Bioenergetics MCQ - Biotechnology Engineering (BT) MCQ

Negative Gibbs free energy change for a process indicates that the process is spontaneous

The value of Gibbs tree energy change can be calculated using the formula or equation ΔG = ΔH - TΔS. This relationship indicates that it is not dependent on number of moles of the reacting species.

Randomness of the universe is always increasing.  This is stated in second law of thermodynamics

Option (a) is correct as according to Gibb's free energy equation ΔG = ΔH - TΔS.
Now if. ΔH = —ve (as given in option (a)) (at low temperature) and ΔS = +ve.
then ΔG = -ve (spontaneous)
option (b) is correct if
ΔH = +ve (as given in option (b)) and ΔS = +ve. Also if ΔS > ΔH (conditional), then ΔG = -ve (spontaneous)
Option (c) is correct
If ΔS = —ve (as given in option (c)) and ΔH = -ve. Also ΔH > ΔS (conditional) then. ΔG = -ve (spontaneous)

Complex I  (NADH dehydrogenase), complex III (cytochrome bc 1 complex), and complex IV (cytochrome c oxidase) of electron transport chain (ETC) pump protons across the inner mitochondrial membrane during electron transport. However, complex II (succinate dehydrogenase) which receives electrons from FADH2 is not involved in proton pumping during electron transport.

Option (a) is correct as according to Gibb's free energy equation ΔG = ΔH - TΔS.
Now if. ΔH = -ve (as given in option (a)) (at low temperature) and ΔS = +ve. then ΔG = -ve (spontaneous)
ption (b) is correct if
ΔH = +ve (as given in option (b)) and ΔS = +ve. Also if ΔS > ΔH (conditional), then ΔG = -ve (spontaneous)
Option (c) is conect
If ΔS = -ve (as given in option (c)) and ΔH = -ve. Also ΔH > ΔS (conditional) then. ΔG = -ve (spontaneous)

The value of Gibbs free energy change (ΔG) is zero at equilibrium as the direction of reaction is neither forward nor backward at equilibrium. However, the value of standard Gibbs fr ee energy change (ΔG°) cannot be zero at equilibrium unless the value of equilibrium constant is one (that will be a special case). However at equilibrium ΔG° is minimum
(We define ΔG° (pronounced “delta G naught prime*’) as the fr ee energy change of a reaction under “standard conditions" which are defined as:

• All reactants and products are at an initial concentration of 1.0M
• Pressure of 1.0 atm 
• Temperature is 25°C

Oxidation of one molecule of NADH via the respiratory chain generates 2.5 molecules of ATP in total. One is formed via complex I, 1 via complex III and 0.5 via complex IV. Complex II is not involved in proton pumping.

In the below figure, electron carriers of electron transport chain (ETC) are arranged in increasing order of their redox potential. Oxygen has the most positive redox potential and is the terminal electron acceptor in ETC.  

Oligomycin is a inhibitor of ATP synthase. Oligomycin inhibits ATP synthase by blocking its proton channel (F_o subunit) which is necessary for oxidative phosphorylation of ADP to ATP.

ATP produces high amount of energy, yet it is not the highest free energy molecule. The free energy of ATP hydrolysis is – 30 kJ per mole, while PEP has much higher energy of breakdown i.e. ~ 54 kJ per mole.

PEP has the highest Gibb’s energy of hydrolysis and ATP has two high energy bonds.

Option (b) is incorrect as cytochromes p450 are located mainly in the endoplasmic reticulum but they are also found in mitochondria in some tissues. Cytochrome P450 enzymes also function to metabolize potentially toxic compounds, including drugs and products of endogenous metabolism such as bilirubin, principally in the liver. The Human Genome Project has identified 57 human genes coding for the various cytochrome P450 enzymes.

Option (b) is incorrect as the electrochemical potential difference across the inner mitochondrial membrane caused by electron transport must be negative on the matrix side so that protons are forced to reenter via the ATP synthase to discharge the gradient and promote ATP synthesis.

Statement (a) is false
    Complex III is involved in proton pumping. Complex II is not involved in proton pumping
    Statement (b) is false
    DNP and FCCP are uncouplers. They uncouple electron transport chain from oxidative phosphorylation. Atractyloside is not a uncoupler. Atractyloside is a ADP/ATP translocase inhibitor.  
    Statement (c) is false        
    Oxygen is the terminal electron acceptor in ETC (electron transport chain)
    Statement (d) is false
    Reducing power of NADH is more than FADH₂. 1 molecule of 1 NADH gives 2.5 ATP and 1 molecule of FADH₂ gives 1.5 ATP.

This question can be solved using the formula ΔG° = —nFE°
n is equal to the number of electrons involved and potential must be converted to volts in order to obtain answer in joules.
i.e ΔGº= —2 x 96500 x (-0.03) = 5790 Joules = 5.79 kJ = 5.8 kJ. 

X→Y ; ΔG = 20 kJ mol^-1 ... (1)
ATP →ADP + pi; ΔG = —30 kJ mot^-1 ... (2)
Add reaction (1) and (2)
X + ATP → Y + ADP + p₁  ΔG = 20 — 30 = —10 kJ mol^-1 
In order to calculate the net Gibbs energy of a reaction, if the Gibbs energy of two separate reactions are given, add or substract the two given reactions in such a way that you obtain the desired reaction. In the same way energies are also added or subtracted. 

Correct Answer: 1)

Solution:

Concept: 

• Golden Rice is a crop that is modified genetically and biofortified.
• Biofortified crops have more nutritional value.
• Golden rice is modified in such a way that it can produce beta-carotene.
• When these rice are metabolized by the human body, the beta-carotene present in them is converted to vitamin A.
• These rice were modified by the gene from daffodil (Narcissus pseudonarcissus).
• Normal rice crop does not contain beta-carotene.

Explanation:

Option 1: It is vitamin A enriched, with a gene from daffodil– CORRECT

• Golden rice is rich in beta-carotene which on digesting is converted to vitamin A.
• And the gene is used from daffodil.
• Hence, this option is correct.

Option 2: It is pest resistant, with a gene from Bacillus thuringiensis– INCORRECT

• Pest resistant gene from Bacillus thrungenesis is used in the case of Bt cotton.
• In which the cotton plant is modified to be pest resistant.
• Hence this option is incorrect.

Option 3: It is drought tolerant, developed using Agrobacterium vector– INCORRECT

• Agrobacterium is the vector used in the modification of golden rice.
• But the gene inserted does not make the crop drought tolerant.
• Hence this option is incorrect.

Option 4: It has yellow grains, because of a gene introduced from a primitive variety of rice– INCORRECT

• It is correct that the color of the golden rice grain is yellow and that's why the term golden rice is used.
• But the gene used for modification is from daffodil not from a primitive variety of rice.
• Hence this option is incorrect.

So, the correct answer is option 1). 

This question can be solved using the formula ΔG =ΔGº + 2.303 RT log 
ΔG = -30.000 + 2.303 x 8.31 x 310 x log 10^-5
ΔG = -30.000 + 5933 x logl0^-5 
ΔG = -30000 + 5933 x (-5)
ΔG = -30000 - 29665
ΔG = -59665 = - 59.665 kJ = - 60 kJ