Tag: bio-chemistry

Quizzes (82) Questions (1918)

Questions Related to bio-chemistry

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Which of the following is a coenzyme?

  1. NAD

  2. NADP

  3. FAD

  4. All the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Co-enzymes are organic compounds, are bound to the the enzyme to make the enzyme catalytically active, but their association with the enzyme is only transient, usually occurring during the course of catalysis. Co-enzymes serve as co-factors in a number of different enzyme catalyzed reactions. The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin; flavin adenine dinucleotide (FAD) is derived from riboflavin vitamin.

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

All of the following is true about oxidative phosphorylation, except

  1. It occurs in the inner membrane of the mitochondrion.
  2. It involves O$ _2$ as the final electron acceptor.
  3. It produces 2 ATPs for each FADH$ _2$.

  4. It can occur under anaerobic conditions.

  5. It involves a proton gradient.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Oxidative phosphorylation is an ATP generating process, which takes place in the inner membrane of mitochondria of aerobic organisms. In a generic sense, this process generates ATP via transferring electrons from $FADH _2$ or NADH via a series of complex carriers. Oxygen is a vital constituent of this process for its role as the final electron acceptor. Therefore, oxidative phosphorylation cannot take place in absence of oxygen. Hence, the correct answer is (D).

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Which of the following is produced by oxidative phosphorylation?

  1. Oxygen and water

  2. NADH and ATP

  3. Pyruvate and NADPH

  4. Water and ATP

  5. Oxygen and NADH
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The metabolic process of releasing energy from food can be termed as oxidative phosphorylation. It occurs in the mitochondria of eukaryotic cell. In this process, the electrons are transported through different carriers ultimately to the oxygen molecule. these electrons reduce oxygen to form water and release energy which converts ADP to ATP. 

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

ATP is produced by oxidative phosphorylation in

  1. Glycolysis.

  2. Krebs cycle.

  3. Chemiosmosis.

  4. B and C only.

  5. A, B and C.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Glycolysis and Kreb's cycle form total 4 ATPs by substrate level phosphorylation wherein the direct transfer of phosphate group to ADP or GDP during chemical reactions leads to the synthesis of ATP/GTP. Oxidative phosphorylation is the process wherein oxidation of reducing equivalent generate energy to drive ATP synthesis. Chemiosmosis includes the use of proton gradient generated across the inner mitochondrial membrane, during transfer of electrons from NADH and FADH$ _2$ to O$ _2$, to drive ATP synthesis. During chemiosmosis, 10 molecules of NADH power synthesis of 10*3 = 30 ATP while 2 molecules of FADH$ _2$ power synthesis of 2*2 = 4 ATP.
Thus, the correct answer is option C.
Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Electron carriers such as nicotinamide adenine dinucleotide (NAD) are used in energy capturing processes such as photosynthesis and respiration. They play a central role in the redox reactions that occur at the time of energy harvest from the carbon source.
What is the function of an oxidizing agent?

  1. Molecules that donate electrons.

  2. A molecule that becomes oxidized.

  3. A molecule that gains electrons.

  4. Molecules that combines with oxygen.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

NAD$^+$ accepts electrons/H$^+$ released by water.

So, the correct answer is 'A molecule that gains electrons'

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Enzymes required for phosphorylation are located in .......... of chloroplast.

  1. Peristromium

  2. Plastidome

  3. Stroma

  4. Quantosome
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In chloroplast, the space enclosed by the inner membrane is called the stroma. It is colorless and homogeneous fluid. Phosphorylation is the process of addition of a phosphate group to ADP. The process of non-cyclic photophosphorylation takes place in the stroma lamellae with the help of enzymes present in it. Thus, the correct answer is option C. 

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Centre of phosphorylation is

  1. Ribosome

  2. Oxisome

  3. Peroxisome

  4. Spherosome.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • Oxidative phosphorylation refers to the process by which ATP molecules (energy currency) are produced in the mitochondria.
  • ATP is produced by the transfer of electrons from NADH or FADH2 to oxygen molecule with the help of electron carriers.
  • Oxysomes or F0-F1 particles refers to small round structures present within the folds of the cristae of the inner mitochondrial membrane.
  • F0 and F1 particles are found in the inner mitochondrial region and are attached to the cristae and help in ATP production and oxidation.
So, the correct answer is 'Oxisome'.

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Terminal oxidation comprises

  1. Synthesis of metabolic water

  2. Electron transport

  3. Oxidative phosphorylation

  4. All the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The respiratory breakdown of glucose in the presence of oxygen is an oxidative process. During this process, several intermediates such as pyruvic acid, isocitric acid, succinic acid and oxalic acid are oxidized. Each oxidation step involves the release of 2 H which goes to reduce various coenzymes i.e. NAD+ and FAD. Reduced NAD+ and FAD released in the glycolysis and Krebs cycle finally reduce oxygen to water. This transfer of H+ and e- from NADH + H+ or FADH2 to oxygen is not a simple process and the direct transfer of electrons from coenzymes to oxygen is thermodynamically not possible. To facilitate this transfer, many intermediate cytochromes and other carriers are arranged in a series which transport electrons from NADH or FADH2 to oxygen. This sequence of electron carriers constitutes electron transport system. The electron transport proceeds from carriers that have low redox potential to those having high redox potential. The electron transport down to the energy gradient through electron transport system leads to the formation of ATP from ADP and inorganic phosphate. This generation of ATP is called oxidative phosphorylation. 

Thus, the correct answer is option D. 

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Kreb's cycle takes place in

  1. Vesicles of E.R

  2. Mitochondria

  3. Dictyosomes

  4. Chloroplasts
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Kreb cycle is also known as the citric acid cycle or tricarboxylic acid cycle takes place in the inner membrane of mitochondria. It occurs there because the necessary enzyme for the Krebs cycle, succinic dehydrogenase is only found in the inner membrane of the mitochondria.

This is the only enzyme that has FAD as coenzymes and thus there is a formation of FADH₂ molecule.
Mitochondria are only associated with aerobic respiration.
So, the correct option is 'Mitochondria'

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

When a pair of electrons from NADH+$H^+$ transported through respiratory ETS, results in the formation of 

  1. 2 ATPs

  2. 4 ATPs

  3. 3 ATPs

  4. 5 ATPs
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Glycolysis and Krebs cycle yield certain reduced coenzymes like NADH+H+ and FADH2.
  • ETS is metabolic pathway of electron transport that oxidizes these coenzymes to release energy from them.
  • NADH+H+ gets oxidized at Complex I of ETS and as the electrons are transferred to other Complexes, it creates a proton gradient for ATP production. One NADH+H+ yields 3 ATPs and one FADH2 yields 2 ATPs.
  • So the correct answer is '3 ATPs'.