Bioenergetic Past Paper
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1 / 28
What is the product formed at the end of the respiratory chain in inner membrane of mitochondria?
Explanation: ★ At the end of the electron transport chain, electrons are transferred to oxygen ★ Oxygen acts as the final electron acceptor ★ It combines with electrons and protons to form water ★ This step is essential to keep the chain functioning and produce ATP ★ Correct answer is C) Water
2 / 28
Which of the following receives electrons from FADH₂ during oxidative phosphorylation in cristae of mitochondria?
Explanation: ★ During oxidative phosphorylation, FADH₂ donates electrons to the electron transport chain ★ These electrons are first accepted by Coenzyme Q (ubiquinone) ★ Coenzyme Q then passes electrons to the cytochrome complexes ★ This helps in creating the proton gradient for ATP synthesis ★ Correct answer is B) Coenzyme Q
3 / 28
The production of energy is:
Explanation: ★ Anaerobic respiration produces energy very quickly ★ It does not require oxygen, so ATP is formed in fewer steps ★ Aerobic respiration is slower but produces more ATP ★ Hence, the rate of energy production is higher in anaerobic respiration ★ Correct answer is A) Faster in anaerobic respiration ⚡
4 / 28
The type of phosphorylation which involves the transfer of electrons from NADH to Coenzyme Q in the inner mitochondrial membrane is called:
Explanation:
★ In the inner mitochondrial membrane, NADH donates electrons to the electron transport chain ★ These electrons are transferred to Coenzyme Q (ubiquinone) ★ The energy released is used to synthesize ATP ★ This ATP formation linked with oxidation–reduction reactions is called oxidative phosphorylation ★ Correct answer is C) Oxidative Phosphorylation
5 / 28
During glycolysis, isomerisation takes place in the form of:
Explanation: ★ Isomerisation means conversion of one compound into another with the same formula ★ In glycolysis, Glucose-6-phosphate is isomerised into Fructose-6-phosphate ★ Also, Dihydroxyacetone phosphate is isomerised into G3P ★ These isomerisation steps help the pathway proceed smoothly ★ That’s why option B is correct
6 / 28
In aerobic respiration, glucose molecule is completely broken down into CO₂, H₂O and:
Explanation:Complete aerobic breakdown yields much more energy than glycolysis. It involves the Krebs cycle and Electron Transport Chain. The standard net yield cited for eukaryotes is 36 ATP. 2 ATP are lost shuttling electrons into mitochondria. Prokaryotes can yield 38 ATP.
7 / 28
Which of the following is used in baking?
Explanation:Baking relies on the fermentation process by yeast. Yeast performs anaerobic respiration (alcoholic fermentation) in the dough. It converts sugars into ethanol and carbon dioxide (CO₂). The produced CO₂ gas gets trapped in the dough. This trapped gas causes the dough to rise (leavening).
8 / 28
Net ATP produced at the end of glycolysis:
Explanation:Glycolysis produces a gross total of 4 ATP. However, it requires an investment of 2 ATP to start. Net ATP = Total Produced (4) - Total Invested (2). So the net gain for the cell is 2 ATP molecules. This occurs regardless of oxygen presence.
9 / 28
Each carrier in electron transport chain is first _______ and then _______.
Explanation: ★ In the electron transport chain, electrons are passed along carriers in a specific order ★ Each carrier first gains electrons (is reduced) and then loses electrons (is oxidized) as it passes them on ★ This redox cycle is essential for creating the proton gradient for ATP synthesis ★ Oxidation happens after reduction, not before ★ Correct answer is D) Reduced, oxidized
10 / 28
Explanation:Baking relies on yeast fermentation. Yeast converts sugars in dough into alcohol and CO₂. This occurs in an anaerobic (oxygen-poor) environment inside dough. The CO₂ bubbles get trapped, causing the dough to rise. The alcohol evaporates during the baking heat.
11 / 28
What is the end product of glucose by yeast in anaerobic respiration?
Explanation:Yeast performs alcoholic fermentation without oxygen. Glucose converts to Pyruvate, then to Acetaldehyde and CO₂. Acetaldehyde is reduced to Ethanol to regenerate NAD+. The final products released are Ethanol and Carbon Dioxide. This process is used in baking (CO₂ rises dough) and brewing.
12 / 28
The major enzymes involved in transfer of phosphate group from ATP to Glucose is:
Explanation: ★ The enzyme that transfers a phosphate group from ATP to another molecule is called a kinase ★ In glycolysis, hexokinase transfers phosphate from ATP to glucose to form glucose-6-phosphate ★ Isomerases, dehydrogenases, and decarboxylases perform different functions ★ Kinases are essential for the phosphorylation steps in metabolism ★ Correct answer is C) Kinase
13 / 28
The amount of energy present in bonds of glucose which is converted into ATP during anaerobic respiration is:
Explanation: ★ Anaerobic respiration releases very little energy from glucose ★ Only 2 ATP molecules are produced during anaerobic respiration ★ This corresponds to about 2% of the total energy stored in glucose ★ Most energy remains unused and is lost as heat ★ Correct answer is A) 2%
14 / 28
Out of 36 ATPs, how many are produced in electron transport chain?
Explanation: ★ The complete oxidation of one glucose molecule produces 36 ATP in eukaryotes ★ Glycolysis and Krebs cycle produce a small portion of ATP directly (4 ATP) ★ The majority of ATP is generated by the electron transport chain and oxidative phosphorylation ★ This contributes approximately 32 ATP ★ Correct answer is C) 32
15 / 28
What is the number of carbon atoms in pyruvic acid?
Explanation:Pyruvic acid (Pyruvate) is the end product of glycolysis. Glycolysis breaks down one 6-carbon Glucose molecule. The glucose is split into two identical molecules of Pyruvate. Therefore, each Pyruvate molecule contains 3 Carbon atoms. Its chemical formula is C₃H₄O₃.
16 / 28
The ATP formed in the preparatory phase of glycolysis is (are):
Explanation: The preparatory phase is an investment phase. The cell uses (consumes) 2 ATP molecules. No ATP is produced in this first half. ATP production happens in the oxidative (payoff) phase. Therefore, the amount formed in the prep phase is zero.
17 / 28
In alcoholic fermentation ________ ATP molecules are produced from 1 glucose molecule.
Explanation:Fermentation consists of glycolysis followed by reduction steps. Glycolysis produces a net gain of 2 ATP molecules. The subsequent steps to form ethanol do not produce more ATP. Therefore, the total energy yield is just the 2 ATP from glycolysis. This is much lower than the yield of aerobic respiration.
18 / 28
Which of the following steps of glycolysis does not involve ATP directly?
Explanation: ★ Conversion of glucose to glucose-6-phosphate uses ATP ★ Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate also consumes ATP ★ Conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate produces ATP ★ Conversion of G3P to 1,3-bisphosphoglycerate uses NAD⁺ and Pi, not ATP ★ Correct answer is C) Conversion of Glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate
19 / 28
Fats and proteins can be used as respiratory fuel. Which of the following serves as common molecule produced through their catabolism?
Explanation: ★ Fats are broken down by β-oxidation to form Acetyl-CoA ★ Proteins after deamination also enter respiration as Acetyl-CoA or its derivatives ★ Acetyl-CoA is a key molecule that enters the Krebs cycle ★ Pyruvate and G3P are mainly related to carbohydrate metabolism ★ Correct answer is A) Acetyl-CoA
20 / 28
The end product of glycolysis in anaerobic respiration is:
Explanation: ★ Glycolysis always produces pyruvate as the direct end product, whether oxygen is present or not ★ In anaerobic conditions, pyruvate is later converted into lactate (in animals) or ethanol + CO₂ (in yeast) ★ So the immediate end product of glycolysis itself is pyruvate ★ This pyruvate can then enter fermentation or aerobic pathways ★ Correct answer is C) Pyruvate
21 / 28
Pyruvic acid is acid of:
Explanation:Glycolysis splits one Glucose molecule (6 Carbons). It splits it exactly in half into two molecules. The result is two molecules of Pyruvic acid. Therefore, each Pyruvic acid has 3 Carbon atoms. Its formula is C₃H₄O₃.
22 / 28
The process of ATP synthesis through a combination of electrochemical and osmotic events is known as:
Explanation:This process relies on the Electron Transport Chain. It creates a proton gradient across a membrane (electrochemical). Protons move through ATP synthase (osmosis-like diffusion). This coupling of oxidation and gradient flow is Chemiosmosis. It is the definition of Oxidative Phosphorylation.
23 / 28
Which is the main event in electron transport chain?
Explanation:The ultimate purpose of the ETC is to generate ATP. It pumps protons to create a gradient. This gradient drives ATP synthase to make ATP. This process is called Oxidative Phosphorylation. Decarboxylation happens earlier in the Krebs cycle.
24 / 28
Which of the following is not a consequence of anaerobic respiration in human muscles cells?
Explanation:Anaerobic respiration produces very little energy (2 ATP). Aerobic respiration produces high energy (36 ATP). Therefore, anaerobic respiration is not a source of 'High consumption'. It is an emergency low-yield pathway. The buildup of lactic acid leads to cramps, pain, and tiredness.
25 / 28
The pathway to the breakdown of glucose, carried out by micro-organisms, is called:
Explanation:Microorganisms like yeast differ from human muscles. They break glucose down into ethanol and CO₂. This is Alcoholic Fermentation. Lactic acid fermentation is typical of animal muscles. Cellular respiration usually implies the aerobic process.
26 / 28
If oxygen is available, complete breakdown of glucose produces ______ ATP molecules in prokaryotes.
Explanation: ★ In prokaryotes, aerobic respiration occurs without mitochondria, so no energy is lost in transport ★ Complete oxidation of one glucose molecule produces 38 ATP in prokaryotes ★ This includes ATP from glycolysis, Krebs cycle, and electron transport chain ★ Eukaryotes produce slightly less (36 ATP) due to transport losses into mitochondria ★ Correct answer is C) 38
27 / 28
Electron transport chain explains:
Explanation:The ETC creates an electrochemical proton gradient. Protons flow back through ATP synthase to generate ATP. This process is known as Chemiosmosis. While it occurs in photophosphorylation, the ETC is the mechanism. It explains how the energy is physically converted to ATP.
28 / 28
Living cells do NOT directly acquire energy released from the breakdown of food molecules because:
If cells released food energy in one step, most of it would be lost as heat.Cells capture energy in small, controlled steps by making ATP.ATP stores usable energy for cellular work, preventing excessive heat loss and damage.
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