🔬 Biology · Class 11 · NEET
Respiration in Plants - Practice Questions with Answers 75 free MCQs on Respiration in Plants, each with its own worked answer and explanation. Glycolysis, the Krebs cycle, the electron transport chain, fermentation, and the respiratory quotient. The cellular energy-release counterpart to photosynthesis.
Take the timed Respiration in Plants chapterwise test → 75 practice questions on Respiration in Plants , sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Respiration in Plants notes .
Aerobic Respiration: Three Stages Glycolysis cytoplasm net 2 ATP, 2 NADH → Krebs Cycle mitochondrial matrix per glucose: 6 NADH, 2 FADH2, 2 ATP → Electron Transport Chain inner mitochondrial membrane ~32-34 ATP (bulk of total) Total: ~36-38 ATP per glucose - the ETC alone supplies most of it O2 is required only at the LAST step (ETC), as the final electron acceptor Aerobic respiration unfolds in three locations: glycolysis in the cytoplasm yields a small amount of ATP directly, the Krebs cycle in the mitochondrial matrix harvests electron carriers (NADH, FADH2 ), and the electron transport chain in the inner mitochondrial membrane uses those carriers to generate the bulk of the ATP, with O2 needed only at this final stage.
Easy - 25 questions Q2.
The coenzyme NAD, a hydrogen carrier in respiration, is derived from the vitamin:
A Vitamin CB Niacin (B3)C Vitamin DD Vitamin KShow answer & explanation →
Q3.
Acetyl CoA combines with oxaloacetate at the start of the Krebs cycle to form:
A Malic acidB Pyruvic acidC Citric acidD Lactic acidShow answer & explanation →
Q4.
A sudden rise in respiration rate (climacteric) accompanies the ___ of fruits:
A FloweringB GerminationC WiltingD RipeningShow answer & explanation →
Q5.
The complete aerobic breakdown of glucose is an ___ process, releasing energy:
A ExothermicB EndothermicC NeutralD ReversibleShow answer & explanation →
Q7.
One molecule of glucose is broken down by glycolysis into:
A 2 molecules of pyruvic acidB 1 molecule of CO<sub>2</sub>C 2 molecules of glucoseD Acetyl CoA directlyShow answer & explanation →
Q9.
The Electron Transport Chain (ETC) is located in the:
A Mitochondrial matrixB Inner mitochondrial membraneC Outer mitochondrial membraneD CytoplasmShow answer & explanation →
Q10.
Alcoholic fermentation by yeast converts pyruvate into:
A Lactic acidB Ethanol and CO<sub>2</sub>C Citric acidD Acetyl CoAShow answer & explanation →
Q11.
The approximate net ATP yield from the complete aerobic respiration of one glucose molecule is:
A 2 ATPB 4 ATPC 36-38 ATPD 100 ATPShow answer & explanation →
Q12.
Respiratory Quotient (RQ) is defined as:
A O<sub>2</sub> absorbed / CO<sub>2</sub> releasedB CO<sub>2</sub> released / O<sub>2</sub> absorbedC ATP produced / O<sub>2</sub> absorbedD Glucose used / CO<sub>2</sub> releasedShow answer & explanation →
Q13.
Fermentation, an anaerobic process, yields how much net ATP per glucose molecule compared to aerobic respiration?
A Considerably more ATP than aerobic respiration givesB Hardly any ATP is produced during fermentationC Roughly the same amount of ATP as aerobic respirationD Considerably less ATP than aerobic respiration givesShow answer & explanation →
Q14.
The breakdown of glucose into pyruvate, the first step common to both aerobic and anaerobic respiration, is called:
A Krebs cycle, occurring in the mitochondrial matrixB Glycolysis, occurring in the cytoplasmC Oxidative phosphorylation, at the inner membraneD Beta oxidation, breaking down fatty acidsShow answer & explanation →
Q15.
In lactic acid fermentation, pyruvate is reduced directly to lactic acid using:
A ATP generated by the electron transport chainB NADH produced earlier during glycolysisC CO<sub>2</sub> released from the Krebs cycle reactionsD Oxygen drawn in from the surrounding airShow answer & explanation →
Q19.
Respiration that uses oxygen is called:
A aerobic respirationB anaerobic respirationC photosynthesisD only fermentationShow answer & explanation →
Q20.
Respiration that occurs in the absence of oxygen is called:
A anaerobic respirationB aerobic respirationC photosynthesisD transpirationShow answer & explanation →
Q21.
The organelle called the "powerhouse of the cell" is the:
A mitochondrionB the chloroplastC the nucleusD the ribosomeShow answer & explanation →
Q22.
The gas released during aerobic respiration is:
A carbon dioxideB pure oxygenC pure nitrogenD pure hydrogenShow answer & explanation →
Q25.
Respiration occurs in the ___ cells of a plant, both day and night:
A all livingB only leafC only rootD deadShow answer & explanation →
Medium - 25 questions Q28.
The enzyme that makes ATP on the inner mitochondrial membrane is:
A RubiscoB HexokinaseC DehydrogenaseD ATP synthaseShow answer & explanation →
Q29.
In one turn of the Krebs cycle, substrate-level phosphorylation makes ATP (as GTP) numbering:
A OneB ThreeC SixD TwelveShow answer & explanation →
Q30.
Oxidative decarboxylation of pyruvate removes:
A Only waterB CO<sub>2</sub> with oxidationC Only oxygenD Only ATPShow answer & explanation →
Q31.
Pyruvate is converted to Acetyl CoA before entering the Krebs cycle, releasing:
A O<sub>2</sub>B CO<sub>2</sub>C ATP onlyD GlucoseShow answer & explanation →
Q32.
Lactic acid fermentation occurs in muscle cells when:
A Mitochondrial electron transport chains are saturated with surplus oxygenB Oxygen supply is insufficient (anaerobic conditions/oxygen debt)C Glycogen stores are fully depleted after prolonged starvationD Cytoplasmic ATP concentration exceeds the cell's regulatory thresholdShow answer & explanation →
Q33.
A germinating seed respiring purely on stored fat would show an RQ:
A Equal to 1B Less than 1C Greater than 1D Exactly 0Show answer & explanation →
Q34.
Each NADH produced during respiration contributes approximately how many ATP via the electron transport chain?
A 1 ATPB 2.5-3 ATPC 10 ATPD 0 ATPShow answer & explanation →
Q35.
Glycolysis, the first stage of respiration, takes place in which part of the cell?
A CytoplasmB NucleusC Mitochondrial matrixD Inner mitochondrial membraneShow answer & explanation →
Q37.
In anaerobic conditions, yeast cells convert pyruvate into:
A Acetyl CoA and waterB Glucose and oxygenC Ethanol and carbon dioxideD Lactic acid onlyShow answer & explanation →
Q38.
Which step of the Krebs cycle directly combines a 2-carbon compound with a 4-carbon compound to begin the cycle?
A Citrate combining with NADH to form isocitrateB Acetyl CoA combining with oxaloacetate to form citrateC Pyruvate combining with CO<sub>2</sub> to form oxaloacetateD Succinyl CoA combining with fumarate to form malateShow answer & explanation →
Q39.
During aerobic respiration, the role of oxygen is to:
A Activate the enzyme hexokinase to begin glucose breakdown under most conditions studiedB Provide carbon atoms that are incorporated into ATP in standard reference materialC Act as the final electron acceptor at the end of the electron transport chainD Directly combine with glucose in the cytoplasm during glycolysis as widely reportedShow answer & explanation →
Q40.
A respiratory substrate that gives a respiratory quotient (RQ) of exactly 1 is most likely:
A A protein rich in nitrogenB A fat such as tripalmitinC A carbohydrate such as glucoseD An organic acid such as oxalic acidShow answer & explanation →
Q41.
The first stage of respiration, in which glucose is split into pyruvate, is:
A glycolysisB the Krebs cycleC electron transportD the Calvin cycleShow answer & explanation →
Q43.
The Krebs cycle takes place in the ___ of the mitochondrion:
A matrixB outer membraneC cytoplasmD nucleusShow answer & explanation →
Q44.
Anaerobic respiration in yeast is also known as:
A fermentationB only glycolysisC photosynthesisD transpirationShow answer & explanation →
Q47.
In alcoholic fermentation, glucose is converted into ethanol and:
A carbon dioxideB some lactic acidC pure oxygenD plain waterShow answer & explanation →
Q49.
The electron transport chain of respiration is located in the:
A inner mitochondrial membraneB the whole cell cytoplasmC the entire cell nucleusD the plant cell wall layerShow answer & explanation →
Hard - 25 questions Q53.
The proton (H<sup>+</sup>) gradient that powers ATP synthesis builds up across the:
A Inner mitochondrial membraneB Outer mitochondrial membraneC Nuclear envelope layerD Plant cell wallShow answer & explanation →
Q54.
Fats give a respiratory quotient below 1 because their oxidation needs:
A Less oxygenB More oxygenC No oxygenD Only waterShow answer & explanation →
Q55.
The three CO<sub>2</sub> released for each pyruvate fully oxidised come from the link reaction and:
A Glycolysis onlyB Fermentation onlyC The Krebs cycleD The electron chainShow answer & explanation →
Q56.
Respiration is described as an 'amphibolic pathway' because:
A It mainly channels every carbon atom from glucose toward ATP generation, with little diversion permitted regardless of the cell's current biosynthetic demand for amino acid or lipid precursorsB Its intermediates (pyruvate, acetyl CoA, oxaloacetate, etc.) serve as starting points for biosynthesis of fatty acids and amino acids, not just energy releaseC It is physically split between the cytoplasm for glycolysis and the mitochondrial matrix for the Krebs cycle, a spatial separation that defines compartmentalization rather than its amphibolic characterD It can be run largely in reverse to regenerate glucose directly from carbon dioxide using the same enzymes and without any net energy input required to drive the reactionShow answer & explanation →
Q57.
In the electron transport chain, the final electron acceptor is:
A NAD+, regenerated for further use in glycolysisB FAD, embedded in Complex II of the inner membraneC Oxygen, reduced to waterD Pyruvate, shuttled into the mitochondrial matrixShow answer & explanation →
Q58.
The chemiosmotic mechanism of ATP synthesis in mitochondria is functionally analogous to:
A The semi-conservative unwinding and copying of the double helix by DNA polymeraseB The proton gradient mechanism in chloroplast thylakoids during photosynthesisC The stepwise cytoplasmic breakdown of glucose into pyruvateD The carrier-mediated movement of glucose against its concentration gradientShow answer & explanation →
Q59.
Substrate-level phosphorylation, in contrast to oxidative phosphorylation, refers to ATP synthesis that occurs:
A Generally during the light reactions of photosynthesis in chloroplasts according to standard texts in general clinical practiceB Directly during a reaction step of glycolysis or the Krebs cycle, without involving the electron transport chainC Mainly within the mitochondrial inner membrane through ATP synthase activity under most conditions studiedD Mostly after oxygen acts as the final electron acceptor at the chain's end in most observed cases under typical physiological conditionsShow answer & explanation →
Q60.
The complete oxidation of one glucose molecule via aerobic respiration yields a much higher net ATP than fermentation mainly because:
A Aerobic respiration fully oxidizes glucose to CO<sub>2</sub> and water, extracting far more energy via the electron transport chainB Aerobic respiration skips glycolysis largely, conserving more energy in typical laboratory settings under usual circumstancesC Fermentation occurs mainly in the mitochondrial matrix, limiting enzyme access under normal conditions as generally observedD Fermentation produces additional CO<sub>2</sub> that aerobic respiration does not release as frequently documented in most reference accountsShow answer & explanation →
Q61.
Cyanide inhibits aerobic respiration mainly by:
A Blocking cytochrome oxidase, the terminal enzyme of the electron transport chainB Competing with glucose for the active site of hexokinase in glycolysis according to most studiesC Inhibiting ATP synthase directly at the F<sub>0</sub> proton channel as widely reportedD Preventing pyruvate from entering the mitochondrial matrix in the majority of documented casesShow answer & explanation →
Q62.
In the Krebs cycle, the step converting succinate to fumarate is notable because it is the only step where:
A ATP is generated directly through substrate-level phosphorylation in most observed cases under typical physiological conditionsB The enzyme involved sits in the inner mitochondrial membrane and feeds electrons to the transport chainC Acetyl CoA condenses with oxaloacetate to begin the cycle according to standard texts in general clinical practiceD Carbon dioxide is released as a byproduct of the reaction in standard reference material under most conditions studiedShow answer & explanation →
Q63.
A respiratory quotient (RQ) greater than 1 is typically observed when a plant tissue is respiring substrates that are:
A Proteins mainly, since amino acid oxidation usually yields RQ above 1 in typical laboratory settingsB Fats, since their high hydrogen content raises the RQ above 1 under normal conditions as generally observedC Pure carbohydrates, since glucose oxidation usually gives an RQ above 1 as frequently documented in most reference accountsD Organic acids, which are more oxidized than carbohydrates and release relatively more CO<sub>2</sub> per O<sub>2</sub> consumedShow answer & explanation →
Q64.
Mitochondria are described as semi-autonomous organelles mainly because they:
A Replicate mainly when directed by chloroplast DNA in plant cells according to most studiesB Contain their own DNA and ribosomes, enabling synthesis of some of their own proteinsC Can move independently between cells without any external signal under usual circumstancesD Function largely independently of any nuclear-encoded proteins in the majority of documented casesShow answer & explanation →
Q65.
During oxidative decarboxylation of pyruvate, the pyruvate dehydrogenase complex requires several cofactors. Which of the following is essential for this multi-step reaction?
A Coenzyme A, NAD+, and thiamine pyrophosphate acting togetherB Water alone, since the reaction is a straightforward hydrolysisC ATP alone, since the reaction is a simple phosphorylation stepD Oxygen alone, since this is where O<sub>2</sub> is first consumed in respirationShow answer & explanation →
Q67.
The synthesis of ATP using energy released by the electron transport chain is called:
A oxidative phosphorylationB the process of glycolysisC the process of photolysisD the process of fermentationShow answer & explanation →
Q70.
The energy released during respiration that is not stored in ATP is lost mainly as:
A heatB visible lightC soundD electricityShow answer & explanation →
Q71.
Respiration is called an amphibolic pathway because it also provides intermediates for:
A biosynthesisB only breakdownC photosynthesisD excretionShow answer & explanation →
Q74.
The link reaction, in which pyruvate is converted to acetyl-CoA, takes place in the:
A mitochondrial matrixB the cell cytoplasmC the cell nucleusD the plant cell wallShow answer & explanation →