Test: Respiration in Plants - Class 9 MCQ

Stomata are small openings on the surfaces of leaves that facilitate gas exchange. They allow oxygen to enter the plant for respiration and carbon dioxide to exit, thus playing a crucial role in the respiratory process of plants.

At night, when photosynthesis ceases due to the lack of sunlight, plants may switch to anaerobic respiration if oxygen is scarce. This adaptation allows them to continue generating energy, although at a lower efficiency compared to aerobic respiration.

Anaerobic respiration occurs in the absence of oxygen and typically results in the production of ethanol and carbon dioxide, along with a lower yield of ATP (only 2 ATP per glucose molecule). This process is temporary and cannot sustain plant parts for long periods.

Anaerobic respiration in yeast primarily produces ethanol and carbon dioxide. This process is utilized in fermentation, which is important in baking and brewing, illustrating how organisms can thrive in environments lacking oxygen by using alternative metabolic pathways.

Carbon dioxide is released as a byproduct of aerobic respiration. During this process, glucose is broken down, and carbon dioxide is produced alongside water and energy. This carbon dioxide can then be utilized in photosynthesis, demonstrating the complementary relationship between these two processes.

Respiration is a biochemical process that occurs in multiple steps and is catalyzed by enzymes, whereas combustion is a physico-chemical process that typically occurs in a single step and releases energy as heat and light. This distinction highlights the complexity and efficiency of respiration in living organisms.

The use of limewater is a classic experiment to demonstrate carbon dioxide production during respiration. When carbon dioxide from the plant's respiration is bubbled through limewater, it turns milky, indicating the presence of this gas. This experiment effectively highlights the respiratory process in plants.

Waterlogged soil limits oxygen availability for root respiration, leading to decreased respiration rates. This can hinder energy production, ultimately affecting plant health and growth, as roots rely on oxygen to perform cellular respiration efficiently.

Plants primarily perform photosynthesis during the day when sunlight is available. This is because they rely on sunlight to convert carbon dioxide and water into glucose and oxygen.

• Photosynthesis occurs mainly in the morning and afternoon when light intensity is high.
• At night, plants do not perform photosynthesis as there is no light.
• Sunlight is essential for this process to take place.

Therefore, it is during the day that plants are most active in photosynthesis.

During fermentation, particularly in anaerobic conditions, glucose is only partially broken down, resulting in the production of ethanol and a limited yield of ATP (2 ATP per glucose molecule). This process allows certain organisms, like yeast, to generate energy without oxygen.

ATP (adenosine triphosphate) serves as the primary energy currency of the cell. During respiration, energy released from glucose breakdown is captured in the form of ATP, which can then be utilized for various cellular functions, including growth, repair, and active transport.

Respiration is essential for plants as it converts glucose into energy, which is necessary for various cellular activities. During this process, glucose is broken down, releasing energy stored in its chemical bonds, which is then used by the plant to perform functions such as growth and maintenance.

In plants, gases diffuse directly from cell to cell, as they lack a circulatory system for gas transport like animals do. This means that oxygen and carbon dioxide must move through the plant tissues via diffusion, making respiration in plants distinct from that in animals.

The Krebs cycle occurs in the mitochondria of cells. This organelle is often referred to as the powerhouse of the cell because it is where the majority of ATP is produced during aerobic respiration, following the glycolysis phase in the cytoplasm.

To demonstrate heat production during respiration, an experiment with soaked seeds placed in two thermos flasks can be conducted. The flask with live seeds will show a temperature increase due to the heat generated from cellular respiration, while the control flask with boiled seeds will remain unchanged.

Soil compaction reduces the spaces between soil particles, decreasing the availability of oxygen for root respiration. This can severely impact plant health, as roots require oxygen to carry out cellular respiration and thus produce the energy necessary for growth and function.

Respiration is classified as a catabolic process because it breaks down complex molecules, such as glucose, to release energy. This energy is then used for various metabolic activities within the cell, highlighting its role in energy metabolism.

During the day, the carbon dioxide produced from respiration can be utilized in photosynthesis, as plants convert it into glucose. This interdependence between respiration and photosynthesis illustrates the cyclical nature of energy and matter in plant life.

Aerobic respiration can yield up to 38 ATP molecules per mole of glucose. This high energy yield is due to the complete oxidation of glucose in the presence of oxygen, allowing for efficient energy production, which is vital for the plant's metabolic processes.

Glycolysis is the first phase of cellular respiration and takes place in the cytoplasm. In this phase, glucose is broken down into pyruvate, producing a small amount of ATP in the process. This is crucial as it prepares the products for further breakdown in the Krebs cycle within the mitochondria.