1) The blood's oxygen-carrying capacity is significantly increased by the presence of the respiratory pigment .
2) Haemoglobin has a high for, and loads up with, oxygen when the concentration in its surroundings is high. Haemoglobin has a low affinity for, and releases when the concentration in the surroundings is low.
3) The disc shapes of red blood cells presents a relatively large of haemoglobin molecules to the surrounding environment for oxygen uptake and release. Their tiny size and enable them to pass through capillaries easily.
4) The production of red blood cells takes place in and requires a supply of iron and .
5) Red blood cells live for about 120 days and then undergo breakdown in the liver, bone marrow and . from haemoglobin is stored and the remaining haem molecules are converted to .
6) and amino acids are absorbed directly into the bloodstream from the small intestine. Vitamin B12 needs in order to be absorbed.
7) Bile salts act as an . By maintaining an emulsion of tiny droplets, bile salts increase the relative surface area of lipid exposed to the enzyme and therefore promote the action of lipase.
8) Lipid is absorbed into in villi and transported through the body in the system.
9) Three blood vessels are associated with the liver. Comparison of their contents after a meal shows the hepatic portal vein's plasma to be rich in and glucose, the hepatic vein's plasma to be rich in and the hepatic artery's plasma to be normal compared with arterial blood in other parts of the body.
10) Glucose is transported in the bloodstream to living cells to provide them with a source of .
11) Amino acids are used by cells to synthesise various types of .
12) Lipid molecules act as a further source of energy. Excess are stored as fat in tissues.
13) Certain vitamins and minerals are needed to act as in enzyme reactions.
14) Blood sugar concentration is conserved at optimum level by excess glucose being converted to and stored in the liver.
15) Poisonous materials undergo in the liver.
16) Bilirubin from the breakdown of haemoglobin is removed from the bloodstream by the converted to bile pigments and excreted in .
17) Excess amino acids are in the liver to form urea.
18) of blood in kidneys forces filtrate out of each into a Bowman’s capsule and on through a proximal tubule, loop of and convoluted tubule before reaching a collecting duct. During this journey, various substances are from the filtrate, leaving which is removed from the body.
19) The are organs of excretion and . The water content of the blood is controlled by .
20) Since excretion means the elimination of the waste products of metabolism, the are also excretory organs since they remove carbon dioxide from the body.