Mix Examples- Respiration in Plants Questions in English

(B) The primary objective of cellular respiration,which includes glycolysis,the Krebs cycle ($TCA$ cycle),and the electron transport system $(ETS)$,is to extract energy from glucose.
This energy is released in a controlled manner through a series of metabolic pathways.
Instead of releasing all energy at once,which would be inefficient and potentially damaging to the cell,the energy is captured in the form of $ATP$ (adenosine triphosphate) in small,manageable,stepwise units.
This allows the cell to efficiently utilize the energy for various biological processes.

(C) Cellular respiration is the process by which cells derive energy from glucose.
While glycolysis occurs in the cytoplasm,the major stages of aerobic respiration,including the Krebs cycle and the Electron Transport System $(ETS)$,take place within the mitochondria.
Therefore,mitochondria are often referred to as the 'powerhouse of the cell' because they are the primary sites for $ATP$ production via cellular respiration.

(C) $1$. Respiratory substrates are the organic compounds that are oxidized during respiration to release energy.
$2$. When carbohydrates or fats are used as respiratory substrates,the process is called 'floating respiration'.
$3$. When proteins are used as respiratory substrates,the process is called 'protoplasmic respiration'.
$4$. Therefore,since both carbohydrates and fats are involved in floating respiration,the correct option is $(C)$.

(C) The $HMP$ shunt (Hexose Monophosphate Shunt) or Pentose Phosphate Pathway is primarily involved in the production of $NADPH$ and pentose sugars rather than direct $ATP$ production.
However,when considering the complete oxidation of one molecule of glucose through this pathway,the net yield of $ATP$ is equivalent to that of aerobic respiration.
In the $HMP$ shunt,$12\ NADPH$ molecules are produced.
Since each $NADPH$ molecule yields approximately $3\ ATP$ during oxidative phosphorylation,the total $ATP$ produced is $12 \times 3 = 36\ ATP$.
Accounting for the $ATP$ consumed in the initial steps,the net gain is typically considered $35\ ATP$ to $36\ ATP$ depending on the shuttle system used.
Among the given options,$35\ ATP$ is the standard accepted value for the net energy yield equivalent in this context.

(D) The metabolic rate of an organism is directly proportional to the rate of cellular respiration. During a state of rest,the body's energy demand decreases,which leads to a reduction in the rate of oxygen consumption ($O_2$ uptake) and carbon dioxide production ($CO_2$ release). Since respiration is the process of gas exchange that supports metabolism,monitoring the pulse (heart rate) and the rate of breathing (respiration) provides a direct measure of these metabolic requirements. Therefore,all these parameters are indicators of the metabolic state.

(B) The human dentition consists of four types of teeth: $Incisors$,$Canines$,$Premolars$,and $Molars$.
$Retrica$ is not a biological term for any type of tooth in humans or mammals.
Therefore,$Retrica$ is the correct answer.

(B) The process of adding a phosphate group to $ADP$ to form $ATP$ is generally known as phosphorylation.
When this process occurs specifically during metabolic pathways like glycolysis or the Krebs cycle,where a phosphate group is transferred directly from a substrate molecule to $ADP$,it is called substrate-level phosphorylation.
Photophosphorylation refers to the synthesis of $ATP$ from $ADP$ and inorganic phosphate in the presence of light in chloroplasts.
Therefore,the general term for the conversion of $ADP$ to $ATP$ is phosphorylation.

(B) The correct matches are as follows:
$(1)$ Mitochondrial matrix is the site for the $(R)$ Krebs cycle.
$(2)$ Chloroplast stroma is the site for the $(S)$ Dark reaction (Calvin cycle).
$(3)$ Cristae (inner mitochondrial membrane) is the site for $(Q)$ Oxidative phosphorylation (Electron Transport System).
$(4)$ Granum (thylakoids) is the site for $(P)$ Photophosphorylation (Light reaction).
Therefore, the correct matching is $(1-R), (2-S), (3-Q), (4-P)$.

(D) Water $(H_2O)$ is a polar molecule that acts as a universal solvent,making it an excellent medium for the transport of various chemicals in biological systems.
It has a very high specific heat capacity and latent heat of vaporization,which helps in thermoregulation.
Due to its polar nature,it forms hydrogen bonds.
However,water is known for its relatively high thermal conductivity compared to many other liquids,which aids in distributing heat within organisms. Therefore,the statement that water has low thermal conductivity is incorrect.

(A) Carbohydrates,especially glucose,serve as the primary fuel for cellular respiration to produce $ATP$.
Living organisms break down glucose through glycolysis and the Krebs cycle to release energy.
Since glucose is a carbohydrate,it confirms that carbohydrates are the primary source of energy.
Therefore,both the assertion and the reason are true,and the reason correctly explains why carbohydrates are the primary energy source.

(A) Assertion $(A)$ is true because carbohydrates,especially glucose,are the primary fuel molecules that provide energy to cells through metabolic processes.
Reason $(R)$ is also true because glucose is the most common respiratory substrate that enters the glycolytic pathway to produce $ATP$.
Since the primary reason carbohydrates serve as the main energy source is that they are readily broken down into glucose for respiration,$R$ is the correct explanation of $A$.

(A) Succinate dehydrogenase is a key enzyme of the Krebs cycle (Citric Acid Cycle) that catalyzes the oxidation of succinate to fumarate. It is also a component of Complex $II$ in the Electron Transport System $(E.T.S.)$. Cytochrome oxidase (Complex $IV$) is an essential enzyme complex located in the inner mitochondrial membrane that functions exclusively in the $E.T.S.$ to reduce oxygen to water. Therefore,the correct association is Krebs cycle and $E.T.S.$

(D) In the given diagram,pathway $A$ represents glycolysis,pathway $B$ represents the Krebs cycle,and pathway $C$ represents oxidative phosphorylation.
During glycolysis (pathway $A$),$ATP$ is produced as a net product (arrow $4$).
During the Krebs cycle (pathway $B$),$ATP$ (or $GTP$) is produced as a net product (arrow $8$).
During oxidative phosphorylation (pathway $C$),$ATP$ is produced as a net product (arrow $12$).
Therefore,arrows numbered $4, 8,$ and $12$ all represent the production of $ATP$.

(D) The correct answer is $D$.
Respiration is an energy-releasing,enzymatically controlled,multistep catabolic process involving the stepwise breakdown of organic substances (hexose sugars) inside living cells.
Aerobic respiration includes three major processes: glycolysis,Krebs' cycle,and the electron transport chain.
During these processes,the substrate is completely broken down to form $CO_2$ and water.
$A$ large amount of energy is released in a stepwise manner in the form of $ATP$ molecules,rather than in a single large reaction,which prevents the loss of energy as heat.

(B) The metabolic rate of an organism is inversely proportional to its body size.
Smaller animals have a higher surface area to volume ratio,which results in a higher metabolic rate to maintain their body temperature and physiological functions.
Because of this higher metabolic rate,small animals can generate energy more rapidly,allowing them to perform strenuous activities like running uphill more easily compared to larger animals,which have a lower metabolic rate relative to their body size.
Therefore,the correct option is $(b)$.

(B) The correct answer is $B$.
Mustard is a plant that is known to absorb water equal to its own weight in approximately $5$ hours.
This high rate of water absorption is essential for its rapid growth and metabolic processes.
Other plants have different rates of transpiration and absorption depending on their environmental adaptations.

(A) Facilitated diffusion and active transport both involve the movement of molecules across the cell membrane using specific membrane proteins known as carrier proteins or transporters.
These carrier proteins are sensitive to inhibitors that react with their protein side chains,as these inhibitors can alter the conformation of the protein,thereby blocking the transport process.
Facilitated diffusion is a passive process that does not require $ATP$,whereas active transport is an active process that requires $ATP$ to move molecules against their concentration gradient.
Therefore,the common feature between them is the reliance on specific carrier proteins that can be inhibited by chemicals affecting protein side chains.

(B) The correct answer is $B$.
$1$. Tripalmitin is a fatty acid,and its Respiratory Quotient $(RQ)$ is indeed $0.7$,which is correct.
$2$. The intermediate compound that links glycolysis with the Krebs cycle is Acetyl-CoA,not malic acid. Malic acid is an intermediate within the Krebs cycle itself. Therefore,this statement is incorrect.
$3$. In aerobic respiration,the complete oxidation of one glucose molecule yields a net gain of $36$ or $38 \ ATP$ depending on the shuttle system,so $36 \ ATP$ is a standard accepted value.
$4$. During fermentation,only glycolysis occurs,which results in a net gain of $2 \ ATP$ molecules,which is correct.

(B) Glycolysis is the partial oxidation of glucose into two molecules of pyruvic acid. It occurs in the cytoplasm and does not involve the release of $CO_2$. Therefore,the statement that $4$ molecules of $CO_2$ are released during glycolysis is incorrect. The Kreb's cycle occurs in the mitochondrial matrix and is responsible for the complete oxidation of pyruvate into $CO_2$ and $H_2O$.

(B) $1$. Glycolysis is an anaerobic process where glucose is converted into pyruvic acid without the requirement of oxygen. Thus,option $A$ is correct.
$2$. In eukaryotic organisms,the net gain of $ATP$ during aerobic respiration is typically $36$ or $38 \ ATP$ molecules,not $42$. Thus,option $B$ is incorrect.
$3$. Carbohydrates are the primary respiratory substrates used by cells to produce energy. Thus,option $C$ is correct.
$4$. Glycolysis involves substrate-level phosphorylation,not oxidative phosphorylation. Furthermore,the net gain of $ATP$ in glycolysis is $2 \ ATP$,not $6$. Thus,option $D$ is also incorrect. However,in the context of standard multiple-choice questions where one must identify the most glaring error regarding respiratory yields,$B$ and $D$ are both factually wrong. Given the standard curriculum,$D$ is often cited as a common misconception regarding the mechanism of $ATP$ production in glycolysis.

(D) The correct answer is $D$. Aerobic respiration does not begin with the Krebs cycle; it begins with glycolysis,which is common to both aerobic and anaerobic respiration. After glycolysis,the end product (pyruvate) enters the mitochondria to undergo the link reaction and then the Krebs cycle. Therefore,the statement 'Aerobic respiration begins with Krebs cycle' is incorrect.

(D) Statement $(i)$ is correct: Complete combustion of glucose produces $CO_2$ and $H_2O$,releasing energy mostly as heat.
Statement $(ii)$ is correct: Glycolysis is known as the $EMP$ pathway after Embden,Meyerhof,and Parnas.
Statement $(iii)$ is incorrect: In glycolysis,$ATP$ is utilized at only $2$ steps (hexokinase and phosphofructokinase reactions).
Statement $(iv)$ is incorrect: In fermentation,less than $7$ percent of the energy in glucose is released.
Statement $(v)$ is correct: Pyruvate is transported from the cytoplasm into the mitochondria for the link reaction and the Krebs cycle.

(C) Aerobic respiration is the process of breaking down glucose in the presence of oxygen to produce energy.
The overall chemical equation for aerobic respiration is: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}$.
As shown in the equation, the end products are carbon dioxide $(CO_2)$, water $(H_2O)$, and energy (in the form of $ATP$).

(D) The conversion of pyruvic acid into acetyl $CoA$ is catalyzed by the pyruvate dehydrogenase complex. This reaction is an oxidative decarboxylation process. The essential cofactors and coenzymes required for this reaction include:
$1$. $TPP$ (Thiamine pyrophosphate)
$2$. $NAD^+$ (Nicotinamide adenine dinucleotide)
$3$. $CoA$ (Coenzyme $A$)
$4$. $LAA$ (Lipoic acid)
$5$. $Mg^{2+}$ ions.
Since all the listed substances are essential components of this enzymatic complex,the correct answer is $D$.

(D) The primary objective of cellular respiration,which includes glycolysis,the Krebs cycle,and the Electron Transport System $(E.T.S.)$,is to extract energy from organic molecules like glucose.
Instead of releasing all the energy at once in a single large oxidation process,which would be inefficient and potentially damaging to the cell,these processes break down the substrate in a series of small,controlled steps.
This stepwise oxidation allows the cell to capture the released energy efficiently and store it in the form of $ATP$ molecules,which act as the energy currency of the cell.

(C) In the schematic representation of aerobic respiration:
- Pathway $A$ is Glycolysis,Pathway $B$ is the Link Reaction (Pyruvate oxidation),and Pathway $C$ is the Krebs Cycle ($TCA$ cycle).
- In Glycolysis (Pathway $A$),$ATP$ is produced (arrow $4$).
- In the Link Reaction (Pathway $B$),$ATP$ is not directly produced,but in the Krebs Cycle (Pathway $C$),$ATP$ (or $GTP$) is produced (arrow $12$).
- However,looking at the standard representation of these pathways,arrows $4, 8,$ and $12$ represent the net energy currency produced in these stages,which is $ATP$.

(C) Sunken stomata are stomata that are located in small pits or depressions on the leaf surface.
This adaptation helps in reducing the rate of transpiration by creating a humid microclimate around the stomatal pore.
This is a critical survival mechanism for plants living in dry or arid environments where water conservation is essential.
Therefore,sunken stomata are a characteristic feature of $Xerophytes$.

(C) The correct answer is $C$.
$1$. Glycolysis requires $NAD^+$ to act as an electron acceptor to form $NADH + H^+$.
$2$. The enzymes of the $TCA$ cycle (Krebs cycle) are located in the mitochondrial matrix.
$3$. Oxidative phosphorylation (the electron transport system) takes place in the inner mitochondrial membrane,not the outer membrane.
$4$. Glycolysis occurs in the cytosol of the cell.

(D) $P-$ proteins (phloem proteins) are found in the sieve tube elements of angiosperms. Their primary function is to act as a sealing mechanism. When the sieve tube is injured or wounded,these proteins,along with callose,rapidly accumulate at the sieve plate pores to plug them,thereby preventing the loss of phloem sap.

(D) Glycolysis is the process of breakdown of glucose or similar hexose sugar into two molecules of pyruvic acid through a series of enzyme-mediated reactions,releasing energy $(ATP)$ and reducing power $(NADH_2)$.
It is the first step of respiration,which occurs inside the cytoplasm and is independent of $O_2$.
In glycolysis,two molecules of $ATP$ are consumed during the double phosphorylation of glucose to form fructose $1, 6$-diphosphate.
Four molecules of $ATP$ are produced in the conversion of $1, 3$-diphosphoglycerate to $3$-phosphoglycerate and phosphoenolpyruvate to pyruvate.
Additionally,two molecules of $NADH_2$ are formed during the oxidation of glyceraldehyde $3$-phosphate to $1, 3$-diphosphoglycerate.
Since each $NADH$ is equivalent to $3\, ATP$,the net gain in glycolysis is $8\, ATP$.
Therefore,both the Assertion and the Reason are incorrect.

(B) The inner mitochondrial membrane contains the electron transport system $(ETS)$ and $ATP$ synthase,which are essential for oxidative phosphorylation.
The mitochondrial matrix contains the enzymes required for the $Kreb's$ cycle (citric acid cycle) and fatty acid oxidation.
Both statements are scientifically correct,but the presence of $Kreb's$ cycle enzymes in the matrix does not explain why the electron transport system is located in the inner membrane. Therefore,the Reason is not the correct explanation for the Assertion.

(N/A) Respiration and Combustion

Respiration	Combustion
$(1)$ It is a biochemical process.	$(1)$ It is a physiochemical process.
$(2)$ It occurs in living cells.	$(2)$ It does not occur in living cells.
$(3)$ $ATP$ is generated.	$(3)$ $ATP$ is not generated.
$(4)$ Enzymes are required.	$(4)$ Enzymes are not required.
$(5)$ It is a biologically-controlled process.	$(5)$ It is an uncontrolled process.

$(b)$ Glycolysis and Krebs' cycle

Glycolysis	Krebs' cycle
$(1)$ It is a linear pathway.	$(1)$ It is a cyclic pathway.
$(2)$ It occurs in the cytoplasm.	$(2)$ It occurs in the mitochondrial matrix.
$(3)$ It occurs in both aerobic and anaerobic respiration.	$(3)$ It occurs only in aerobic respiration.
$(4)$ It generates $2$ $NADH$ and $2$ $ATP$ molecules per glucose.	$(4)$ It produces $6$ $NADH$, $2$ $FADH_2$, and $2$ $ATP$ per two acetyl-$CoA$ molecules.

$(c)$ Aerobic respiration and Fermentation

Aerobic respiration	Fermentation
$(1)$ Oxygen is used for energy derivation.	$(1)$ Occurs in the absence of oxygen.
$(2)$ Occurs in the cytoplasm and mitochondria.	$(2)$ Occurs only in the cytoplasm.
$(3)$ End products are $CO_2$ and $H_2O$.	$(3)$ End products are ethyl alcohol and $CO_2$.
$(4)$ Complete oxidation of substrate occurs.	$(4)$ Incomplete oxidation of substrate occurs.
$(5)$ About $36$ $ATP$ molecules are produced.	$(5)$ Only $2$ $ATP$ molecules are produced.

The major steps in aerobic respiration and the sites where they occur are listed in the given table.

Step	Site of occurrence
$(1)$ Glycolysis	$(1)$ Cytoplasm
$(2)$ Krebs cycle	$(2)$ Matrix of mitochondria
$(3)$ Electron transport system	$(3)$ Inner mitochondrial membrane
$(4)$ Oxidative phosphorylation	$(4)$ $F_{0}-F_{1}$ particles in the inner mitochondrial membrane

(A-D) Aerobic respiration and Anaerobic respiration

Aerobic respiration	Anaerobic respiration
$(1)$ It uses oxygen for deriving energy.	$(1)$ It occurs in the absence of oxygen.
$(2)$ It occurs in cytoplasm and mitochondria.	$(2)$ It occurs in cytoplasm.
$(3)$ The end products are carbon dioxide and water.	$(3)$ The end products are ethyl alcohol and carbon dioxide (or lactic acid).
$(4)$ Complete oxidation of respiratory substrate takes place.	$(4)$ Incomplete oxidation of respiratory substrate takes place.
$(5)$ $36-38$ $ATP$ molecules are produced.	$(5)$ Only $2$ $ATP$ molecules are produced.

$(b)$ Glycolysis and Fermentation

Glycolysis	Fermentation
$(1)$ Glycolysis occurs during both aerobic and anaerobic respiration.	$(1)$ Fermentation is a type of anaerobic respiration.
$(2)$ Pyruvic acid is produced as its end product.	$(2)$ Ethanol or lactic acid is produced as its end product.

$(c)$ Glycolysis and Citric acid Cycle

Glycolysis	Citric acid Cycle (Krebs cycle)
$(1)$ It is a linear pathway.	$(1)$ It is a cyclic pathway.
$(2)$ It occurs in the cell cytoplasm.	$(2)$ It occurs in the mitochondrial matrix.
$(3)$ It occurs in both aerobic and anaerobic respiration.	$(3)$ It occurs only in aerobic respiration.
$(4)$ One glucose molecule generates $2$ $NADH$ and $2$ $ATP$ molecules.	$(4)$ It produces $6$ $NADH$, $2$ $FADH_2$, and $2$ $ATP$ molecules per glucose molecule.

(B) For aerobic respiration to take place within the mitochondria,the final product of glycolysis,pyruvate,is transported from the cytoplasm into the mitochondria.
The crucial events in aerobic respiration are:
$1$. The complete oxidation of pyruvate by the stepwise removal of all the hydrogen atoms,leaving three molecules of $CO_{2}$.
$2$. The passing on of the electrons removed as part of the hydrogen atoms to molecular $O_{2}$ with simultaneous synthesis of $ATP$.

(N/A)

Glycolysis	Fermentation
$(1)$ It is the partial oxidation of glucose into two molecules of pyruvic acid.	$(1)$ It is the incomplete oxidation of glucose under anaerobic conditions,leading to ethanol or lactic acid.
$(2)$ It occurs in the cytoplasm of all living cells.	$(2)$ It occurs in yeast,certain bacteria,and muscle cells under anaerobic conditions.
$(3)$ It does not require oxygen.	$(3)$ It occurs in the absence of oxygen.
$(4)$ $CO_{2}$ is not released during this process.	$(4)$ $CO_{2}$ is released during alcoholic fermentation.
$(5)$ Net gain is $2$ $ATP$ and $2$ $NADH + H^{+}$.	$(5)$ Net gain is $2$ $ATP$ (produced during glycolysis) and no further $ATP$ is produced in fermentation.

(N/A)

Glycolysis	Citric acid cycle
$(1)$ This process occurs in the cytoplasm of the cell.	$(1)$ This process occurs in the mitochondrial matrix.
$(2)$ $O_2$ is not required for this process.	$(2)$ $O_2$ is indirectly required for the regeneration of $NAD^+$ and $FAD$.
$(3)$ One molecule of glucose is broken down into two molecules of pyruvic acid.	$(3)$ Acetyl-$CoA$ is completely oxidized to release $CO_2$.
$(4)$ It is a linear metabolic pathway.	$(4)$ It is a cyclic metabolic pathway.
$(5)$ $CO_2$ is not produced during this process.	$(5)$ Two molecules of $CO_2$ are released per acetyl-$CoA$ molecule.
$(6)$ Discovered by Embden,Meyerhof,and Parnas ($EMP$ pathway).	$(6)$ Discovered by Hans Krebs.

(N/A) $(1)$ $RQ$ stands for Respiratory Quotient. It is defined as the ratio of the volume of $CO_2$ evolved to the volume of $O_2$ consumed during respiration.
$(2)$ $TCA$ stands for Tricarboxylic Acid. It refers to the $TCA$ cycle,also known as the Krebs cycle or Citric Acid cycle,which is a series of chemical reactions used by all aerobic organisms to release stored energy.

(N/A) The three metabolic fates of pyruvic acid are:
$(a)$ Lactic acid: Formed during anaerobic respiration in animal muscle cells (e.g., striated muscles) when oxygen is limited.
$(b)$ Ethanol and $CO_2$: Formed during anaerobic respiration (fermentation) in microorganisms like yeast.
$(c)$ Acetyl $CoA$: Formed during aerobic respiration in the mitochondria, which then enters the Krebs cycle.
The conversion of pyruvic acid to Acetyl $CoA$ is represented by the reaction:
Pyruvic acid $+ CoA + NAD^+ \xrightarrow{Mg^{+2}, \text{Pyruvate dehydrogenase}} \text{Acetyl } CoA + CO_2 + NADH + H^+$

(N/A)

Aerobic Respiration	Anaerobic Respiration
$(1)$ In aerobic respiration,there is complete oxidation of substrate molecules,leading to a higher yield of $ATP$ molecules.	$(1)$ In anaerobic respiration,there is incomplete oxidation of substrate molecules,resulting in a significantly lower yield of $ATP$ molecules.
$(2)$ Aerobic respiration of one molecule of glucose typically produces $36$ to $38$ $ATP$ molecules,along with $H_{2}O$ and $CO_{2}$.	$(2)$ Anaerobic respiration (fermentation) of one molecule of glucose,for example in yeast,produces only $2$ $ATP$ molecules,along with ethanol and $CO_{2}$.

(N/A) The events occurring in the mitochondrial matrix include the Tricarboxylic Acid $(TCA)$ cycle (Krebs cycle). The cycle begins with the condensation of an acetyl group $(2C)$ with oxaloacetic acid ($OAA$,$4C$) and water to yield citric acid $(6C)$,catalyzed by citrate synthase.
Following this,citric acid undergoes isomerization to isocitrate,followed by two successive steps of decarboxylation,forming $\alpha$-ketoglutaric acid and then succinyl-$CoA$.
Succinyl-$CoA$ is then oxidized to $OAA$ to complete the cycle. During this process,$GTP$ is synthesized via substrate-level phosphorylation,which is then converted to $ATP$. Additionally,$NAD^{+}$ is reduced to $NADH + H^{+}$ at three points,and $FAD^{+}$ is reduced to $FADH_{2}$ at one point.
The event occurring in the inner mitochondrial membrane is the Electron Transport System $(ETS)$. In this process,electrons from $NADH$ and $FADH_{2}$ (produced in the matrix) are passed through a series of complexes ($Complex-I$ to $IV$).
As electrons move through the $ETS$,protons $(H^{+})$ are pumped into the intermembrane space,creating a proton gradient. This gradient drives $ATP$ synthase $(Complex-V)$,which synthesizes $ATP$ from $ADP$ and inorganic phosphate $(Pi)$ as protons flow back into the matrix. Oxygen acts as the final electron acceptor,combining with electrons and protons to form water.

(D) $(1)$ In plants,gas exchange occurs through stomata (in leaves) and lenticels (in stems). Thus,the answer is stomata and lenticels.
$(2)$ In animals,anaerobic respiration (e.g.,in muscle cells) produces lactic acid. In other organisms like yeast,it produces ethanol and $CO_2$. Given the context of animal physiology,the primary product of anaerobic respiration is lactic acid.

(N/A) $(1)$ Embden,Meyerhof,and Parnas ($EMP$ pathway).
$(2)$ Presence of oxygen.

(A) $(1)$ The $TCA$ cycle (Tricarboxylic Acid cycle) begins with the condensation of the acetyl group with oxaloacetic acid $(OAA)$ and water to yield citric acid,a reaction catalyzed by the enzyme citrate synthase.
$(2)$ Fermentation is a process of incomplete oxidation of glucose that occurs under anaerobic conditions (in the absence of oxygen). In yeast,this process converts glucose into ethanol and carbon dioxide.

(B) $(1)$ Sucrose is a disaccharide. It is hydrolyzed into glucose and fructose by the enzyme $Invertase$.
$(2)$ Fermentation is a type of anaerobic respiration where glucose is partially oxidized into ethanol and $CO_2$ by yeast in the absence of oxygen ($Anaerobic$ conditions).

(A) $(1)$ Glycolysis produces a net gain of $2 \, ATP$ molecules per glucose molecule. Fermentation also results in a net gain of $2 \, ATP$ molecules.
$(2)$ The Respiratory Quotient $(RQ)$ for carbohydrates is $1.0$,while for fats,it is approximately $0.7$. Since the statement claims $RQ$ is less than one for both fats and carbohydrates,it is incorrect because it is not less than one for carbohydrates.

(A) $(1)$ Fermentation is an anaerobic process that does not involve an electron transport system $(ETS)$,whereas aerobic respiration relies on the $ETS$ located in the inner mitochondrial membrane.
$(2)$ Respiration is a controlled biochemical process occurring within living cells,whereas combustion is a rapid,uncontrolled physical-chemical process that releases energy as heat and light.

(D) $ATP$ can be synthesized through three primary mechanisms: photophosphorylation,oxidative phosphorylation,and substrate-level phosphorylation.
$1$. Photophosphorylation: $ATP$ is synthesized from $ADP$ and inorganic phosphate using light energy,typically occurring in chloroplasts.
$2$. Substrate-level phosphorylation: $A$ phosphoryl group is directly transferred from a high-energy substrate molecule to $ADP$ to form $ATP$,occurring in glycolysis and the Krebs cycle.
$3$. Oxidative phosphorylation: $ATP$ is synthesized by $ATP$ synthase using the energy derived from the electron transport system,where electrons are transferred from $NADH$ or $FADH_2$ to $O_2$.

(D) Energy is released during the breakdown of glucose in both aerobic and anaerobic respiration.
$1$. The conversion of glucose into pyruvate (Glycolysis) is a catabolic process that releases energy in the form of $ATP$ and $NADH$.
$2$. The conversion of glucose into lactic acid (Lactic acid fermentation) is an anaerobic process that also releases energy in the form of $ATP$.
$3$. The formation of proteins from amino acids is an anabolic process that requires energy ($ATP$ consumption),not its release.
Therefore,both $(a)$ and $(c)$ are processes where energy is released.

(B) When a twig is freshly cut from a plant,the fluid that exudes from the cut surface is primarily phloem sap.
Phloem sap consists of water,sugars (mainly sucrose),amino acids,and other organic nutrients being transported from the source (leaves) to the sink (other plant parts).
Since the phloem is under positive pressure (pressure flow hypothesis),cutting the stem causes the sap to exude from the phloem tubes.
Therefore,the correct answer is $B$.