Biochemistry: Introduction cont'd Flashcards
the missing information
What are two regions of the titration curve?
- flat zone
- midpoint
What is the flat zone?
- zone where pH barely changes
- It extends 1 pH unit on both sides of the midpoint
Define midpoint
- where the buffering power is maximum
- where pH=pKa
- where concentration of proton donor= conc of proton acceptor
- [HA]=[A-]
[HA] is the ____ while [A-] is the ____
[HA] : acid
[A-] : conjugate base
What are the 2 Types of Buffer in the Body?
- Chemical Buffers
- Organs
Chemical buffers are the ____ line of defence
first
Which is the second line of defence and how long does it take to respond?
Organs are the 2nd line of defence, acting within a few days
How fast do chemical buffers react?
Within a few minutes
Chemical buffers include…
- Bicarbonate system
- Phosphate system [ex. Glucose-6-phosphate & Nucleotide]
- Plasma proteins
- Haemoglobin
The organ buffers include…
- liver
- lung
- kidney
What is the reaction chain of the Bicarbonate Buffer System?
H2O + CO2 —-> H2CO3 —-> HCO3 + H+
Components of bicarbonate buffer system:
- Weak acid and conjugate strong base
1. W.A: Carbonic acid (proton donor)
2. congugate base: bicarbonate (proton acceptor)
Properties of the bicarbonate buffer system are:
- the most effective buffer in the body
- the major buffer of blood plasma (pH near 7.4)
- has a base/acid ration of 20:1
- a good buffer in acidosis but very poor buffer in alkalosis
How can carbonic acid be formed?
It is easily formed from CO2 by carbonic anhydrase.
How can carbonic acid be excreted?
as CO2 through the lungs
Why is the bicarbonate buffer system so effective?
- present in high concentration
- the amount of CO2 is controlled by respiration/lungs
- amount of bicarbonate is controlled by excretion/kidneys
Which chemical rxn in lungs?
H2CO3 < —- > H2O + CO2
Which chemical rxn happens in the kidneys?
H2CO3 < —- > HCO3 + H+
Plasma bicarbonate is regulated by the…
organ
kidney
Features of the Phosphate System:
- major buffer system in biological fluids
- includes intracellular and extracellular cytoplasmic fluids
- an effective buffer at pH range 6.9-7.4
Where does the phosphate system mainly act in?
Urine, it is the main buffer in urine
What molecules are considered buffers because they contain phosphate?
- Glucose-6-phosphate
- nucleotides eg. ATp & GTP
Plasma protein buffering
Why are free a.as and proteins considered buffers?
contain a free carboxyl and free amino group
- (COOH) & (NH2)
a.as and protein buffering
What happens to these free groups at physiological pH (7.4)?
They ionize into carboxylate ion and amino ion
- (COO-) & (NH3+)
- the amino group accepts the hydrogen from the carboxyl group
What does the ionization of plasma protein cause?
Ionization enable to consume [H+] or [OH-] ions when an acid or base is added to the system [blood]
What happens to amino acids when dissolved in water?
It exists in solution as dipolar ion or zwitterions
How can zwitterions act?
Both acid and base
Haemoglobin features include…
- has 6 times the buffering capacity of plasma proteins
- contains 38 histandine residues (a.a)
Haemoglobin is responsible for…
buffering most of the CO2 added to the blood by tissue
What does a histadine residue contain?
an imidazole group
What makes hemoglobin such a good buffer?
the dissociation of imidazole group
Where does CO2 bind to?
- the N-terminal of Hb forming carbaminohemoglobin
How does liver regulate pH
By synthesis of neutral…
1. glycogen from acidic lactic acid
2. urea from alkaline ammonia
How do the lungs affect pH?
- function to reduce pCO2 in blood
- this increases the [HCO3-]/[H2CO3] ratio
How do kidneys produce bicarbonate?
- generate it by converting carbonic acid to bicarbonate and H+
- process carboxyl group of a.a to produce HCO3-
- glutamine is converted to bicarbonate and ammonia in kidney
where are amino groups of a.a processed and what do they produce?
They are processed in the kidneys to produce NH4+ (ammonium)
How much H+ do the kidneys excrete daily and by what?
- phosphate is used to excrete about 40mmol of H+ per day
From where is glutamine sent to the kidneys?
It is sent by the liver to kidneys, and sometimes synethisized in kidney BOTH
