2 2 1 Identify The Form S In Which Each Of The Following Is

Oxygen : when oxygen diffuses from the lungs respiratory surface into the blood, 98.5% of it is combined with haemoglobin. Red blood cells are ideally adapted to carrying oxygen, they have no nucleus (which allows for maximum transportation space), they contain haemoglobin (which has an affinity for oxygen, making it easier to transport), the shape of blood cells (biconcave) allows for maximum surface area to volume ratio, allowing for maximum diffusion. When blood combines with haemoglobin it forms oxyhaemoglobin, which has a bright red colour as opposed to the darker red of deoxygenated blood. Arteries carry bright red oxygenated blood and veins carry dark red deoxygenated blood.

Carbon Dioxide: most carbon dioxide is transported in the form of hydrogen carbonate ions, which are formed in red blood cells but carried in plasma. The remaining carbon dioxide is carried either as dissolved in the plasma or combined with haemoglobin. Carbon dioxide produced as a waste product, diffuses into the bloodstream where some of it dissolves into the plasma and the rest combines with water to form carbonic acid. It is not ideal for the carbon dioxide to dissolve into the plasma, as that would alter to pH of the blood as a result most of it enters the red blood cells where there are two possible scenarios.
1) Most of the carbon dioxide mixes with water to form carbonic acid which is them rapidly converted into hydrogen carbonate ions. These hydrogen carbonate ions move out of the red blood cells and into the plasma. This can be summarised as
Carbon dioxide + water  carbonic acid + hydrogen carbonate + buffered hydrogen ions
2) Some carbon dioxide binds to haemoglobin forming carbaminohaemoglobin. Unlike with oxygen, which bonds to the iron part of the haemoglobin, carbon dioxide bonds to the amino group – this reaction is also reversible.

Water and Salts : Water is the medium of transport for all substances in the body, it forms the basis of cytoplasm in all cells, along with the interstitial fluids (fluids between cells), blood and lymph (transport fluid in animals). Salts are carried in blood as ions dissolved in the plasma, for example sodium chloride is transported as sodium ions and chloride ions. Ionic solutions are known as electrolytes, as they can conduct electricity.

Lipids and other products of digestion: carbohydrates become glucose, proteins become amino acids, lipids become fatty acids and glycerol, and nucleic acids become nucleotides.

Glucose and amino acids are water soluble so they are transported in the bloodstream dissolved in the plasma, along with other soluble substances nitrogenous bases, vitamins and glycerol, absorbed from the digestive tract.

Lipids are harder to transport, as they are not water soluble and cannot be carried in the plasma. Most of the lipids are packaged into the lymphatic system and then into the blood stream. These are transported in small spherical particles called micelles, these are transported in a colloidal solution - not quite a true solution and a suspension. The lipids are absorbed into the lacteals inside of the villi of the small intestine, rather than directly into the bloodstream like water soluble substances. During absorption, they are processed to form micelles called chylomicrons, it is transported in this form. The lacteals, carrying the chylomicrons, are a part of the lymphatic circulation and eventually these join into the main blood supply.

Nitrogenous wastes: Nitrogenous wastes are harmful products formed in the body by the breakdown of proteins. These substances are transported in diluted form, from the cells to areas in which they can be excreted from the body. Nitrogenous wastes in the form of ammonia, urea, uric acid and creatinine are all carried dissolved in the blood plasma.