2. Acid base concept -calculations. 3. Buffert -calculations. 5. Physiologic ph regulation -calculations

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Acid Base lecture 15-16 September 2014 Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3. Buffert -calculations 4.

1 Acid Base lecture September 2014 Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3. Buffert -calculations 4. Titration 5. Physiologic ph regulation -calculations 6. Measure ph? -Read: Kemiboken från gymnasiet, Harvey & Ferrier, sid 6-9, Kompendiet Syra-Bas Introduction to ph 1

Introduction to ph 2M HCl -0.3 0.1 M HCl 1 Coca Cola 2.3 Schampo 5-6 active/resting muscle 6.1/6.9 Saliva 6.

43 The cell has low amounts of H +, around 10-7 M, =>ph=7 same as 0,0001 mm.

2 Introduction to ph 2M HCl M HCl 1 Coca Cola 2.3 Schampo 5-6 active/resting muscle 6.1/6.9 Saliva Blood (venous) Blood (arteriell) The cell has low amounts of H +, around 10-7 M, =>ph=7 same as 0,0001 mm. (compare with [Na + ]=140 mm in the cell) Introduction to ph ph describes the concentration of H + or H 3 O + in water solution. The lower the ph, the greater the hydronium ion concentration. 2

Introduction to ph ph = -Log[H + ] It is easier to think in log of concentrations but it takes practice!! Example : If the ph of a solution is 3.4, what is the hydronium ion concentration?

3 Introduction to ph ph = -Log[H + ] It is easier to think in log of concentrations but it takes practice!! Example : If the ph of a solution is 3.4, what is the hydronium ion concentration? [H 3 O + ] = 10 -ph = = M= 3.98x10-4 M Introduction to ph Dissociation of H 2 O Where does the H + come from? Neutral water has a tendency to ionize H 2 O <-> H + + OH - The free proton is associated with a water molecule to form the hydronium ion H 3 O + High ionic mobility due to proton jumping 3

Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3.

4 Introduction to ph Dissociation of H 2 O Proton Jumping Hydronium ion migration; hops by switching partners at per second Acid Base lecture September 2014 Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3. Buffert -calculations 4. Titration 5. Physiologic ph regulation -calculations 6. Measure ph? 4

Base is a substance that can accept a proton.

5 Relationship between ph and [H + ] / [OH - ] concentration H 2 O <-> H + + OH - Acidic if [H + ] > 10-7 M Basic if [H + ] < 10-7 M Lowry definition Acid is a substance that can donate a proton. Base is a substance that can accept a proton. Conjugate acid base pair HA + H 2 O H 3 O + + A - /OH - Acid1 Base2 Conjugate Conjugate Acid2 Base1 or HA A - + H + Acid1 Conjugate Conjugate Base2 Acid 5

6 Relative strength of acids and bases The stronger acids are those that loose their hydrogen ions more easily than other acids. Similarly, the stronger bases are those that hold onto hydrogen ions more strongly than other bases. Relative strength of acids and bases HCl + H 2 O Cl - + H 3 O + Strong acid undergoes complete dissociation Ex. HCl 6

7 Relative strength of acids and bases HCl + H 2 O Cl - + H 3 O + HCl H 3 O + Cl - Strong acid undergoes complete dissociation Ex. HCl Relative strength of acids and bases HA + H 2 O A - + H 3 O + Weak acid undergoes partial dissocation Ex. Acetic acid 7

8 Relative strength of acids and bases HA + H 2 O A - + H 3 O + Weak acid undergoes partial dissocation Ex. Acetic acid HA HA H+ A- Neutralisation A solution of strong acids and bases (ex HCl och KOH) H + + Cl - + K + + OH - H 2 O + K + + Cl - If we take same amount of HCl as KOH it becomes neutral = neutralisation, otherwise it becomes acidic or basic. 8

9 Proteolysis of a weak acid A weak acid is not completely proteolysed Equilibrium to the left. Weak acids/bases HAc + H 2 O Ac - + H 3 O + around 1% of HAc will react. The relative stability of the acid form as compared to its conjugated base form Determines if it is a weak or a strong acid. If the acid form is stable = the proton is not lost easily = weak acid(ex HAc) If the base form is stable = the proton will easily be lost = strong acid (ex HCl) Weak acids/bases Determine ph in a solution HCl + H 2 O Cl - + H 3 O + Easy! Strong acid, equilibrium shifted to the right,completely shifted as for HCl HAc + H 2 O Ac - + H 3 O + Difficult! Weak acid, at equilibrium there is still acid left ex Acetic acid HAc where 1% of HAc will react. How can we calculate ph in a solution of a weak acid? 9

10 Law of Mass action Calculate ph in a solution of a weak acid. We need: Law of mass action (massverkans lag): The rate of a chemical reaction is proportional to the concentrations of the reacting substances. and experimental values of K a (acid base constant) is used to determine ph in a solution of a weak acid. Law of Mass action HAc + H 2 O 2 delreaktioner: 1) HAc + H 2 O 2) Ac- + H 3 O + k 1 k 2 at equilibrium same rates Ac- + H 3 O + Ac- + H 3 O + v 1 =k 1 [HAc] [H 2 O] HAc + H 2 O v 2 = k 2 [Ac-] [H 3 O + ] k 1 [HAc] [H 2 O] = k 2 [Ac-] [H 3 O + ] Vid jämvikt är v 1 =v 2 dvs Som kan omformuleras till k [Ac-] [H 3 O + 1 ] = k 2 [HAc] [H 2 O] där k 1 /k 2 =K a (syrakonstanten) 10

11 Law of Mass action HAc + H 2 O 2 reactions: 1) HAc + H 2 O 2) Ac- + H 3 O + k 1 k 2 at equilibrium same rates Ac- + H 3 O + Ac- + H 3 O + v 1 =k 1 [HAc] [H 2 O] HAc + H 2 O v 2 = k 2 [Ac-] [H 3 O + ] k 1 [HAc] [H 2 O] = k 2 [Ac-] [H 3 O + ] Vid jämvikt är v 1 =v 2 dvs Som kan omformuleras till k [Ac-] [H 3 O + 1 ] = k 2 [HAc] [H 2 O] där k 1 /k 2 =K a (syrakonstanten) Law of Mass action HAc + H 2 O 2 reactions: 1) HAc + H 2 O 2) Ac- + H 3 O + k 1 k 2 at equilibrium same rates Ac- + H 3 O + Ac- + H 3 O + v 1 =k 1 [HAc] [H 2 O] HAc + H 2 O v 2 = k 2 [Ac-] [H 3 O + ] At equilibrium v 1 =v 2 k 1 [HAc] [H 2 O] = k 2 [Ac-] [H 3 O + ] k [Ac-] [H 3 O + 1 ] = k 2 [HAc] [H 2 O] där k 1 /k 2 =K a (Acid constant) 11

12 Law of Mass action Law of Mass Action [Ac-] [H 3 O + ] K = [HAc] [H 2 O] [H 2 O] = 55,6 M I utspädd lösning är H 2 O ungefär konstant ca 55M och kan inneslutas i jämvikts- konstanten och man får: K a = [Ac-] [H 3 O + ] [HAc] Ka betecknar syrakonstant och har ett specifickt värde för varje syra, ex. stort värde på K a, stark syra Acid constant Law of Mass Action [Ac-] [H 3 O + ] K = [HAc] [H 2 O] [H 2 O] = 55,6 M In water H 2 O is considered constant and can be included in the equilibrium constant K. K a = [Ac-] [H 3 O + ] [HAc] K a is the acid constant and it has a specific value for each acid, ex. large value of K a, strong acid 12

13 Acid constant, Ka Acid constant, Ka K a = [Ac-] [H 3 O + ] [HAc] HAc + H 2 O Ac- + H 3 O + 1. An acid with stable conj. Base has a tendency to loose its proton and its equil. Is shifted to the right and we get a large Ka. 1. A weak acid with a unstable conj. Base has a small tendency to loose its proton and equilibrium is shifted to the left small Ka. and analogous to the ph terminology the pka = -lgka Acid constant, Ka Which are the experimental values of K a? 13

14 Acid constant, Ka K a describes acid strength [A- ] [H 3 O+ ] K a = HA + H 2 O A - + H 3 O + [HA] Syra K a pk a (-lg K a ) stark svag HCl H 2 SO H 3 PO 4 6, ,2 Mjölksyra 1, ,8 ß-OH-smörsyra 4, ,4 Acetic acid 1, ,76 Base constant, Kb Base constant Ac- + H 2 O HAc + OH - Law of Mass action for bases K b = [HAc] [OH - ] [Ac - ] A strong base has a tendency to take up protons the equilibrium is shifted to the right and Kb is large. A small Kb is a weak base lower tendency to take up a proton. and analogous to the ph terminology the pk b = -lgk b 14

15 Base constant, Kb K b describes base strength A - + H 2 O HA + OH - [HA] [OH - ] K b = [A - ] Base K b pk b (-lg K b ) strong weak OH - (lut) 8, ,74 CO 2-3 (soda) 2, ,7 NH 3 1, ,76 HCO 3- (bikarbonat) 1, ,9 acetate 5, ,24 Acid/Base constant For conjugated acid-base pair: pk a + pk b = 14 HAc / Ac - : 4,76 + 9,24 = 14 H 2 O / OH - : 15,74 + (-1,74) = 14 H 3 O + / H 2 O : -1, ,74 = 14 H 2 CO 3 / HCO 3- : 6,1 + 7,9 = 14 K b can be calculated from its conjugated acid Ka value: K b =K w /K a 15

16 Now we know Law of Mass action And some experimental values of K a So now we can calculate ph in a solution of a weak acid! Weak acids Protolysis of a weak acid Ex. 0.1 mol acetic acid (CH 3 COOH) in 1 liter H 2 O HAc + H 2 O Ac - + H 3 O + Before equil. 0,1 noll 10-7 After equil. 0,1 - X X X K a = K a = [Ac - ] [H 3 O + ] [HAc] X (X+10-7 ) 0,1-X 2:a grade equation... Make two approximations: 1) X << 0,1 2) X >>

17 Weak acids Protolysis of a weak acid Ex. 0.1 mol acetic acid (CH 3 COOH) in 1 liter H 2 O HAc + H 2 O Ac - + H 3 O + Before equil. 0,1 noll 10-7 After equil. 0,1 - X X X K a = K a = [Ac - ] [H 3 O + ] [HAc] X (X+10-7 ) 0,1-X Weak acids Protolysis of a weak acid Ex. 0.1 mol acetic acid (CH 3 COOH) in 1 liter H 2 O HAc + H 2 O Ac - + H 3 O + Before equil. 0,1 noll 10-7 After equil. 0,1 - X X X K a = [Ac - ] [H 3 O + ] [HAc] K a = X X K a HAc =1, ,1 K a = X (X+10-7 ) 0,1-X 17

18 Weak acids Protolysis of a weak acid Ex. 0.1 mol acetic acid (CH 3 COOH) in 1 liter H 2 O HAc + H 2 O Ac - + H 3 O + Before equil. 0,1 noll 10-7 After equil. 0,1 - X X X K a = K a = [Ac - ] [H 3 O + ] [HAc] X (X+10-7 ) 0,1-X K a = X X K a HAc =1, ,1 1, = X2 0,1 Weak acids Protolysis of a weak acid Ex. 0.1 mol acetic acid (CH 3 COOH) in 1 liter H 2 O HAc + H 2 O Ac - + H 3 O + Before equil. 0,1 noll 10-7 After equil. 0,1 - X X X K a = K a = [Ac - ] [H 3 O + ] [HAc] X (X+10-7 ) 0,1-X K a = X X K a HAc =1, ,1 1, = X2 0,1 X = 1, M = [H 3 O + ] ph = 2,88 18

19 Amphoteric species An amphoteric species is a molecule or ion that can react as an acid as well as a base. For ex water. a) acid H 2 O H + + OH - b) base H 2 O + H + H 3 O + H 2 O + H 2 O H 3 O + + OH - K = K w = [H 3 O + ] [OH - ] [H 2 O] [H 2 O] [H 3 O + ] [OH - ] Waterconcentrationen is constant 55.5 M K is the dissociation constant K becomes K w K M 2 w = K w = ion product of water Ion product of water K w = Ion product of water pkw = -lg 1x10-14 = ph + poh = 14 Neutral water OH - = H 3 O + Kw = (H 3 O + )(OH - ) = (10-7 )(10-7 ) = log 10 Therefore the ph is 7 In pure water pkw = ph + poh 19

20 Amphoteric species Ex. of other amphoteric species Vätesulfat Monovätefosfat Divätefosfat vätekarbonat a) HSO 4- + H 2 O SO H 3 O + b) HSO H 2 O H 2 SO 4 + OH - c) HPO H 2 O PO H 3 O + d) HPO H 2 O H 2 PO 4 + OH - e) H 2 PO 4- + H 2 O HPO H 3 O + f) H 2 PO 4- + H 2 O H 3 PO 4 + OH - g) HCO H 2 O CO H 3 O + h) HCO H 2 O H 2 CO OH - Acid Base lecture September 2014 Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3. Buffert -calculations 4. Titration 5. Physiologic ph regulation -calculations 6. Measure ph? 20

21 Observation If you add 0.01 ml of 1M HCl to 1000 ml of water ph 7, the ph of the water drops from 7 to 5!! i.e 100 fold increase in H + concentration: Log = 2 change. Problem: Biological properties change with small changes in ph, usually less than 1 ph unit. How does a system prevent fluctuations in ph? 3. Buffer Buffer solutions A buffer consists of corresponding pairs of weak acids and weak bases HA H + + A - Weak acid proton conjugated base A buffer solution is keeping the ph relatively constant when strong acid or base is added A buffer keeps the ph constant during dilution with water. 21

3. Buffer The buffer capacity is largest at

Buffer Tris buffer X pka of Tris buffer is 8.

22 3. Buffer The buffer capacity is largest at the pka. By definition the pk is the ph where [HA] = [A - ] : 50% dissociated 3. Buffer Tris buffer X pka of Tris buffer is 8.08 the buffering range is By definition the pk is the ph where [HA] = [A - ] : 50% dissociated 22

23 3. Buffer Make a buffer 1) Choose a buffer that can buffer at the ph interval. Check pka for conj. acid, should be close to desired ph. HAc + H 2 O Ac - + H 3 O + Acetat buffer, can buffer at ph=4,76 ± 1,5 2) The higher conc. of ([HAc] + [Ac-]), the better buffering capacity. 3. Buffer Make a buffer Example of different conjugate acid base pairs. ph 7 Fig

24 3. Buffer Make a buffer How to make a buffer solution 1) Mix a weak acid with its corresponding weak base 2) Mix weak acid with a strong base 3) Mix weak base with stron acid 4) Or, first mix buffer as solid add water to desired volume and then adjust the ph by adding acid or base to the ph you want 3. Buffer Make a buffer Exempel: Make 0,2 M acetatbuffert in 1L H 2 O. HAc + H 2 O Ac - + H 3 O + Take 0,1 mol 0,1 mol (same as 0.1 M in 1 L water) Conjugate acid and base added in similar amounts best buffering capacity at 50:50 24

25 3. Buffer Buffer equation How can we determine the ph in a buffer? Example: HAc + H 2 O Ac - + H 3 O + 0,1 M 0,1 M 3. Buffer Buffer equation We use the buffer equation: A variant of Law of Mass action ph = pk a + lg [Ac- ] [HAc] -Can only be used to calculate ph in buffers. -Only valid if 1/30 < base/acid < 30 25

26 3. Buffer Buffer equation Deduction of the buffer equation HAc + H 2 O Ac - + H 3 O + 0,1 M 0,1 M [Ac - ] [H 3 O + ] Law of Mass action K a = [HAc] lg K a = lg [Ac - ] + lg [H 3 O + ] lg [HAc] -lg [H 3 O + ] = -lg K a + lg [Ac - ] lg [HAc] Taking the logaritm Replacement ph = pk a + lg [Ac- ] [HAc] Buffer equation! (Hendelson-Hasselbach) 3. Buffer Buffer equation How does ph change in a buffer upon dilution Exempel: 0,2 M acetatbuffert (0,1 mol HAc, 0,1 mol Ac -, 1 liter H 2 O) 0,1 HAc + H 2 O Ac - + H 3 O + ph = pk a + lg 0,1 0,1 0,1 ph = pk a + lg 1 ph = 4,76 Tillför 1 liter vatten 0,05 HAc + H 2 O Ac - + H 3 O + ph = pk a + lg 0,05 0,05 0,05 ph = pk a + lg 1 ph = 4,76 26

27 3. Buffer Buffer equation Vid pka är HAC/Ac - 50:50 x ekvivalenspunkt When the buffer is buffering, the equilibrium is changed: After addition HCl x HAC/Ac - 50:50 ph=4,28 3. Buffer Buffer equation When the buffer is buffering, the equilibrium is shifted: HAc + OH - Efter tillsats HCl Efter tillsats OH - x x Ac - + H 2 O Ac - x ekvivalenspunkt 27

28 Acid Base lecture September 2014 Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3. Buffert -calculations 4. Titration 5. Physiologic ph regulation -calculations 6. Measure ph? 4. Titration The buffer effect can be seen in a titration curve. Titration is a common laboratory method to determine the unknown concentration of an identified analyte. Take a weak acid HAc, add or titrate NaOH while monitoring ph (x-axis) amount NaOH added (y-axis). Buffer capacity: highest at pka 28

29 4. Titration Titration of a weak acid with a strong base. Best buffertkapacitet Half-equivalenspoint pk a ± 1,5 Ac - x equivalenspoint At the equivalenspoint amount base added = amount mole acid at start HAC/Ac - 50:50 pk a - punkt At pka HAc/Ac 50:50 ph=4.76 Distribution curves for acetate and acetic acid pka = 4.76 Best buffer capacity HAc/Ac 50:50 29

1 M NaOH to the equivalenspoint. What is the concentration of HCl? An acid with one proteolytic step is titrated against a strong base.

30 4. Titration Often characteristic for an acid - good analytical method. Ex. Titration curve for the amino acid alanine 2 groups on alanine that can be deprotonated, 2 pka s -COOH / -COO - -NH 3+ / -NH 2 pka2 pka1 4. Titration Ex. 20 ml HCl is titrated with 16 ml of 0.1 M NaOH to the equivalenspoint. What is the concentration of HCl? An acid with one proteolytic step is titrated against a strong base. At the equivalenspoint, the n(acid) in the solution is the same as the amount (n) of base added. How much base do we have? We use n=cv => 0.1M x L = 1.6 x 10-3 mol = mol At the equivalenspoint the n(acid) = n(base) => Which means that n(acid)= mol. What is the concentration of acid? c = n/v = mol / 0.02 L = 0.08 M. equivalenspoint Answer: The concentration of the HCl solution is 80 mm. 30

31 Acid Base lecture September 2014 Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3. Buffert -calculations 4. Titration 5. Physiologic ph regulation -calculations 6. Measure ph? 4. Physiologic ph regulation Life 6 7 normal, arteriell 8 [H 3 O + ]: 10-6 M 10-7 M blood 10-8 M [OH - ]: 10-8 M 10-7 M 10-6 M Normal value blood ph 7.4 Blood (venous) Blood (arteriell) How can we keep the ph so constant? 31

32 5. Physiologic ph regulation Buffers in body fluids Our body uses 3 different systems to keep the ph constant: 1) Buffers in body fluids (the first minutes) Phosphatbuffer (in the cell) Proteins (albumin,hemoglobin) in the cell Bicarbonate buffer (blood, plasma) 2) Regulate breathing (adjust pco 2 ) 3) Long term regulation via kidneys 5. Physiologic ph regulation Buffers in body fluids Our body uses 3 different systems to keep the ph constant: 1) Buffers in body fluids (the first minutes) Phosphatbuffer (in the cell) Proteins (albumin,hemoglobin) in the cell Bicarbonate buffer (blood, plasma) 2) Regulate breathing(justera pco 2 ) 3) Long term regulation via kidneys Bicarbonate most significant buffer in blood Formed from gaseous CO 2 32

33 5. Physiologic ph regulation Buffers in body fluids Buffering at ph= 7 Phosphate buffert H 2 PO 4- + H 2 O HPO H 3 O + korr. syra korr. bas Proteins, (ex. albumin, Hb) buffrande förmåga - Histidin proth + H 2 O prot - + H 3 O + korr. syra korr. bas Bicarbonate buffer CO 2 + 2H 2 O H 2 CO 3 +H 2 O HCO 3- + H 3 O + korr. syra korr. bas 5. Physiologic ph regulation Phosphate buffer Can loose protons 3 times= 3 proteolytic steps H 3 PO 4 + H 2 O H 2 PO 4- + H 3 O + korr. syra korr. bas H 2 PO 4- + H 2 O HPO H 3 O + korr. syra korr. bas HPO H 2 O PO H 3 O + korr. syra korr. bas!two of the ions are amphoteric species! 33

34 5. Physiologic ph regulation Phosphate buffer H 3 PO 4 + H 2 O H 2 PO 4- + H 3 O + H 2 PO 4- + H 2 O HPO H 3 O + HPO H 2 O PO H 3 O + At pk a best buffer capacity 5. Physiologic ph regulation Phosphate buffer What kind of phosphate ions do we have in the cell? Many phosphate groups on molecules in the, t ex ATP, ADP, AMP, P-creatine. 34

35 5. Physiologic ph regulation Proteins as a buffer When a protein acts as a buffer, only a few amino acids are responsible Ex of proteins that can act as a buffer: Albumin och Hemoglobin 5. Physiologic ph regulation Proteins as a buffer Amino acids that can buffer: + Histidin korr. syra korr. bas - Cystein korr. syra korr. bas When the amino acid is buffering, the charge will change! 35

36 5. Physiologic ph regulation The protein structure can change due to ph When Histidin-side chain buffer, it will take up a proton. It becomes positively charged. H 3 O + The new + gives a new electrostatic interaction with a neighbouring - Structure will change. Maybe even the function of the protein? + 5. Physiologic ph regulation Proteins as a buffer ph sensitive protein is protected by other proteins, and other buffers H 3 O + ProteinX ProteinX H 3 O + Protein Protein Protein ProteinX Protein Protein Protein Protein Protein Protein Protein Protein ProteinX H 3 O + ProteinX exposed ProteinX protected H 2 PO 4- /HPO 2- Protein 4 Protein H 2 PO 4- /HPO Protein 2-4 ProteinX H 2 PO 4- /HPO Protein 2-4 Protein H 2 PO 4- /HPO Protein 2-4 Protein H 2 PO 4- /HPO Protein 2-4 Protein H 2 PO 4- /HPO Protein 2-4 Protein ProteinX H 2 PO 4- /HPO 2-4 H 2 PO 4- /HPO

37 5. Physiologic ph regulation Proteins as a buffer Good with overlapping buffers One buffer Mix of buffers Buffertkapacitet 5. Physiologic ph regulation Bicarbonate buffer 2 proteolytic steps H 2 CO 3 +H 2 O HCO 3- + H 3 O + Conjugate acid. Conjugate base HCO 3- +H 2 O CO H 3 O + Conjugate acid Conjugate base First proteolytic step important. 37

38 5. Physiologic ph regulation Bicarbonate buffer In body fluids H 2 CO 3 +H 2 O HCO 3- + H 3 O + Conj. Acid conj.. base CO 2 (d) + 2H 2 O H 2 CO 3 +H 2 O HCO 3- + H 3 O + conj. acid conj. base Dihydrogen carbonate (kolsyra) (H 2 CO 3 ) can exist in water but will quickly become CO 2 bubbles. The acid in bicarbonate buffer consists of H 2 CO 3 and CO 2 (d) together. 5. Physiologic ph regulation Bicarbonate buffer CO 2 is dissolved in water CO 2 CO 2 [CO 2 ] + [H 2 CO 3 ] = 0,23 p CO2 kpa, mm H 2 CO 3 CO 2 H 2 CO CO 2 3 H 2 CO 3 H 2 CO 3 CO 2 Water with dissolved, dihydrogen carbonate and CO 2 The concentration of dissolved CO 2, is proportional to the partial pressure for CO 2 (p CO2 ). 38

39 5. Physiologic ph regulation Bicarbonate buffer Buffer formula for bicarbonate buffer CO 2 + 2H 2 O H 2 CO 3 +H 2 O HCO 3- + H 3 O + conjugate acid Conjugate base ph = pk a + lg [base] [acid] ph = pk a + lg [HCO 3 - ] [CO 2 ] + [H 2 CO 3 ] ph = pk a + lg [HCO 3 - ] 0,23 p CO2 Henderson Hasselbalch s formula [CO 2 ] + [H 2 CO 3 ] = 0,23 p CO2 5. Physiologic ph regulation Regulate ph by breathing Our body uses 3 different systems to keep the ph constant: 1) Buffers (the first minutes) Phosphatbuffert (in the cell) Proteiner (albumin,hemoglobin) in the cell Carbonate buffert (blood, plasma) 2) Regulate breathing Acids are formed during metabolism. In tissues CO 2 forms - transported to lungs as HCO 3-. CO 2 can be released in lungs. If problems with lungs: can get acidosis. 1) Long term regulation via kidneys 39

5. Physiologic ph regulation Gases affecting ph Gas transport O

in tissues is transported back to the lung.

Hemoglobin transport O 2. It has 4 Heme groups O 2 O 2 O 2 5.

(2,3-bisfosfoglycerat) attenuates Hb s affinity for O 2 High O

40 5. Physiologic ph regulation Gases affecting ph Gas transport O 2 is transported from the lung to the tissues and CO 2 formed in tissues is transported back to the lung. The transport of these gases is coupled to ph: O 2. Hemoglobin transport O 2. It has 4 Heme groups O 2 O 2 O 2 5. Physiologic ph regulation Hemoglobin ph, CO 2, O 2 and BPG (2,3-bisfosfoglycerat) attenuates Hb s affinity for O 2 High O 2 affinity Low O 2 affinity Low ph +[H + ] +[CO 2 ] +BPG Relaxed form Tense form Binds O 2 releases O 2 40

5. Physiologic ph regulation Lungs: High ph, Low CO 2 and O 2 affinity increases, Shift left Bohr effekt: An increase of CO 2 and a decrease in ph results in reduced affinity of Hb for O 2.

Physiologic ph regulation Our body uses 3 different systems to keep the ph constant: 1) Buffers (the first minutes) Phosphatbuffert (in the cell) Proteiner (albumin,hemoglobin) in the cell Carbonate

41 5. Physiologic ph regulation Lungs: High ph, Low CO 2 and O 2 affinity increases, Shift left Bohr effekt: An increase of CO 2 and a decrease in ph results in reduced affinity of Hb for O 2. Tissue= Low ph, High CO 2 O 2 affinity decrease and is released to tissues Shift right 5. Physiologic ph regulation Our body uses 3 different systems to keep the ph constant: 1) Buffers (the first minutes) Phosphatbuffert (in the cell) Proteiner (albumin,hemoglobin) in the cell Carbonate buffert (blood, plasma) 2) Regulate breathing Acids are formed during metabolism. In tissues CO 2 forms - transported to lungs as HCO3-. CO 2 can be released in lungs. Problems with lungs: can get acidosis. 1) Long term regulation via kidneys During normal metabolism of food we produce acids - excreted via urine. The kidneys excrete/retain H + and HCO 3-. If you are acidotic, your kidneys will try to excrete H + and retain HCO

Acid Base lecture 15-16 September 2014 Agnes

Physiologic ph regulation -calculations 6. Measure ph?

light absorbance ph meter: Measures the voltage

of a known standard solution, and uses the difference

42 Acid Base lecture September 2014 Agnes Rinaldo-Matthis 1. Introduction to ph 2. Acid base concept -calculations 3. Buffert -calculations 4. Titration 5. Physiologic ph regulation -calculations 6. Measure ph? 6. Measuring ph ph paper: acid base form have different light absorbance ph meter: Measures the voltage produced by the solution, compares it with the voltage of a known standard solution, and uses the difference in voltage to calculate the ph. In vivo: measure in plasma or urine. Difficult to measure inside the cell, microelektrodes. 42

43 6. Measuring ph Approximate ph values of various body fluids Boron & Boulpaep Compartment ph Gastric secretions 0.7 Lysosome 5.5 Cytosol, typical cell more acidic 7.2 Arterial blood plasma Mitochondrial inner matrix 7.5 Secreted pancreas fluid 8.1 END of lecture 43

BIOMEDICAL SCIENCE MIN WAN

ACID-BASE LECTURE BIOMEDICAL SCIENCE MIN WAN (min.wan@ki.se) SEPT. 12-13, 2016 9/6/2016 1 Acid Base lecture 14-15 September 2015 Min Wan 1. Introduction to ph 2. Acid base concept -calculations 3. Buffer