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 Multiple Choice QuestionsMultiple Choice Questions

1.

In gymnosperms, the Ovule is naked because

  • Ovary wall is absent

  • Integuments are absent

  • Perianth is absen

  • Nucellus is absent


A.

Ovary wall is absent

Gymnosperms are commonly known as 'naked seed plants because the ovary wall is not present and hence, the ovules remain unprotected or naked.


2.

How many ATP molecules could maximally be generated from one molecule of glucose, if the complete oxidation of one mole of glucose to CO2 and H2O yields 686 kcal and the useful chemical energy available in the high energy phosphate bond of one mole of ATP is 12 kcal?

  • Two

  • Thirty

  • Fifty seven

  • One


B.

Thirty

30 ATP molecules could be generated from 686 Kcal energy.

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3.

A competitive inhibitor of succinic dehydrogenase is 

  • malonate

  • oxaloacetate

  • alpha-ketoglutarate

  • malate


A.

malonate

Succinic dehydrogenase oxidised the succinate to fumarate. In eukaryotes, succinate dehydrogenase is tightly bound to the inner mitochondrial membrane, in prokaryotes to the plasma membrane. Electrons pass from succinate through the FAD and iron-sulphur centres before entering the chain of electron carriers in the mitochondrial inner membrane malonate, an analogue of succinate is a strong competitive inhibitor of succinate dehydrogenase and therefore, blocks the activity of citric and cycle.

In Krebs cycle, the reversible hydration of fumarate to malate is catalysed by fumarase enzyme.

In the last reaction of Krebs cycle NAD- linked L-malate dehydrogenase catalyses the oxidation of L-malate to oxaloacetate.

The isocitrate dehydrogenase in Krebs cycle catalyses oxidative decarboxylation of isocitrate to form alpha-ketoglutarate, which in next step through oxidative decarboxylation converted to succinyl Co-A

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4.

The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes  that Adenosine Triphosphate (ATP) is formed because

  • High energy bonds are formed in mitochondrial proteins

  • ADP is pumped out of the matrix into the intermembrane space

  • a proton gradient forms across the inner membrane

  • there is a change in the permeability of the inner mitochondrial membrane toward Adenosine Diphosphate (ADP)


C.

a proton gradient forms across the inner membrane

The production of ATP with the help of energy liberated during oxidation of reduced coenzymes and terminal oxidation is called oxidative phosphorylation. Peter Mitchell (1961) put forward a hypothesis known as a chemiosmotic hypothesis for ATP synthesis. According to this when electrons flow from dual proton, electron carrier to a non-hydrogen carrier the H+ in the intermembranous space than the matrix. Due to proton motive force, the protons flow back and energy liberated during this backflow of protons activate ATPase present in F1 head to synthesise ATP. 

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5.

Which one of the following statements is incorrect?

  • The residual air in lungs slightly decreases the efficiency of respiration in mammals

  • The presence of non-respiratory air sacs, increases the efficiency of respiration in birds

  • In insects, circulating body fluids serve to distribute oxygen to tissues

  • The principle of countercurrent flow facilitates efficient respiration in gills of fishes


A.

The residual air in lungs slightly decreases the efficiency of respiration in mammals

Residual air is the air that remains in lungs after the most forceful expiration. It is about 1200 ml. As the residual air remains in the lungs therefore it has no effect on respiration efficiency.

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6.

Cytochromes are found in

  • matrix of mitochondria

  • outer wall of mitochondria

  • cristae of mitochondria

  • lysosomes


C.

cristae of mitochondria

Cytochromes are present on the cristate, i.e. inner foldings of mitochondria. Cytochromes are iron (heme) containing proteins primarily responsible for transfer of electrons in ETC from ubiquinone to complex-V for generation of ATP(energy molecules) and terminal acceptor O2 in electron transport chain.
They are also called respiratory pigments, which are capable of performing both the oxidation and reduction reactions.

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7.

The overall goal of glycolysis, Krebs cycle and the electron transport system is the formation of

  • ATP in small stepwise units

  • ATP in one large oxidation reaction

  • Sugars

  • Nucleic acids


A.

ATP in small stepwise units

Glycolysis, Krebs cycle and electron transport system are meant for ATP synthesis in different steps. ATP is the energy currency of cell.

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8.

The energy -releasing process in which the substrate is oxidised without an external electron acceptor called

  • fermentation

  • photorespiration

  • aerobic respiration

  • glycolysis


D.

glycolysis

Glycolysis is the first stage of the breakdown of glucose in the cytoplasm of the cell without using oxygen (electron acceptor). It is a stepwise process in which one molecule of glucose breaks into two molecules of pyruvic acid and a net gain of energy is 2 ATP and 2NADH2 molecules.
The stepwise breakdown of the respiratory substrate to CO2 and H2O in presence of oxygen is referred as aerobic respiration. It is a catabolic process and generates a large amount of energy to form ATP.

Anaerobic respiration n micro-organisms are called fermentation. Alcoholic fermentation is a breakdown of glucose into ethyl alcohol and CO2 in presence of enzyme of micro-organism. Photorespiration is light-induced oxidation of photosynthetic intermediates with the help of oxygen without releasing energy.

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9.

Which statement is wrong for Krebs' cycle?

  • There are three points in the cycle where NAD+ is reduced to NADH + H+

  • There is one point in the cycle where FAD+ is reduced to FADH2

  • During conversion of succinyl CoA to succinic acid, a molecule of GTP is synthesised

  • The cycle starts with condensation of acetyl group (acetyl CoA) with pyruvic acid to yield citric acid


D.

The cycle starts with condensation of acetyl group (acetyl CoA) with pyruvic acid to yield citric acid

Krebs cycle starts with condensation of acetyl CoA (2C) with oxaloacetic acid (4C) to form citric acid (6C).

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10.

Which of the following statements regarding mitochondrial membrane is not correct?

  • The outer membrane is permeable to all kinds of molecules

  • The enzymes of the electron transfer chain are embedded in the outer membrane

  • The inner membrane is highly convoluted forming a series of infoldings

  • The outer membrane resembles a sieve


B.

The enzymes of the electron transfer chain are embedded in the outer membrane

In mitochondria, the enzymes of electron transport chain are found in the inner membrane while outer membrane contains enzymes involved in mitochondrial lipid synthesis and those enzymes that convert lipid substrates into forms that are subsequently metabolised in the matrix.
The outer membrane resembles a sieve that is permeable to all molecule of 10,000 daltons mole. weight or less including small proteins.
The inner membrane is impermeable and highly convoluted, forming a series of infoldings, known as cristate, in the matrix space.

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