Molecules and Their Interactions part 2

Values of T_m (midpoint of denaturation), ΔH_m (enthalpy change at T_m) and ΔC_P (constant-pressure heat capacity change) of a protein are measured in a differential scanning calorimeter. ΔG_D(T), the Gibbs free energy change at any temperature T(K) can be estimated using the following form of the Gibbs-Helmholtz equation with the values obtained from these
measurements:

The stability curve for the protein simulated using the observed thermodynamic values is given below:

The shape of the stability curve is due to
(1) hydrogen-bonding and electrostatic interactions only.
(2) van der Waals and electrostatic interactions only.
(3) only electrostatic interactions.
(4) only hydrophobic interaction.

A protein in 100 mM KCl solution was heated and the observed T_m (midpoint of unfolding) was 60⁰C.
When the same protein solution in 500 mM KCl was heated, the observed T_m was 65⁰C. What is the most probable reason for this increase in T_m?
(1) Hydrophobic interaction is increased and electrostatic repulsion is decreased.
(2) Hydrophobic interaction is decreased and electrostatic repulsion is increased.
(3) Hydrogen-bonding is increased.
(4) van der Waals interaction is increased

It has been observed that for the DNA double helix melting, the value of ΔH (enthalpy change of denaturation) are 80 and 90 kcal/mole at 70⁰ and 80⁰, respectively. Assuming that ΔC_P (constant-pressure heat capacity change) is independent of temperature, estimate ΔH associated with the denaturation of DNA at 37⁰C. This estimated value of ΔH (kcal/mole) is
(1) 27                                           (2) 37
(3) 47                                          (4) 57

The Temperature of Melting (Tm) is defined as the temperature at which 50% of double stranded DNA is changed to single-standard DNA. Tm of DNA does not depends on
(1) Length of DNA (2) % GC content
(3) Presence of cations (4) Presence of anions

The graph between the concentration of Single stranded DNA (Y-axis) and decrease in temperature (X- axis during renaturation of DNA can be represented as

Denaturation profiles of DNA are shown below

The differences in the profiles arise because
(1) the DNA is single stranded but of different sizes
(2) A + T content of A > B > C and the DNA are from complex genomes
(3) G + C content of C > B > A in DNA of comparable sizes isolated from simple genomes
(4) G + C content is identical but A + T content in A > B > C in DNA of comparable sizes isolated from simple genomes

Heating of some nucleic acids shows an increase in the absorbance at 260 nm (A260)
typified by the plot shown above. The sharp transition midpoint is defined as melting temperature (Tm). Which one of the following nucleic acid samples is NOT expected to
generate such a typical profile upon heating of its solution?
(1) Double stranded DNA
(2) Double stranded RNA
(3) DNA:RNA hybrid DNA:RNA
(4) Single stranded DNA having imperfect secondary structures

The half reaction during reversible lactate dehydrogenase reaction and standard redox potential are

Pyruvate + 2H⁺ + 2e^– à lactate E⁰ = -0.185V

NADH + H⁺ à NAD⁺ + 2H⁺ +2e^– -0.315V

On basis of above information the correct statement is
(1) The electron are readily picked up by NAO from pyruvate under standard conditions
(2) NADH: provide electrons to pyruvate for reduction to lactate under standard conditions
(3) Both reaction are independent
(4) Reaction occurs spontaneously in direction lactate to pyruvate under standard conditions

In mitochondria the enzymes of electron transport chain are located at
(1) Outer membrane
(2) Inter membrane space
(3) Inner membrane
(4) Matrix

NADH donates its electron to electron transport chain through primary acceptor
(1) CoQ          (2) FMN
(3) FAD          (4) Cytochrome oxidase

Iron-sulphur clusters (Fe-S) are the key prosthetic groups that carry electrons in of the below EXCEPT.
(1) NADH – CoQ reductase
(2) Succinate – CoQ reductase
(3) Cytochrome c oxidase
(4) COQH2 – Cytochrome C reductase

In prokaryotes, the terminal electron acceptor in anaerobic conditions are generally
(1) Glucose, fructose,  maltose
(2) Fatty acids
(3) SO₄^2-,  NO₃^2- , S
(4) Antioxidants such as Vitamin K

Proton motive force during oxidative phosphorylation is generated in mitochondria by
(1) exchanging protons for sodium ions
(2) pumping protons out into intermembrane space
(3) pumping hydroxyl ions into the mitochondria
(4) hydrolysis Of ATP

Electron transfer from donors such as NADH and FADH₂ to O₂ occurs in
(1) membranes of ER, chloroplast and mitochondria
(2) chloroplast only
(3) mitochondria only
(4) organellar membranes which possess ATP synthase

Which of the following proteins acts as an energy transducer?
(1) G-protein.
(2) Bacteriorhodopsin.
(3) Hemoglobin.
(4) Heat shock protein.

Among the following which chemical inhibits the mitochondrial electron transport chain-
(1) Streptomycin       (2) Nystatin
(3) Azides                (4) Penicillin

From the following statements:
A. Biosynthesis of proteins and nucleic acids from precursors results in production of chemical energy in the form of ATP. NAOH. NADPH and FADH₂
B. The spontaneity of a reaction in cells does not depend whether ΔG₀ for the reaction is positive or negative.
C. Both oxidative phosphorylation and photo-phosphorylation involve oxidation of H₂O to O₂
(D) Only chemical potential energy contributes to proton motive force in mitochondria.
Which one of the following combinations represents all INCORRECT statements?
(1) A, B, C             (2) B, C, D
(3) A, B, D             (4) A, C, D

Coupling of the reaction centers of oxidative phosphorylation is achieved by which one of the following?
(1) Making a complex of all four reaction centers.
(2) Locating all four complexes in the inner membrane.
(3) Ubiquinone and cytochrome C.
(4) Pumping of protons.

The respiratory chain is relatively inaccessible to experimental manipulation in intact mitochondria. Upon disrupting mitochondria with ultrasound, however, it is possible to isolate functional sub mitochondrial particles, which consist of broken cristae that have resealed inside out into small closed vesicles. In these vesicles the components that originally faced the matrix are now exposed to the surrounding medium. This arrangement helps in studying electron transport and ATP synthesis because:
(1) it is difficult to manipulate the concentration of small molecules (NADH, ATP, ADP, Pi) in the matrix of intact mitochondria
(2) in broken cristae, the enzymes and other molecules responsible for electron transport are more active
(3) intact mitochondria are more unstable than broken cristae
(4) purification of intact mitochondria is not possible

In a mitochondrial respiration experiment, a researcher observed the following profile of oxygen consumption upon addition of following compounds at times I, II and III.
(a) ADP + Pi
(b) Dinitrophenol, an uncoupler
(c) Oligomycin, an ATPase inhibitor
(d) Cyanide
(e) Succinate

Which of the following describes the profile appropriately?
(1) I-b; II-d; III-e
(2) I-a; II-d; III-c
(3) I-a; II-e; III-c
(4) I-a; II-c; III-b

Rotenone is an inhibitor of the electron transport chain. The addition of rotenone to cells results in which of the following?
(1) Generation of mitochondrial reactive oxygen species and block in ATP generation.
(2) Block in ATP generation but no generation of reactive oxygen species.
(3) Generation of reactive oxygen species but no block in ATP generation.
(4) Permeabilization of the inner membrane to compounds which are usually not able to traverse the membrane.

A practical class was going on where the students were demonstrating ATP synthesis in vitro using active mitochondria. Some students added one of the following to their tubes
A. Dinitrophenol (DNP), an uncoupler
B. Mild acidification of the medium
C. Glutilferone, that permeabilizes both the membranes
D. An outer membrane permeable He quencher compound. Elila
In which one of the above, ATP synthesis will be detected?
(1) A            (2) B
(3) C            (4) D

Which statement is NOT correct regarding brown fat?
(1) It is present in negligible amount in new born baby
(2) It produces little ATP
(3) It produces more heat
(4) In Mitochondria associated with this electron transport chain and phosphorylation are uncoupled

Cyanide, a chemical warfare agent, is toxic because it:
A. binds to the heme a3 in mitochondrial cytochrome C oxidase (in complex IV)
B. inhibits electron transport and thus oxidative phosphorylation
C. directly blocks mitochondrial DNA replication
D. blocks the protein trafficking inside the
mitochondria by affecting TIM and TOM channels
Choose the combination with all correct statements.
(1) A and C         (2) A and B
(3) B and C         (4) A, B and D

At which one of the following electron transport chain complexes does Antimycin A typically inhibit the respiratory chain?
(1) Complex I       (2) Complex II
(3) Complex III    (4) Complex IV

Which of the following represents the most oxidized form of carbon?
(1) HCOOH       (2) HCHO
(3) CH₃OH        (4) CO₂    

The F₁ subunit of F₀F₁ ATP synthase synthesizes ATP from ADP in the mitochondrial inner membrane. Purified F₁ subunit hydrolyses ATP to ADP. Which one of the following reasons explains the difference between the activities of the F₁ subunit in soluble and membrane bound form?
(1) A conformational change in the F₁ subunit between the two environments.
(2) The lipid bilayer environment facilitates the synthesis of ATP by enhancing the rate of the dehydration reaction.
(3) The ATP synthesis reaction is driven by coupling to an electrochemical potential across the inner mitochondrial membrane.
(4) In the soluble form, the electrochemical potential drives the F₁ subunit to hydrolyze ATP.

Which one of the following correctly describes the effect of a mutation in phosphofructokinase (PFK), that leads only to the loss of allosteric regulation by ATP?
(1) Decrease in the activity of PFK
(2) Increase in the activity of PFK
(3) Decrease in the amount of ATP generated by PFK
(4) Increase in amount of ATP generated by PFK