Erythrocytes consist mainly of hemoglobin, a complex molecule containing heme groups whose iron atoms temporarily link to oxygen molecules in the lungs or gills and release them throughout the body. Oxygen can easily diffuse through the red blood cell's cell membrane. Hemoglobin also carries some of the waste product carbon dioxide back from the tissues. (In humans, less than 2% of the total oxygen, and most of the carbon dioxide, is held in solution in the blood plasma). A related compound, myoglobin, acts to store oxygen in muscle cells.
The color of erythrocytes is due to the heme group of hemoglobin. The blood plasma is straw-colored alone, but the red blood cells change colors due to the state of the hemoglobin: when combined with oxygen the resulting oxyhemoglobin is scarlet and when oxygen has been released, the resulting deoxyhemoglobin is darker, appearing bluish through the blood vessel walls.
The keeping of oxygen-binding proteins in cells (rather than having them dissolved in body fluid) was an important step in the evolution of vertebrates; it allows for less viscous blood and longer transport ways of oxygen.
Showing posts with label Oxygen. Show all posts
Showing posts with label Oxygen. Show all posts
Monday, January 8, 2007
Blood Oxygenation
Blood oxygenation is measured in several ways, but the most important measure is the hemoglobin (Hb) saturation percentage. This is a non-linear (sigmoidal) function of the partial pressure of oxygen. About 98.5% of the oxygen in a sample of arterial blood in a healthy human breathing air at normal pressure is chemically combined with the Hb. Only 1.5% is physically dissolved in the other blood liquids and not connected to Hb. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species .
With the exception of pulmonary and umbilical arteries and their corresponding veins, arteries carry oxygenated blood away from the heart and deliver it to the body via arterioles and capillaries, where the oxygen is consumed; afterwards, venules and veins carry deoxygenated blood back to the heart.
Differences in infrared absorption between oxygenated and deoxygenated blood form the basis for realtime oxygen saturation measurement in hospitals and ambulances.
Under normal conditions in humans at rest, haemoglobin in blood leaving the lungs is about 98-99% saturated with oxygen. In a healthy adult at rest, deoxygenated blood returning to the lungs is still approximately 75% saturated. Increased oxygen consumption during sustained exercise reduces the oxygen saturation of venous blood, which can reach less than 15% in a trained athlete; although breathing rate and blood flow increase to compensate, oxygen saturation in arterial blood can drop to 95% or less under these conditions. Oxygen saturation this low is considered dangerous in an individual at rest (for instance, during surgery under anesthesia): "As a general rule, any condition which leads to a sustained mixed venous saturation of less than 50% will be poorly tolerated and a mixed venous saturation of less than 30% should be viewed as a medical emergency."
A fetus, receiving oxygen via the placenta, is exposed to much lower oxygen pressures (about 20% of the level found in an adult's lungs) and so fetuses produce another form of hemoglobin with a much higher affinity for oxygen (hemoglobin F) in order to extract as much oxygen as possible from this sparse supply.
Substances other than oxygen can bind to the hemoglobin; in some cases this can cause irreversible damage to the body. Carbon monoxide for example is extremely dangerous when absorbed into the blood. When combined with the hemoglobin, it irreversibly makes carboxyhemoglobin which reduces the volume of oxygen that can be carried in the blood. This can very quickly cause suffocation, as oxygen is vital to many organisms (including humans). This damage can occur when smoking a cigarette (or similar item) or in event of a fire. Thus carbon monoxide is considered far more dangerous than the actual fire itself because it reduces the oxygen carrying content of the blood.
With the exception of pulmonary and umbilical arteries and their corresponding veins, arteries carry oxygenated blood away from the heart and deliver it to the body via arterioles and capillaries, where the oxygen is consumed; afterwards, venules and veins carry deoxygenated blood back to the heart.
Differences in infrared absorption between oxygenated and deoxygenated blood form the basis for realtime oxygen saturation measurement in hospitals and ambulances.
Under normal conditions in humans at rest, haemoglobin in blood leaving the lungs is about 98-99% saturated with oxygen. In a healthy adult at rest, deoxygenated blood returning to the lungs is still approximately 75% saturated. Increased oxygen consumption during sustained exercise reduces the oxygen saturation of venous blood, which can reach less than 15% in a trained athlete; although breathing rate and blood flow increase to compensate, oxygen saturation in arterial blood can drop to 95% or less under these conditions. Oxygen saturation this low is considered dangerous in an individual at rest (for instance, during surgery under anesthesia): "As a general rule, any condition which leads to a sustained mixed venous saturation of less than 50% will be poorly tolerated and a mixed venous saturation of less than 30% should be viewed as a medical emergency."
A fetus, receiving oxygen via the placenta, is exposed to much lower oxygen pressures (about 20% of the level found in an adult's lungs) and so fetuses produce another form of hemoglobin with a much higher affinity for oxygen (hemoglobin F) in order to extract as much oxygen as possible from this sparse supply.
Substances other than oxygen can bind to the hemoglobin; in some cases this can cause irreversible damage to the body. Carbon monoxide for example is extremely dangerous when absorbed into the blood. When combined with the hemoglobin, it irreversibly makes carboxyhemoglobin which reduces the volume of oxygen that can be carried in the blood. This can very quickly cause suffocation, as oxygen is vital to many organisms (including humans). This damage can occur when smoking a cigarette (or similar item) or in event of a fire. Thus carbon monoxide is considered far more dangerous than the actual fire itself because it reduces the oxygen carrying content of the blood.
Blood
Blood is a highly specialized circulating tissue consisting of several types of cells suspended in a fluid medium known as plasma. The cellular constituents are: red blood cells, which carry respiratory gases and give it its red color because they contain hemoglobin (an iron containing protein that binds oxygen in the lungs and transports it to tissues in the body), white blood cells (leukocytes), which fight disease, and platelets, cell fragments which play an important part in the clotting of the blood. Medical terms related to blood often begin with hemo- or hemato- (BE: haemo- and haemato-) from the Greek word "haima" for "blood." Anatomically, blood is considered a connective tissue from both its origin in the bones and its function.
Anaerobic Biochemistry
Anaerobics are activities that are carried out 'without oxygen'. This terminology refers to the molecular level of respiration, not the respiration of the organism as a whole (i.e., breathing). During anaerobic exercise, the muscles being exercised have insufficient oxygen to meet the demands of the activity, and thus must also use alternate, non-oxygen-dependent processes to produce energy. The muscle does still receive oxygen during anaerobic exercise; the average drop in blood oxygen content throughout the body is likely minimal.
Anaerobic exercise begins with muscles utilizing stored creatine phosphate to generate the ATP that produces muscle contraction. After several seconds, further ATP energy is made available to muscles by metabolizing muscle glycogen into pyruvate through glycolysis, as it normally does through the aerobic cycle. What differs is that pyruvate, rather than be broken down through the slower but more energy efficient aerobic process, is fermented to lactic acid.
Muscle glycogen is restored from blood sugar, which is either released from the liver, from digested carbohydrates, or amino acids which have been turned into glucose.
Anaerobic exercise begins with muscles utilizing stored creatine phosphate to generate the ATP that produces muscle contraction. After several seconds, further ATP energy is made available to muscles by metabolizing muscle glycogen into pyruvate through glycolysis, as it normally does through the aerobic cycle. What differs is that pyruvate, rather than be broken down through the slower but more energy efficient aerobic process, is fermented to lactic acid.
Muscle glycogen is restored from blood sugar, which is either released from the liver, from digested carbohydrates, or amino acids which have been turned into glucose.
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