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 bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Respiratory substrate yielding maximum number of ATP molecules is

  1. Ketogenic amino acids

  2. Glucose

  3. Amylose

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

The process of glycolysis in respiration requires glucose as the primary substrate to be oxidised. Any other substrate is first converted to glucose before it can enter glycolysis. Certain substrates like ketogenic amino acids, amylose, glycogen need to be converted to glucose first at a cost of some energy in the form of ATP. Hence their net yield of ATP is less than that of glucose as a substrate.

So the answer is 'Glucose'.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Metabolism of one palmitic acid yields 

  1. 36 ATP

  2. 56 ATP

  3. 129 ATP

  4. 48 ATP
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Oxidation of palmitic acid yields 7 NADH + 7 FADH2 + 8 acetyl-CoA in 7 cycles of mitochondrial beta-oxidation. Every acetyl-CoA yields 3 NADH + 1 FADH2 + 1 GTP (=ATP) during Krebs cycle. An average production of 3 ATP/NADH and 2 ATP/FADH2 using the respiratory chain, We get  131 ATP molecules. However, you have to use 2 ATP molecules for the initial activation of every fatty acid that is going to be oxidized in the mitochondria.

So the correct option is '129 ATP'.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

How many ATP molecules are released when one molecule of glucose is oxidised in our liver cells?

  1. 36

  2. 38

  3. 2

  4. 8
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

38 ATP molecules are produced for the oxidation of one molecule of glucose. 2 from glycolysis, 2 from the Citric acid cycle, and about 34 from the electron transport system.

So the correct option is '38.'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

How many ATPs are formed per glucose molecule in Krebs cycle?

  1. 2

  2. 24

  3. 6

  4. 28
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

During the process of Krebs cycle 2 molecules of ATP, 8 molecules of NADH and 2 molecules of FADH2 were produced per molecule of glucose. A total of 28 ATPs are produced during Krebs cycle per a glucose molecule.

So the correct option is '28.'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

From the oxidation of one molecule of palmitic acid (fatty acid), the number of ATP molecules gained as net are

  1. $131$
  2. $129$
  3. $38$
  4. $142$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The oxidation of fatty acid occurs in the following step in mitochondria:

1. activation of fatty acid
2. beta-oxidation
3. Kreb's cycle
Palmitic acid is made up of 16 carbons, so going by the formula C$ _{2n}$, then 2n=16 for palmitic acid, hence, n=8. So, 8 acetyl Co-A are produced. Now, n-1 will be the number of NADH and FADH$ _{2}$ produced, so, n-1=7 for palmitic acid. Hence, there will be 7 FADH$ _{2}$ and 7 NADH.
Now, 1 NADH gives 3 ATP, so 7 NADH will give 21 ATP
          1 FADH$ _{2}$ gives 2 ATP, so 7  FADH$ _{2}$ will give 14 ATP
          1 Acetyl Co-A through Kreb's cycle gives 12 ATP, so 8 Acetyl Co-A will give 96 ATP.
Hence, a total of 131 ATP will be formed. But 2 ATPs have been used in the activation of the fatty acid in the first step so, 131-2=129 ATPs as net will be formed. 
Hence, the correct answer is '129'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

In aerobic respiration,if 38 molecules of ATP are produced,then the number of ATP produced in glycolysis (X), pyruvate to acetyl- CoA (Y) and Krebs cycle (Z) will be

  1. X- 2,Y-6,Z-30

  2. X-8,Y-6,Z-24

  3. X-8,Y-10,Z-24

  4. X-2,Y-12,Z-24
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  •  Glycolysis: (2 ATP)
ATP formation by substrate phosphorylation = 4 ATP
ATP consumed in Glycolysis = 2 ATP 
  •  Pyruvate to Acetyl CoA: (2 NADH$ _{2}$ = 6 ATP) 
  • Kreb's Cycle: (30 ATP)
ATP formation by substrate phosphorylation = 2 ATP
ATP formation by oxidative phosphorylation = 28 ATP
So, the correct option is 'A) X- 2, Y - 6 ,Z-30'.
Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

Choose the correct answers from the alternatives given :
In certain organisms and under certain conditions, which of the following can be used as an energy alternative to glucose

  1. fatty acids

  2. glycerol

  3. amino acids

  4. all of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • in certain conditions such as starvation when sufficient amount of glucose is not present in the blood the foremost priority of the body is to provide brain with the sufficient amount of glucose.
  • So for the other body parts the energy that is to be provided can be done by the use of other substrates instead of glucose.
  • First alternative of glucose is fatty acid which is stored in the body. These fatty acid molecules are converted to acetyl coA by the process of beta oxidation and used in the kerbs cycle to provide the cell with energy.
  • Glycerol is also a fatty acid which is used as the other fatty acid in the kerbs cycle.
  • Amino acids are the part of protein molecules which are usually not stored in the body but can be used in the kerbs cycle whenever they are provided to the cell.
  • Therefore the answer 'all of these' is correct.
Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

Buchner was successful in extracting a respiratory enzyme complex

  1. ATP

  2. NADH

  3. Zymase

  4. Mitochondria
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Eduard Buchner was a German chemist who won the Noble prize in chemistry for his chance discovery in 1907. His brother Hans Buchner was a physician who conducted early research on blood proteins that could destroy bacteria. Eduard Buchner assisted his brother in his research. He produced yeast cell-free extracts for his brother who wanted to use them for immunological applications. In order to preserve the protein extract from yeast cells, he added sugar and while doing this he noticed the formation of bubbles. This meant that carbon dioxide and alcohol were being produced. Buchner had obtained an enzyme mixture called zymase from yeast that caused glycolysis and transformed the sugar into alcohol. Thus he discovered zymase, a complex of the enzyme that caused glycolysis in 1903. 

Thus, the correct answer is option C. 

Multiple choice biology respiration in plants fermentation cell respiration living organisms and energy production

In respiratory process which step is not related with decarboxylation?

  1. Alcoholic fermentation

  2. TCA cycle

  3. Oxidative decarboxylation of Pyruvate

  4. Lactic acid fermentation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
 Name of process   Decarboxylation occurence
 Alcoholic fermentation  Pyruvate (3C) $\rightarrow$  Acetaldehyde (2C)
 TCA cycle  Isocitrate$\rightarrow$ $\alpha$ ketoglutarate
 Oxidative decarboxylation Pyruvate $\rightarrow$ Acetyl CoA
 Lactic acid fermentation  No decarboxylation process occurs

So, the correct answer is ' Lactic acid fermentation '.

Multiple choice biology respiration in plants fermentation cell respiration living organisms and energy production

In anaerobic respiration of yeast

  1. ${ O } _{ 2 }$ is given out
  2. ${ CO } _{ 2 }$ is given out
  3. ${ CO } _{ 2 }$ is taken in
  4. ${ O } _{ 2 }$ is taken in
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Yeast respires anaerobically (in the absence of oxygen) . The process is known as fermentation. Glucose is the respiratory substrate.

The glucose is converted to pyruvate by the process of glycolysis. This process is independent of oxygen. If oxygen is absent, the pyruvate is broken by yeast into ethanol releasing carbon dioxide along with the production of 2 ATP.
So, the correct answer is 'CO$ _2$ is given out'.

Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

During fermentation what does not occurs ___________________.

  1. Oxidation of glucose into pyruvate

  2. Substrate level phosphorylation
  3. Oxidation of $NADH _2$

  4. Oxidative phosphorylation.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Answer is option D i.e. "Oxidative phosphorylation"
Fermentation occurs only when there is no oxidative phosphorylation to maintain the production of ATP by glycolysis. During fermentation, pyruvate is metabolized to various compounds such as lactic acid, ethanol and carbon dioxide or other acids. Also, fermentation reactions occur in the cytoplasm while oxidative phosphorylation occurs in mitochondria.

Multiple choice biology respiration in plants fermentation cell respiration living organisms and energy production

Select the number of incorrect statements for the process of fermentation.
A . It involves only partial breakdown of glucose.
B $NADH _2$ is oxidized to NAD by reduction of organic compound.
C. No ATP are produced during fermentation as it is extracellular process in some microbes.
D. There is no ETS and Kreb's cycle.
E. Maximum concentration of alcohol in alcohol in alcoholic brevarage is 100 %.

  1. 2

  2. 3

  3. 4

  4. 5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Fermentation can be defined as the partial breakdown of glucose to produce ethyl alcohol and carbon dioxide.
  • It releases energy in form of  ATP molecules.
  • 2 ATP molecules are produced per glucose.
  • 2NADH molecules provide energy which converts pyruvate into lactic acid.
  • The maximum concentration of alcohol in alcoholic beverages is 15%-16%.
  • Option C and E are incorrect statements.
  • So, the correct answer is'2'.