Biology

Cellular Respiration and Enzymes

1,721 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 zoology endocrine system and chemical co-ordination mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

Which of these is a second messenger?

  1. ATP

  2. cAMP

  3. GTP

  4. ATP and AMP
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Second messengers are the intracellular molecules released by the cell in response to exposure to extracellular molecules i.e. first messengers. Extracellular molecules trigger the release of the secondary messengers.
  • The cAMP is a derivative of the ATP. It is used for many intracellular signalling pathways.
  • ATP is a nucleotide. It is created during respiration in the mitochondria of eukaryotic cells.
  • AMP is nucleoside triphosphate i.e. a type of nucleotide. AMP is used as a monomer of RNA, also used to generate ATP.
  • GMP is a nucleotide, that is used as a monomer of RNA
So, the correct answer is 'cAMP' 
Multiple choice biology chemical coordination and integration mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

A major regulatory mechanism for multistep reactions is

  1. Presence of inhibitors

  2. Availability of activators

  3. Feed-back mechanism

  4. All the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • A feedback mechanism for multistep reactions is a biological occurrence wherein the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback).
  • For example, a positive feedback system is childbirth. During labour, a hormone called oxytocin is released that intensifies and speeds up contractions and facilitates childbirth.
  • Hence A major regulatory mechanism for multistep reactions is the feedback mechanism.
  • So, the correct answer is 'Feed-back mechanism'.
Multiple choice biology chemical coordination and integration mechanism of hormone action coordination in human beings- chemical control endocrine system in humans

In feedback inhibition, a metabolic pathway is switched off by the accumulation of end products.

  1. True

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

Accumulation of end products triggers an inhibiting action as a feedback inhibition of the metabolic pathway causing its inhibition. as a result, the metabolic pathway is switched off or halted. For example, the absence of the suckling stimulus leads to inhibition of the milk secretion.

Hence, the correct answer is 'true'.

Multiple choice zoology soil pollution industrial chemicals and their harmful effects toxic wastes and their effects soil pollution-causes

Which of the following determines the action of protective enzyme?

  1. Catalyses the removal of hydrogen atoms from a particular molecule

  2. Phosphorylation of hexose

  3. Breaks the pesticide into less toxic chemicals

  4. Both A and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The question specifically asks about the action of a protective enzyme in the context of pesticides. These enzymes function by chemically breaking down the toxic pesticide molecules into less harmful compounds.

Multiple choice biology food and it's constituents energy giving food carbohydrate and its test biological molecules

Which one will yield less than $4$ ${kcal}/{mol}$ of energy when phosphate bond is hydrolysed?

  1. ADP

  2. ATP

  3. Creatine phosphate

  4. Glucose 6-phosphate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The bond between two phosphate groups is a phosphoanhydride bond which is considered as high energy bond. ATP has two high energy phosphoanhydride bond. ADP has one phosphoanhydride bond. Creatine phosphate also has high phospahte bond between the nitrogen and phosphate. The phosphate bond in glucose phosphate is the weakest so it will yield less than 4kcal/mol of energy when phosphate bond is hydrolysed.

So, the correct answer is option D.

Multiple choice biology human system gas exchange and smoking gas exchange gas exchange in humans

The energy releasing process in living organisms is

  1. Reflex action

  2. Respiration

  3. Blood circulation

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

  • Respiration is the movement of oxygen from the outside environment to the cells within tissues and the transport of carbon dioxide in the opposite direction.
  •  During cellular respiration, glucose is broken down in the presence of oxygen to produce carbon dioxide and water. 
  • The energy released during the reaction is captured by the energy-carrying molecule ATP (adenosine triphosphate). Hence, The energy releasing process in living organisms is respiration.
So, the correct answer is 'respiration'.

Multiple choice biology digestive system of human assimilation of food and egestion assimilation of food components and importance of food

What fraction of $CO _2$ exhaled by animals is generated by the reactions of citric acid cycle, if glucose is the sole source of energy?

  1. $2/6$
  2. $3/6$
  3. $1/6$
  4. $6/6$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

One molecule of glucose (C6H12O6) produces 6 molecules of CO2. In the citric acid cycle, 2 CO2 are produced per acetyl-CoA, and 2 acetyl-CoA are produced per glucose, totaling 4 CO2 from the cycle. The remaining 2 CO2 come from the pyruvate dehydrogenase reaction.

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Isomaltase catalyzes the hydrolysis of bonds as shown in

  1. glc(1-6)glc

  2. glc(1-4)glc

  3. gal(1-6)glc

  4. fru(1-6)glc
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Isomaltase is an enzyme that breaks the bonds linking saccharides, which cannot be broken by amylase or maltase. It digests polysaccharides at the alpha 1-6 linkages

So, the correct option is 'glc(1-6)glc'

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Glucose is transported to cell by 

  1. ${ Na }^{ + }$ Symport
  2. ${ K }^{ + }$Symport
  3. ${ Na }^{ + }$ Antiport
  4. ${ K }^{ + }$Antiport
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Carbohydrates are hydrolysed by concerning enzymes and converted into monosaccharides like glucose and fructose. Monosaccharides are absorbed via the capillary blood with in the villus to finally reach into portal vein. Absorption of glucose molecules occurs along with, Na+ by active import. Fructose is absorbed passively through facilitated diffusion.

Multiple choice evs louis pasteur contribution of louis pasteur discoveries by louis pasteur discovery of microorganisms

Pasteur effect is due to

  1. Change from aerobic to anaerobic

  2. Providing oxygen to anaerobically respiring structures

  3. Rapid utilisation of ATP

  4. Nonsynthesis of ATP
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Most microorganisms such as fungi and bacteria can grow and flourish in the complete absence of oxygen and is known as fermentation. Pasteur described that fermentation is directly associated with the growth of metabolism of living matter. He observed that the rate of fermentation was considerably higher under anaerobic conditions as compared to aerobic conditions. The inhibition of anaerobic breakdown of sugars into carbon dioxide and ethyl alcohol due to the presence of oxygen under aerobic conditions is known as Pasteur effect. 

Thus, the correct answer is 'Providing oxygen to anaerobically respiring structures'.

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

What is ATP?

  1. A hormone

  2. A protein

  3. An enzyme which brings about oxidation

  4. A molecule which contains high energy bond
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Adenosine triphosphate (ATP) is a nucleotide with three phosphates. The ATP is produced by the addition of phosphorous to nucleoside adenosine.
  • The first phosphate is attached by an ester bond. This bond is a normal covalent bond and not a high energy bond. 
  • The two-terminal phosphates are bonded by high energy acid anhydride bonds. 

Thus one molecule of ATP contains two high energy bonds.

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

ATP stands for which of the following?

  1. Adenosine phosphate

  2. Adenine triphosphate

  3. Adenosine diphosphate

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

Chemically ATP is a nucleotide. In fact it is a higher order nucleotide because it contains not one but three phosphates. Compounds made up of (pentose) sugar and a nitrogenous base are called nucleosides. If the base is adenine, the nucleoside will be called adenosine. 

If one phosphate is attached to adenosine through an ester bond then the compound becomes a nucleotide and in this case it is called adenylic acid or adenosine monophosphate.
When second phosphorous is attached to the first phosphorous, through an acid anhydride bond, the nucleotide is called adenosine diphosphate. When third phosphorous is attached to the second phosphate through another acid anhydride bond, the nucleotide is called adenosine triphosphate or ATP.

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

Conversion of ATP to ADP releases

  1. Energy

  2. Enzyme

  3. Hormone

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

Adenosine Triphosphate or ATP has stored energy in its bond with the third phosphate group. However when required, ATP loses its third phosphate group to release energy and gets converted back to ADP. The energy released is in the form of chemical energy that the cells can use.

So the answer is 'Energy'.

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

How many ATPs are required by $C _4$ plants in synthesis of one molecule of glucose

  1. 18 ATP

  2. 30 ATP

  3. 12 ATP

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Most of the plants that are adapted to dry tropical regions have the $C _{4}$ pathway. e.g. Sugarcane, Maize, Sorghum,etc. These plants are known as $C _{4}$ plants.For the formation of sugars, $C _{4}$ plants undergo $C _{4}$ cycle as well as $C _{3}$ cycle or Calvin cycle. In these plants double fixation of carbon dioxide occurs.

ATP consumed in $C _{4}$ plants:
$C _{4}$ cycle - 2 ATP per $CO _{2}$ fixed
$C _{3}$ cycle - 3 ATP per $CO _{2}$ fixed 
Total - 5 ATP per $CO _{2}$ fixed
Thus, to form one molecule of glucose or to fix 6 $CO _{2}$, 6 X 5 = 30 ATP are consumed.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell
How many ATP and NADPH molecules are respectively required to make one molecule of glucose through the Calvin cycle?

  1. 3 and 2

  2. 9 and 6

  3. 18 and 12

  4. 12 and 18
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For every $CO _{2}$ molecule entering the Calvin cycle, $3$ molecules of $ATP$ and $2$ molecules of NADPH are required. To make one molecule of glucose, $6$ turns of the cycles are required 

$(6\times 3 ATP =18 ATP$ and $6\times 2 NADPH=12 NADPH)$.

In                            Out   
$6$ $CO _{2}$ $1\,\, glucose$
$18 ATP$ $18 ADP$
$12 NADPH$  $12 NADP$ So, the correct answer is '

18 and 12'.