2. Organisms and the Environment

3. Chapter Four: Physical Science Connections 4.1 Elements and Compounds 4.2 The Compounds of Life 4.3 Physical Variables

4. 4.2 Carbon compounds and cells Life as we know it is carbon based. A carbon atom can form chemical bonds with other carbon atoms in long chains or rings.

5. 4.2 Carbon compounds and cells Carbon compounds in living things include: carbohydrates, proteins, lipids and nucleic acids.

7. 4.2 Carbohydrates, fats and proteins Carbohydrates are energy-rich compounds made from carbon, hydrogen, and oxygen. Cells use carbohydrates to get and store energy. Carbohydrates are also called sugars or starches.

8. 4.2 Carbohydrates Plant cells store energy as starch. Rice, potatoes, and wheat are plant starches.

9. 4.2 Lipids Lipids are made by cells to store energy for long periods of time. Lipids include fats, oils, and waxes. Can you think of examples of lipids in plants or animals?

10. 4.2 Proteins Proteins are very large molecules made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Protein molecules are made of smaller molecules called amino acids.

11. 4.2 Nucleic acids Nucleic acids are compounds made of long, repeating chains called nucleotides. DNA is a nucleic acid that contains the information cells need to make all of their proteins.

12. 4.2 DNA Some scientists refer to DNA as the “blueprints” for life. What is a blueprint and why might scientists use this “analogy”?

13. Investigation 4A How is carbon dioxide important to living things? Carbon Dioxide and Living Things