11.1 The chemistry of carbon Organic chemistry is the branch of chemistry that specializes in carbon and carbon compounds. Organic molecules are found in all living things. Scientists classify the organic molecules in living things into four basic groups: carbohydrates, fats, proteins, and nucleic acids.

11.1 Carbohydrates Carbohydrates are mainly composed of carbon, hydrogen, and oxygen in a ratio of about 1:2:1. Carbohydrates exist as small molecules, like glucose, and long-chain molecules, like starches. Table sugar is a carbohydrate called sucrose.

11.1 Carbohydrates Carbohydrates are relatively small molecules used to store and transfer energy in living systems. Carbohydrates are classified as either sugars or starches.

11.1 Carbohydrates Starches are long chains of simple sugars joined together. Cellulose is the primary molecule in plant fibers, including wood.

11.1 Proteins, fats and nucleic acids Carbohydrates are the simplest of the important biological molecules. Proteins, fats, and nucleic acids are more complex molecules, including thousands of individual atoms in a single molecule.

11.1 Photosynthesis Photosynthesis is the foundation of the food chain on Earth. For every glucose sugar molecule produced, six molecules of carbon dioxide are removed from the air, and six molecules of oxygen are produced.

11.1 Respiration Animals get energy and nutrients by breaking up glucose, starch, and other organic molecules. Cellular respiration breaks down glucose into water and carbon dioxide again, extracting energy in the process. Each cell converts the energy in glucose into chemical energy stored in molecules of ATP.

Cellular Respiration

11.1 The importance of water Liquid water is essential to life as we know it. The human body is typically between 60 and 65 percent water by weight. Most of the chemical reactions that sustain life only work in solution.

11.1 The importance of water There are 3 important characteristics of water that make it essential for life: –Water is a good solvent. –Liquid water has a wide temperature range. –Water has a high specific heat capacity.

Health Connection Good Fats vs. Bad Fats We need a reasonable amount of fat in our diets. Fat helps support cell function and helps our bodies absorb vitamins. But a diet too high in certain fats can lead to many health problems, including obesity, diabetes, and heart disease.

Activity A nutrition label shows the amount of calories, fat, cholesterol, carbohydrates, protein, and several vitamins and minerals in one serving of the food. The exact amount of each nutrient a person needs depends on gender, age, activity level, and weight. The Scoop on Nutrition Labels

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

Fats Fats are high-energy molecules that plants and animals use for long term energy storage. A fat molecule has a two-part structure.

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.

Proteins Proteins are among the largest organic molecules. Muscle, skin, blood and organs are made from proteins. Proteins are made from amino acids. Why is the shape of a protein important?

Enzymes/Catalysts Enzymes are special proteins that act as catalysts to help control chemical reactions in our bodies. You can think of catalysts as helper molecules that allow a reaction to proceed at lower temperatures and in many small steps instead of all at once.

11.2 Enzymes Enzymes are special protein catalysts.

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 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.