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Carbonic anhydrase.

(b) Low oxygen concentration

Bicarbonate.

Correct Answer is : 5.

(d) tuberculosis

(a) tracheal tubes

(C) mitochondria

Glycolysis, TCA cycle and electron transport chain are linked in the following manner:

1. The coenzymes are initially present in the form of NAD⁺ and FAD⁺ which latter get reduced to NADH+H⁺ and FADH+H⁺ by accepting the hydrogen from organic substrate during glycolysis, link reaction and Krebs cycle. 

2. During glycolysis, glucose is oxidised to two molecules of pyruvic acid with net gain 2 molecules of NADH+H⁺ . 

3. This pyruvic acid undergoes link reaction to form two molecules of acetyl COA and two molecules of NADH+H⁺ . 

4. Acetyl COA, thus formed enters into the Krebs cycle and it gets completely oxidised to CO₂ and H₂O; with a net gain of 6 NADH+H⁺ and 2 FADH+H⁺ are formed. 

5. During ETS, reduced coenzymes are reoxidized to NAD⁺ and FAD⁺ with a net gain of 34 ATPs. The ATPs thus formed are used during glycolysis.

6. The oxidized NAD⁺ and FAD⁺ will again accept the hydrogen from organic substrate. Thus, reduced coenzymes are converted back to their oxidized forms by dehydrogenation to keep the process going.

Respiration in yeast can be demonstrated with the help of an experiment. 

Anaerobic respiration in yeast: 

1. A pinch of dry baker’s yeast suspended in water containing 10ml of 10% glucose in a test tube (test tube A). 

2. The surface of the liquid is covered with oil to prevent entry of air and the test tube is closed tightly with rubber stopper to prevent leakage. 

3. One end of a short-bent glass tube is inserted through it to reach the air inside the tube. 

4. Other end of the glass tube is connected by a polyethylene or rubber tubing to another bent glass tube fitted into a stopper. 

5. The open end of the glass tube (delivery tube) is dipped into lime water containing in a test tube (Tube B). 

6. Stoppers of both the tubes are fitted tightly to prevent leakage of gases. First test tube is placed in warm water (37° C-38° C) in a beaker. 

7. Lime water gradually turns milky, indicating the evolution of carbon dioxide from the yeast preparation. 

8. Level of the lime water in the delivery tube does not rise, showing that there is no decline in volume of gas in test tube A and consequently no utilization of oxygen by yeast. Preparation is stored for a day or two. 

9. When we open the stopper of tube A we will notice a smell of alcohol indicating the formation of ethanol. 

10. From this activity it may be inferred that yeast respires anaerobically to ferment glucose to ethanol and carbon dioxide.

Aerobic respiration in yeast: 

Experiment explained can be carried out for demonstrating aerobic respiration in yeast. 

1. If the level of the lime water in the test tube B rises, indicating intake of oxygen, hence the level of volume of gas rises.

2. The preparation tube is stored for a day or two, if no smell of alcohol is noticed it indicates that the yeast respires aerobically.

In ETS energy is released in step wise manner to prevent damage of cells. 

1. A stepwise release of the chemical bond energy facilitates the utilization of a relatively higher proportion of that energy in ATP synthesis.

2. Activities of enzymes for the different steps may be enhanced or inhibited by specific compounds. This provides a means of controlling the rate of the pathway and the energy output according to need of the cell. 

3. The same pathway may be utilized for forming intermediates used in the synthesis of other biomolecules like amino acids.

The inner mitochondrial membrane is the site for ETS in mitochondrial respiration.

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 inner mitochondrial membrane in the form of various complexes as complex I, II, III, VI and V. 

3. NADH+H⁺ is oxidised by NADH dehydrogenase (complex I) and it’s electrons are transferred to ubiquinone (coenzyme Q-CoQ) present on inner membrane of mitochondria. Reduced ubiquinone is called as ubiqunol. 

4. FADH₂ is oxidised 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 canned forward whereas protons are released into outer chamber of mitochondria (intermembrane space). 

6. Ubiquinol is oxidised by complex-III (Cytochrome bcl complex) and it’s electrons are transferred to cytochrome C. Cytochrome C is a small, ironcontaining protein, loosely associated with inner membrane. It acts as a mobile electron carrier, transferring the electrons between complex III and IV. 

7. Cytochrome C is oxidised 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 water molecule called as metabolic water.

9. Protons necessary for this are channelled from outer chamber of mitochondria into inner chamber by F₀ part of oxysome (complex V) present in inner mitochondrial membrane. 

10. This proton channelling by F₀ is coupled to catalytic site of F₁ which catalyses the synthesis of ATP from ADP and inorganic phosphate. This is oxidative phosphorylation. 

11. As transfer of protons is accompanied with synthesis of ATP, this process is named as ‘Chemiosmosis’ by Peter Mitchell.

1. Respiratory quotient (R.Q.) or respiratory ratio is the ratio of volume of CO₂ released to the volume of O₂ consumed in respiration. 

2. R.Q. = Volume of CO₂ released / Volume of O₂ consumed

1. Respiration is considered as a catabolic process; however, it is not entirely correct in case of Krebs cycle. 

2. Many reactions of Krebs cycle involve oxidation of acetyl CoA to release energy and CO₂. 

3. However, the breakdown of respiratory substrates provides intermediates like a-ketoglutarate, oxaloacetate are used as precursors for synthesis of fatty acids, glutamic acid and aspartic acid respectively. 

4. Thus, as the same respiratory process acts as catabolic as well as anabolic pathway for synthesis of various intermediate metabolic products, it is called amphibolic pathway.

Two industrial uses of alcoholic fermentation: 

1. In bakeries, it is used for preparing bread, cakes, biscuits. 

2. In beverage industries for preparing wine and alcoholic drinks.

The RQ for different respiratory substrates are: 

1. Carbohydrates (R.Q. is 1) 

When carbohydrates are used as substrate, equal volumes of CO₂ and O₂ are released and consumed respectively, thus its R.Q. is 1. 

C₆H₁₂O₆ + 6O₂ → 6 CO₂ + 6H₂O

R.Q. = 6CO₂ / 6O₂ = 1.0 

2. Fats (R.Q. is less than 1) 

Substrates like fats are poorer in oxygen than carbohydrates. Thus, more oxygen is utilized for its complete oxidation. 

2(C₅₁H₉₈O₆) + 145O₂ → 102CO₂ + 98H₂O + Energy 

R.Q. = CO₂ / O₂ = 102 / 145 = 0.7 

3. Protein respiration (R.Q. is less than 1)

1. When proteins serve as respiratory substrate, they are first degraded to amino acids. 

2. Then, amino acids are converted into various intermediates of carbohydrates. 

3. However, amino acids have low proportion of O₂ as compared to carbohydrates. 

4. Thus, they require more O₂ during their complete oxidation and value of R.Q. becomes less than 1. 5. In case of proteins, the R.Q. is approximately 0.9.

A) They are not of same size and are spongy in nature.

(D) Carbon dioxide