Test 3 - Acid/Base Physiology Flashcards
What aspects of a protein do protons interact with and what are the consequences?
- Negative R groups
- Hydrogen bonds
Both of these contribute to the shape of a protein. Changes in proton concentration can alter these interactions and denature the proteins. E.g. enzymes (including those for protein synthesis, DNA replication, etc), transporters, Na/K ATPase, receptors
In the case of receptor and enzyme denaturation, what changes?
Receptors and enzymes are a specific shape in order to recognize their specific substrates. Denaturation would cause decreased enzymatic rates or decreased effectiveness of hormones/neurotransmitters.
How do changes in proton concentration change Na/K ATPase?
This changes Na/K ATPase activity. This has implications on:
- Nephron reabsorption/secretion
- Membrane Potential all over the body
TRUE/FALSE.
Animals produce more buffer according to its need and it simply accumulates in the body.
FALSE.
Cells do manufacture more buffer according to their needs. However, waste is excreted. Acid specifically is removed through the lungs and kidneys.
What are the defenses against changes in proton concentration?
- Intracellular buffers
- Transporters to send waste into the interstitium and subsequently plasma
- Ultimate Excretion Routes: Breathing and urinating
TRUE/FALSE.
Plasma is dead. Therefore, acid/base problems start at living cells.
TRUE.
Cells export their waste into plasma as a mode of waste removal.
Where are buffers present?
Intracellularly
Interstitium
Plasma (this ultimately takes waste to get excreted and we can start all over)
What are the major methods of proton removal? Which is the most efficient?
- Exhalation of CO2 (thousands of times more efficient than urination).
- Urination
What are the main roles of the kidney and lungs specifically in acid/base balance?
Kidney - Buffer manufacturing
Lungs - Acid removal through CO2 exhalation
Describe the changes in CO2 as it travels in the RBC to the lungs.
RBCs convert CO2 to H+ and HCO3-
Once it gets to the lungs, it is converted back to CO2 so that it can diffuse accross the alveloar membrane
TRUE/FALSE.
An animal can have more than one acid/base disorder at a time.
TRUE.
CO2 is a(n) ______ (acid/base) in aqueous solution.
ACID
What buffers are RBCs full of?
Hemoglobin
What will cause an animal to become more acidic, kidney or lung damage?
Lung Damage
What is the concentration of water?
55.55… moles/liter
This is treated as a constant
______ and _____ are the most abundant anions in plasma.
What does changes in their concentrations elicit?
Chloride (#1) and Bicarb (#2)
They are anions of a strong and weak acid, respectively. Changes in their concentrations has significant consequences on pH.
More Acidic or basic?
- Add more CO2
- Lose bicarb and gain Cl-
- Lose Cl- and gain bicarb
- Acidic
- Acidic
- Bicarb
Who adds HCO3 to plasma without adding H?
PCT cells
a-intercalated cells
How can you tell if an acid is stronger or weaker based on the Ka?
A stronger acid has a larger Ka
_____ is the most important buffer in extracellular fluid.
HCO3-
TRUE/FALSE.
If you know the pH of plasma, you know the pH of the fluid bathing the cells/interstitium.
TRUE.
What pH is optimal for cells?
7.4
What kind of acid would we want for buffers? Optimally, what state(s) should it exist in under normal conditions?
A weak acid would make the best buffer that exists at 50% associated and 50% dissociated states. This gives you the best chances for maintaining proton concentration.
What is the pK of a buffer?
The particular pH at which a buffer does its best buffering. This is when it exists at 50/50.
What is the weak acid that is used to buffer plasma? What is its pK?
Carbonic Acid (H2CO3)
pK = 6.1
Explain the pK of carbonic acid and why it works in plasma.
pK = 6.1
We want to defend a pH of 7.4
a pK of 6.1 suffices becauses because HCO3- exists in 20x the amount of carbonic acid.
pH = pK + Log10 ([A-]/[HA])
pH = pK + Log10[20]
pH = 6.1 + 1.3 = 7.4
Define:
- Acidosis
- Acidemia
- Alkalosis
- Alkalemia
- A condition which causes increased [H+]
- The presence of greater than normal [H+] in blood
- A condition which causes a decrease in [H+]
- The presence of less than normal [H+] in blood
TRUE/FALSE.
Drug effectiveness can be influence by changes in proton concentration.
Why or why not?
TRUE.
Changes in proton concentration changes the structures that drugs bind to but also because many drugs are acids or bases. Therefore, changes in proton concentration would alter their ability to donate or accepto protons. Their structure would be altered and thire ability to cross cell membranes would change.
Discuss the differences between a strong and a weak acid.
A strong acid readily dissociates and exhibits high acidity.
Weak acids do not dissociate as readily. pK is typically used to describe weak acids. The stronger a weak acid, the higher the pK.
What is important about pK?
At pK, a weak acid is best able to resist changes in pH in the face of addiition or removal of H+ from solution, i.e., to buffer changes in [H+]. The reason why a buffer does its best buffering at its pK is because it exists abundantly in both the protonated and dissociated forms. This permits it to donate significant amounts of H+ if [H+] decreases and tirate significant amounts of H+ if [H+] increases.
Describe the titration curve for phosphoric acid.
The pK = 6.8, where it does its best buffering.
Within 1 pH of its pK it still maintains buffering power but the greater the deviation from the pK, the less it is capable of blunting the changes in [H+]. After a certain point, the same incremental increase in addition causes a more significant change in pH.
Who should exist at a higher concentration, CO2 or HCO3-? What happens if one of these is not in this ratio?
HCO3- should exist 20x more than CO2.
If there is more bicarb, then plasma would be alkaline. More CO2 would make plasma acidic.
What are the forms of CO2 found in plasma? What gives you TCO2?
CO2 (gas), H2CO3, HCO3-
Addition of these concentrations gives TCO2 (Total concentration of carbon dioxide).
Total CO2 (mM) = [HCO3-] (mM) + (0.3) PCO2 (mmHg)
H2CO3 can be regarded as zero because it exists 400x less than CO2
What are the acids produced as a result of metabolism (acidosis)? Where are they produced?
- Lactic Acid - Skeletal muscle
- Ketoacids - liver
- Acids of ethylene glycol metabolism - liver
TRUE/FALSE.
Once bicarb is used by the addition of acid, it must be converted to a form such that waste is excreted and bicarb can is recycled.
FALSE.
The kidney will produce more bicarb to replenish what has been used.
TRUE/FALSE.
CO2 is a form of bicarb and so it is a weak base in aqueous solution.
FALSE.
It is also a source of proton and so it is a weak acid.
What is the best way to get rid of acid?
Through exhalation of CO2.
What is the partial pressure of oxygen (PO2) in RBCs going to cells? What is it travelling to the lungs?
Travelling to cells from the lungs PO2 = 100mmHg
Travelling to lungs from cells PO2 = 40 mmHg