Module 4 - Acids and Bases Flashcards
What are electrolytes?
a solution containing charged ions that therefore conduits electricity
CATIONS with +positive charge e.g Na+, K+, Ca2+
ANIONS with -negative charge e.g Cl-, PO4-
therefore compounds that form electrolytes in solution contain at least one IONIC BOND
they include inorganic compounds such as salts, acids and bases. Some proteins are also electrolytes
What is an ionic bond?
An ionic bond involves the transfer of electrons
What are the most cations and anions inside the cell?
Intracellular fluid
- K+ is the major cation
- Phosphate is the major anion
- large amounts of protein anions in intracellular fluid
- Ca2+ is normally extremely low and tightly controlled since it mediates lots of cellular processes, including neurotransmitter release, skeletal muscle contraction, cardiac muscle contraction
What are the most cations and anions outside the cell?
Extracellular fluid (plasma and interstitial fluid)
- Na+ is the major cation
- cation concentrations similar in both plasma and interstitial fluid
- Cl- is the major anion
- Ca2+ is much higher outside than inside
What is the role of the Sodium-Potassium Pump?
- maintenance of Na+ and K+ concentration gradients across cell membranes is vitally important, as we saw in nerve and muscle function
- mainly a result of sodium-potassium pumps
- function relies on having adequate supply of ATP
Why are electrolytes important? What are the 3 most important electrolytes?
- transmission of electrical impulses in neurons and muscles
- stabilize protein structures in enzymes
- some aid in releasing hormones from endocrine glands
- all of the ions control the movement of water between cells and their environment through osmosis
- therefore electrolytes are highly regulated in the body by homeostatic mechanisms, in particular by the kidneys. an ELECTROLYTE IMBALANCE is a sign of illness and itself contributes to that ilness
-The three mmost important electrolytes are:
Na+, K+ and Ca2+
What are the 3 blood electrolyte imbalances?
Sodium (Na+)
hyponatremia - due to decreased sodium intake
hypernatremia - dehydration, water deprivation
Potassium (K+)
hypokalemia - excessive ost due to vomiting or kidney disease
hyperkalemia - renal failure, crushing injuries
Calcium (Ca2+)
hypocalcemia - hypoparathyroidism
hypercalcemia - hyperparathyroidism, cancer
What is an acid?
ACID
- a substance that dissociates in water and releases hydrogen ions (H+) in a solution
- responsible for the sour taste of foods
ex. when hydrochloric acid (HCl) is added to water
HCl –> H+ and Cl-
What is a base?
BASE
-a substance that removes H+ ions from a solution
molecules with HYDROXYL (OH-) groups can do this, forming water
ex. adding sodium hydroxide (NAOH) to water produces:
NaOH –> Na+ + OH-
Any free H+ ions immediately react with OH- forming H2O
H+ + OH- –> H2O
What is pH?
because acids and bases have opposite effects on H+ concentrations, we need a scale in order to measure this
pH is a measure of the concentration of H+ per liter of solution
Ranging from 0-14
- pH7 indicates a neutral solution (i.e OH-, and H+ are at equally very low concentrations in pure water)
- pH above 7 - basic/alkaline solution
- pH below 7 - acidic solution
NOTE the more acidic, the greater the H+ concentration, the lower the pH and vice versa
NOTE a one unit change in pH value represents a 10x change in H+ concentration (a log scale)
e.g pH 5 indicates 10x more H+ ions than pH 6, pH 9 has 100x less (i.e., 1/100) H+ ions than pH 7
BLOOD HAS A PH OF ABOUT 7.35-7.45
Why is pH homeostasis important?
-Normal blood pH is between 7.35 and 7.45
-Acidosis = pH below 7.35
-Alkalosis = pH above 7.45
-Note how narrow the normal range is
-Excessive pH changes interfere with protein shape and protein function i.e., proteins become denatured
-This will effect, for example, enzyme function and disrupt normal cell metabolism
-acidosis is often a serious complication of many illnesses
IMPORTANT NOTE: Acidotic is NOT the same as acidic e.g if your blood pH is 7.2 is it acidotic? acidic? ACIDOTIC
What are the 3 ways the body maintains pH homeostasis?
- Chemical buffer systems
- respiratory compensation (ventilation)
- renal compensation (kidneys)
What are buffer systems?
- Chemical buffers are substances that act quickly to temporarily bind H+, removing the highly reactive, excess H+ from solution (but not from the body)
- to maintain homeostasis, the challenge is keeping the H+ level (pH) of body fluids in the appropriate range
- the normal pH of systemic arterial blood is 7.35 to 7.45 the homeostasis of pH is maintained by buffer systems
- CARBONIC ACID-BICARBONATE BUFFER SYSTEM
- phosphate buffer system
- protein buffer system
What is the carbonic acid - bicarbonate buffer system? How does it work?
If there is an excess of H+, the HCO3- can function as a *weak base and remove the excess H+ ions
H+ (hydrogen ion) + HCO3- (bicarbonate ion) –> H2CO3 (carbonic acid)
If there is a shortage of H+ the H2CO3 can function as a weak base and release its H+ ions
H2CO3 (carbonic acid) –> H+ (hydrogen ion) + HCO3- (bicarbonate ion)
*a “weak” acid or base does not fully dissociate H+ ions in solution.
This ability to hold onto a proportion of H+ depending on pH, stabilizes the H+ concentration
How is carbonic acid concentration linked to carbon dioxide concentration?
- as you know, CO2 is an important gas waste product from cellular respiration – there is a normal range of CO2 concentration in our blood
- in any solution, CO2 quickly reacts with water molecules to form carbonic acid, which dissociates into bicarbonate ions and H+ ions
CO2 + H2O –> H2CO3 –> H+ + HCO3-
- you can see from the equation that as CO2 concentration changes, H+ concentration also changes
- but CO2 concentration varies with breathing rate: the faster and deeper you breath, the more CO2 is released from your blood into the atmosphere
- this means that the body has yet another way to maintain pH homeostasis. VARYING THE BREATHING RATE VARIES CO2 BLOOD CONCENTRATION, WHICH ULTIMATELY VARIES BLOOD H+ ION CONCENTRATION
