WE ALL KNOW WE INHALE OXYGEN AND EXHALE CARBON DIOXIDE, BUT WHY? AND HOW IS THIS INVOLVED IN MUSCLE CONTRACTION?
Exercise results in the diffusion of O2 from the blood into metabolically active cells, such as contracting skeletal muscle fibers. Active cells use more O2 for ATP production via metabolic intermediate Acetyl-Coa derived from glucose, fatty acids, or amino acids and ketone bodies.
The rate of pulmonary and systemic gas exchange depends on several factors in sum;
A)Partial pressure difference of the gases
B)Surface area available for gas exchange.
C)Diffusion distance.
D) Molecular weight and solubility of the gases.
Without getting too technical; mechanistically on a chemical level the processes in which carbon dioxide and oxygen are transported is described below (see figure 23.2 for biochemical details; Ultimately, we exhale CO2 transported from tissue cells and provide our working cells with O2. Note that CO2 transportation occurs in the following ways 7% dissolved in blood plasma, 23% as Hb–CO2 (carbaminohemoglobin) 70% as HCO3- (bicarbonate ions) Transport of O2 is dissolved in blood plasma (1.5%) and 98.5% as Hb–O2 (oxyhemoglobin)
Okay great, so then how does what does O2 have to do with muscle contraction and ATP (cellular energy) Note that not all ATP requires O2 for production. (ATP-PCR System and Anaerobic Glycolysis ie., non-oxidative metabolic systems). Hemoglobin in blood or Myoglobin in muscle fibers carry the bound O2 which allows Krebs cycle and the Electron Transport chain to function; hence we get a great yield of ATP from a series of chemical reactions. (see figure below (10.11 C)
ATP (cellular energy) hydrolysis causes ATP to broken down into ADP and an inorganic phosphate by the enzyme ATPase the energy release changes the position of the myosin head which then binds to actin and ultimately cause the power stoke in which thin muscle (actin) filaments move past the thick filaments (myosin) which are pulled towards the centre of the sarcomere which is basically muscle contraction or the “power stroke or sliding filament theory” in which provides us with movement (muscle’s torque force on bone). (see figure 10.6)
In summary, we breathe in O2 exhale CO2, O2 aids in aerobic metabolism which yields ATP (but can also be created without the presence of Oxygen) and ATP allows our muscles to contract. Not to mention more so importantly many metabolic reactions yielding ATP from oxidative breakdown of glucose within the body’s cells which allows us to sustain life.
Source: Tortora, G. J., & Derrickson, B. H. (2014). Principles of anatomy and physiology. Milton, Qld: John Wiley & Sons Australia (all information and diagrams)
