| Substance + explaination |
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| 1. Carbon Dioxide → product of aerobic respiration → carbon dioxide level in our blood is usually not harmful → in certain cases where there is abnormally high level of in our blood → a condition called hypercarbia occurs. → person may suffer from headache, confusion, rapid breathing and premature heartbeats. ⇒ excretory organ is the lungs. and it is excreted as gas in expired air. |
| 2. Urea digestive system breaks down proteins into amino acids. Absorbed amino acids ⇒ transported to liver, distributed around the body and then assimilated. Liver → is involved in assimilation of amino acids. → uses amino acids to synthesise proteins found in blood plasma these plasma proteins ⇒ include fibrinogen, which is essential for clotting of blood. Human Transport System Main Note if we consume more proteins than we need → we will have excess amino acids in the blood → excess amino acids → are transported to the liver where they are deaminated through a process called deamination. During deamination → part of the amino acid molecule is removed and converted to urea. → urea is then removed by kidneys Is urea in blood harmful? Urea → is a waste product formed in the breakdown of proteins Nomral concentration of urea in blood is nor harmful ⇒ abnormally high urea concentration in blood → may cause abdominal pain, nausea, or vomiting → rare cases → can result in irregular heartbeat and muscle cramps |
| 3. Mineral salts or ions Bodies → need mineral salts Deficiency of certain ions → may result in deficiency diseases. Example: lack of calcium results in weakening of bones or osteoporosis Excess salts or ions in blood → can be harmful. ⇒ may lower WP in blood plasma Water may pass out of tissue cells into blood by osmosis. Cells may become dehydrated (crenated) = Movement of Substances Main Note ⇒ Kidneys help to remove excess salts from the body |
| 4. Water Water → essential to life ⇒ produced during aerobic respiration hence it is also a metabolic product However → excess water in body is harmful → will increase WP in blood plasma By Osmosis→ Water will enter tissue cells → cells may swell and burst Hence excess water also has to be removed. |