Respiratory System
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
Everybody knows that breathing is an essential requirement for good health and that failure to do so will, in a relatively short period of time, lead to asphyxia and death. However, it is important to recognise that there are three types of respiration occurring simultaneously at different locations within the human body: external, internal and cellular respiration. External respiration describes the process of gaseous exchange that takes place in the lungs. That is to say: oxygen (O2) from the atmosphere is exchanged for carbon dioxide (CO2) from the pulmonary blood supply (capillaries). Internal respiration refers to the process by which oxygen in the blood is made available to the cells and exchanged for carbon dioxide across the plasma membrane. Lastly, cellular respiration refers to the production of energy (ATP) within the cells (by oxidative metabolism) described in Chapter 2 (glucose + O2→ ATP + CO2+ H2O). All three processes are absolutely essential for health and take place at the same time. In general terms, external and internal respiration ensure that the blood is provided with a constant supply of oxygen for cellular metabolism and provide a means for the excretion of carbon dioxide. However, before we look at how the respiratory tract facilitates this process, it is necessary to first consider the air that we breathe.
Chapter Paper 1 Answers
James Day, Amy Thomson, Tamsin McAllister, Nawal Bahal in Get Through, 2014
Cellular respiration involves the oxidation of fuel molecules to generate adenosine triphosphate (ATP). Aerobic metabolism of 1 glucose molecule yields 38 molecules of ATP, however, this is only 40% of the total energy produced (60% is heat energy). The chain of reactions comprising aerobic metabolism of glucose begins in the cytoplasm with glycolysis, generating pyruvate, which is converted into acetyl coenzyme A (acetyl-CoA). Acetyl-CoA enters the mitochondrion and combines with oxaloacetate to form citric acid in the Krebs cycle (also known as the ‘citric acid cycle’). The Krebs cycle takes place on the inner mitochondrial membrane and produces NADH and FADH2, which act as reducing agents in the electron transport chain in the process of oxidative phosphorylation. The Pasteur point is the PO2 threshold below which oxidative phosphorylation cannot occur; aerobic metabolism continues until the mitochondrial PO2 falls below 0.4 kPa (3 mmHg).
Multiphoton imaging of the retina
Pablo Artal in Handbook of Visual Optics, 2017
Coenzymes such as NAD(P)H and flavoproteins like FAD are crucial for mitochondria-based cellular respiration pathways such as oxidative phosphorylation. Many retinal layers are densely packed with mitochondria because the retina is more metabolically active than the brain per unit weight (Wong-Riley, 2010). These molecules are of critical importance for cell survival and play the following roles during cellular respiration: NADH and NADPH are the reduced forms of the coenzymes nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), respectively, and serve as reducing agents. NADH, a key component of cellular respiration, is generated in the cytoplasm during glycolysis. It is also produced in the mitochondria by the Krebs cycle (also known as the citric acid cycle) during aerobic respiration. NADH donates electrons in complex I, the first stage of the electron transport chain (oxidative phosphorylation), which generates adenosine triphosphate (ATP), a unit of intracellular energy. Thus, glycolysis and the Krebs cycle produce NADH, while the electron transport chain consumes NADH.Flavin adenine dinucleotide (FAD) is also strongly fluorescent. FAD moves electrons between the Krebs cycle and complex II, the second stage of the electron transport chain. FAD is used during the Krebs cycle and produced during the electron transport chain.
Detrimental effects of fructose on mitochondria in mouse motor neurons and on C. elegans healthspan
Published in Nutritional Neuroscience, 2022
Divya Lodha, Sudarshana Rajasekaran, Tamilselvan Jayavelu, Jamuna R. Subramaniam
Neurodegeneration is a major concern in the world today because of the increase in prevalence of the neurodegenerative diseases – Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and Amyotrophic Lateral Sclerosis (ALS). None of the neurons, including hippocampal neurons and motor neurons, and non –neuronal cells, astrocytes10 and other glial cells11, can escape the fate of degeneration. Mitochondrial impairment in ALS is well documented12. Mitochondria, responsible for nutrient metabolism and energy (ATP) production, are the hub of cellular respiration. Previous studies have shown that excessive amounts of fructose when metabolized, generate Reactive Oxygen Species (ROS) in the mitochondria of skeletal muscles, resulting in cell death13,14. This ROS generation and accumulation causes oxidative stress in the mitochondria of neurons15 and leads to neurodegeneration. But the direct effect of fructose on the mitochondrial function in neurons has not been studied in detail.
Acute exposure to C60 fullerene damages pulmonary mitochondrial function and mechanics
Published in Nanotoxicology, 2021
Dayene de Assis Fernandes Caldeira, Flávia Muniz Mesquita, Felipe Gomes Pinheiro, Dahienne Ferreira Oliveira, Luis Felipe Silva Oliveira, Jose Hamilton Matheus Nascimento, Christina Maeda Takiya, Leonardo Maciel, Walter Araujo Zin
Similar to other nanomaterials, fullerene exposure has been strongly related to mitochondrial dysfunction by means of different toxic mechanisms (Freyre-Fonseca et al. 2011; Liu et al. 2019; Santos et al. 2014; Dong et al. 2016; Xu et al. 2016). Mitochondria play an essential, but not unique, role in cellular respiration, where oxygen is consumed and adenosine triphosphate (ATP) is produced during oxidative phosphorylation. Indeed, during this process superoxide anion (O2−) is also generated and converted into hydrogen peroxide (H2O2) by manganese superoxide dismutase (MnSOD), which crosses the mitochondrial membrane (Spinelli and Haigis 2018). An impaired oxidative phosphorylation may lead to mitochondrial dysfunction and trigger an oxidative imbalance, which can be used to gauge the toxicity (Moreno et al. 2007; Yang et al. 2016). C60 and derivatives can induce cytotoxicity, trigger apoptosis by the increase in reactive oxygen species (ROS), and reduce mitochondrial membrane potential and capacity (Jacobsen et al. 2008; Lee et al. 2011). However, most studies investigate isolated mitochondrial activity or on the cellular level, with no further detail about the possible change at the organ level, especially those broadly exposed to nanopollutants, as the lung.
Effect of mycobacterial proteins that target mitochondria on the alveolar macrophages activation during Mycobacterium tuberculosis infection
Published in Experimental Lung Research, 2022
Iris Selene Paredes-González, Omar Emiliano Aparicio-Trejo, Octavio Ramos-Espinosa, Manuel Othoniel López-Torres, Milena Maya-Hoyos, Monserrat Mendoza-Trujillo, Alejandra Barrera-Rosales, Dulce Mata-Espinosa, Juan Carlos León-Contreras, José Pedraza-Chaverri, Clara Espitia, Rogelio Hernández-Pando
Mitochondria are involved in catabolic and anabolic reactions and are critical for respiratory ATP production. Interestingly, the organelle’s morphology is directly related to their function. The fusion and fission processes constantly modify the mitochondrial network. Fission exscinds a mitochondrial tubule into two, while fusion connects two tubules to form a longer one.15,16 Cycles of mitochondrial fusion and fission are essential for maintaining mitochondrial activity, influenced by metabolic and cellular signals, depending on the cell type and organism.17,18 Interconnected (fused) mitochondria are frequently present in cells with active mitochondrial respiration, while metabolically quiescent cells are characterized by presenting small fragmented (fission) mitochondria.19,20 Thus, part of the mitochondrial morphology can be represented by changes in cellular respiration.21
Related Knowledge Centers
- Combustion
- Oxygen
- Metabolism
- Catabolism
- Oxidation State
- Adenosine Triphosphate
- Cell
- Nutrient
- Redox
- Sugar