0506 - Intro to acid base regulation - VY

Question 1

What is the bronsted definition of an acid and base

Answer 1

Acid - any chemical substance that can donate a hydrogen ion. Base - any chemical substance that can accept a hydrogen ion

Question 2

What is pH (what does it quantify, what is the formula)? What does a pH shift of 1 indicate

Answer 2

pH is a measure of the amount of free hydrogen ions, pH = -log [H+}. A pH shift of 1 = a 10 fold change in [H+]

Question 3

Even a small change in internal pH can affect the biological activity of an organism. What are some biological components that can be affected?

Answer 3

Enzymes, ligands, ion channels, transporters, and structural proteins are all sensitive to pH changes

Question 4

What is the significance of a bell curve shape of enzymatic activity when graph across a pH axis

Answer 4

It shows the optimal pH level of activity for a certain enzyme. It is important because it demonstrates that enzymes have an optimal level of normal activity and deviations from this pH will have consequences in terms of enzyme efficiency

Question 5

What is the key principle behind acid-base balance in our body

Answer 5

The amount of acid excreted per day must equal the amount produced per day

Question 6

What is the pH value of arterial blood plasma? What are 2 areas of the body with low and high pH

Answer 6

Blood plasma is 7.4pH. Low pH is anywhere that is acidic (Gastric secretions in stomach, lysosomes, etc). High pH is anywhere that is basic (e.g. pancreatic fluid in pancreas)

Question 7

What is the definition of a buffer? Why are they so biologically significant

Answer 7

A buffer is any substance that reversibly consumes or release H+. They are very important in biological systems because they contribute to pH homeostassis (minimise pH changes)

Question 8

Describe the pattern of undissociated acid, free anion and free H+ you would see in a strong acid

Answer 8

High free anion and free H+. Low undissociated acid

Question 9

Describe the pattern of undissociated acid, free anion and free H+ you would see in a weak acid

Answer 9

Low free anion and H+. high undissociated acid

Question 10

What are monoprotic and polyprotic acids? How many equivalence points do each have

Answer 10

Monoprotic acids are acids that can only donate one proton (hydrogen ion). They have one equivalence point. Polyprotic acids are acids that can donate more than one proteon. They have multiple equivalence points

Question 11

What is buffering power? Why is the optimal pH in terms of buffering power important?

Answer 11

Buffering power describes the number of moles of a strong acid or base that is needed to shift the pH by 1. Optimal pH for buffering power is important because that is when a buffer is most effective at regulating pH changes

Question 12

What is the advantage (in terms of buffering power) of having multiple buffers rather than one buffer in our bodies

Answer 12

Multiple buffers often have multiple optimal pH ranges (in terms of buffering power). This means that our body is more capable of counteracting pH change over a wider scale of pH values because we have a variery of buffers

Question 13

Where would you expect to find buffers in our body

Answer 13

Interstitial fluid, blood, intracellular fluid, urine, bone

Question 14

How does CO2 make our bodies more acidic

Answer 14

Although CO2 is not originally an acid nor a base (no pH change), as it enters water, a series of reaction means it produce H+ ions . CO2 +H2O => H+ and HCO3-

Question 15

Using the nernst equation, why might cytosolic pH (pH inside a cell) be lower than the predicted value based on an extracellular pH and membrane potnetial

Answer 15

Because our cells have active mechanisms to extrude H+. This is how they regulate intracellular pH. The nernst equation does not account for this

Question 16

Describe an intracellular response to HCl being administered into a cell (acidosis)

Answer 16

Na/H exchanger pumps out H+ and brings in Na, lowering intracellular [H+]

Question 17

What is the affect of a higher than normal pH value in the extracellular environment on the Na/H exchanger on a cell membrane

Answer 17

A high extracellular pH would stimulate the exchanger (pumping our H+ ions to lower extracellular pH). Vice versa for a low extracellular pH

Question 18

Describe an intracellular response to KOH being administered into a cell (alkalosis)

Answer 18

A HCO3-/CL exchanger removes HCO3- and pumps in Cl-, lowering intracellular concentration of [HCO3-]

Question 19

What is the affect of a higher than normal pH value in the extracellular environment on the HCO3-/Cl- on a cell membrane

Answer 19

A high extracellular pH would inhibit the exchanger (AS there is already a basic extracellular environment). Vice versa for a low extracellular pH

Question 20

What is the affect of an acidic and basic extracellular environment on intracellular response to acidosis

Answer 20

Acidic extracellular environment means intracellular regulation of acidosis will be slower (longer to neutralise). Basic extracellular environment means intracellular regulation of acidosis will be faster (faster to neutralise)