1. Elements and compounds in living organisms Changting luo

2. Elements in living oraginsms living organisms contain many chemical elements,some in large quantities and some in very small amounts.

3. Elements in living oraginsms

4. The four commonest chemical elements of life are carbon,hydrogen,oxygen and nitrogen.

5. Elements in living oraginsms

6. Organic and inorganic compounds Living organisms contain many chemical compounds.Some of them are organic and some are inorganic. All compounds that contain no carbon are inorganic. Organic compounds are defined as compounds containing carbon that are found in living organisms,but there are a few carbon compounds are inorganic.

7. Chemical elements and their roles Sulphur(S)--Needed to make two of the twenty amino acids that proteins contain Calcium(Ca)--Acts as a messenger,binding to calmodulin and other proteins that regulate processes inside cells,including transcription Phosphorus(P):Part of the phosphate groups in ATP and DNA molecules

8. Elements in living oraginsms Some elements have other specific rolesin some organisms.For example,iron is needed to make hemoglobin in many animals and calcium is needed to make the minerals that strengthen bones and teeth.

9. Subunit of organic macromolecules The molecules of many organic compounds are large and so are called macromolecules. They are built up using small and relatively simple subunits. Main subunits are proteins, carbohydrates and lipids.