Chemist Muslim

QUESTION:
1. What is the dogma central of molecular biology?
2. What is buffer?
3. in the cells,enzymes works and active at certain pH
    how the cell maintaince the pH solution in the cell-> what chemical in the cel play a rule as buffer?
    what is buffering capacity?
ANSWER :
1. central dogma can defined as all the information about DNA; and then will use to produce RNA molecul with trancription and another information about ARN will use produce protein with translation process.
the mecanism dogma central biology molecular is :
a. the DNA replicates its informasion in a process that involves many enzymes. this process is replication.
b. the DNA codes for the production of messenger RNA (mRNA) during trancription.
c. in eucaryotic cell ,mRNA  is processed and migrates from the nucleous to cytoplasm.
d. messenger RNA carries coded information to ribosomes. The ribosomes "read" this ionformation and use it to protein synthesis. This process is called translastion
2Buffer can defined as the aqueous solution which can consisting of mixtur of a weak acid and its conjugates base or amount of strong acid or base is added to it.Buffer soution use to keeping pH at a nearly constant value in a wide variety of chemical aplication
3.enzyme we known as organic compounds or a protein generated catalyst in a reaction cell enzymes work as catalyst in our body called biokatalisator. enzyme also know as biolgymoleules such as protein that function as catalys in organic reaction.
buffer capacity can defined as maximum amount of either strong acid or strong base that can be add  before a significant change in the pH will occur(www.chembuddy.com)

AIR, LARURAN DAN BUFFER
Referensi;
1. Biochemical Calculation
2. Biochemistry & Genetics - Pretest Self-Assessment & Review

Tugas .
Selesaikan problem dibawah
a. Berapa gram NaOH(s) yang dibutuhkan untuk membuat 250 mL larutan 0,04 M. Tentukan konsentrasi dari larutan ini dalam satuan N, g/Liter, mg% dan osmolaritas.
b. Berapa mL 4 M H2SO4 yang dibutuhkan untuk membuat 2 L larutan H2SO4 0,002 M.
c. Tentukan kekuatan ion (ionic strength) dari 0.03M larutan Fe2(SO4)3
d. Saudara diberi HCl pekat (28% b/b), Specific gravity =1.15). Buatlah 2 Liter larutan 0,5 M HCl dari HClpekat yang saudara punyai.
e. Hitung 1. Molalitas dari HCl pekat (28% b/b), Specific gravity =1.15), 2. Hitung fraksi mol didalam larutan.
f. Spesifik volume dari amonimum sulfat (solid) adalah 0,565 mL/g. Kelarutan ammonium sulfat pada 0⁰C adalah 706 g/1000g air. Hitung (a) konsentrasi ammonium sulfat didalam larutan jenuh pada 0⁰C dan (b) jumlah ammonium sulfat yang harus ditambahkan pada 0⁰C kedalam 750 mL dari larutan “40%-jenuh” untuk membuat nya 60%-jenuh).
Berapa mililiter dari larutan ammonium sulfat jenuh yang harus ditambahkan kedalam 40 mL larutan 25% jenuh untuk membuat larutan 70% jenuh?. Dianggap bahwa volumenya bertambah.
Answer of buffer task:
a. Diket : V =250 mL = 0,25 L
M = 0,04 M

The answer :
• g = 0,250 L x 0,04 mol NaOH x 1 g NaOH
1 L NaOH 1 mol NaOH
= 0,4 g
• N = molek = 0,4 g NaOH x 1L NaOH x 1 mol ekivalen
L 40 g NaOH 0,250 L
= 0,04 N

• g/L = 0,04 mol NaOH x 40 g NaOH
1 L 1 mol NaOH
= 1,6 g/L
• mg % (m/V ) % = g/100 mL
= 1, 69 g/Liter
= 0,16 /100 mL
= 0,16 %
mg % = mg/100 mL
= 0,16/100
= 160 mg/100
= 160 mg %
• Osmolarity
NaOH terdiri dari dua partikel ( Na+ dan OH- )
Osmolarity = 2 x 0,04 M
= 0,08 osmolar
b. Diket : M1 H2SO4 = 4 M
V2 = 2 L
M2 = 0,002 M
Answer :
V1x M1 = V2x M2
? x 4 M = 2 L x 0,002 M
V1 = 1 mL
c. Answer
T = ½ zi 2
2
= ½ ( M Fe3+ + z2 Fe3+ + MSO4-1 – z2SO42-)
0,03 M Fe2(SO4)3 terdiri dari 0,06 Fe3+ dan 0,09 M SO42-
T/2 = ( 0,06 ) (3)2 + ( 0,09 ) (-2)2 = ( 0,06 ) ( 9 ) + ( 0,09 ) (4)
2 2
= 0,54 + 0,36
2
T/2 = 0,45
d. Diket : n = VxM = 1 x 36,5 = 36,5 g HCl
Density = 1,15 g/L
HCl pekat 28 % b/b
Dit : buat 2 Liter larutan 0,5 M HCl dari HCl pekat yang ada
Jawab :
36,5 g HCl/0,28 = 130,6 g yang dibuat
Volume = m/p = 130,36/1,15
= 113,35 mL yang dapat dibuat

e. Diket : HCl pekat 28 % ( b/b )
Density = 1,15 g/L
Dit : Molalitas
Fraksi mol
Jawab :
a. 28 % (b/b ) HCl = 28 g HCl/100 g total
g HCl = 100 – 28 = 72 g air
28 g HCl x 1000 = 388,9 HCl/1000 g H2O
72 g H2O
n = g/Mr
= 388,9 g HCl/36,5
= 10,65 mol HCl/1000 g H2O
b. Dalam 100 gr
28 gr HCl = 0,767 mol of HCl
36,5 g/m
72 g H2O = 4 moles of H2O
18 g/m
Fraksi mole HCl = n HCl
n HCl + n H2O
= 0,767
0,767 + 4
= 0,161
f. Diket : spesific volume NH3SO4 = 0,565 mL/g
Melarutkan pd 0o C = 706 g/1000 g of water
Ditanya :
* Molaritas
* m ke dalam 750 mLdari 40 % jenuh – 60 % jenuh
Answer :
* at 0o C add 706 g amonium sulfat to 1000 of H2O occupies
1000 Ml+ (706)(0,565) = 1399 mL

706 = 0,505 g/mL
1399
= 505 g/L
Mr = 132,14
505 = 3,82 M
132,14
W = 505 (52-51)
1- 0,280 S2
W = 505 (0,60 – 0,40 )

1- 0,285(0,6)
= 101
0,289
= 121,89 = 60 g/500 mL

g. Diket : 40 Ml larutan 25 % jenuh untuk membuat 70% jenuh
Dit : v
Answer:
40 mL(0,25) + (xmL) – (1,00) = (40 + xmL) (0,70)
10 + x = 28 + 0,70 x
0,3x = 18
X

107. Water, which constitutes 70% of body weight, may be said to be the “cell solvent.” Which of the following properties of water most contributes to its ability to dissolve compounds? a. Strong covalent bond formed between water and salts
b. Hydrogen bond formed between water and biochemical molecules
c. Hydrophobic bond formed between water and long-chain fatty acids
d. Absence of interacting forces
e. Fact that the freezing point of water is much lower than body temperature
The answer is (b)

97. A solution of acid is prepared for cleaning surgical instruments by
adding 0.5 L of 2 mM hydrochloric acid (HCl) to 0.5 L of pure water,
which has a hydrogen ion concentration of 10−7 M. The initial pH of the
pure water, then the pH after adding the HCl, are
a. 7, then 3
b. 7, then 4
c. 7, then 1
d. 14, then 3
e. 14, then 4

98. The greatest buffering capacity at physiologic pH would be provided
by a protein rich in which of the following amino acids?
a. Lysine
b. Histidine
c. Aspartic acid
d. Valine
e. Leucine
the answer is (a)



99. The relationship between the ratio of acid to base in a solution and its
pH is described by the Henderson-Hasselbalch equation
pH pK log [base]/[acid]
The pK of acetic acid is 4.8. What is the approximate pH of an acetate solution
containing 0.2 M acetic acid and 2 M acetate ion?
a. 0.48
b. 4.8
c. 5.8
d. 6.8
e. 10.8
answer :
CH3COOH + H2O ---- H3O+ + CH3COO-
0,2 M 2 M
pH=pK + log ( CH3COO- )
( CH3COOH)
pH= 4,8 + log ( 2 M )
(0,2 M)
pH = 4,8 + log 10
pH = 4,8 + 1
pH = 5,8
So the answered is ( C )

100. Since the pK values for aspartic acid are 2.0, 3.9, and 10.0, it follows
that the isoelectric point (pI ) is
a. 3.0
b. 3.9
c. 5.9
d. 6.0
e. 7.0
The answer is 2,0 + 10,0 = 6,0 (D)

101. A 0.22 M solution of lactic acid (pKa 3.9) is found to contain 0.20 M
in the dissociated form and 0.02 M undissociated. What is the pH of the
solution?
a. 2.9
b. 3.3
c. 3.9
d. 4.9
e. 5.4
The answer is
Lactic acid + H2O - H3O+ + konjugate lactic acid
Initial: 0,22 M
Dissos: 0,20 M 0,20 M
Undisso: 0,02 M 0,20 M
pH = pK+ log ( base )
( acid )
pH = 3,9 + log ( 0,20 )
( 0,02 )
= 3,9 + 1
= 4,9 (D)

102. Which of the combinations of laboratory results below indicates compensated metabolic alkalosis?
a. Low PCO2, normal bicarbonate, high pH
b. Low PCO2, low bicarbonate, low pH
c. Normal PCO2, low bicarbonate, low pH
d. High PCO2, normal bicarbonate, low pH
e. High PCO2, high bicarbonate, high pH


103. The graph below shows a titration curve of a common biochemical
compound. Which of the following statements about the graph is true?
a. The compound has one ionizable function
b. The compound has three ionizable side chains
c. The maximum buffering capacity of the compound is represented by points A
and B on the graph
d. Point A could represent the range of ionization of an amino function
e. Points A and B represent the respective pKs of and side chain carboxyl groups


104. The pH of body fluids is stabilized by buffer systems. Which of the
following compounds is the most effective buffer at physiologic pH?
a. Na2HPO4, pKa5 12.32
b. NH4OH, pKa5 9.24
c. NaH2PO4, pKa5 7.21
d. CH3CO2H, pKa5 4.74
e. Citric acid, pKa5 3.09
the answer is (c),because the pH NaH2PO4 most effective buffer and near with pH of body fluids is 7,4

105. Water, which constitutes 70% of body weight, may be said to be the
“cell solvent.” The property of water that most contributes to its ability to
dissolve compounds is the
a. Strong covalent bond formed between water and salts
b. Hydrogen bond formed between water and biochemical molecules
c. Hydrophobic bond formed between water and long-chain fatty acids
d. Absence of interacting forces
e. Fact that the freezing point of water is much lower than body temperature
the answer is (b