Biochemistry: Introduction ls3-6 Flashcards
Define
Electrolytes
and one of their features
(a) Substances that readily react with water
(b) carry an electric charge (ionized)
2
Types of Electrolytes & Example
- Cations (+ charged electrolytes) and move TOWARDS Cathode
- ex. Na+ - Anions (- charged electrolytes) and move TOWARDS Anode
- ex. Cl-
6
Major Cations
- Sodium (Na+)
- Potassium (K+)
- Calcium (Ca++)
- Magneiusm (Mg++)
- Ammonium (NH4+)
- Protons (H+)
4
Major Anions
and their chemical formula
- Chlorine (Cl-)
- Bicarbonate (HCO3-)
- Phosphate (HPO4-)
- Carboxylate (COO-)
What are the major electrolytes of the ECF?
sodium and chlorine
What are the major electrolytes of the ICF?
potassium and phosphate
what is found in teeth and skeleton bones?
Ca++ and HPO4- in the form of calcium phosphate
Cations of ICF
Major: K+
Minor: Mg++
Anions of ICF
main: phosphate
also: proteins
Cations of ECF
main: Na+
also: Ca++
Anions of ECF
main: Cl-
also: HCO3-
9
Functions of Electrolytes
- Hormonal Stimulation [CALCIUM]
- Maintain Osmotic Pressure [Na, Cl, K]
- a) Nerve Conduction & b) Muscle Contraction [Ca, Mg, K]
- Blood Coagulation [Ca, Mg]
- Regulation of ATPase pump [Mg]
- Production & Use of Energy [PO4, Mg]
- Cofactor of Enzyme [Mg, Ca, Zn, Se]
- Contribute to buffer system [HCO3, PO4]
- Heme synthesis [Fe++]
Muscle Contraction is rooted in…
myocardial rhythm & contractility which is determined by neuromuscular excitability.
Define
Solution
with example
A solution is formed of a solute dissolved in a solvent
ex NaCl dissolved in water
How can concentration be measured?
It is measured as a percent ratio between solute & solvent:
1. Weight per Volume [mg% or g%]
2. Parts per Million [1:10^6]
- (for trace elements like Se and Zn)
3. Molarity [mol/L]
Define
Molarity
The number of moles of solute per litre of solution
Molarity=(m/M)x(1/V) so it’s n/V
example of ppm
10g of milk was found to have 15 micrograms of selenium, what is the conc. of Se?
1.5ppm
Reminder that ppm is literally just taking the ratio of solute to solvent and multiplying is by 10^6.
What is a mole?
A mole is the amount of a substance that is equal to its atomic mass. It is Avagadro’s number of atoms for a give entity.
When is dilution required?
When there is high concentration in a fluid.
eg. high blood glucose in diabetic patients
What is a dilution factor?
Dilution factor= total volume of fluid/ substance volume
How do you estimate the d.f of protein serum?
extract 0.2mL of protein serum, add 3.8mL of normal saline and divde all of that by 0.2 to get a d.f. of 20.
What is pH?
pH is the logarithmic function that determines how acidic or basic a substance is.
pH=-log[H+]
How does water ionize?
Due to its dipolarity, water can ionize into protons and hydroxide ions when combined with another polar molecule or with itself.
Synonym
For Dissociation
ionization of water, since water dissociating produces 2 ions.
Reaction when water reacts with itself is:
H2O + H2O —> H3O+ + OH-
a hydronium ion is produced from one 1 water accepting a hydrogen ion [proton] from the other. [transfer of proton]
Define
Amphoteric
a molecule that can act as both a base and acid.
- can donate or accept protons
What is the difference between Alkalies and Bases?
All alkalies are bases, but not all bases are alkalies. This is because bases can only accept proton, whereas alkalies can both accept protons and release OH- hydroxide ions.
What is an example of a base?
NH3 ammonia (weak base)
6
Importance of pH:
- increase in blood pH will cause alkalosis
- decrease in blood pH will cause acidosis
- enzyme catalysts need a specific pH for activity
- ANTIBACTERIAL purposes of gastric juices, saliva, vaginal fluids all need a low pH.
- O2 transportation by haemoglobin
- severe changes in pH can cause coma or death.
What is the pH range that can yield life?
6.8-7.8
pH of blood plasma
7.4
pH
gastric juice
1.5-3.0 (acidic)
pH
pancreatic juice
7.8-8.0 (b)
ph
Saliva
6.4-7.0 (a)
pH
urine
5.0-8.0 (a to b)
pH
lysosomal matrix
5.5-6.5 (a)
pH
ICF in liver
6.9 (a)
pH
human milk
7.0-7.4 (n to b)
So what is the bodily fluid with the highest pH (most basic)?
pancreatic juice
What is the bodily fluid with the lowest pH (most acidic)?
gastric juice
What bodily fluids need a low pH to serve their antibacterial function?
- Gastric juice
- Saliva
- Vaginal fluids
What is pKw?
It is the -log of the dissociation constant of water.
It is always equal to 14.
What is Kw?
it is the dissociation constant of water and is the product of the hydroxide and proton concentrations.
Kw=[H+][OH-]
1x10^-14=(1x10^-7)(1x10^-7)
When water dissociates to give away protons, it is acting as…
an acid!
When water dissociates to yield hydroxide ions it is…
a base! (Bronsted-Lowry base)
A proton is a…
hydrogen cation that has lost its electron.
What is the Molar Concentration of pure water?
55.56mol/L since it is (m/M)x(1/1L)= 1000g/(18g/mol)
The Kw is measured at the temperature…
25 degrees Celsius
True or False: the hydroxyl ion conc. is equal to the hydrogen ion conc. in pure water
true! pOH=pH=7
The pH of 1 mole of H ion is
0
the pH of 1.0x10^-14 moles of H+ is
14
True or False: NaOH is an alkali.
True; it is considered an alkali salt since it accepts a proton AND gives away OH-.
a salt is a substance which…
contains a) a cation instead of H+ AND
b) an anion rather than OH-
What are 2 salts?
NaCl and MgSO4
What happens when acids and bases react?
they neutralize to form salt and water.
products of NaOH + HCl —>
NaCl + H2O
salt (sodium chloride) and water!
Acid or Base
electron acceptor
acid
acid or base
provides H+ in water
acid
acid or base
NH2 + H+ <—> NH3+
the NH2 (and why)
base because it accepts a proton
acid or base
changes litmus paper to blue
base
acid or base
provides OH- in water
base
true or false
pKa decreases as tendency to dissociate [Ka] inreases
true
true or false
the greater the tendency to dissociate, the weaker the acid
false; the stronger the acid!
strong or weak acid
readily dissociate
strong
weak or strong acid
partially dissociate
weak
strong or weak acid
acetic acid (CH3COOH)
weak
weak or strong acid
Sulphuric acid (H2SO4)
strong
weak or strong acid
Phosphoric acid (H3PO4)
weak
weak or strong acid
Carbonic acid (H2CO3)
weak
weak or strong acid
Ka less than 1
weak
weak or strong acid
have a low pKa
strong
weak or strong acid
dissociate irreversibly and completely
strong
weak or strong acid
donate large amounts of protons
strong
What are polyprotic acids?
acids that are capable of losing more than one proton.
2 examples of polyprotic acids
Carbonic and Phosphoric acids (both weak acids)
Does pKa increase or decrease as phosphoric acid loses a proton?
pKa increases, meaning as it becomes HPO4^-2, the tendency to dissociate decreases, making it an even weaker acid.
pKa1= 4.7
pKa2= 7.2
pKa3= 12.3
Define
Buffer
a solution that resists change in pH when small amounts (increments) of an acid/base are added to it.
Components of buffers:
1.Weak Acid & its conjugate base (salt)
2.Weak Base & its conjugate acid (salt)
3. buffers are simply conjugate acid/base pairs of a weak A/B and its conjugate salt.
so the conjugate is a salt
buffer reaction:
CH3COOH < — >
CH3COO- + H+
acetate and a proton
which of the products in a acetic acid buffer “mops up protons” when an acid is added?
the conjugate base, acetate (CH3COO-)
CH3COOH < — >CH3COO- + H+
When does the reverse reaction occur? (when the weak acid is favoured)
and explain why
when an acid is added. The weak acid increases in concentration because the acetate reacts with the added acid by accepting protons.
CH3COOH < — >CH3COO- + H+
which product reacts with the OH- when an alkaline is added?
The proton becaue it is a cation so it attracts the anion OH-.
CH3COOH < — >CH3COO- + H+
When is the forward reaction favoured for equilibrium?
When OH- / a base is introduced. Makes sense since the H protons would then react with the hydroxide ions much better than acetic acid would.
CH3COOH < — >CH3COO- + H+
When the forward reaction occurs, what increases in concentration?
Water and salt concentrations.
CH3COOH < — >CH3COO- + H+
So when is acetate produced?
When acetic acid reacts with a base.
CH3COOH < — >CH3COO- + H+
And when is acetic acid produced?
When an acid is introduced to acetate, its conjugate base.
describe the graph
it is a titration curve of the buffer solution from acetic acid and acetate. The region that the curves flattens is where the pH of the system changes very minimally as OH- or H+ are added. This zone extends 1.0pH unit about the midpoint and it is called the buffering region. The midpoint is when the concentration of acetic acid is equal to acetate. At this midpoint, pH=pKa, 4.76 here.
when is buffering power at is maximum?
at the midpoint of the buffering region. That means it is at its most resistant to the changes in ion presence.
true or false
pH=pKa at midpoint of buffer solution
true
What equation is used to predict the best buffer solution?
Henderson-Hasselbalch equation
The formula proves that pH=pKa at the midpoint because…
the ratio of proton donor to acceptor would be equal to 1 since they are equal, and when substituted into the formula it become pH=pKa+0.
At neutralization
pH=pKa
an amino acid is it’s ____ form when it can act as both an acid and a base
zwitterion
When does an amino acid exist as a zwitterion
When it is dissolved in water
Base to acid ratio of buffer system
20:1 makes it a good buffer in acidosis but a very poor one in alkalosis
List 4 buffer systems and where
- Bicarbonate Buffer system: lungs and kidneys
- Proteins in plasma, since their (COO-) and (NH3+) can dissociate
- Hemoglobin: dissociation of the imidazol groups of histadine residues in hemoglobin (38 histadine residues)
- Phosphate buffer system: in biological fluids, from ECF to most of cytoplasmic compartmentes) keeps pH 6.9-7.4
True or False
Hemoglobin in blood has 6 times the buffering capacity of plasma proteins
True!
Describe the mechanism that hemoglobin buffers the blood pH
CO2 binds to N-terminal of Hb forming carbaminohemoglobin.
- buffers majority of CO2 added to blood by tissues
