Matter and Change Chapter Nine: Acids, Bases and Solutions Chapter Ten: Chemical Reactions Chapter Eleven: The Chemistry of Living Things

11.1 The Chemistry of Carbon 11.2 Proteins, Fats and Nucleic Acids

Investigation 11B How does a DNA molecule carry information? The Structure of DNA

11.2 Proteins, fats and nucleic acids Four important molecules in living things are: –carbohydrates –proteins –fats –nucleic acids

11.2 Fats Fats are high-energy molecules that plants and animals use to store energy. A fat molecule has a two-part structure.

11.2 Proteins Proteins are basic molecular building blocks of cells and all parts of animals. Proteins are among the largest organic molecules. Why is the shape of a protein important?

11.2 Saturated and unsaturated fats In a saturated fat, carbon atoms are surrounded by as many hydrogen atoms as possible. An unsaturated fat has fewer hydrogen atoms than it could have.

11.2 Enzymes Thousands of chemical reactions are going on in your body each second, involving thousands of chemicals. Catalysts help control chemical reactions. You can think of catalysts as helper molecules that allow a reaction to proceed in many small steps instead of all at once.

11.2 Enzymes Enzymes are special protein catalysts.

11.2 Enzymes Enzymes are special proteins acting as catalysts. The body has thousands of different enzymes. Each one is specific and matched with its target molecule.

11.2 DNA and nucleic acids Cells must continually create the proteins they need. In the process called protein synthesis, proteins are made using the instructions found in DNA molecules. Where does the energy needed for this reaction come from?

11.2 DNA and nucleic acids DNA is a nucleic acid. A DNA molecule is put together like a twisted ladder. This model shows a short piece of the flattened DNA ladder. A DNA molecule is usually twisted and much longer.

11.2 DNA Each side of the ladder is made of: – 5-carbon sugars called deoxyribose –and phosphate groups.

11.2 DNA There are four nitrogen bases in two matched pairs.

11.2 DNA and amino acids The assembly of proteins is coded by a certain sequence of nitrogen bases. Below the sequence of thymine, thymine and adenine would build the amino acid leucine. What base sequence stops the assembly of proteins?

11.2 DNA and reproduction When an organism reproduces, the DNA molecule is able to make exact replicas of itself.

11.2 DNA and reproduction These enzymes play a role when DNA copies itself: –Helicase enzymes untwist the DNA helix. –Ligase enzymes unzip the DNA –Polymerase enzymes rebuild nitrogen bases on the open strands.

11.2 DNA and reproduction Changes in DNA are called mutations. Changes in DNA lead to new proteins, and changes in living organisms that are passed on in successive generations.