medical chemistry 1 st year gm lecture ii mudr vlastimil kulda october 9 th 2012
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Medical Chemistry (1 st year – GM) Lecture II MUDr. Vlastimil Kulda October 9 th , 2012. Water. non-bonding electron pairs. O. H. H. H 2 O. 105 o. bent molecule. d -. O. -. polar character. H. H. +. d +. d +. electrical dipole. Hydrogen bonding. -.

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water
Water

non-bonding electron pairs

O

H

H

H2O

105o

bent molecule

d-

O

-

polar character

H

H

+

d+

d+

electrical dipole

hydrogen bonding
Hydrogen bonding

-

attractions between water molecules

 HIGH melting point

boiling point

specific heat

heat of vaporization

surface tension

+

-

+

-

-

+

+

-

+

0 oC 3.6 / H2O

H bonds - much weaker than covalent bonds !

bond energy of H-bonds in liquid water: about 19 kJ/mol

( covalent H – O bond in water: 460 kJ/mol )

water is most dense at 3.98 °C !!! (when freezing, ice will form first on the surface)

slide4
WATER - very good solvent !

Attraction between water dipoles and ions

"hydrated ions"

Dispersing "amphipathic" molecules

"micelles"

slide5
"Amphipathic" molecules – contain both highly hydrophobic

and highly polar groups

palmitic acid

polar group = hydrophilic

non-polar chain = hydrophobic

(water-fearing)

(water-loving)

Phospholipids

phosphatidylcholine

(lecithin)

polar groups

slide6
Biological membranes

- separate the cells separate the spaces (compartments) of the cell

cell membrane

mitochondria

nucleus

lysosome

endoplasmic reticulum

Phospholipid BILAYER

hydrophilic

hydrophobic

hydrophilic

water in human body
Water in human body

~ 60 % of the body weight

intracellular ~ 40 %

extracellular ~ 20 % PLASMA 5 %

interstitial fluid 15 %

- a very complex solution of inorganic & organic components

Na+K+ Ca2+ Mg2+

Phosphates

Proteins

Cl-HCO3- Phosphates

Na+

K+Na+ Mg2+

K+

Na+/K+ pump ( = Na+/K+ -ATPase )

water balance
Water balance

Intake: ~ 1.5 - 2.0 l / day

metabolic water(produced in human body by oxidation of food) 0.3 – 0.5 l /day

Resorption: stomach, small intestine, LARGE INTESTINE

Secretion: Saliva 1 500 ml / day

Stomach 2 500

Bile 500 8 200 ml /day

Pancreas 700

Small intestine 3 000

Excretion: Urine 60 %

Skin 20 % (perspiration)

Lungs 15 %

Faeces 5 %

slide9
Human blood plasma

pH = 7.36 – 7.44

* Ca "total Ca" Ca2+ "ionized" is about ½ of "total" ~ 1.2 mmol/l

slide10
Blood plasma

( extracellular fluid )

Cell fluid (cytosol)

( intracellular fluid )

slide11
phospholipids

cholesterol

PROTEINS - enzymes

- receptors

- transport systems

SELECTIVE permeability

(membrane = barrier)

The flow of molecules and ions between the cell and environment is

precisely regulated by SPECIFIC TRANSPORT SYSTEMS

They regulate cell volume, ionic composition, pH

They concentrate metabolic fuels and building blocks from the environment

The extrude toxic substances

They generate IONIC GRADIENTS  essential for the excitability

slide12
Transport across membrane

1) Passive transport - does not involve energy

- diffusion from high to low concentration

2) Active transport - uses energy (ATP)

- can transport against the concentration gradient

- one direction, high specificity

3) Secondary active transport - no direct need of energy

- gradient created by active transport is used !

"channels"

"pumps"

ATP

slide13
2

3

1

Passive transport

concentration and

electrochemical

GRADIENT

toward equilibrium

1) Simple diffusion small molecule, NO charge, solubility in lipids !

O2 CO2

2) Ion channels - pore-forming proteins

- can be "GATED"

3) Facilitated diffusion ("carrier proteins") - selective !

- large molecules, insoluble in lipids

"gate" is open

"gate" is closed

ion transport antibiotics
Ion transport antibiotics

Gramicidin - peptide: 15 amino acids

HELIX - hydrophilic groups inside

"wet channel"

- lipophilic groups outside

increase of the permeability of bacterial cell wall

inorganic ions can travel through

equilibration of concentrations = NO GRADIENT

"wide wet pore"

slide15
K+

hydrophillic groups INSIDE = "WET cave"

Valinomycin

hydrophobic (lipophillic) groups OUTSIDE

( = soluble in lipids of membrane)

K+

highly selective carrier for K+

( Na+ with water coating is too big)

K+

equilibration of K+ concentration = NO GRADIENT

slide16
hydrophillic groups

Valinomycin

hydrophobic (lipophillic) groups

slide17
ATP

ADP + Pi

Active transport = "PUMPS"

Transport against

GRADIENT

ENERGY !

Na+/K+ ATPase

(sodium potassium pump)

ATP

3 Na+

INHIBITION:

cardiotonic steroids

2 K+

slide18
Na+/K+ ATPase

in cell membrane of EVERY human cell !

electrogenic = transfers 3 Na+ out and ONLY 2 K+ into the cell

 inner side of the membrane - outer side of the membrane+

inhibitors of this pump: cardiotonic steroids = cardiac glykosides

(oubain, digoxin)

 treatment of heart failure, cardiac arrhytmia

Digitalis purpurea

(foxglove)

slide19
CO2

CO2 + H2O

*

H+

Cl-

H2CO3

K+

ATP

HCO3-

HCO3- + H+

Cl-

lumen of the stomach

pH = 1 - 2

blood pH = 7.4

parietal cell

H+/K+ ATPase

stomach  gastric acid HCl

* carboanhydrase Zn2+

106 increase of H+ concentration !

slide20
Na+

glucose

Na+

Ca2+

Secondary active transport "COTRANSPORT"

Na+ dependent transport of glucose, aminoacids, Ca2+

"energy" = Na+ gradient generated by Na+/K+ ATPase

SYMPORT

ANTIPORT

slide21
glucose

glucose

Na+

Na+

ATP

K+

Na+ - glucose symport

proximal tubulus of each nephron in the kidneys resorption of glucose

intestines  resorption of glucose from GI tract

slide22
Na+/Ca2+ antiport = sodium–calcium EXCHANGER

Ca2+

Ca2+

Na+

Na+

ATP

K+

Ca2+ ATPase

Na+/Ca2+ exchanger

 very low concentration of Ca2+ in cytosol

slide23
Endocytosis

Large (polar) molecules – cannot pass through the hydrophobic membrane

phagocytosis - cell ingests large object such as bacteria

pinocytosis - uptake of solutes and molecules such as proteins

receptor-mediated endocytosis – specific ! LDL receptor

chylomicron remnant receptor

receptors that mediates endocytosis of blood plasma lipoproteins

cell absorbs material by engulfing it with its own membrane

slide24
vesicles with neurotransmitter

Exocytosis

= the opposite of endocytosis

Exocytosis is needed for:

- secretion of large molecules from cells: glands  peptide hormones

B cells  antibodies

- neuronal chemical synapses: realease of the neurotransmitter

receptor

synaptic cleft

slide25
H2O

low osmolality

Water transport across membranes

Water moves by "simple diffusion" through membranes ?

Additional mechanism for water transport:

AQUAPORINS

"water channels"

Water transport - due to osmotic differences (osmotic gradient)

OSMOSIS

high osmolality

slide26
The bioelements (summary)
  • Principal bioelements: O, C, N, H, P, S

( biomolecules: proteins, nucleic acids, lipids, saccharides )

  • Water and ions ( H2O ) Na+, K+, Mg2+, Ca2+, Cl-, ( HCO3- , phosphates)
  • Mineral constituents of bones and teeth Ca

PO43-

  • Microelements (trace elements) Fe, Cu, Co, Zn, I, F, Se, ...

--------------------------------------------------------

5) Contamination (intoxication): Hg, Al, ...

slide27
Elements of group I

Alkali metals

Alkali metals - very reactive

- react with air O2 and H2O

- must be stored under oil

slide28
Hydrogen H

biogenic element - it is present in almost all organic compounds !

H2O

H+ = proton (  H3O+ )

pH = - log [H+]

The pH scale

0 7 14

alkaline (basic) sol.

acidic solutions

neutral

slide29
water is weakly ionized: H2O H+ + OH-

KW = [H+] x [OH-] = 10-14 mol2 / l2 ionic product of water

pH + pOH = 14

pure water: [H+] = [OH-] = 10-7 mol/lpH = pOH = 7

-----------------------------------------------------------------------

Strong acids - fully ionised: monobasic acid: HCl H+ + Cl-

dibasic acid: H2SO4 2 H+ + SO42-

Weak acids– do not disociate completely: CH3COOH H+ + CH3COO-

Strong bases: NaOH, KOH, Ca(OH)2

Weak base: NH4OH

slide30
+

-

human blood plasma: pH = 7.40 0.04

gastric juice: pH = 1 – 2

pancreatic juice: pH = ~ 8

-----------------------------------------------------

H+ very low concentration in blood plasma !!!

pH = 7.40 H+ = 0.000 040 mmol/l (40 nmol/l)

(Na+ 142 mmol/l K+ 4.5 mmol/l)

extreme influence of H+ on biological systems !!!

 ionisation of functional groups in PROTEINS

Ionisation of amino acids

slide31
Lithium Li

compounds: LiCl Li2CO3 crimson (red) colour of flame

Therapy of manic-depressive psychosis (bipolar affective disorder)

= alternating periods of mania (euphoria) and depression

The manic phase - increased activity, decresased need for sleep

- persistent elevated mood

- impaired normal functioning !

The depressive phase - lack of energy

- pessimistic

- self-destructive behavior (risk of suicide !)

Li+  changes of ion transport in CNS

- still in use "mood stabilizing agent"

slide32
Lithium mineral water – therapy of GOUT (type of arthritis)

(Li-urate  more soluble than uric acid)

Uric acid- in humans - the end product of purine catabolism

- poorly soluble in water

- lithium urate – more soluble !

slide33
Sodium Na (Natrium)

Na+ the main EXTRAcellular cation (132 – 145 mmol/l)

Na+ strongly binds water

ionic diameter: Na+

K+

!!! in hydrated form: Na+ larger in diameter than K+

Na+ ( together with Cl- ) large fraction of osmotic pressure (osmolality)

of body fluids

Water and Na balance are closely interdependent !

slide34
NaCl daily intake: 5 – 15 g food (common salt)

Elimination: urine (95 %)

sweat (perspiration)

stool

Kidney

BLOODGlomerular filtrate (180 l H2O / day)

Glomerular

filtration

[ 1.5 kg NaCl ]

Tubular

resorption

URINE

2 l H2O

5 – 15g NaCl

dependent on hormones (aldosteron, ADH)

slide35
Hormones regulating tubular resorption

Aldosteron - steroid hormone (mineralocorticoid)

- produced in the adrenal gland (adrenal cortex)

- acting in the distal tubule of the kidney nephron:

reabsorption of Na+ into blood

secretion of K+ into urine

Vasopressin = antidiuretic hormone (ADH) - peptide hormone

- synthesized in the hypothalamus, released into

blood in the pituitary gland (posterior part)

- ADH increases the permeability of the collecting duct to water

 allows water reabsorption  small volume of concentrated urine

deficiency of ADH: DIABETES INSIPIDUS - polyuria

- excretion of large amounts of diluted urine ( 10 – 20 l /day !)

slide36
Potassium K (Kalium)

K+ the main INTRAcellular cation (cytosol > 100 mmol/l)

  • human blood plasma: only 3.8 - 5.2 mmol/l
  • daily intake: ~ 4g of KCl excretion: URINE
  • proper concentrations of K+ and Na+  functions of membranes

„membrane potential“

most cells – membrane potential relatively stable

neurons, muscle cells – use changes of membrane potential for function !

(nervous system – communication between neurons)

 action potential

slide37
Na+/K+ ATPase

Ion channels

3Na+

2K+

Na+

EXTRAcellular fluid

ATP !

cell membrane

K+

2K+

INTRAcellular fluid

rising phase = depolarisation

ACTION POTENTIAL

falling phase = repolarisation

resting potential

slide38
In cells K+ is bound to GLYCOGEN !

Diabetic coma ( glucose in blood )

Glycogen synthesis

Binding of K+ in cells

Plasma K+ depletionHEART failure !!!

insulin

slide39
Copper Cu (Cuprum)

microelement (in human body 100 - 150 mg)

dietary intake: ~ 2 mg / day

Cu2+ - cofactor of some enzymes: cytochrom c oxidase

(metalloenzymes) superoxide dismutase

- cofactor of HEME biosynthesis

CERULOPLASMIN - transport of Cu2+ in blood plasma ( 8 Cu2+ / mol. )

- a2 globulin synthesized in the liver

- enzymatic activity: Fe2+  Fe3+

WILSON‘s DISEASE - accumulation of copper in tissues

(hepatolenticular degeneration) - low ceruloplasmin levels

- hereditary disease

- neurological symptoms, liver disease

slide40
CuSO4 . 5 H2Ocopper (II) sulphate pentahydrate

= „blue vitriol“

- in Fehling‘s solution (detection of glucose in urine)

copper salts - poisonous !

-------------------------------------------

Hemocyanins - Cu2+ containing proteins

- O2 transport - MOLLUSCA (snail, clam, mussel, ...)

- ARTHROPODA (crabs)

slide41
Silver Ag (Argentum)

precious metal ( + H2S  Ag2S black ! )

AgBr - photosensitive  photography

------------------------------------------------------------------

Ag - useful in dental alloys for fittings and fillings

( Ag + Hg  amalgam )

AgNO3 - caustic effect  treatment of warts

 Bartholin’s gland abscess in women

(removal: silver nitrate stick insertion)

- diluted solution: antiseptic properties  it was dropped into newborn‘s eyes

to prevent gonococcal conjuntivitis !

(Gonorrhoea is a venereal disease caused by the bacteria Neisseria gonorrhoeae)

slide42
Gold Au (Aurum)

precious metal chemically and biologically resistent, inert

in nature – almost exclusively in the native state

pure gold – soft ! in jewellery: alloys (+ Cu, + Ag)  harder

The gold content of gold alloys

in carats or in thousandths

pure gold: 24 carats = 1000/1000

The standard for high quality jewellery: 18 carats = 750 / 1000

What is the gold content (g) of a 100 g piece marked 18 carats?

18

24

x 100g = 75 g

slide43
Elements of group II

Alkaline earth metals

slide44
Magnesium Mg

PLANTS: Mg2+ -central atom of green pigment CHLOROPHYLL (photosynthesis)

in human body: ~ 20 g Mg > ½ in bones ( Ca-Mg phosphates )

intracellular cation

Mg2+ activates number of enzymes !!! ENZYMES using ATP

"kinases"

glucose glucose–6–phosphate

(Enzymes of ATP-dependent reactions require Mg2+ as cofactor)

hexokinase

ADP

ATP

slide45
other effects of Mg2+: anti-convulsive effect

(MgSO4 - prevention of eclamptic convulsions)

influence on neuromuscular excitability

can help to prevent kidney and gall stones

"duodenal reflex" - MgSO4 delivered into the region of the sphincter of Oddi

 relaxation of the sphincter + contraction of the gallbladder

 expulsion of bile to intestine

( the bile release from the gallbladder is stimulated by Mg2+ )

Magnesium mineral water (Karlovy Vary)  purgative effect

slide46
"burning"

CaCO3

CaO + CO2

limestone, chalk

quicklime

"slaking"

Ca(OH)2

CaO + H2O

slaked lime

Ca(OH)2 + CO2

CaCO3 + H2O

Calcium Ca

Hardening of mortar:

slide47
Calcium Ca

in human body ~ 1 kg (99% in bones, teeth)

dietary intake: 800 - 1200 mg / day

human blood plasma: "total Ca" 2.5 mmol/l

(extracellular !) ionized Ca2+ 1.2 mmol/l

resorption: ileum – specific protein carrier

~ 200 mg / day

excretion: urine

liver bile feces

slide48
Hydroxyapatite

Ca5 (PO4)3 OH

Mineral constituents of bones and teeth

Ca [ Mg, Sr, Na ]

PO43- CO32- [ F-, Cl-]

F -

fluoroapatite

enamel

Enamel: - hardest substance of the body

water 1-3 %

organic comp. 1%

mineral > 95 % (bones ~ 60 %)

dentin

cementum

pulp

slide49
Ca2+ in blood

PTH

Hormones regulating Ca metabolism

Parathormone - peptide hormone ( 84 amino acids )

- secreted by parathyreoid glands

- activation of bone mineral degradation

 Ca2+ release from bones

- stimulation of Ca2+ readsorption in kidney

- stimulation of calcitriol formation (kidneys)

- stimulation of Ca-resorption protein formation (ileum)

slide50
Ca2+ in blood

Calcitonin - peptide hormone ( 32 amino acids )

- produced by parafollicular cell of the thyreoid gland

- inhibition of bone mineral degradation

(decrease of „osteoclasts“ activity)

- stimulation of Ca2+ excretion in kidney

Salmon calcitonin is used for the treatment of OSTEOPOROSIS

slide51
Calcitriol = 1,25-dihydroxycholecalciferol

- active form of D–vitamin

- stimulation of Ca-resorption protein formation

 absorption of calcium from the gastrointestinal tract

slide52
PTH

Ca – FOOD (protein-bound)

calcitriol

ILEUM

Ca-resorption protein

calcitonin

PLASMA

Ca 2.5 mmol/l

Ca2+ 1.2 mmol/l

PTH

BONES

URINE

PTH

calcitonin

calcitriol

milk

excrements

Ca2+ increase PTH release inhibition

slide53
Very low concentration of Ca2+ in cytoplasma 10-6 mol/l

MUSCLE - Ca2+ is stored in sarcoplasmic reticulum (SR)

CALSEQUESTRIN = calcium-binding protein of the SR

40 Ca2+ binding sites

Ca2+ in cytoplasma can cause the specific action of the cell:

MUSCLES  contraction

Ca2+ = important SECOND MESSENGER

slide54
endoplasmic reticulum

"SIGNAL"

release of Ca2+

EFFECT

slide55
Xa

Prothrombin

Thrombin

Fibrinogen

Fibrin

Extrinsic pathway

(Tissue factor pathway)

Intrinsic pathway

(Contact activation pathway)

Clotting of BLOOD

Ca2+is required for the proper function of the coagulation CASCADE

slide56
COO -

COO

+ Ca2+

Ca

COO

COO -

Removing of Ca2+ = NO clotting !

Anticoagulants - bind Ca2+ ions

( "in vitro" = outside the body)

Oxalate

Citric acid

EDTA = ethylenediamine tetraacetic acid

slide57
heating

CaSO4 . 2 H2O

CaSO4 . 1/2 H2O

Gypsum, plaster of Paris

+ H2O

hardening

CaSO4 . 2 H2O

When the dry plaster powder is mixed with water, it re-forms into gypsum

bandage impregnated with plaster = support for broken bones

slide58
Strontium Sr

- similar to Ca2+ incorporation in BONES

(naturally present in bones in trace amounts)

- new treatment for osteoporosis: „Strontium ranelate“

(improves bone density and strenght)

excess: Strontium rickets

radioisotope Sr bone marrow irradiation  LEUKEMIA

(important isotope regarding health impacts after the Chernobyl disaster)

radioisotope Sr - treatment of bone cancer

90

half life 28 years

89

half life 50 days

slide59
Barium Ba

toxic heavy metal

water-soluble compounds - strongly neurotoxic

[ Ba(NO3)2 BaCl2 ] - painful cramps, tremor

BaSO4 (barium sulphate)

- almost insoluble in water !

- radiocontrast agent for X-ray imaging

( "barium meal" )

  • imaging of the gastrointestinal tract

large intestine

slide60
Zinc Zn (Zincum)

microelement dietary intake: 12 -15 mg / day

cofactor of many ENZYMES:

carboxypeptidase - protein digestion

carbonic anhydrase H2O + CO2 H2CO3 H+ + HCO3-

alcohol dehydrogenase- oxidation of ethanol to acetaldehyde

CH3CH2OH CH3CHO

NAD+

NADH+H+

slide61
Insulin binds ZINC ! "Zn – insulin hexamers"

Metallothionein - protein synthesized in kidneys rich of -SH groups

- can bind metals ( Zn2+ Cd2+ .... )

- zinc transport, heavy metal detoxification (Hg2+) ?

Zinc is an essential nutrient for proper sperm production !

------------------------------------------------

compounds used in medicine: ZnO- a basis of powders, pastes, creams

( in DERMATOLOGY )

dental fillings (cements):Zn3(PO4)2 . 4 H2O "hopeit"

slide62
Cadmium Cd

toxic heavy metal

metallothionein – strongly binds Cd2+

Cd intoxication

kidney damage

"Itai itai disease"- mass Cd poisoning in Japan in 1950

- the name comes from painful screams

( "itai" in Japanese = PAIN )

- the bones become soft and weak  severe pain, fractures

"Chemical castration" = destruction of seminiferous epithelium

of testicles ( Zn2+ antagonism )

slide63
Mercury Hg (Hydrargyrum)

Toxic effects

1) elemental Hg - very toxic when absorbed as a vapour through lungs

- poorly absorbed through the gastrointestinal tract !!!

(only purgative effect)

2) inorganic Hg compounds

HgCl2 - "sublimate" - soluble in water = toxic

- corrosive ulceration of GI tract

- renal failure

Hg2Cl2– "calomel" - low solubility = less toxic

- it was used in medicine ! (diuretic and purgative

effect, ointments in dermatology)

- calomel electrod (reference electrod - measurement of pH)

slide64
2) organic Hg compounds

- often extremely toxic

- dimethylmercury Hg(CH3)2damage of CNS (central nervous system)

- one of the strongest known neurotoxins !

"The Minamata Disease" - mass Hg poisoning in Japan in 1956

- Minamata Bay – waste industrial water with Hg2+

 biomethylation by a variety of microorganism

 bioaccumulation in FISH

 dietary intake from fish diets

Poison grain disaster in Iraq (1971) - seed grain mercury-treated to prevent rot

was used as FOOD

slide66
Boron B (Borum)

PLANTS – micromineral

Boric acid H3BO3 - a very weak acid

- disinfectant (used in dermatology and ophtalmology)

- also toxic properties !

glutamine synthetase

glutamine

NH3 + glutamate

H3BO3 = inhibitor

toxic to BRAIN

Sodium tetraborate Na2B4O10 = borax (fusible glaze for pottery)

slide67
Aluminium Al

in human body – only traces – contamination ?

Al(OH)3 together with MgO or Mg(OH)2oral antacid

(neutralization of acid in the stomach)

Al – also considered as toxic

ACID RAIN  SOIL  release of Al3+ !

slide69
Carbon C (Carboneum)

the most important biogenic element

organic compounds (covalent bonds C-C, chains, rings)

biomolecules: proteins, nucleic acids, lipids, carbohydrates

combustion  CO, CO2

respiration  CO2

Toxic: CO competes with O2 for hemoglobin

HCN reaction with cytochromes  inactivation of cell respiration

slide70
Silicon Si (Silicium)

abundant element in lithosfere, but not useful in human body

SiO2 (silica) Quartz - common mineral in the Earth‘s crust

- many varieties: amethyst (purple)

citrine (yellow)

morion (dark-brown)

rose quartz (pink)

- in many rocks (granit, sandstone), metallic ores

cutting, breaking, crushing, ...

inhalation of fine SiO2 dust SILICOSIS - lung disease

occupational disease (miners, ceramics workers)

progressive, signs of it will appear years after exposure !

slide71
Silicic acids: general formula n SiO2 . m H2O

H4SiO4 orthosilicic acid

Silicates - salts of silicic acids SiO44-

Si atom - tetrahedral coordination by 4 oxygens

complex structure - different degrees of "polymerization"

linear arrangement  FIBERS (asbestos)

planar arrangement  MICAS

Silicate minerals - largest class of rock-forming minerals

ad