Glycaemic index is a scale from 1-100 that basically refers to how fast something is converted to glucose - which is the form sugar is carried around in the blood. If something is high GI (e.g. lollies) then it is absorbed really fast and your blood sugar levels rise rapidly, followed by a sharp fall. If something is low GI - (e.g. complex carbohydrates like wholegrain breads) then sugar (glucose) is released into the blood slowly and over a long period of time.
Haemoglobin is the form that Oxygen is carried in the blood. Haem - meaning 'iron' and globin being the protein. Each haemaglobin molecule associates with a red blood cells, where it carries around oxygen to tissues from the lungs. It is very important that oxygen is carried in this way because oxygen is highly reactive. If it were to float around in the blood by itself then it would cause damage to other cells through oxidation of them Think about why they are always telling you that you need vegetables because they contain antioxidants. Cells need oxygen, but oxidation of cells is damaging.
When the body needs energy, it uses glucose to produce ATP. This is done through one of two ways that involve pyruvic acid. The first is anaerobic - meaning 'without oxygen'. The body converts glucose to pyruvic acid and then to lactic acid and as a result obtains 2 molecules of ATP (aka free energy). This can be done in any cell in the body but lactic acid build up is bad because it changes the pH of the blood, so the system is quite limited.
The second use of pyruvic acid occurs in the aerobic energy system. Glucose, fat or amino acids (protein) are again converted to pyruvic acid, which is then converted to acetyl CoA and carbon dioxide (which is why we breath out carbon dioxide to get rid of it). The acetyl CoA is then further used to power the electron transport system. It is this system that ultimately provides the energy to resynthesise ADP to ATP. When ADP is synthesised to ATP, then the cells in the body can once again break apart the ATP and release energy.
Remember that energy comes from:
Adenosine - 1.Phosphate - 2.Phosphate - 3.phosphate
When you break apart phosphate two and three, then energy is released.
So overall pyruvic acid is an Intermediate compound in the anaerobic and aerobic energy systems.
That should help you. Ive tried to put it as simply as possible. Just post if there are anymore questions.
