Session 1: Water and hydrogen ions Flashcards
List the 4 consequences of water having a dipolar nature.
- Allows interactions between water molecules
- Forms hydration shells (acts as a solvent)
- Provides an aqueous medium for the chemical
reactions - Determines biomolecule properties:
* higher order structure of macromolecules
* formation of supramolecular aggregates
Explain the polarised bonds in water molecules.
- The two H atoms are bonded to the O atom at an
angle of 105 degrees - The H atoms share its electrons with the unshared
electrons of the O atom - The O atom has a high electron affinity
- The H atoms has have partial positive and the O
atom has partial negative charge - Thus a water atom forms a dipole
Express the relationship between pH and H+ as a formula.
pH = log ( 1/[H+] )
Give the normal blood plasma values of [H+] and pH.
[H+] = 40 nmol/L pH = 7.4
Define acidosis.
Excess concentration of the hydrogen ion (excess acid)
Define alkalosis.
Low hydrogen ion concentration (excess base)
Give the intracellular pH.
7.0
Give the range of the pH range.
6.0 - 7.5
Give the pH range of gastric acid.
1.5 - 3.5
Give the average plasma pH range and its average.
7.37 - 7.43, average 7.4
Give the venous and arterial blood hydrogen ion concentration.
Venous blood = 43 nmol/L (7.37)
Arterial blood = 37 nmol/L (7.43)
List 5 acids produced in the body.
- Acetoacetic acid
- B-hydroxybutyric
- Lactic acid
- Carbonic acid
- Phosphates
Define and explain the meaning of an acid.
A compound that donates protons to a solution.
Define and explain the meaning of a base.
A compound that accepts protons.
Define and explain what a buffer is.
A combination of of two compounds (a weak acid and its conjugate base) that minimises pH changes when H+ is produced and added to a body fluid compartment.
Write down and explain the Henderson- Hasselbalch equation for the bicarbonate buffer in the blood.
pH = pKa + log ( [HCO3-]/ [H2CO3] )
The ratio of HCO3- to H2CO3 determines the pH and therefore the acidity of blood and other body fluids.
Write down the Henderson- Hasselbalch equation and explain it.
pH = pKa + log ( [A-]/ [HA] )
What determines osmolality ?
The total concentration of all dissolved ions, together with organic molecules.
What is used to express the low hydrogen ion concentration of pure water?
The pH notion.
Define pH.
The log of the reciprocal of the hydrogen ion concentration.
Describe the process of protein unfolding.
Most enzymes and proteins do not function outside the pH range of 7.37- 7.43. If the hydrogen ion concentration is increased, its high affinity for negatively charged groups on proteins leads to protein unfolding where proteins lose their 3D shape and therefore their functioning as well.
What is a structural formula?
It shows the chemical bonds between atoms in a molecule.
Define ketoacidosis.
A type of metabolic acidosis where the pancreas is unable to produce adequate amounts of insulin.
Name the two factors that determine the effectiveness of a buffer.
- Its pKa relative to the pH of the solution
2. Its concentration
List in order of occurrence, the mechanisms responsible for maintaining the normal blood pH.
- Extracellular buffer systems
- Ventilatory regulation of CO2 elimination
- Regulation of hydrogen ion excretion and
bicarbonate ion reabsorption (kidneys and lungs)
Explain how the bicarbonate buffer functions in the blood.
The acid-base pair H2C03 / HCO3- acts as a buffer. The ratio of HCO3- to H2CO3 determines the pH and therefore the acidity of the blood and other body fluids.
Define Kussmaul respiration.
When high levels of carbonic acid are produced, it leads to high [H+] in the brain, stimulating chemoreceptors located in the medulla oblongata and linked to the respiratory centre in the brain stem, which leads to deeper and more frequent breathing.
