Explain ETS.
An electron transport chain or system (ETS) is a series of coenzymes and cytochromes that take part in the passage of electrons from a chemical to its ultimate acceptor. Reduced coenzymes participate in electron transport chain. Electron transport takes place on cristae of mitochondria [oxysomes ( F0 -F1 , particles) found on the inner surface of the membrane of mitochondria]. NADH formed in glycolysis and citric acid cycle are oxidised by NADH dehydrogenase (complex I) and the electrons are transferred to ubiquinone. Ubiquinone also receives reducing equivalents via FADH2 through the activity of succinate dehydrogenase (complex II). The reduced ubiquinone is then oxidised by transfer of electrons of cytochrome c via cytochrome Fc, complex (complex III). Cytochrome c acts as a mobile carrier between complex III and complex IV. Complex IV refers to cytochrome c oxidase complex containing cytochromes a and a3and two copper centres. When the electrons are shunted over the carriers via complex I to IV in the electron transport chain, they are coupled to ATP synthetase (complex V) for the formation of ATP from ADP and Pi. Oxygen functions as the terminal acceptor of electrons and is reduced to water along with the hydrogen atoms. Reduced coenzymes (coenzyme I, II and FAD) do not combine directly with the molecular O2. Only their hydrogen or electrons are transferred through various substances and finally reach O2. The substances useful for the transfer of electron are called electron carriers. Only electrons are transferred through cytochromes (Cyt F1 Cyt c,,C2, a, a3) and finally reach molecular O2. Both cytochrome a and a3 form a system called cytochrome oxidase. Copper is also present in Cyt a3 in addition to iron. The molecular oxygen that has accepted electrons now receives the protons that were liberated into the surrounding medium to give rise to a molecule of water. The liberated energy is utilised for the synthesis of ATP from ADP and Pi.
We commonly call ATP as the energy currency of the cell. Can you think of some other energy carriers present in a cell? Name any two.
The energy yield in terms of ATP is higher in aerobic respiration than during anaerobic respiration. Why is there anaerobic respiration even in organisms that live in aerobic condition like human beings and angiosperms?
Name the site(s) of pyruvate synthesis. Also, write the chemical reaction wherein pyruvic acid dehydrogenase acts as a catalyst.
Comment on the statement – Respiration is an energy producing process but ATP is being used in some steps of the process.
Energy is released during the oxidation of compounds in respiration. How is this energy stored and released as and when it is needed?
Respiratory pathway is believed to be a catabolic pathway. However, nature of TCA cycle is amphibolic. Explain.
ATP produced during glycolysis is a result of substrate level phosphorylation. Explain.
Mention the important series of events of aerobic respiration that occurs in the matrix of the mitochondrion as well as one that takes place in the inner membrane of the mitochondrion.
Give an account of Glycolysis. Where does it occur? What are the end products? Trace the fate of these products in both aerobic and anaerobic respiration.
The energy yield in terms of ATP is higher in aerobic respiration than during anaerobic respiration. Explain.
Respiration requires 02. How did the first cells on the earth manage to survive in an atmosphere that lacked 02?
The product of aerobic glycolysis in skeletal muscle and anaerobic fermentation in yeast are respectively ________ and ______.
Match the following and choose the correct option from those given below.
| Column A | Column B | ||
| A. | Molecular oxygen | (i) | a-Ketoglutaric acid |
| B. | Electron acceptor | (ii) | Hydrogen acceptor |
| C. | Pyruvate dehydrogenase | (iii) | Cytochrome C |
| D. | Decarboxylation | (iv) | Acetyl Co A |
(a) A(ii), B(iii), C(iv), D(i)
(b) A(iii) B(iv) C(ii) D(i)
(c) A(ii)B(i)C(iii)D(iv)
(d) A(iv) B(iii) C(i) D(ii)
Do you know any step in the TCA cycle where there is substrate level phosphorylation. Which one?
In the following flow chart, replace the symbols a,b,c and d with appropriate terms. Briefly explain the process and give any two application of it.
In a way green plants and cyanobacteria have synthesised all the food on the earth. Comment.
When a substrate is being metabolised, why does not all the energy that is produced get released in one step? It is released in multiple steps. What is the advantage of step-wise release?
Oxygen is an essential requirement for aerobic respiration but it enters the respiratory process at the end? Discuss.
It is known that red muscle fibres in animals can work for longer periods of time continuously. How is this possible?
Enumerate the assumptions that we undertake in making the respiratory balance sheet. Are these assumptions valid for a living system? Compare fermentation and aerobic respiration in this context.
Explain the term "Energy Currency". Which substance acts as energy currency in plants and animals?
Respiration is an energy releasing and enzymatically controlled catabolic process which involves a step-wise oxidative breakdown of organic substances inside living cells. In this statement about respiration explain the meaning of
1. Step-wise oxidative breakdown and
2. Organic substances (used as substrates).
The figure given below shows the steps in glycolysis. Fill in the missing steps A, B, C, D and also indicate whether ATP is being used up or released at step E?
If a person is feeling dizzy, glucose or fruit juice is given immediately but not a cheese sandwich, which might have more energy. Explain.
RuBP carboxylase, PEPcase, Pyruvate dehydrogenase, ATPase, cytochrome oxidase, Hexokinase, Lactate dehydrogenase. Select/choose enzymes from the list above which are involved in
a. Photosynthesis
b. Respiration
c. Both in photosynthesis and respiration
Which of the following will release more energy on oxidation? Arrange them in ascending order?
a. 1 g of fat b. 1 g of protein
c. 1 g of glucose
d. 0.5 g of protein + 0.5 g glucose
Distinguish between the following:
(a) Aerobic respiration and Anaerobic respira ¬tion.
(b) Glycolysis and Fermentation.
(c) Glycolysis and Citric acid cycle.
Differentiate between
(a) Respiration and Combustion
(b) Glycolysis and Krebs’cycle
(c) Aerobic respiration and Fermentation