Biology

Cellular Respiration and Enzymes

1,551 Questions

Explore key concepts of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. These questions also cover ATP production, anaerobic respiration, and essential metabolic pathways. This topic forms a core part of the biology syllabus for many competitive examinations.

Glycolysis and metabolic pathwaysKrebs cycle processesElectron transport chainATP production countAnaerobic respiration products

Cellular Respiration and Enzymes Questions

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

For bacteria to continue growing rapidly when they are shifted from an environment containing $O _{2}$ to an anaerobic environment, they must

  1. Produce more ATP per mole of glucose during glycolysis

  2. Produce ATP during oxidation of glucose

  3. Increase the rate of glycolysis

  4. Increase the rate of TCA cycle
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For bacteria to continue growing rapidly when they are shifted from an environment containing O2 to an anaerobic environment, they must increase the rate of glycolysis. Although the amount of ATP produced by anaerobic glycolysis (2) is very less as compared to ATP produced by aerobic glycolysis (38), glycolysis under anaerobic condition is very quick process. It generates ATP very quickly. 

Thus, the correct answer is 'Increase the rate of glycolysis.'

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

How many molecules of oxygen are used during the glycolysis of one glucose molecule?

  1. 2

  2. 32

  3. 38

  4. Zero

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Glycolysis is the process of partial oxidation of glucose into two molecules of pyruvic acid through the enzyme-mediated reaction series.
  • Here two molecules of ATP are utilized. First during the conversion of Glucose to Glucose-6-phosphate and second during the conversion of Fructose-6-phosphate to Fructose-1,6-biphosphate.
  • 4 molecules of ATP are synthesized during 2 substrate based phosphorylated reaction. 
  • First 2 molecules of ATP released during the conversion of 2 molecules of 1,3 bisphosphoglyceric acid to 2 molecules of 3 phosphoglyceric acids. Next 2 molecules are released during the conversion of 2 molecules of phosphoenolpyruvate to 2 molecules of pyruvic acid. 
  • In splitting of one glucose molecule into two pyruvates only the enzymes present in the cytoplasm are used and no oxygen is required. 
  • It is an anaerobic process.
So, the correct option is D ' zero'.
 

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Choose the correct answers from the alternatives given :
Which of these processes occurs in the cytosol?

  1. Krebs cycle

  2. Glycolysis

  3. Electron transport system

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

The process of cellular respiration occurs into three steps :

  1. Glycolysis
  2. Krebs cycle 
  3. Terminal oxidation
Glycolysis is the basic step of respiration where glucose is broken down into two molecules of pyruvate which occurs in the cytoplasm and does not require oxygen while other processes like Krebs cycle, electron transport system and transition reaction occurs in the mitochondria of the cell.
So, the correct option is ' Glycolysis'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

The inner membrane of mitochondrion is very selective in respect to entering, molecule. Name a molecule that regularly enters in it

  1. Pyruvic acid

  2. Glucose

  3. ATP

  4. Oxaloacetic acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Cellular respiration occurs firstly in the cytoplasm and then in mitochondria. Glycolysis occurs in the cytoplasm in which glucose breaks into two pyruvates which are transported to mitochondria through an inner mitochondrial membrane which performs the Krebs cycle. This pyruvate regularly enters the mitochondria to start the Krebs cycle and complete cellular respiration.

So, the correct option is ' pyruvic acid'. 

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Choose the correct answers from the alternatives given :
Glycolysis takes place in

  1. eukaryotic cells only

  2. cyanobacteria only

  3. anaerobic bacteria

  4. virtually all cells
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Glycolysis is the foremost step in the process of cellular respiration which breakdown glucose molecule to extract energy. It is the part of the metabolism of nearly all the cells and organisms as it is the basic process, it does not require oxygen hence it is anaerobic. it occurs in the cytoplasm of both prokaryotes as well as eukaryotes.

So, the correct option is ' Virtually all cells'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Choose the correct answers from the alternatives given :
The rate of glycolysis is

  1. stimulated by ATP

  2. stimulated by oxygen

  3. inhibited by ADP

  4. stimulated by ADP
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • For the glycolysis to start the glucose molecule is firstly to be converted to Glucose 6 phophaste after that only will the reaction proceed for which ATP is required which is converted to ADP after the conversion.
  • So when the amount of the ATP in the cell is reduced and the amount of ADP is increased the process is to be started to provide the cell with the required ATP.
  • So the receptors of the cells or the gene that regulate the process of glycolysis are somewhat stimulated by the presence of increased amount of ADP as there are other factors also which control the process of glycolysis such as the amount of ATP, Pyruvic acid etc.
  • Therefore it can be said that the ADP is one of the stimulating factors for the Glycolysis process.
  • Therefore the correct answer is option 'stimulated by ADP'.
Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Choose the correct answers from the alternatives given :
Which metabolic pathway is common to both the aerobic and anaerobic catabolism of sugar?

  1. Synthesis of acetyl CoA from pyruvic acid

  2. Glycolysis

  3. Krebs cycle

  4. Electron transport chain
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • First part for both type of respiration aerobic and anaerobic is glycolysis where the sugar is broken down to pyruvic acid.
  • Glycolysis takes place in the cytoplasm of the cells and does not require for the presnece of any organelles.
  • So both kind of organisms are able to perform glycolysis whether they perform aerobic or anaerobic reactions.
  • Thus it can be said that in both kind of respiration glycolysis is a common process which provides substrate for further reactions in both kind of respiration. Pyruvic acid which converts to acetyl coA and takes part in kerb cycle while pyruvic acid converts to lactic acid or alcohol in fermentation reaction.
  • Therefore the correct answer is option 'Glycolysis'.










Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Choose the correct answers from the alternatives given :
Glycolysis starts and ends m the 

  1. cytoplasm

  2. plasma membrane

  3. nucleus

  4. mitochondrion
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • The whole process of glycolysis takes place in the cytoplasm it does not require any membrane bound organelles to perform the reaction.
  • GLycolysis is the main process to obtain energy in the prokaryotic organisms where there are no membrane bound organelles present and glycolysis is the only source of obatining energy.
  • Therefore the enzymes and substrate required for the process of glycolysis are present in the cytoplasm and the whole reaction takes place in the cytoplasm.
  • Therefore the answer 'cytoplasm' is correct.
Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Choose the correct answers from the alternatives given :
Select the true statement

  1. glycolysis produces equal numbers of ATP molecules regardless of the presence or absence of oxygen

  2. more ATP molecules are produced per molecule of glucose when glycolysis occurs in aerobic conditions

  3. more ATP molecules are produced per molecule of glucose wvhen glycolysis occurs in anaerobic conditions

  4. none of the above are true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation


  • As the reaction of glycolysis takes place in the cytoplasm of cell where it can proceed in the absence of oxygen molecule. 
  • It does not require the presence of oxygen of to proceed further.
  • It will produce 4 ATP molecules and use 2 molecules of ATP, which gives the cell the net gain of 2 ATP at the end of the glycolysis process.
  • Presence of oxygen or absence of oxygen does not hinder the process of glycolysis and prodution of ATP by glycolysis.
  • Therefore the answere option 'glycolysis produces equal numbers of ATP molecules regardless of the presence or absence of oxygen' is true.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

State whether the following statements are true or false.
Glycolysis and fermentation are thought to be older processes than the electron transport system and the Krebs cycle 

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The initial processes for energy generation by prokaryotes included anaerobic processes such as Glycolysis and Fermentation. The latter happening of endosymbiosis was the major revolution in bringing up aerobic respiration with the advent of mitochondria within the cells.

Before that, the energy generation was an anaerobic process without using oxygen in Glycolysis and Fermentation.
So, the correct option is 'True'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

State whether the following statements are true or false.
The most efficient pathway for ATP production in animal cells is by glycolysis.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • Glycolysis is the pathway were one molecule of glucose is broken down to 2 molecules of pyruvate by the phosphorylation and dephosphorylation reactions.
  • 2 molecules of ATP are used in phosphorylation reaction of glycolysis. First while conversion of glucose to glucose-6-phosphate and the second one during conversion of fructose to fructose1,6-biphosphate.
  • While 4 ATP molecules are produced in the dephosphorylation reaction. 2 ATP are produced while conversion of  1,3 bisphosphoglyceric acid to 3-phosphoglyceric acid and another 2 ATP during conversion of phosphophenolepyruvate to pyruvic acid.
  • So the net gain of ATP at the end of one glycolysis reaction is 2. SO glycolysis is not a efficient pathway for the production of ATP in animal cells, in turn it is a part of the chain of reaction which take place before aerobic or anaerobic respiration in animal cells.
  • Glycolysis provided the reaction of aerobic and anaerobic respiration with the substrates to carry the reaction further and produce ATPs in mitochondria where the prominent reactions for production of energy in animal cell takes place.
  • Glycolysis takes place in the cytoplasm of the cell and the product of the glycolysis is transported to the mitochondria.
  • Therefore Glycolysis is not the most efficient pathway for ATP production. So the sentence above is FALSE and therefore the option 'False' is correct.
Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Choose the correct answers from the alternatives given :
Which of the following does not form during glycolysis?

  1. NADH

  2. ATP

  3. Pyruvate
  4. $FADH _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • NADH is formed in the glycolysis after the reaction of conversion Glyceradehyde 3 phosphate to 3 phosphoglyeric acid when electrons re released and are accepted by the NAD.
  • ATP is formed  while conversion of 1,3 bisphosphoglyceric acid to phospoglyceric acid and also while conversion of phosphophenol to pyruvic acid.
  • And pyruvate is the end product of the glycolysis.
  • FADH is the product which is formed  during the the kerb cycle while formation of succunic acid to malic acid.
  • Thereofte the correct answer is '$FADH _2$'
Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration
During complete metabolism of glucose, the number of ATP formed is

  1. 2

  2. 12

  3. 36

  4. 44
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
There is a gain of $2$ ATP molecules during glycolysis and $2$ ATP(GTP) molecules during double Krebs cycle. A total of $10$ ${NADH} _{2}$ molecules are formed in aerobic respiration. Thus, the net gain from complete oxidation of a molecule of glucose in muscle and nerve cells is 36 ATP molecules ($10$ ${NADH} _{2}=30 ATP, 2{FADH} _{2}=4 ATP$, four formed by substrate-level phosphorylation in glycolysis and Krebs' cycle and two consumed in transport of the ${NADH} _{2}$ molecules into mitochondria). In aerobic prokaryotes, heart, liver and kidneys, $38$ ATP molecules are produced per glucose molecule oxidised. passage of ATP molecules from inside of mitochondria to the cytoplasm is through facilitated diffusion.
Thus, there is a net gain of $36$ or $38$ ATP molecules depending upon the type of aerobic respiration.
[Note: $1{NADH} _{2}=3ATP$ and $1{FADH} _{2}=2ATP$].
So the correct answer is '36'.
Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration
Which of the following statements regarding metabolic pathways is incorrect?

  1. Many of the steps of glycolysis can run in reverse

  2. Starch, sucrose or glycogen must be hydrolysed before it can enter the glycolysis.

  3. After fats are digested, glycerol enters glycolysis by forming DHAP.

  4. After fat digestion, fatty acids can no longer participate in cellular respiration.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

After fats are digested into fatty acids and glycerol, the following products can take place in cellular respiration.

So, the correct option is 'After fat digestion, fatty acids can no longer participate in cellular respiration.'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

The balance sheet for ATP production in glycolysis has been given below. Select the option which correctly fills up the blanks for P,Q,R and S. ['X' stands for 'nil'].

Steps ATP Utilisation ATP Production
1. $Glucose\rightarrow Glucose-6-phosphate$ P X
2. $Fructose-6-phosphate\rightarrow Fructose-1, 6-bisphosphate$ 1 Q
3. $1,3-bisphosphoglyceric acid\rightarrow 3-Phospho-glyceric acid$ X R
4. $2-Phosphoenol pyruvic acid\rightarrow Pyruvic acid$ S 2

  1. P-1; Q-X; R-X; S-2

  2. P-1; Q-X; R-2; S-X

  3. P-2; Q-1; R-X; S-1

  4. P-X; Q-1; R-2; S-X
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
During glycolysis, the conversion of glucose into glucose-6-phosphate requires the utilization of one ATP molecule and no ATP molecules are produced. Similarly, there is no production of ATP molecules during the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate and only one ATP molecule is utilized. Also, during the conversion of 1,3−bisphosphoglycericacid to 3−Phospho−glycericacid and that of 2−Phosphoenolpyruvicacid to pyruvic acid, tow molecules each of ATP as utilized and no ATP is produced.

So, the correct answer is 'P-1; Q-X; R-2; S-X'.