Exam 1 (Ch. 1-4)
What is the term regarding the clustering of molecules in water?
a) Ionic Bonding
b) Hydrogen Effect
c) Van der Waals interaction
d) Hydrophobic Effect
d) Hydrophobic Effect
What kind of inhibitors are allosteric inhibitors usually classified as?
a) competitive inhibitors
b) noncompetitive inhibitors
c) uncompetitive inhibitors
d) irreversible inhibitors
c) uncompetitive inhibitors
Which of the following changes would cause an increase in melting point of a fatty acid at low temperatures?
a) Increasing the number of double bonds
b) Increasing the fatty acid chain length
c) Introducing methyl groups
d) Introducing cholesterol
e) Introducing cis double bonds
b) Increasing the fatty acid chain length
What products of glucose oxidation are essential for oxidative phosphorylation?
a) Acetyl CoA
b) Pyruvate
c) NADH and FADH2
d) NADPH
e) ATP
c) NADH and FADH2
What is the role of ketone bodies?
a) To increase the breakdown of muscle proteins for energy
b) They are an alternative fuel source
c) The liver uses it as a primary source of fuel
d) To manufacture glucose for immediate use
b) They are an alternative fuel source
*Remember that they are made in the liver!
Which following description fits the characteristics of secondary structure of proteins?
a) Folding of polypeptide chain into shapes like α-helices and β-sheets
b) Link of amino acids held together by peptide bonds
c) 3D structure made by folding helices and sheets
d) A single amino acid
a) Folding of polypeptide chain into shapes like α-helices and β-sheets
Fill in the blanks for the following statement:
A/an _______ helps turn an inactive enzyme, also called a/an _______, into an active enzyme, also called a/an _______.
A cofactor (or coenzyme) helps turn an inactive enzyme, also called an apoenzyme, into an active enzyme, also called a holoenzyme.
Glucose enters the cell through a transporter that pumps Na+ ions into the cell, along with glucose. This is an example of:
a) an ATPase
b) an antiporter
c) simple diffusion
d) symporters
e) a uniporter
d) a symporter
What type of enzyme is Phosphofructokinase?
a) transferase
b) oxidoreductase
c) lyase
d) hydrolase
e) translocase
a) transferase
What additional enzymes are needed to oxidize fatty acids that are unsaturated and have an even number of carbons?
a) isomerase
b) amylase
c) reductase
d) two of the above
e) all of the above
d) two of the above (isomerase and reductase)
What is the pH of a 50 mM solution of hydrochloric acid? (Note that HCl is a strong acid and will completely dissociate.)
a) -1.7
b) 1.3
c) 1.7
d) 6.2
50 mM (1M/1000mM) = 0.05 M
pH = -log [0.05M] = 1.3
b) 1.3
Classify each protein according to its primary use: (A) purification, or (B) analysis:
1. Gel filtration chromatography
2. SDS-PAGE
3. Isoelectric focusing
4. Ion exchange chromatography
5. Affinity chromatography
1. (A)
2. (B)
3. (B)
4. (A)
5. (A)
Match the terms to their descriptions:
1. Different order of atom attachment
2. Differs at one of the several asymmetric carbon atoms
3. Isomers that are not mirror images
4. Isomers that differ at a new asymmetric carbon atom formed on ring closure
a) epimer
b) anomer
c) diasteromer
d) constitutional isomer
1. (d)
2. (a)
3. (c)
4. (b)
Identify the best molecule for long-term energy storage.
a) Glycogen
b) Triacylglycerol
c) ATP
d) Cholesterol
e) Glucose
b) Triaglycerol
What are the four steps to fatty acid metabolism (oxidation and synthesis)?
Oxidation: oxidation by FAD, hydration, oxidation by NAD+, thioloysis by coenzyme A
Synthesis: condensation, reduction, dehydration, second reduction
If the pKa of meth is 8.6, what is the ratio of deprotonated to protonated meth molecules at physiological pH (7.4)?
a) 0.063
b) 0.52
c) 3.7
d) 15.8
pH = pKa + log ([A-]/[HA])
7.4 = 8.6 + log ([A-]/[HA])
-1.2 = log ([A-]/[HA])
[A-]/[HA] = 10-1.2
[A-]/[HA] = 0.063
At what V0 does Km = [S]? Use the Michaelis-Menten Equation to prove it.
V0 = (Vmax [S])/(Km + [S])
1/2 Vmax =(Vmax [S])/(Km + [S])
1/2 Km + 1/2 [S] = [S]
1/2 Km = 1/2 [S]
Km = [S]
ATP has a high phosphoryl-transfer potential because:
a) The structure stabilizes due to resonance
b) ADP and Pi are more soluble in water than ATP
c) There is high electrostatic repulsion between the three phosphate groups
d) two of the above
e) all of the above
e) all of the above
Which enzymes are different between glycolysis and gluconeogenesis? State the function of each.
Glycolysis -
Hexokinase: Phosphorylates glucose
Phosphofructokinase: Phosphorylates fructose 6-phosphate
Pyruvate Kinase: Converts PEP to pyruvate
Gluconeogenesis -
Pyruvate Carboxylase: Converts pyruvate to oxaloacetate
Phosphoenolpyruvate Carboxykinase (PEPCK): Converts oxaloacetate to PEP
Fructose-1,6-bisphosphatase: Dephosphorylates fructose 1,6-phosphate
Glucose-6-phosphatase: Dephosphorylates glucose 6-phosphate
How many cycles of the synthesis pathway are needed to produce myristic acid (CH₃(CH₂)₁₂COOH)?
a) 5 cycles
b) 14 cycles
c) 7 cycles
d) 6 cycles
d) 6 cycles
At what pH will 40% tyrosine R groups be in their deprotonated form? (pKa = 10.9)
a) 11.37
b) 10.53
c) 10.72
d) 11.27
e) 10.5
pH = pKa + log (deprot. / prot.)
pH = 10.9 + log (0.4 / 0.6)
pH = 10.9 + (-0.176)
pH = 10.72
You have the following overlapping peptides obtained from a sequence analysis of your hexapeptide. After one cycle of Edman degradation on a sample of the peptide, you produce a PTH derivative of phenylalanine. After cleavage with chymotrypsin and trypsin you obtain the following fragments:
Peptides from chymotrypsin: phenylalanine-arginine-glutamate & lysine-glycine-threonine
Peptides from trypsin: arginine-glutamate-lysine & glycine-threonine
Which of the following represents the correct full peptide sequence?
a) phenylalanine-arginine-glutamate-lysine-glycine-threonine
b) phenylalanine-arginine-glutamate-lysine
c) glycine-threonine-phenylalanine-arginine-aspartate-lysine
d) phenylalanine-arginine-glutamate-glycine-arginine-glutamate
a) phenylalanine-arginine-glutamate-lysine-glycine-threonine
Consider the phosphorylation of glucose:
Glucose + ATP <- -> glucose-6-phosphate + ADP
Glucose + Pi -> G6P = +13.8 kJ/mol
ADP + Pi -> ATP = +30.5 kJ/mol
Find the Gibbs free energy and the Keq of the phosphorylation of glucose at 298 K
Gibbs free energy:
+13.8 kJ/mol + (-30.5 kJ/mol) = -16.7 kJ/mol
Keq:
-16.7 kJ/mol = -(8.315 x 10 kJ/(mol K))(298 K) ln(Keq)
Keq = 845 kJ/mol
Use the following terms to describe the different steps of glucose metabolism: (a) Substrate-level phosphorylation, (b) Oxidative phosphorylation, or (c) neither
1. Glycolysis
2. Conversion of pyruvate to Acetyl CoA
3. Citric acid cycle
4. ATP synthesis in the mitochondria
1. (a)
2. (c)
3. (a)
4. (b)
Calculate the net ATP generated from the oxidation of an 18-carbon saturated fatty acid
a) 108
b) 112
c) 120
d) 78
c) 120
NADH: 8 x 2.5 ATP = 20 ATP
FADH2: 8 x 1.5 ATP = 12 ATP
Acetyl Co-A: 9 x 10 ATP = 90 ATP
90 + 20 + 12 = 122 ATP - 2 = 120 ATP