Free Objective Test 02 Practice Test - 11th and 12th
Question 1
Which of the following molecules enters the citric acid cycle, after being broken down to acetyl CoA?
Lysine
Leucine
Fatty acids
SOLUTION
Solution : D
When carbohydrates are not available, other substrates are used for respiration. Proteins are broken down to amino acids and the amino acids can be used for respiration. Some amino acids enter the oxidative phosphorylation pathway as acetyl CoA, while others form pyruvate, oxaloacetate, alpha-ketoglutarate etc. Fatty acids basically enter citric acid cycle as acetyl CoA.
Question 2
The mechanism of ATP formation both in chloroplast and mitochondria is explained by ______.
SOLUTION
Solution : C
As per Peter Mitchell’s chemiosmotic – coupling hypothesis, outward pumping of protons across the inner chloroplast or mitochondrial membrane results in accumulation of protons between outer and inner membrane. A proton gradient is thus established. As protons now flow back passively down the gradient, the proton motive force is utilized to synthesize ATP.
Question 3
Cyanide resistant pathway is _____.
SOLUTION
Solution : A
Cyanide is a deadly poison of respiration and inhibit the activity of cytochrome –c oxidase complex (which contains cytochrome a and cytochrome a3) of the electron transport chain in aerobic respiration. Thus, no proton gradient will be established and no ATP will be formed. As the reoxidation of NADH and FADH2 ceases, due to the blockage of the ETC, the availability of hydrogen acceptors like NAD+ and FAD for Kreb’s cycle and glycolysis pathways also ceases. Thus stopping respiration. In anaerobic respiration the electron acceptors NAD+ and FADH2 can be regenerated anaerobically and therefore anaerobic respiration is a cyanide resistant pathway.
Question 4
When one molecule of glucose is completely oxidised during aerobic respiration, how many molecules of carbon dioxide are released due to tricarboxylic acid cycle?
SOLUTION
Solution : D
Six carbon dioxide molecules are released by complete oxidation of one glucose molecules. Two carbon dioxide molecules are released during oxidative decarboxylation reaction when the glycolytic products, that is two molecules of pyruvate are converted into two molecules of acetyl CoA and channelled into the Kreb's cycle. And four carbondioxide molecules are released during the Kreb’s cycle, during the breakdown of two molecules of isocitrate to alpha-ketoglutarate and the breakdown of alpha-ketoglutarates to succinyl CoA.
Question 5
In Kreb’s cycle ______.
SOLUTION
Solution : B
Kreb’s cycle, also known as tricarboxylic acid cycle is a process in which the glycolytic product - pyruvic acid is converted to CO2 and H2O. Pyruvic acid enters Kreb's cycle as acetyl-CoA. Kreb's cycle takes place in the mitochondria.
Question 6
The mechanism of ATP formation both in chloroplast and mitochondria is explained by ______.
SOLUTION
Solution : C
As per Peter Mitchell’s chemiosmotic – coupling hypothesis, outward pumping of protons across the inner chloroplast or mitochondrial membrane results in accumulation of protons between outer and inner membrane. A proton gradient is thus established. As protons now flow back passively down the gradient, the proton motive force is utilized to synthesize ATP.
Question 7
Cyanide resistant pathway is _____.
SOLUTION
Solution : A
Cyanide is a deadly poison of respiration and inhibit the activity of cytochrome –c oxidase complex (which contains cytochrome a and cytochrome a3) of the electron transport chain in aerobic respiration. Thus, no proton gradient will be established and no ATP will be formed. As the reoxidation of NADH and FADH2 ceases, due to the blockage of the ETC, the availability of hydrogen acceptors like NAD+ and FAD for Kreb’s cycle and glycolysis pathways also ceases. Thus stopping respiration. In anaerobic respiration the electron acceptors NAD+ and FADH2 can be regenerated anaerobically and therefore anaerobic respiration is a cyanide resistant pathway.
Question 8
When one molecule of glucose is completely oxidised during aerobic respiration, how many molecules of carbon dioxide are released due to tricarboxylic acid cycle?
SOLUTION
Solution : D
Six carbon dioxide molecules are released by complete oxidation of one glucose molecules. Two carbon dioxide molecules are released during oxidative decarboxylation reaction when the glycolytic products, that is two molecules of pyruvate are converted into two molecules of acetyl CoA and channelled into the Kreb's cycle. And four carbondioxide molecules are released during the Kreb’s cycle, during the breakdown of two molecules of isocitrate to alpha-ketoglutarate and the breakdown of alpha-ketoglutarates to succinyl CoA.
Question 9
In Kreb’s cycle ______.
SOLUTION
Solution : B
Kreb’s cycle, also known as tricarboxylic acid cycle is a process in which the glycolytic product - pyruvic acid is converted to CO2 and H2O. Pyruvic acid enters Kreb's cycle as acetyl-CoA. Kreb's cycle takes place in the mitochondria.
Question 10
The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that adenosine triophosphate (ATP) is formed because _______.
SOLUTION
Solution : C
As per chemiosmotic hypothesis ATP synthetase becomes active in ATP formation only where there is a protein gradient having a higher concentration of H+ or protons on the inner side as composed to the outer side
Question 11
All enzymes of TCA cycle are located in the mitochondrial matrix except one, which is located in the inner mitochondrial membranes in eukaryotes and cytosol in prokaryotes. This enzyme is ______.
SOLUTION
Solution : D
Succinate dehydrogenase enzyme is present on inner membrane of mitochondria and is a part of the complex II in the ETC. It catalyses the oxidation of succinate to fumarate in the Kreb's cycle and channels the FADH2 produced during this reaction into the ETC.
Question 12
Glycolysis takes place in ______.
SOLUTION
Solution : A
Glycolysis is a series of reactions that takes place in the cytoplasm of all prokaryotes and eukaryotes. The role of glycolysis is to produce energy (both directly and by supplying substrate for the citric acid cycle and oxidative phosphorylation) and to produce intermediates for biosynthetic pathway.
Question 13
Link enzyme in cellular respiration which catalyzes the substrate produced during glycolysis, and funnels it into the Kreb's cycle is ______.
SOLUTION
Solution : B
Pyruvic acid synthesized in glycolysis must enter inside the mitochondria, where oxidative decarboxylation occurs in the presence of NAD+ and coenzyme-A. This results in the formation of acetyl CoA which can enter the Kreb's cycle. This reaction is catalyzed by pyruvate dehydrogenase.
Question 14
Which of the following molecules is a product in respiration and substrate in photosynthesis?
SOLUTION
Solution : B
CO2 is released during respiration and forms the product of respiration. Whereas in photosynthesis, the carbon dioxide molecule is fixed to form glucose. Therefore CO2 forms the substrate in photosynthesis.
Question 15
Pyruvate dehydrogenase is the enzyme that converts __________.
SOLUTION
Solution : C
Pyruvatepyruvate dehydrogenase−−−−−−−−−−−−−−→Acetyl CoA
Pyruvate dehydrogenase is the enzyme that catalyzes the oxidation of pyruvate, by decarboxylating it to release carbon dioxide and it adds a coenzyme molecule to synthesize acetyl-CoA.