What we breathe in is far from pure oxygen, but roughly by volume 78 per cent nitrogen, 21 per cent oxygen, 0.965 per cent argon and 0.04 per cent carbon dioxide (plus some helium, water and other gases).The permanent gases in air we exhale are roughly 78 per cent nitrogen, 15 to 18 per cent oxygen (we retain only a small amount), 4 to 5 per cent carbon dioxide and 0.96 per cent argon, the CO2 being of course used by plants during photosynthesis. Matt Wormald, Neutral Bay Trees and plants give off carbon dioxide when they breathe, and when they die and rot.John Moir, Mollymook How is it decided which side of the street will be numbered odd and the other even? Jim Dewar, North Gosford You don't have to be a Rhodes scholar to know that even numbers are streets ahead of those rather odd figures, hence the even numbers are situated on the best side of the street Steve Barrett, Glenbrook I have lived in different towns and in different countries and I have lived on the odd side of the street.It seems strange - odd, even - that the odd numbers are usually on the left, even on the right. Therefore my side is odd and the other side is even! That's where the carbon in carbon dioxide comes from.Howard Clark, Ryde Like other things in life, breathing isn't that simple.The street usually starts at the closest point to the nearest GPO in a town or city.
In this process, energy is produced in the mitochondria of cells. When that reacts with oxygen (O2) in the cells, it produces carbon dioxide (CO2) and water (H2O). We use the energy and the carbon dioxide is breathed out as gas.In Elderslie (Camden Municipality), we're No 22 on our street and still on the left. Donald Howard, Elderslie If Adolf Hitler had not come to power would World War II have ever happened?The foundation of WWII started in 1937 when Japan invaded China, creating tensions with the USA.We breathe in oxygen and some of this carbon dioxide.When we exhale, we breathe out less oxygen but more carbon dioxide than we inhale.Paul Roberts, Lake Cathie The carbon we breathe out as carbon dioxide comes from the carbon in the food we eat.The carbohydrates, fat and proteins we consume and digest are eventually converted by a number of different biochemical pathways in the body to glucose (C6H12O6).John Moir, Mollymook The odd versus even system is found in most English speaking countries, with the odd numbers being assigned to the western or southerly aspects of a street.In Australia, the boundary between councils may instigate a restart in numbering.Dr John Frith, Paddington Every living cell of our body carries out the energy-releasing process of respiration, where glucose (a simple sugar) is slowly "burnt" (oxidised) to give off carbon dioxide (excreted through the lungs) and water.Glucose is a carbohydrate and is also a digestive breakdown product of starch (in potatoes, etc).