Question

Assertion: Glucose is a respiratory substrate. Reason: Glucose is oxidised during process of cellular respiration.

Short answer

Yes, the reason correctly explains the assertion. Glucose is a respiratory substrate that is used and oxidized during cellular respiration to extract energy.

Step-by-step solution

Understanding the Assertion

The assertion states that 'Glucose is a respiratory substrate'. In cellular respiration, a respiratory substrate is a molecule which is broken down or metabolized to release energy. Usually, glucose, a simple sugar, is used as a respiratory substrate for most organisms.

Understanding the Reason

The reason stated is 'Glucose is oxidized during the process of cellular respiration'. In cellular respiration, glucose is indeed oxidized to produce carbon dioxide, water, and energy.

Checking whether the Reason explains the Assertion

Given the above explanations, it can be stated that the reason correctly explains the assertion. Glucose is a respiratory substrate that is oxidized during cellular respiration to release energy.

Key concepts

Respiratory Substrate

A respiratory substrate is a fundamental concept in cellular respiration, acting as the fuel for the process. In essence, it's the molecule that cells 'break down' to retrieve energy. Glucose, the most commonly known respiratory substrate, is akin to gasoline for a car. It is the preferred energy source for many cells due to its high-energy bonds and widespread availability.

During respiration, enzymes within the cells orchestrate the breakdown of glucose, or other substrates, into smaller molecules. This breakdown not only provides energy in a form that cells can use but also generates byproducts like carbon dioxide and water. Other examples of respiratory substrates include fatty acids, glycerol, and amino acids, which the body can use if glucose is in short supply.

Understanding respiratory substrates is pivotal because it underpins the energy production for every cell, tissue, and organ in the body. Without these molecules, our cells would lack the necessary energy to perform their functions, leading to a systemic shutdown of biological processes.

Glucose Oxidation

Glucose oxidation is a specific type of metabolic reaction where glucose, a six-carbon sugar, undergoes a process where it's stripped of electrons, effectively 'burnt up' to release energy. This process takes place in a step-by-step manner within the powerhouse of the cell, the mitochondria.

The journey of glucose starts with glycolysis, where a glucose molecule is partially oxidized and split into two molecules of pyruvate. This occurs in the cytoplasm and provides a net gain of energy-carrying molecules ATP and reduced NADH.

• Glycolysis: Glucose becomes 2 Pyruvate + 2 ATP + 2 NADH

The pyruvate then enters the mitochondria and is fully oxidized through the Krebs cycle and electron transport chain, resulting in a more significant release of energy.

• The Krebs Cycle: Oxidation of acetyl-CoA to CO₂ and additional production of ATP and electron carriers.

Both NADH and another molecule called FADH2 shuttle these high-energy electrons to the electron transport chain, where a large amount of ATP is produced, along with water as a byproduct.

Understanding glucose oxidation can help grasp how the human body extracts energy from food and why glucose is so central to energy metabolism.

Energy Metabolism

Energy metabolism refers to all the chemical processes that occur in living organisms to maintain life, involving the production and use of energy. At its core is the conversion of nutrients into energy - a currency that cells can spend on growth, repair, and maintenance activities.

This energy production occurs through catabolic pathways where complex molecules, such as carbohydrates, fats, and proteins, are broken down into simpler ones, releasing energy in the form of ATP. ATP acts as a molecular energy shuttle, transporting energy where it's needed inside the cell.

• Catabolic pathways: Break down molecules to produce ATP.

The body balances these energy-producing reactions with anabolic pathways, where ATP is used to create more complex molecules that form cell structures or are stored for future energy use.

• Anabolic pathways: Use ATP energy to build complex molecules.

These processes are regulated to ensure that the right amount of energy is available, mirroring the balance between income and expenditure in a financial budget. An imbalance can lead to weight gain or loss, disorders, and affects overall health. Thus, managing energy metabolism is crucial for sustaining life and supporting health.

Metabolic Pathways

Metabolic pathways consist of a sequence of chemical reactions that occur within a cell, governed by enzymes. These pathways are crucial because they control the flow of energy and the formation or breakdown of molecules in the body.

Each step in a metabolic pathway is catalyzed by a specific enzyme, ensuring reactions occur swiftly and efficiently. These pathways are grouped into two main categories:

• Anabolic pathways: these pathways synthesize complex molecules from simpler ones, consuming energy in the process.
• Catabolic pathways: conversely, these pathways break down complex molecules into simpler ones, releasing energy that can be used by the cell.

These reactions can be linear, branched, or cyclical, depending on the specific needs of the cell at any given time. For instance:

• Glycolysis: a linear pathway where glucose is converted into pyruvate.
• Krebs Cycle: a cyclical pathway that generates energy through the complete oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

The regulation of metabolic pathways is essential because it ensures cells have a balanced supply of energy and building blocks necessary for survival. Disruptions in these pathways can lead to metabolic diseases such as diabetes and can be a focus of treatment strategies.