fle3 Flashcards
on TLC which will travel furthest?
the most non polar has highest Rf value. Rf= distance traveled by solute/ strange traveled by one polar solvent.
In which solvent is P4 least soluble?
polar solvent such as H2O
For an acid-base equilibrium at constant temperature, which value remains constant?
pKa
Under anaerobic conditions, pyruvate is converted to lactate rather than being funneled into the PDH complex and the Citric Acid cycle. Which statement best explains the purpose of this condition-specific biochemical alteration?
A) To generate additional energy from the pyruvate molecule.
B) To regenerate NAD+ so that glycolysis can continue.
C) To generate lactate, a required precursor for glycogen synthesis.
D) To generate lactate, a precursor for subsequent energy-rich oxidation steps.
b
Boron trifluoride was once used in the synthesis of a tooth fluoridation product, but was later discontinued because of its acidic properties. What characteristic of the BF3 molecule allows it to act as a Lewis acid?
A) The electronegativy of boron and fluorine are significantly different.
B) Boron has an incomplete octet of valence electrons
c) CFluoride can dissociate and has an ionic radius similar to that of hydrogen.
d) /
b
At physiological conditions, the autoionization constant of water (Kw) is approximately 1 x 10-14. If temperature is increased by a factor of four, and pressure is increased to 25 MPa, Kw is increased by a factor of 100. How does the pH of water at this elevated temperature and pressure differ from pH under physiological conditions?
A) It decreases by one pH unit.
B) The pH is equal to 7 under both conditions.
C) It increases by one pH unit.
D) It increases by five pH units.
a
at room temperature, Kw = [H+][OH –] = 1 x 10–14. The stem uses this same figure for physiological conditions (pH ~ 7.4). We are told this value increases by a factor of 100, which would be 100 x 10–14, or 1 x 10–12. Thus, at the conditions stated in the problem, [H+][OH –] = 1 x 10–12 and [H+] = 10–6 M. From this we see that pH = 6 and the pH has decreased by one pH unit (Answer A)
what’s the structure of glycogen?
two glucose in alpha 1-4 linkage
The α(1-4) linkage between glucose molecules in glycogen is cleaved via what mechanism?
A) E1 B) E2 C) SN1 D) SN2
c
(Glycogen)n + Pi ↔ (Glycogen)n-1 + Gluocse-1-phosphate
Reaction 1
In Reaction 1, the PLP phosphate group: A) acts as a proton donor. B) stabilizes the inorganic phosphate. C) acts as a nucleophile. D) forms a π bond with glucose.
Answer A is correct because the phosphate on the PLP donates its proton to the inorganic phosphate (Figure 1), allowing the inorganic phosphate to protonate the glycosidic linkage. Answer B is not correct because PLP does not stabilize inorganic phosphate. Inorganic phosphate is a reactant in the GP reaction, so stabilizing it would impede the reaction. Answers C and D are not correct since the PLP phosphate does not directly interact with the glycogen, which would be necessary for either of these answers to be correct.
Suppose that all access to the mitochondrial matrix, including the ATP synthase molecule, is blocked and the pH on either side of the inner mitochondrial membrane is equal. If 14 NADH molecules and 5 FADH2 molecules donate their electrons to the electron transport chain (ETC), how many protons will be pumped into the intermembrane space? A) 114 B) 134 C) 170 D) 190
Choice C is the correct answer. Each pair of electrons from NADH result in translocation of 10 protons while FADH2 electrons result in translocation of 6 protons. This results in 170 protons based on the number of NADH and FADH2 molecules in the question. Answer A would be the result if only 6 protons were translocated both NADH and FADH2. Answer B would be the result if FADH2 translocated 10 protons and NADH translocated 6 protons. Answer D would be correct if FADH2 translocated 10 protons like NADH.
Biologists introduced 35S into bacteriophage proteins and inoculated cultured bacteria with the labeled phages. From what bacterial centrifugation fraction will the radiolabel be detected?
A) Viral coat proteins from the extracellular fraction
BBacterial proteins from the bacterial cytosol fraction
C) Viral coat proteins from the intracellular fraction
D) Bacterial proteins from both the intracellular and extracellular fractions
Choice A is correct. Identifying the correct answer requires two pieces of information. First, 35S will be incorporated into the viral protein, primarily the protein coat. It will not be incorporated into viral nucleic acid, which contains no sulfur. Second, when bacteriophage viruses infect cells, the protein coat remains outside the cell and the viral nucleic acids are injected into the cell. Thus, the radioactivity would be recovered from the protein coat, outside the cell, and not inside the cell. This information allows the other three choices to be eliminated: it will not be inside the bacterial cells, as suggested in Answer B; and it will not be found in the bacterial cell at all, which eliminates Choices C and D.
Blood pressure is reported as two numbers, systole over diastole. During diastole, the left:
A) and right ventricles are relaxed and fill with blood.
B) ventricle only is relaxed and fills with blood.
C) and right ventricles are contracted and eject blood.
D) ventricle only is contracted and ejects blood.
Answer A is the correct choice. During the majority of diastole, the entire heart is relaxed. The blood pressure reading reported as diastole is the minimum arterial blood pressure during this period. During this time, both ventricles are relaxed and are being filled with blood. Answers B and D can be eliminated because the ventricles contract in tandem, and the atria also contract in tandem. Therefore, during diastole both ventricles will be relaxed. Answer C is false because ventricular contraction occurs during systole, not diastole.
During prolonged strenuous exercise, the lactate produced by anaerobic glycolysis is transported to the liver, where it is converted to glucose and metabolized. This process requires the conversion of: A) lactate to glucose in the liver. B) pyruvate to acetate in the muscle. C) lactate to pyruvate in the muscle. D) NAD+ to NADH in the blood.
Choice A is the correct answer. The question stem describes the Cori cycle, although recognizing the name of the cycle is not necessary to answer the question. During prolonged exercise, anaerobic glycolysis becomes the primary source of ATP with pyruvate being converted to lactate in order to regenerate necessary NAD+. This eliminates choice D, as it suggests that NADH is produced during this state, and also because none of these conversions are likely to take place in the blood. Answers B and C can be eliminated because they suggest illogical conversions for this state, including turning lactate back into pyruvate, and turning pyruvate into acetate (continued function of the PDH complex and Citric Acid Cycle, which cannot occur anaerobically). This leaves Answer A as the only plausible choice.
What are the primary functions of the colon and rectum in the human digestive tract?
A) Absorption of macromolecular nutrients and water B) Mechanical mixing of waste products, storage and elimination
C) Absorption of water and vitamins, storage and elimination
D) Storage and elimination only
Choice C is the correct answer. The colon is often considered to include the rectum and anus as well as the large intestine. The primary function of the large intestine is to absorb (reclaim) water from the waste and the primary function of the rectum and anus is to store and expel waste. None of the other answers include both of these functions.
what are characteristics of bacteria?
I. is unicellular. II. is prokaryotic. III. has a circular chromosome. IV. reproduces via binary fission. V. has a cell wall made of chitin.
I, II, III, and IV only
