Internal Respiration

Internal Respiration

Internal Respiration is the exchange of gases that happens in your tissues.  Oxygen is being dropped off to your tissues and carbon dioxide is being picked up.  Remember that oxygen travels bound to hemoglobinThe oxygen-carrying protein in red blood cells that gives blood its red color. and carbon dioxide travels in the plasmaThe liquid component of blood. portion of whole blood.  Oxygen must first diffuse out of the plasma and into the interstitial fluids.  Wait, one more step.  Then oxygen has to diffuse into the cellsThe basic structural and functional units of life..  There is this compartment of interstitial fluidThe fluid surrounding cells within tissues. that stands between the gases in the blood and the cells needing them.  Luckily, the gradients are set up perfectly to allow this to happen.

Making DEOxyhemoglobin

Hemoglobin can carry 4 oxygen moleculesGroups of atoms bonded together., as I have pictured here.  However, how many it will pick up depends in what is known as hemoglobin’s affinity, or love, for oxygen.  Hemoglobin is fickle.  It depends on what’s going on around the hemoglobin if it has love for oxygen or not.  This is discussed in detail in another minilecture where external respirationThe exchange of gases between the lungs and the blood in the pulmonary capillaries. is also incorporated.

Carbon Dioxide

Carbon dioxide does not travel bound to hemoglobin in red blood cells.  Carbon dioxide is picked up by the plasma portion of whole blood in internal respirationThe exchange of gases between the blood and body tissues..  The gradient of oxygen is set up for oxygen to diffuse down its gradient. The same gradient works similarly for carbon dioxide.   Your cells are always pumping out carbon dioxide as a waste product of making ATPThe energy currency of cells used for muscle contraction..  This causes your body tissues to have a high concentration of carbon dioxide. The carbon dioxide diffuses out of your tissues and into the atmosphere, which contains very little carbon dioxide.

There are 3 ways in which carbon dioxide is transported.: 1) 10% is dissolved in plasma, 2) 20% is bound to hemoglobin, 3) 70% travels as bicarbonate(HCO₃⁻) – A crucial buffer in blood that helps maintain pH balance; formed when carbon dioxide anionA negatively charged ion..  When carbon dioxide hits the plasma an enzyme called carbonic anhydraseAn enzyme in red blood cells that helps convert carbon dioxide and water into carbonic acid. ushers a two-step reaction.  First, carbon dioxide and waterThe universal solvent essential for life. are changed into carbonic acid(H₂CO₃) – A weak acid formed when carbon dioxide dissolves in water; plays a key role in blood. This immediately dissociates into the bicarbonate anion. A lone hydrogen cation makes hemoglobin drop off the oxygen it is carrying.