Answer the following question. Write explanatory notes on Electron transport chain. - Biology

Short Note

Answer the following question.

Write explanatory notes on Electron transport chain.



  1. NADH2 and FADH2 produced during glycolysis, connecting link reaction and Krebs cycle are oxidized with the help of various electron carriers and enzymes.
  2. These carriers and enzymes are arranged on the inner mitochondrial membrane in the form of various complexes as complex I, II, III, VI, and V.
  3. NADH+H+ is oxidized by NADH dehydrogenase (complex I) and it's electrons are transferred to ubiquinone (coenzyme Q-CoQ) present on the inner membrane of mitochondria. Reduced ubiquinone is called as ubiquinol.
  4. FADH2 is oxidized by complex II (Succinate dehydrogenase) and these electrons are also transferred to CoQ.
  5. During oxidation of NADH+H+ and FADH2, electrons and protons are released but only electrons are carried forward whereas protons are released into the outer chamber of mitochondria (intermembrane space).
  6. Ubiquinol is oxidized by complex-III (Cytochrome bc1 complex) and it's electrons are transferred to cytochrome C. Cytochrome C is a small, iron-containing protein, loosely associated with the inner membrane. It acts as a mobile electron carrier, transferring the electrons between complex III and IV.
  7. Cytochrome C is oxidized by complex IV or cytochrome C oxidase consisting of cytochrome a and a3. Electrons are transferred by this complex to the molecular oxygen. This is terminal oxidation.
  8. Reduced molecular oxygen reacts with protons to form a water molecule called as metabolic water.
  9. Protons necessary for this are channelled from the outer chamber of mitochondria into inner chamber by F0 part of oxysome (complex V) present in the inner mitochondrial membrane. This proton channelling by F0 is coupled to the catalytic site of F1 which catalyzes the synthesis of ATP from ADP and inorganic phosphate. This is oxidative phosphorylation. As the transfer of protons is accompanied by a synthesis of ATP, this process is named 'Chemiosmosis' by Peter Mitchell.

Significance of ETS:

  1. Major amount of energy is generated through ETS or terminal oxidation in the form of ATP molecules.
  2. Per glucose molecule 38 ATP molecules are formed, out of which 34 ATP molecules are produced through ETS.
  3. Oxidized coenzymes such as NAD and FAD are regenerated from their reduced forms (NADH+H+ and FADH2) for recycling.
  4. In this process, energy is released in a controlled and stepwise manner to prevent any damage to the cell.
  5. ETS produces water molecules.
Concept: Formation of ATP
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Chapter 13: Respiration and Energy Transfer - Exercise [Page 159]


Balbharati Biology 11th Standard Maharashtra State Board
Chapter 13 Respiration and Energy Transfer
Exercise | Q 3. (G) (iii) | Page 159


Fill in the blank and explain the statement.

At the end of glycolysis, ________ molecules are obtained.

Write definition.

Aerobic respiration

Distinguish between

Aerobic and anaerobic respiration.

Give scientific reason.

Cell division is one of the very important properties of cells and living organisms.

Write the correct option from the given multiple options.
Which of the following vitamin is necessary for synthesis of NADH2?
a) Vitamin B2
b) Vitamin B5
c) Vitamin C
d) Vitamin K

Choose the correct option.

Which step of Kreb's cycle operates substrate-level phosphorylation?

Fill in the blank with a suitable word.

In the prokaryotes ______ molecules of ATP are formed per molecule of glucose oxidised.

Fill in the blank with a suitable word.

F1- F0 particles participate in the synthesis of _______.

Fill in the blank with a suitable word.

During glycolysis ______ molecules of NADH+H+ are formed.

Answer the following question.

When and where does anaerobic respiration occur in man and yeast?

Answer the following question.

Why is less energy produced during anaerobic respiration than in aerobic respiration?

Answer the following question.

Which compound is the terminal electron acceptor in aerobic respiration?

Answer the following question.

Where is the respiration electron transport system located in a cell?

Protein located in bones is ___________.

We get __________ energy from lipids.

Give scientific reason.

We feel tired after exercising.

Give scientific reason.

Some higher plants, animals and aerobic microorganisms also sometimes perform anaerobic respiration.

Which amino acids are obtained after digestion of proteins?

Explain the use of fatty acids.

State two groups/types of vitamins.

State six types of vitamins.

What are the main steps of anaerobic respiration?

Which hormones are formed from the fatty acids?

Why is water an essential nutrient?

Write the importance of fibers in our diet.

Complete the following concept map.

During which of the following steps of glycolytic pathway ATP is directly formed?

  1. 3 - phospboglyceric acid to 2 phosphoglycerate
  2. Phosphoenolpyruvate to pyruvic acid
  3. 1, 3 - bisphosphoglyceric acid to 3 phosphoglycerate
  4. Fructose 1, 6 - bisphospbate to glyceraldehyde - 3 - phosphate

Identify the CORRECT way/s of Phosphorylation.

Read the following statements and select the CORRECT option.

Statement I: In oxidative phosphorylation ATP is synthesized by using the energy released during the oxidation of substrates like NADH+ H+ and FADH2.

Statement II: Substrate-level phosphorylation is a direct phosphorylation of ADP by transfer of a phosphate group from any suitable substrate.

Oxidative phosphorylation refers to ______

In glycolysis,____________ ATP molecules are formed directly.

Where does the oxidative phosphorylation occur?

Complete the following analogy and select the correct option.

Respiration: Catabolic process:: ______ : Anabolic process

In the mitochondrion, energy is stored in the form of ____________.

The main purpose of respiration is to convert ______

Which of the following statement is incorrect about ATP?


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