Acid Base Equilibrium

Question 1

Most important biological buffers?

Answer 1

Phosphate
Bicarbonate
Proteins

Question 2

Buffers consist of:

Answer 2

Weak acid and its conjugate base that are in equilibrium

Question 3

The difference between strong and weak acids?

Answer 3

Weak acids are not completely dissociated under conditions within the biological system

Question 4

Benefit of Henderson-Hasselbalch equation?

Answer 4

calculation of the amounts of undissociated acid and its conjugated base at any PH

Question 5

Change of 1 pH unit results in? “Hassel equation”

Answer 5

10-fold change in the ratio of acid to conjugate base

Question 6

Titration?

Answer 6

The addition of a strong acid to a weak base, or a strong base to a weak acid for the purpose of buffering the solution (maintaining pH)

Question 7

Buffering capacity depends on 2 factors?

Answer 7

1. The concentration of the buffer

2. Its pH

Question 8

The buffer is most effective when the……. equals …….

Answer 8

pH , pKa

Question 9

The buffer in plasma and interstitial fluid is………

While in the intracellular fluid is……..

Answer 9

Bicarbonate,

Phosphate and proteins

Question 10

Hemoglobin is a good buffer because of?

Answer 10

The presence of Histidine

* It is a basic amino acid

Question 11

What makes carbonic acid a strong buffer?

Answer 11

The ability of the acid to convert to carbon dioxide

Question 12

Normal pH of blood plasma is?

Answer 12

7.4

Question 13

Acidosis results from?

Answer 13

1. Hypoventilation (respiratory acidosis)

2. Accumulation of lactic acid, acetoacetic acid and beta hydroxybutyric acid (metabolic acidosis)

Question 14

Alkalosis results from?

Answer 14

1. Hyperventilation (respiratory alkalosis)

2. Loss of stomach acids (metabolic alkalosis)

Question 15

Phosphate buffer is of little importance in plasma?

Answer 15

Because of its low concentration in ECF

Question 16

Phosphate buffer is important in?

Answer 16

Red blood cells and kidney tubules

Question 17

Why proline differs from the rest of the amino acids?

Answer 17

because the side chain forms a cyclic structure with the amino group

Question 18

Histidine is the the only amino acid with good buffering capacity. True/False?

Answer 18

True.. Because easily and reversibly accepts and donates protons.
* The imidazole side chain of histidine has a pKa of 6.5 (pKa is withing the physiologic pH range, means a good buffer)

Question 19

In general, the protein folds so that the ….. is to the out side of the molecule.

Answer 19

the hydrophilic side chain

Question 20

Hydrophobic aminoacids have …….. or ……. groups within the side chains

Answer 20

aliphatic or aromatic

Question 21

Hydrophilic side chains contain?

Answer 21

S, O or N atoms

Question 22

Serine and threonine have uncharged side chain containing……….

Answer 22

Hydroxyl groups

Question 23

Cysteine side chain contains……….

Answer 23

sulfur

Question 24

Asparagine and glutamine side chains have…..

Answer 24

amide groups

Question 25

Cystine is formed by………. . Its function is …….

Answer 25

1. disulfide linkage between two cysteines (the only covalent cross linkage in proteins)
2. stabilize the 3 dimensional structure of extracellular proteins
   * Abundant in Insulin and Ig

Question 26

Post translational modification is ?

Answer 26

modification of common amino acids after the protein has been synthesized.

Question 27

Hydroxyproline is formed by…….. in ……… where it functions as………

Answer 27

1. O2 dependent hydroxylation of proline
2. Fibroblasts
3. stabilization of the triple helical structure of collagen

436

Question 28

Phosphotyrosine, phosphoserine and phosphothreonine are formed by…… and function for…….

Answer 28

1. transferring a phosphate from ATP to hydroxyl group

2. signal transduction

Question 29

why glycine is differenet

Answer 29

the alpha carbon is connected to a hydrogen atom as a side chain

Question 30

Which stereoisomer is incorporated in proteins?

Answer 30

L-amino acids

Question 31

Define PI?

Answer 31

isoelectric point. The pH where the a molecule is not charged (neutral)

Question 32

Define Zwitterion

Answer 32

The protein that has both positive and negative charge at neutral pH
* Glycine has a net negative charge at any pH above its isoelectric point, so it moves toward the positive electrode. At any pH below its isoelectric point (pI), glycine exhibits a net positive charge and moves toward the negative electrode