Number of carbon compounds in the substrate molecules of citric acid cycle are:- oxalo acetic acid- 4 , citric acid- 6, alpha-ketoglutaric acid- 5, succinic acid- 4 and malic acid- 4.

In Krebs cycle the FAD participates as electron acceptor during the conversion of succinic acid to fumaric acid. Then the FAD is converted to $$FADH_2$$.

Substrate level phosphorylation means when energy from breakdown of glucose is directly released as ATP or GTP. In Krebs cycle, only in one step GTP is released i.e., during the conversion of succinyl CoA to succinic acid. In all the other steps, energy is released as either NADH or FADH. Thus, the correct answer is option C.

Citric acid is produced during Krebs cycle. Because of that reason it is also called as citric acid cycle. It is the first product of Krebs cycle.

When succinyl CoA is converted to succinic acid GTP molecules are produced and the coenzyme part is released. This reaction is done in presence of succinyl-CoA synthetase.

The pyruvic acid formed during glycolysis enters into a cycle of events called Krebs cycle where it is oxidised to form carbon dioxide and water. It forms the aerobic pathway of respiration. 

• Glycolysis is the breakdown of complex carbohydrates into the simpler form, i.e., pyruvic acid. Thus, X represents glycolysis. 
• In the absence of oxygen pyruvic acid further converts into alcohol and carbon dioxide with a lesser amount of energy i.e., fermentation or anaerobic respiration or anoxybiotic. Thus, Z represents anoxybiotic. 
• In the presence of oxygen (aerobic respiration), pyruvic acid will be converted into carbon dioxide, water, and a large amount of energy. Aerobic respiration is also known as oxybiotic respiration. Thus, Y represents oxybiotic. 

Hence, the correct answer is option C.

The respiratory quotient (or RQ or respiratory coefficient), is a dimensionless number used in calculations of basal metabolic rate (BMR), when estimated from carbon dioxide production.
RQ = CO$$_{2}$$ eliminated / O$$_{2}$$ consumed. Thus, option A is incorrect. Photosynthetic coefficient is the specific light spectrum at which chlorophyll absorbs light. Thus, option B is wrong. Photosynthetic yield is the quantity of the end product of the photosynthesis. Thus, option C is wrong. The temperature coefficient (Q$$_{10}$$) represents the factor by which the rate (R) of a reaction increases for every 10-degree rise in the temperature (T). The rate (R) may represent any measure of the progress of a process. Thus option D is correct.

In Fermentation, the ATP are generated only during the glycolysis. In order to make sure that the glycolysis continues to occur, the electron acceptor called NAD is required to be supplied constantly. Therefore, in fermentation process, the regeneration of these NAD occurs which now exists in the form of NADH (after accepting electron in glycolysis). Since, there is no usage of oxygen, there is no external electron acceptor. Oxygen acts as electron acceptor in aerobic respiration during the electron transport chain. In fermentation, either the pyruvate or the acetaldehyde , which have been formed internally in the process. 

• Glycolysis is the process of partial oxidation of glucose into two molecules of pyruvic acid through ten enzyme-mediated reactions releasing ATP and reducing NADH$$_2$$. 
• It is common in both aerobic and anaerobic respiration. It occurs in the cytoplasm. 
• It has two phases, preparatory and pay off. 
• In the preparatory phase, glucose is broken down to glyceraldehyde-3-phosphate. 
• In the pay off phase, it is changed into pyruvate and produces NADH and ATP.

• The citric acid cycle is also known as the TCA cycle (tricarboxylic acid cycle) or the Krebs cycle. 
• It is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins, into adenosine triphosphate (ATP) and carbon dioxide.
•  In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion.
•  In prokaryotic cells, such as bacteria, which lack mitochondria, the citric acid cycle reaction sequence is performed in the cytosol. 
• Hence, Mitochondria is the site for the Krebs cycle.
• So, the correct answer is 'Krebs cycle'.

$$\textbf{Correct Option B & C}$$

$$\textbf{Solution}$$

$$\bullet$$ Breathing and respiration are two different process.

$$\bullet$$  During the process of respiration, the plants get the oxygen from the air through the stomata and releases carbon dioxide.
$$\bullet$$  The process of respiration occurs in the mitochondria of the cell in the presence of oxygen.
$$\bullet$$  During the process of respiration the gases move in and out of the plant through the stomata using the process of diffusion.
$$\bullet$$  So during respiration the oxygen diffuses inside the plant and the carbon dioxide diffuses outside the plant.
$$\bullet$$   So both the options B and C are correct.

The overall mechanism of cellular respiration involves four subdivisions: glycolysis, in which glucose molecules are broken down to form pyruvic acid molecules; the Krebs cycle, in which pyruvic acid is further broken down and the energy in its molecule is used to form high-energy compounds such as NADH; the electron transport system, in which electrons are transported along a series of co-enzymes and cytochromes and the energy in the electrons is released; and chemiosmosis, in which the energy given off by electrons is used to pump protons across a membrane and provide the energy for ATP synthesis. Thus, option A is correct.

Fermentation is a metabolic process in which an organism converts a carbohydrate, such as starch or a sugar, into an alcohol or an acid. For example, yeast performs fermentation to obtain energy by converting sugar into alcohol. Bacteria perform fermentation, converting carbohydrates into lactic acid.
$$C_6H_{12}O_6$$ (glucose) ------>2 $$C_2H_5OH$$ (ethanol) + 2 $$CO_2$$ (carbon dioxide).
The substrate for the fermentation is any carbohydrate (glucose) and the end products are such as acids or alcohols and $$CO_2$$. 

The pyruvic acid enters Krebs cycle in form of acetyl CoA where it is oxidatively decarboxylated into CO$$_2$$. The complete Kreb cycle leads to the net formation of 2 molecules of ATP by substrate-level phosphorylation, 8 molecules of NADH plus 2 molecules of FADH$$_2$$ (via succinate dehydrogenase). The NADH and FADH$$_2$$ then enter the ETS to drive ATP production by substrate level phosphorylation. 

The quantum requirements of the individual light reactions of photosynthesis are defined as the number of light photons absorbed for the transfer of one electron. The quantum requirement for each light reaction has been found to be approximately one photon. The total number of quanta required, therefore, to transfer the four electrons that result in the formation of one molecule of oxygen via the two light reactions should be eight. 
The quantum yield of a process in which molecules give up their excitation energy (or "decay") is the fraction of excited molecules that decay via that pathway.
The Emerson effect is the increase in the rate of photosynthesis after exposure to light of wavelength 670 nm far red light and 700 nm, red light respectively. When simultaneously exposed to light of both wavelengths, the rate of photosynthesis is far higher than the sum of the red light and far red light photosynthesis rates. 
Red drop effect is the photosynthetic efficiency of monochromatic light is greatly reduced above 680 nm, even though chlorophyll absorbs well up to 700 nm. 

The chemical breakdown of glucose in the absence of oxygen is called as fermentation. This process is also called anaerobic respiration. In this conversion, the intermediate produced is pyruvate followed by oxidation of NADH and formation of lactic acid. The bacterium Lactobacillus is used for the commercial production of lactic acid. Thus the correct answer is option A.

Correct Option: B

Explanation for the correct option:

•  Glycolysis converts glucose into two 3-carbon molecules called pyruvate. 
• The energy released during glycolysis is used to make ATP. 
• Enolase is used to convert 2-phosphoglycerate (2PG) to phosphoenolpyruvate (PEP) in the 9th reaction of glycolysis. 
• It is a reversible dehydration reaction. 

• During light reactions, 4e- will be released.

2H$$_{2}$$O 4H+ + 4e- + O$$_{2}$$

• During dark reactions, 8e- will be released.
• All together 12 electrons are involved for the formation of 1 mole of glucose and 6 O$$_{2}$$ molecules.

The Krebs cycle (or citric acid cycle) is part of cellular respiration. it is a series of chemical reactions used by all aerobic organisms to generate energy. Krebs cycle starts with the formation of a six carbon compound by the reaction between oxaloacetic acid and acetyl CoA. The 6 carbon compound formed is citric acid and this reaction is catalyzed by citrate synthase. 

Fermentation is incomplete oxidation of food substances into alcohol and lactic acid with the small amount of energy being released. Both lactic acid and ethanol fermentation do not produce oxygen. It is carried out by anaerobic bacteria and fungi. Aerobic bacteria and fungi carry out aerobic respiration. Thus, the correct answer is option C.  

Fumarate, malate or oxaloacetate are the intermediates of Krebs cycle, where succinate gets converted to fumarate, fumarate gets converted to malate and malate gets converted to oxaloacetate. So, the correct sequence in Krebs cycle is fumarate - malate - oxaloacetic acid.

CAM plants open their stomata only at night and absorbs $$CO_2$$, which then converted into malate by acidification. During night time oxygen is absorbed continuously but no $$CO_2$$ is evolved. There fore R.Q in night is zero. During day time, malate gets converted to $$CO_2$$ and $$C_3$$ photosynthesis occurs. During day time amount of $$CO_2$$ evolved is equal to the amount of $$O_2$$ absorbed. So, R.Q at day time is 1. So, in CAM plants, R.Q will be zero at night. Thus, option A is correct and other options are incorrect.

Acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. It is produced by pyruvate by under the influence of enzyme pyruvate dehydrogenase. It also plays a major role in beta-oxidation of fatty acid.

Pyruvic acid is the end product of glycolysis, which occurs in the cytoplasm of the cell. Pyruvic acid before combining with the oxaloacetic acid of citric acid cycle changes into acetyl CoA, which is a 2 carbon compound. This reaction is catalysed by pyruvate dehydrogenase. 

The respiratory quotient (R.Q) is the ratio of $$CO_2$$ produced to $$O_2$$ consumed, while food is being metabolized.
RQ = $$CO_2$$ eliminated / $$O_2$$ consumed.
The respiratory quotient for carbohydrate metabolism can be demonstrated by the chemical equation for oxidation of glucose.
$$C_6H_{12}O_6$$ + 6 $$O_2$$-----> 6 $$CO_2$$+ 6 $$H_2O$$
Because the gas exchange in this reaction is equal, the respiratory quotient for carbohydrates is: RQ = 6 $$CO_2$$ / 6 $$O_2$$ = 1. So, if man consumes only carbohydrate the R.Q. for such substance will be 1. 

The respiratory quotient (R.Q) is the ratio of $$CO_2$$ produced to $$O_2$$ consumed, while food is being metabolized.
RQ = $$CO_2$$ eliminated / $$O_2$$ consumed
R.Q for proteins is less than 1 since, amount of $$CO_2$$ evolved is lesser than amount of $$O_2$$ consumed.
When organic acids are broken down as respiratory substrates under aerobic conditions the R.Q is more than one. Organic acids contain more oxygen than carbohydrates and therefore require less oxygen for their oxidation.
R.Q is equal to zero for CAM plants at night time since, no $$CO_2$$ is evolved and $$O_2$$ is continuously consumed.
Thus, option D is correct.

The three processes are involved in the anaerobic respiratory process, glycolysis, Calvin cycle and electron transport chain. There are no steps where the oxygen molecule is released. The oxygen molecule is used for the breakdown through oxidation of the carbohydrate. There is release if the carbon dioxide molecule in this process.

Pyruvate decarboxylation is a reaction that uses pyruvate to form acetyl-CoA, releasing NADH, a reducing equivalent, and carbon dioxide via decarboxylation. This reaction is very common in most organisms as a link between glycolysis and the citric acid cycle. In organisms that perform aerobic respiration, the reaction is usually catalyzed by the pyruvate dehydrogenase complex. The prosthetic groups involved in this reaction are TPP, co-enzyme A, lipoic acid and NAD. Mn does not act as a prosthetic group to the above reaction. 

The Krebs cycle (or citric acid cycle) is a part of cellular respiration. Direct formation of ATP in Krebs cycle occurs during the conversion of ketoglutarate to succinate, which is the intermediate reaction. 
Glucose-1-phosphate to glucose-6-phosphate conversion does not occur in Krebs cycle. Thus, option A is wrong.
Citrate to isocitrate conversion occurs in Krebs cycle but does not leads to formation of ATP. Thus, option B is wrong.
Isocitrate to cis-aconitate conversion does not occur in Krebs cycle but reverse reaction takes place and does not lead to production of ATP. 

The respiratory quotient (R.Q) is the ratio of $$CO_2$$ produced to $$O_2$$ consumed, while food is being metabolized.
RQ = $$CO_2$$ eliminated / $$O_2$$ consumed
R.Q for proteins is less than 1. Because, amount of $$O_2$$ consumed is higher than amount of $$CO_2$$ eliminated. So, protein rich pulses have R.Q less than 1. Thus, option C is correct and other options are incorrect.

Conversion of succinic acid to fumaric acid is the intermediate step in TCA cycle catalyzed by succinate dehydrogenase, which produce 1 $$FADH_2$$ molecule, that is equal to 2 ATP molecules. 

The form in which carbon leaves the citric acid cycle is carbon dioxide. CO$${_2}$$ gets released from the citric acid cycle in the conversion of isocitrate to ketoglutarate and ketoglutarate to succinate. 
Acetaldehyde, ethanol and lactate are not produced during the citric acid cycle. Thus, the correct answer is option D. 

Glycolysis or EMP pathway is the metabolic pathway, that converts glucose into pyruvate. The free energy released in this process is used to form the high-energy compounds ATP and NADPH. Glycolysis occurs in cytosol due to availability of enzymes. This pyruvate then enters into mitochondrial matrix for further process. Thus, option A is correct.
The enzymes of EMP are not located in mitochondria, lysosomes and ribosomes. Thus, other options are incorrect.

Solution:

Correct answer is option B.

Explanation for correct option:

• Kreb cycle is the second phase of aerobic respiration and starts with the condensation of acetyl CoA with OAA forms citrate, the first tricarboxylic acid of Kreb cycle. That's why it is also called as citric acid cycle and tricarboxylic acid cycle.
• Calvin cycle refers to the enzymatic reaction that fixes carbon dioxide into carbohydrates. Series of reactions that produce urea from ammonia are collectively termed the urea cycle. 

Alcoholic fermentation also referred to as ethanol fermentation, is a biological process in which elements, such as glucose, fructose and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as a metabolic waste product. 

CAM plants open their stomata only at night and absorbs $$CO_2$$, which then converted into malate by acidification. During night time oxygen is absorbed continuously but no $$CO_2$$ is evolved. There fore R.Q in night is zero. During day time, malate gets converted to $$CO_2$$ and $$C_3$$ photosynthesis occurs. During day time amount of $$CO_2$$ evolved is equal to the amount of $$O_2$$ absorbed. So, R.Q at day time is 1. Since succulents are CAM plants, their R.Q at night is zero and day is 1. Thus, option D is correct and other options are incorrect.

The one turn of the citric acid cycle releases two carbon dioxide molecules and produces three NADH, one FADH2, and one ATP or GTP. As the cycle turns twice so the number of CO$$_2$$ molecule produce will be 2X2=4 molecules.

Kreb cycle produces 8 molecules of NADH plus 2 molecules of $$FADH_2$$ (via succinate dehydrogenase) in the mitochondrial matrix. During electron transport through the inner mitochondrial membrane, NADH and $$FADH_2$$ pump electrons through a series of electron transport proteins to final acceptor oxygen. This electron transport chain ensures availability of NAD and FAD for next round of Kreb cycle. Nonavailability of these reducing powers results in entry of pyruvate in anaerobic respiration pathway. So, to maintain continuity of Kreb cycle, oxidation of NADH and $$FADH_2$$ by oxygen is prerequisite and the cycle is considered aerobic. Thus, the correct answer is option D.

Pyruvic acid is the product of glycolysis that takes place in the cytosol. Pyruvate dehydrogenase complex is a cluster of three enzymes and is present in multiple copies in the matrix mitochondria of eukaryotic cells. It catalyzes irreversible oxidative decarboxylation of pyruvate into acetyl-CoA and carbon dioxide. Inner mitochondrial membrane carries electron transport chain. $$F_1$$ particles of mitochondria catalyze the synthesis of ATP using the protonmotive force. Thus, the correct answer is option C. 

The last acid produced in the Krebs cycle of aerobic respiration is oxaloacetic acid. Oxaloacetic acid is produced by the conversion of malate by malate dehydrogenase. 
Malic acid, succinic acid and ketoglutaric acid are the intermediate acids in Krebs cycle. 

The respiratory quotient (R.Q) is the ratio of $$CO_2$$ produced to $$O_2$$ consumed, while food is being metabolized.
RQ = $$CO_2$$ eliminated / $$O_2$$ consumed
In the above reaction, 102 $$CO_2$$ molecules are produced and 146 $$O_2$$ molecules are consumed. Therefore,
RQ = 102 / 146 = 0.7
Thus, option A is correct and other options are incorrect.

Alcoholic fermentation, also referred to as ethanol fermentation. It is a biological process in which elements, such as glucose, fructose and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide, as metabolic waste products. Because yeasts perform this conversion in the absence of oxygen, alcoholic fermentation is considered an anaerobic process. So, option B is correct.

Respiratory quotient is the ratio of the amount of CO$$_2$$ eliminated to that of O$$_2$$O2 consumed. Thus, it is evident that it solely depends on the nature of the substrate. For example, hexose sugar will have the value of R.Q = 1 because the volume of CO$$_2$$ and volume of O$$_2$$ stays the same. Fats have an R.Q less than one. There is consumption of more O$$_2$$ than the carbon dioxide which gets eliminated and the organic acids will have their R.Q. values more than 1 because of the elimination of more CO$$_2$$ molecules than the consumption of molecules.