Question

Select the incorrect statement: (a) Plants have no special system for breathing or gaseous exchange. (b) Acetyl-CoA enter in TCA cycle running in matrix of mitochondria. (c) The RQ depends upon the type of respirarory substance used during respiration. (d) In fermentation, the complete oxidation of glucose occur in some bacteria.

Short answer

The incorrect statement is (d): In fermentation, the complete oxidation of glucose does not occur.

Step-by-step solution

Analyzing Statement (a)

Plants exchange gases with their environment mainly through stomata (small openings in the leaf's surface), and no special 'system' like lungs or gills are used. Therefore, statement (a) is correct.

Analyzing Statement (b)

Acetyl-coenzyme A does indeed enter the tricarboxylic acid (TCA) cycle within the matrix of mitochondria to produce energy. Therefore, statement (b) is correct.

Analyzing Statement (c)

The Respiratory Quotient (RQ) is indeed dependent on the type of respiratory substrate used. Different substrates, such as fats, proteins, and carbohydrates, yield different RQs due to the variations in their oxidation processes. Therefore, statement (c) is correct.

Analyzing Statement (d)

Fermentation is an anaerobic process and it doesn't involve the complete oxidation of glucose. Rather, it results in partial breakdown of glucose. This means that statement (d) is incorrect.

Key concepts

Plant Gas Exchange

Within the realm of biology, plant gas exchange is a fundamental process essential for photosynthesis and respiration. Unlike animals, plants do not possess specialized respiratory systems. Instead, they rely on a passive process of diffusion for the exchange of gases.

Through tiny openings called stomata primarily located on leaf surfaces, plants can take in carbon dioxide (CO2) for photosynthesis and release oxygen (O2) as a byproduct. Simultaneously, another gas, water vapor, is also lost to the atmosphere during transpiration, a process that directly impacts the plant's water balance.

The regulation of these stomatal openings is crucial and influenced by various environmental factors such as light intensity, humidity, and carbon dioxide levels. This intricate regulation ensures that plants maintain an optimal rate of gas exchange for their metabolic needs without losing excessive water.

Tricarboxylic Acid Cycle

Diving deeper into cellular metabolism, the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle, forms the core of cellular energy production. Located within the matrix of the mitochondria, the TCA cycle processes Acetyl-CoA, a derivative from carbohydrates, fats, and proteins, to produce vital energy molecules.

Acetyl-CoA enters the cycle and undergoes a series of chemical transformations. It ultimately contributes to the production of ATP, the energy currency of the cell, as well as NADH and FADH2, which are essential for the electron transport chain that drives ATP synthesis. CO2 is also released as a byproduct of this cycle.

The efficiency and regulation of the TCA cycle are vital for the energy needs of the cell, and it serves as a point of intersection for various metabolic pathways.

Respiratory Quotient

Bioenergetics includes an understanding of the respiratory quotient (RQ), which is a dimensionless number that helps in analyzing the types of substrates being used for respiration. The RQ is determined by the ratio of the volume of CO2 evolved to the volume of O2 consumed during respiration.

Carbohydrates have an RQ of approximately 1.0, since the volume of oxygen required for their oxidation is almost equal to the volume of carbon dioxide released. Lipids and proteins result in lower values of RQ since they require more oxygen relative to the amount of carbon dioxide they produce. For instance, the RQ for lipids is around 0.7.

This concept is critical in physiological studies as it provides insights into the metabolic processes and can indicate whether an organism is predominantly using carbohydrates, fats, or proteins as its source of energy.

Fermentation in Bacteria

When delving into the metabolism of bacteria, fermentation is a process to consider, especially in the context of energy production in the absence of oxygen. Some bacteria can undergo fermentation to produce energy, but it is crucial to understand that this process does not involve the complete oxidation of glucose, unlike aerobic respiration.

Fermentation pathways lead to the partial breakdown of glucose into simpler molecules such as lactic acid or ethanol and carbon dioxide in bacteria, along with the generation of small amounts of ATP. The process allows for the regeneration of NAD+, which is necessary for glycolysis to continue in the absence of oxygen.

This process is exploited in many industrial applications, such as yogurt and cheese production, where lactic acid bacteria are utilized for fermentation, and in the production of alcoholic beverages, where yeast is used to ferment sugars.