Biological Buffers Flashcards
What is a base?
A chemical substance that can accept a hydrogen ion
What is an acid?
A chemical substance that can donate a hydrogen ion
This is a (strong/weak) that (completely/partially) dissociates or ionises in solution.
-strong
-completely
This is a (strong/weak) that (completely/partially) dissociates or ionises in solution.
-weak
-partially
What is an acid-base buffer?
solution consisting of two or more chemical compounds that resist large changes in hydrogen ion conc when either an acid or base is added to the solution.
How does a buffer keep the pH of a solution relatively constant?
Due to a buffers ability to bind or release protons in solution.
Why are buffers important in human body?
-minimise pH changes when small amounts of acid or alkali are added.
-contain mixtures of weak acids and their salts (or weak bases and their salts).
-many metabolic processes produce acid end products (e.g. lactic acid, CO,)which interfere with normal function of cells
What is the normal pH range of plasma?
7.35-7.45
When does acidosis occur?
When pH of plasma falls below 7.35
When does alkalosis occur?
When the pH of plasma rises above 7.45
What are the two origins acidosis and alkalosis are associated with?
Respiratory and metabolic
What are the 3 homeostatic control mechanisms for pH?
-buffers
-ventilation by lungs
-kidneys
How are buffers a homeostatic control mechanisms for pH?
-acid-base buffer systems immediately combine with any acid or alkali
-preventing excessive changes in H+ ion concentration and hence pH.
How is ventilation by lungs a homeostatic control mechanism for pH?
-stimulation of the respiratory centre by change in arterial ph or Pco, levels alters the rate and depth of breathing
-modifying the amount of CO, exhaled and changing pH.
How are kidneys a homeostatic control mechanism for pH?
-excretion of acid or alkaline urine enables changes to be made by the kidneys
-in response to alterations in plasma pH.
Name three biological buffers
-bicarbonate buffer system: major buffering system in extracellular fluid
-Protein buffer system: important buffering system in both intracellular and extracellular fluid.
-Phosphate buffer system: important buffering system in intracellular fluid and major buffer in urine
What is the main buffering system of extracellular fluid?
Bicarbonate buffer system
What is the bicarbonate buffer system composed of?
weak acid, carbonic acid, and its conjugate base, the bicarbonate ion.
In plasma:
[H2CO3] = …….meq/L
[H+] = ………meq/L
[HCO3-] =……meq/L (600,000 times that of [H+])
- 1.2
- 0.00004
- 24
How does carbon dioxide travel from tissue to lungs?
1.Carbon dioxide produced in the tissue dissolves into venous blood.
2.Carbon dioxide from aerobic respiration diffuses into red blood cell where it is converted to carbonic acid.
3.Carbonic acid dissociates to produce bicarbonate ions and protons.
4.Bicarbonate ions exit red blood cells, in exchange for chloride ions, and accumulate in plasma.
5.Protons are buffered within red blood cells by haemoglobin.
6.When the red blood cell is near alveoli, carbon dioxide diffuses into it.
How many histidine amino acid molecules are in a haemoglobin molecule?
38
Haemoglobin has ….. times the buffering capacity of plasma proteins
6
