Test: Respiration in Plants - 1 - NEET MCQ

The organism that depends on dead and decaying organic matter is called a saprophyte. Saprophytes are a type of decomposer that obtain their nutrients and energy by breaking down dead plant or animal material. They play a vital role in the ecosystem by recycling nutrients and returning them to the environment for other organisms to use. 

Example: Moulds, Mushroom etc. 

• Autotrophs, on the other hand, are organisms that can produce their own food using inorganic substances and an external energy source, such as sunlight. They convert carbon dioxide and water into organic compounds through the process of photosynthesis (in plants) or chemosynthesis (in some bacteria). Autotrophs do not rely on dead organic matter for their nutrition.
• Carnivores are organisms that primarily consume the flesh of other animals. They obtain their energy and nutrients by hunting and feeding on other living organisms, rather than on dead organic matter.
• Herbivores are organisms that primarily consume plant material. They obtain their energy and nutrients by feeding on plants or plant parts. Herbivores generally do not depend directly on dead and decaying organic matter as their main source of nutrition.

Topic in NCERT: Saprophytes

Line in NCERT: "Saprophytes like fungi are dependent on dead and decaying matter."

Energy is a fundamental requirement for all living organisms to carry out their various biological processes. Within cells, energy is stored and transferred in different molecules. The molecule that primarily stores and transfers energy in living systems is called adenosine triphosphate, or ATP.

A: FAD (Flavin adenine dinucleotide) is another molecule involved in energy transfer within cells, but it is not the primary molecule for energy storage.

B: NADH (Nicotinamide adenine dinucleotide) is an important molecule in cellular respiration, which is involved in the transfer of electrons and hydrogen ions during energy production. While it plays a role in energy transfer, it is not the primary molecule for energy storage.

D: ADP (Adenosine diphosphate) is the molecule that forms when one phosphate group is removed from ATP. It is the "lower energy" form of ATP and can be converted back into ATP by adding a phosphate group. However, it is not the primary molecule for energy storage.

Topic in NCERT: Energy storage in respiration

Line in NCERT: "it is trapped as chemical energy in the form of ATP."

The TCA cycle begins with a condensation reaction. In this step, an acetyl group, derived from the breakdown of glucose or fatty acids, combines with oxaloacetic acid (OAA), a four-carbon molecule, in the presence of water. This condensation reaction forms a six-carbon compound called citric acid or citrate.

The complete reaction is as follows:
Acetyl-CoA + OAA + H₂O → Citric Acid (Citrate)

The condensation step is significant because it marks the entry of the acetyl group into the TCA cycle and the beginning of a series of enzymatic reactions that ultimately lead to the release of energy and the regeneration of OAA.

Topic in NCERT: Tricarboxylic acid cycle

Line in NCERT: "The TCA cycle starts with the condensation of acetyl group with oxaloacetic acid (OAA) and water to yield citric acid."

During anaerobic respiration, less energy is produced compared to aerobic respiration because incomplete oxidation of glucose occurs. Anaerobic respiration occurs in the absence of oxygen, typically in situations where oxygen is not readily available or during strenuous exercise when oxygen demand exceeds supply.

Topic in NCERT: Fermentation

Line in NCERT: "In fermentation there is a net gain of only two molecules of ATP for each molecule of glucose degraded to pyruvic acid whereas many more molecules of ATP are generated under aerobic conditions."

The two molecules of pyruvic acid (produced from one glucose molecule during glycolysis). The acetyl CoA then enters a cyclic pathway, tricarboxylic acid cycle, more commonly called as Krebs’ cycle. Thus, acetyl-CoA interconnecting between two cyclic pathways.

Topic in NCERT: Tricarboxylic acid cycle

Line in NCERT: "The acetyl CoA then enters a cyclic pathway, tricarboxylic acid cycle,"

Plants unlike animals have no special systems for breathing or gaseous exchange. Stomata and lenticels allow gaseous exchange by diffusion.

(a) Stomata: Stomata are tiny openings present on the surface of leaves, primarily on the underside. These openings are surrounded by specialized cells called guard cells. Stomata regulate the exchange of gases, including the intake of carbon dioxide (CO₂) for photosynthesis and the release of oxygen (O₂) and water vapor (H₂O) during transpiration. Stomata play a crucial role in the gas exchange process in plants.

(d) Lenticels: Lenticels are small openings or pores in the bark of woody plant stems. They allow for gaseous exchange between the internal tissues of the stem and the external environment. Lenticels facilitate the exchange of gases, such as oxygen (O₂) and carbon dioxide (CO₂), in stems and other woody parts of plants.

Topic in NCERT: Do plants breathe?

Line in NCERT: "Plants, unlike animals, have no specialised organs for gaseous exchange but they have stomata and lenticels for this purpose."

Acetyl CoA is a 2-carbon compound and 3-phosphoglycerate molecule enter into cyclic reactions during Calvin cycle.

Topic in NCERT: Fermentation

Line in NCERT: "Under anaerobic conditions either lactic acid fermentation or alcohol fermentation occurs."

Aerobic respiration is the process that leads to a complete oxidation of organic substances in the presence of oxygen, and releases carbon dioxide, water and a large amount of energy present in the substrate. This type of respiration is most common in higher organisms.

Aerobic Respiration:

Topic in NCERT: Aerobic respiration

Line in NCERT: "Aerobic respiration is the process that leads to a complete oxidation of organic substances in the presence of oxygen, and releases CO2, water and a large amount of energy present in the substrate. This type of respiration is most common in higher organisms."

Fermentation is a kind of anaerobic respiration in absence of oxygen to produce ethanol and carbon dioxide gas. Dough kept overnight in warm place becomes soft and spongy due to carbon dioxide gas released during fermentation.

Topic in NCERT: Fermentation

Line in NCERT: "Fermentation takes place under anaerobic conditions in many prokaryotes and unicellular eukaryotes."

Phosphofructokinase is a kinase enzyme that phosphorylates fructose-6-phosphate in glycolysis. The enzyme catalysed transfer of a phosphoryl group from ATP is an important reaction in a wide variety of biological processes.

Because the respiratory pathway is involved in both anabolism and catabolism, it would hence be better to consider the respiratory pathway as an amphibolic pathway rather than as a catabolic one.

Topic in NCERT: Amphibolic pathway

Line in NCERT: "The respiratory pathway is an amphibolic pathway as it involves both anabolism and catabolism."

In animal cells, like muscles during exercise, when oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by lactate dehydrogenase. The reducing agent is NADH+ and H+ which is reoxidised to NAD+ in both the processes.

Topic in NCERT: Glycolysis

Line in NCERT: "The initial stage of cellular respiration takes place in the cytoplasm. Each glucose molecule is broken through a series of enzyme catalysed reactions into two molecules of pyruvic acid. This process is called glycolysis."

Citrate is first isomerised to isocitrate and then followed by decarboxylation, leading to the formation of α-ketoglutaric acid.

Topic in NCERT: Tricarboxylic acid cycle

Line in NCERT: "The reaction is catalysed by the enzyme citrate synthase and a molecule of CoA is released. Citrate is then isomerised to isocitrate. It is followed by two successive steps of decarboxylation, leading to the formation of α-ketoglutaric acid."

Anaerobic respiration in man occurs in muscle cells during sudden activity in cells to form lactic acid. In yeast anaerobic respiration occurs in absence of oxygen to form ethanol.

Topic in NCERT: Anaerobic respiration in man and yeast

Line in NCERT: "Under anaerobic conditions either lactic acid fermentation or alcohol fermentation occurs."

During breakdown and synthesis of protein too, respiratory intermediates form the link. Breaking down processes within the living organism is catabolism, and synthesis is anabolism. Because the respiratory pathway (Kreb’s cycle) is involved in both anabolism and catabolism, it would hence be better to consider the respiratory pathway.

• Oxysomes refer to small round structures present within the folds of the cristae of the inner mitochondrial membrane. It is also known as F₀-F₁ particles.
• F₀ and F₁ particles are found in the inner mitochondrial region and are attached to the cristae and help in ATP production and oxidation.

Cytochrome c is a water soluble protein.

Topic in NCERT: Cytochrome c

Line in NCERT: "Cytochrome c is a small protein attached to the outer surface of the inner membrane and acts as a mobile carrier for transfer of electrons between complex III and IV."

Acetyl CoA is the connecting link between glycolysis and Kreb's cycle. The end product of glycolysis is pyruvate. It is converted to Acetyl CoA which enters the krebs cycle by combining with oxaloacetic acid (OAA) to form a 6 - C compound citric acid.

Topic in NCERT: Tricarboxylic acid cycle

Line in NCERT: "The TCA cycle starts with the condensation of acetyl group with oxaloacetic acid (OAA) and water to yield citric acid."

CoA is acetylated to acetyl CoA by the breakdown of carbohydrates through glycolysis and by the breakdown of fatty acids through β-oxidation.

Topic in NCERT: Breakdown of pyruvate

Line in NCERT: "Pyruvic acid is transported into the mitochondria where it is converted into acetyl CoA with the release of CO2."

The ratio of the volume of carbon dioxide evolved to the volume of oxygen consumed in respiration is called the respiratory quotient(RQ) or respiratory ratio

Topic in NCERT: Respiratory quotient

Line in NCERT: "The ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration is called the respiratory quotient (RQ) or respiratory ratio."

Formation of pyruvate is not a prerparatory phase or energy spending phase of Glycolysis. In this phase one ATP molecule is released.

Topic in NCERT: Glycolysis phases

Line in NCERT: "Pyruvic acid is then the key product of glycolysis."

Fermentation is the process of anaerobic respiration in which incomplete oxidation leads to formation of ethanol in absence of oxygen. Fermentation occurs in yeast.

Topic in NCERT: Fermentation

Line in NCERT: "Fermentation takes place under anaerobic conditions in many prokaryotes and unicellular eukaryotes."

There is a sequential, orderly pathway functioning, with one substrate forming the next and with glycolysis, TCA cycle and ETS pathway following one after another.

Topic in NCERT: Glycolysis, TCA cycle and ETS pathway

Line in NCERT: "There is a sequential, orderly pathway functioning, with one substrate forming the next and with glycolysis, TCA cycle and ETS pathway following one after another."

The value of R.Q. depends upon the nature of the respiratory substrate (the organic food matter oxidised in respiration) and its oxidation.

Topic in NCERT: Respiratory quotient

Line in NCERT: "The respiratory quotient depends upon the type of respiratory substrate used during respiration."

There can be a net gain of 38 ATP molecules during aerobic respiration of one molecule of glucose. 

Topic in NCERT: Net gain of ATP in aerobic respiration

Line in NCERT: "Hence, there can be a net gain of 38 ATP molecules during aerobic respiration of one molecule of glucose."