
15%
lipids (mainly triacylglycerols of fatty tissue)
1%
saccharides (poly- and monosaccharides)
1%
nucleic acids, nucleotides
5%
mineral substances
Minerals in human body
(adult man, 70 kg)
Ca
1 500 g
99% in bones and teeth: Ca10(PO4)6(OH)2;
cell signalling, muscle contraction, blood clotting
P
840 g
85% in bones; energy metabol.; structures of
nucleic acids, phospholipids, macroergic comp.
K
180 g
most: intracellularly, maintenance of osmotic
pressure, membrane potential, heart activity
S
140 g
in proteins (Cys, Met), component of biocatalysts
Cl
110 g
most: extracellularly, maint.of osmotic pressure
Na
100 g
most: extracellularly, maintenance of osmotic
pressure, membrane potential
Mg
40 g
60% in bones, intracellul.: stabilisation of ATP
Fe
5g
most in hemoglobin (O2 transport), component of
enzymes (electron transport - redox reactions)
Chemical composition of cells
1.
60 mass% - water
polar solvent, most of chemical reactions in a human body take
place in aqueous solutions
2. 35 mass% - organic compounds
a) high molecular weight (proteins, nucleic acids, glycogen)
b) low molecular weight (glucose, lipids, amino acids, metabolic
intermediates – e.g. organic acids derivatives)
3. 5 mass% - inorganic compounds
water
ions
buffers
crystals in bones
blood gases
reactive oxygen and nitrogen species
toxic heavy metals
PERIODIC TABLE
of elements
The figure is found at http://www.windows.ucar.edu/earth/geology/images/periodic_table.gif (September 2007)
Elements in the nature
• inorganic matter
oxygen (O)
50%
silicon (Si)
25%
aluminium (Al) 7%
iron (Fe)
5%
calcium (Ca)
3%
90%
sodium (Na)
potassium (K)
magnesium (Mg)
hydrogen (H)
• organic matter
„compounds of carbon“
C, O, H, N
oxygen (O)
carbon (C)
hydrogen (H)
nitrogen (N)
phosphorus (P)
sulphur (S)
Biogenic elements
= elements essential for structure and function of
organisms
macrobiogenic elements: C O H N Ca P S Na Cl K Mg
• over 0,005 % of body mass
• recommended daily intake over 100 mg
• blood concentration more than micromolar
microbiogenic (trace) elements Fe Cu Zn Se F I Co Cr Mn Mo Si V
• less than 0,005 % of body mass
• recommended daily intake less than 100 mg
• blood concentration: micromolar or lower
Required knowledge:
1) classification of elements
2) symbols and English names of elements
3) Latin names of elements
4) names of common cations and anions
5) common names of selected compounds
The figure is found at http://www.corrosionsource.com/handbook/periodic/periodic_table.gif (September 2007)
Memorize:
1) classification of elements
see Periodic table
alkali metals: Li, Na, K, Rb, Cs, Fr (IA)
alkali earth metals: (Be, Mg), Ca, Sr, Ba (IIA)
halogens: F, Cl, Br, I (VIIA)
inert gases: He, Ne, Ar, Kr, Xe, Rn (VIIIA)
Memorize:
1) classification of elements
see Periodic table
nonmetals: H (IA)
B (IIIA)
C, Si (IVA)
N, P, As (VA)
O, S, Se (VIA)
halogens (VIIA)
central
atoms of
acids
Memorize:
1) classification of elements
see Periodic table
transition metals: Cu, Ag, Au (IB)
Zn, Cd, Hg (IIB)
Cr, Mn, Fe, Co, Ni, Mo, Pt
other metals: Al, Sn, Sb, Pb, Bi
Memorize:
1) classification of elements
2) symbols and English names of elements
symbols are derived from Latin names of
elements
H = Hydrogenium = hydrogen
Na = Natrium = sodium
Ag = Argentum = silver
(Ar = Argon)
Memorize:
1) classification of elements
2) symbols and English names of elements
3) Latin names of elements
symbols of elements
used in naming of some compounds
used in medicine
Symbol
Na
K
Sn
Pb
Sb
Latin name
Natrium
Kalium
Stannum
Plumbum
Stibium
English name
sodium
potassium
tin
lead
antimony
W
Fe
Cu
Ag
Au
Hg
Wolframium
Ferrum
Cuprum
Argentum
Aurum
Hydrargyrum
tungsten
iron
copper
silver
gold
mercury
Compounds called by their common
names
• H2O
water
H3O+
hydronium
• NH3
ammonia
NH4+
ammonium
• NO
nitric oxide
• NaCl
salt
• HCO3-
bicarbonate
Name these compounds:
• Na2SO3
• Na2B4O7 . 10 H2O
• K3PO4
• KAl(SO4)2
• (NH4)2HPO4
• NaAl(SO4)2 . 12 H2O
• LiH2PO4
• (NH4)2CO3
• Ca(HCO3)2
• CaSO4 . ½ H2O
• Ag2S
• ZnSO4 . 7 H2O
• ZnSO4
• K2Cr2O7
• KMnO4
• KMgF3
• NaBrO
• NH4MgPO4
• Ba(NO3)2
• PbClF
• HgCl2
• Cu3(CO3)2F2
Cytosol is an aqueous solution
H2O
60 % of a cell by mass
water is a polar solvent
it dissolves other
polar compounds
Properties of water
• polar covalent bond between oxygen and
hydrogen ⇒ partial charges in water molecule
• hydrogen bonds in aqueous solutions (weak
attractions – not covalent but important)
• water molecules tend to „stick“ together
resulting in high surface tension
• water makes hydration shell of dissolved
solutes
protein in
water
oil in
water
Autoprotolysis of water
(dissociation of water)
• in aqueous solutions:
Kw = [H3O+]
x
[OH-] = 10-14
[H3O+] = 10-7 ⇒ pH = 7
[OH-] = 10-7
• in pure water:
[H3O+] = [OH-]
• in acidic solutions: [H3O+] > [OH-]
pH < 7
[H3O+] < [OH-]
pH > 7
• in basic solutions:
The figure was found at http://www.colorado.edu/kines/Class/IPHY3430-200/14fluid.html (April 2007)
pH in cells
• lower than in extracellular fluid because
metabolic reactions produce acids
(CO2 → H2CO3, lactic acid)
• cytosol:
pH = 6,8 – 7,0
• in lyzosomes: pH = 4,5 – 5,0
• in the blood: pH = 7,40 ± 0,04
• in the urine:
pH = 5,0 – 6,0
The metabolism produces acids:
CARBON SKELETON → CO2+H2O → HCO3-+ H+
(generally)
• saccharides → glucose → pyruvate, lactate + H+
• triacylglycerols → fatty acids, ketone bodies + H+
• phospholipids → phosphate + H+
• proteins → amino acids → sulfate, urea + H+
Intracellular buffers
• proteins (ampholytes): side chains of amino acids
• phosphates
inorganic:
HPO42- / H2PO4-
organic:
phosphoric acid esters and anhydrides
• bicarbonate buffer is the principal buffer of
extracellular fluid (blood)
HCO3- / H2CO3
Henderson–Hasselbalch equation
pH = pKa + log (cb / ca)
Dissociation constant and buffer pH
! the best buffering properties: pH = pK ± 1 !
a) pH = pK + log (1 / 1) ⇒
pH = pK
b) pH = pK + log (10 / 1)⇒
⇒
pH = pK + 1
c) pH = pK + log (1 / 10)⇒
⇒
pH = pK – 1
pH = pKa + log (cb / ca)
Problems
Calculate a ratio of phosphate buffer components (HPO42/ H2PO4-) in blood, if pH = 7,40
pK(H2PO4-) = 7,0
(2,5 = 25/10 = 5/2, i.e. HPO42- predominates)
Calculate a ratio of phosphate buffer components (HPO42/ H2PO4-) in urine, if pH = 6,0
pK(H2PO4-) = 7,0
(0,1 = 1/10, i.e. H2PO4- predominates)
Use of the dissociation constant
the ratio of phosphate buffer components
(HPO42- / H2PO4-)
pK2 = 7,0
if
a) pH = 7,4 (blood)
2,5 = 25/10 = 5/2
b) pH = 7,0 (cell)
1,0 = 1/1
c) pH = 6,0 (urine)
0,1 = 1/10
Henderson-Hasselbalch equation
for bicarbonate buffer
• at blood pH the buffer base
(HCO3-) predominates
because the value of blood
pH is higher than the value
of buffer pK
(7,4 > 6,1)
• the bicarbonate buffer
which ratio is 20/1 is still
efficient because CO2
formed by buffering is
excreted by lungs
(open buffer system)
[CO2] = α x pCO2
α = 0,226 for pCO2 expressed in kPa
α = 0,03 for pCO2 expressed in mmHg
Conversion of units
pressure = the force acting normally on unit area
of a surface (in pascals, Pa) 1 kPa = 103 Pa
Dalton´s law = the total pressure of a mixture of
gasses or vapours is equal to the sum of the
partial pressures of its components
partial pressure = pressure of one gas present in
a mixture of gases
Conversion of units
Air composition:
78% N2
21% O2
1% water, inert gases, CO2 (0,04%)
Air pressure:
1 atm = 101 325 Pa (~ 101 kPa) = 760 Torr (= mmHg)
1 mmHg = 0,1333 kPa
1 kPa = 7,5 mmHg
Problems
Partial pressures of blood gases were measured
in a laboratory:
pO2 = 71 mmHg
pCO2 = 35 mmHg
Convert the values to kPa.
pO2 = 9,5 kPa
pCO2 = 4,7 kPa
Inorganic ions in cells
• inorganic ions = minerals (0,5% of mass)
• intracellular fluid (ICF)
K+ > > Mg2+ > Na+ > > > > > (Ca2+)
phosphates > proteins > sulfates > HCO3- > Cl• extracellular fluid (ECF) – e.g. in blood plasma:
Na+ > > > K+ > Ca2+ > Mg2+
Cl- > > HCO3- > proteins > phosphates > sulfates
• membrane transport (channels, transporters)
Trace elements (0,005 % of body mass and less)
often act as cofacors of enzymes
1) plasma concentration of 10 – 20 µmol / L
Fe, Zn, Cu / common oxidative statets !
2) low plasma concentrations (µmol/l, nmol/L)
Se, Mn, Mo, Cr, Co, Si, F, I,...
cations of blood
plasma
mmol/l
nmol/l
Na+
142
142 000 000
K+
4,2
4 200 000
Ca2+
2,5
2 500 000
Mg2+
0,9
900 000
Fe3+
0,02
20 000
H+
0,000 04
40
Inorganic products of metabolism
•
C, H, O →
•
N
→ NH3 / NH4+
•
P
→ H2PO4- / HPO42- = „phosphate“
•
S
→ SO42- = „sulfate“
•
I- from degradation of thyroid hormones
•
CO from degradation of heme
•
H+ from acids / H as a „reducing equivalent“
CO2, H2O
→ H2CO3 / HCO3-
Sample test questions
Course 1 – Structure of cells
course test: 3rd November 2014
Choose correct statement(s)
a) the movement of water through a
cellular membrane is called „diffusion“
b) if potassium channel opens in the cellular
membrane K+ flows out of the cell
c) Na+/K+-pump transports these ions along
their concentration gradients
d) when calcium channel opens in the
cellular membrane Ca2+ enters the cell
Choose correct statement(s)
a) the movement of water through a
cellular membrane is called „diffusion“
NO
b) if potassium channel opens in the cellular YES
membrane K+ flows out of the cell
c) Na+/K+-pump transports these ions along NO
their concentration gradients
d) when calcium channel opens in the
cellular membrane Ca2+ enters the cell
YES
In human cells
a) magnesium is the most common cation
b) chloride is the most common anion
c) phosphate acts as a buffer
d) CO is produced as the end product of
oxidation of various organic compounds
In human cells
a) magnesium is the most common cation
NO
b) chloride is the most common anion
NO
c) phosphate acts as a buffer
YES
d) CO is produced as the end product of
oxidation of various organic compounds
NO
Do you agree with the following
statements?
a) a chemical formula of ammonia is NH4+
b) hydrogen phosphate is HPO4-1
c) phosphate buffer in cells is composed
of H2PO4- and H3PO4
d) bicarbonate is a base derived from
carbonic acid
Do you agree with the following
statements?
a) a chemical formula of ammonia is NH4+
NO
b) hydrogen phosphate is HPO4-1
NO
c) phosphate buffer in cells is composed
of H2PO4- and H3PO4
NO
d) bicarbonate is a base derived from
carbonic acid
YES
Choose the correct statement(s)
a) ferrous ion can be oxidized to ferric
ion
b) Cu+II is called cuprous ion
c) when CO2 dissolves in water carbonic
acid is formed
d) H3O+ is called hydrogen cation
Choose the correct statement(s)
a) ferrous ion can be oxidized to ferric
ion
YES
b) Cu+II is called cuprous ion
NO
c) when CO2 dissolves in water carbonic
acid is formed
YES
d) H3O+ is called hydrogen cation
NO
Which statements are correct?
a) as concentration of H3O+ increases pH
of the solution rises
b) concentration of H3O+ in a basic
solution is the same as in pure water
c) pH in cells is often higher than in an
extracellular fluid
d) proteins are important intracellular
buffers
Which statements are correct?
a) as concentration of H3O+ increases pH
of the solution rises
NO
b) concentration of H3O+ in a basic
solution is the same as in pure water
NO
c) pH in cells is often higher than in an
extracellular fluid
NO
d) proteins are important intracellular
buffers
YES
Choose the correct statement(s)
a) kalium is Latin name for calcium
b) magnesium is alkali metal
c) the only biologically important halogen
is chlorine
d) Cu, Zn and Se are trace elements from
group of transition metals
Choose the correct statement(s)
a) kalium is Latin name for calcium
NO
b) magnesium is alkali metal
NO
c) the only biologically important halogen
is chlorine
NO
d) Cu, Zn and Se are trace elements from
group of transition metals
NO