, Which of the following statements is correct about the blood bicarbonarte buff
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Question
, Which of the following statements is correct about the blood bicarbonarte buffer system? Increasing the CO.(Pcoz) in the blood will decrease the (HCO,YH CO,] ratio in the blood which increases the pH of the blood plasma. b. Obstructive lung disease, such as poeumonia or emphysema, causes an increase in CO(Pco) in the blood which lowers the pH. Metabolic acids react react with H-CO, and excessive production of acids by the liver decreases the concentration of [H:CO] which causes metabolic alkalosis. e. d. The plH of the blood is 7.40 because the ratio of [HCO, H CO,] is 1:1. e. Hyperventilation causes the pl of the blood to become more acidic because it causes the Pon to decrease. 8. Which of the following statements is not correet? The lower the pKa of a weak acid, the stronger the acid. Protons dissociate from weak acids as the pll is increased. Allampholytes (amino acids, peptides and proteins) are negatively charged at pH values below their isoelectric pH. a· b. d. Protons bind to conjugate bases as the pH is lowered. e. The net charge of an ampholyte (amino acid, peptide, or protein) is always exactly zero at its isoelectric point, pl (pHi). 9. Which of the following is the predominant structure of "isoelectrie" Threonine? A. C. E. OH B. NH3 the predominant structure of His in the blood at plH 7.402 10.. Which of the following structures is CH, CH-6 one of the 20 common amino acids is not chiral and is often found in sharp reverse turns in 11 , which o the backbone of proteins? c. Leucine e. Threonine aGlycine Alanine d. Proline 12. Some amino acid residues are modified after being incorporated into a protein. What amino acid was modified to produce the structure shown to the right which was isolated from the hydrolyzate of collagen? 0 Arginine a. Histidine b. Proline c. Creatine d. TryptophanExplanation / Answer
7.
Option B is correct.
CO2 + H20 <----> H2CO3 <----> H+ + HCO3-
Obstructive lung disease causes an increase in blood CO2 level. This leads to increased carbonic acid production that ultimately decreases blood pH.
8.
Option C is correct.
An amino acid is positively charged below its pI.
9.
Option B is correct.
At isoelectric point, the amino group is protonated and the carboxyl group is unprotonated so that the net charge is zero. At isoelectric point, the side chain also carries no net charge.
10.
Option E is correct.
Histidine pI = 7.59
pK of carboxyl group = 1.8
pK of side chain = 6.0
pK of carboxyl group= 9.0
At pH = 7.4,
Amino group is protonated = +1 charge
Carboxyl group is deprotonated = -1 charge
Imidazole side chain is udeprotonated = 0 charge
11.
Option A is correct.
Glycine contains 2 Hydrogen atoms attached to alpha carbon atom. Hence it is a non-chiral molecule.
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