Chapter 9: Cell Processes

1. Table of Contents Chapter 9: Cell Processes Section 1: Chemistry of Life Section 2: Moving Cellular Materials Section 3: Energy for Life

2. Energy for Life 3 A. Trapping and Using Energy • All of the activities of an organism involve chemical reactions in some way. • The total of all chemical reactions in an organism is called metabolism. • The chemical reactions of metabolism need enzymes. • Enzymes in cells cause a change, but the enzyme is not changed and can be used again.

3. Energy for Life 3 A. Trapping and Using Energy 5. Enzymes also can cause molecules to join. 6. Without the right enzyme, a chemical reaction in a cell cannot take place. 7. Each chemical reaction in a cell requires a specific enzyme. Click image to view movie.

4. Energy for Life 3 B. Photosynthesis • Living things are divided into two groups— producers and consumers—based on how they obtain their food. • Organisms that make their own food, such as plants, are called producers. • Organisms that cannot make their own food are called consumers.

5. Energy for Life 3 B. Photosynthesis 4. Plants and many other producers can convert light energy into another kind of energy—chemical energy. 5. The process they use is called photosynthesis. 6. During photosynthesis,producers use light energy to make sugars, which can be used as food.

6. Energy for Life 3 C. Producing Carbohydrates • Producers that use photosynthesis are usually green because they contain a green pigment called chlorophyll (KLOR uh fihl). • Chlorophyll and other pigments are used in photosynthesis to capture light energy. • In plant cells, these pigments are found in chloroplasts.

7. Energy for Life 3 C. Producing Carbohydrates 4. The captured light energy is used to drive chemical reactions during which the raw materials, carbon dioxide and water, are used to produce sugar and oxygen. 5. For plants, the raw materials come from air and soil.

8. Energy for Life 3 C. Producing Carbohydrates 6. Some of the captured light energy is stored in the chemical bonds that hold sugar molecules together.

9. Energy for Life 3 D. Storing Carbohydrates • Plants make more sugar during photosynthesis than they need for survival. • Excess sugar is changed and stored as starches or used to make other carbohydrates. • Plants use carbohydrates as food for growth, maintenance, and reproduction. • Consumers take in food by eating producers or other consumers.

10. Energy for Life 3 E. Respiration 1. Some of the energy from the food you eat is used to make you move. 2. Some of it becomes thermal energy, which is why you feel warm or hot when you exercise. 3. Most cells also need oxygen to break down food.

11. Energy for Life 3 E. Respiration 4. During respiration, chemical reactions occur that break down food molecules into simpler substances and release their stored energy. 5. Just as in photosynthesis, enzymes are needed for the chemical reactions of respiration.

12. Energy for Life 3 F. Breaking Down Carbohydrates • The type of food molecules most easily broken down by cells is carbohydrates. • Respiration of carbohydrates begins in the cytoplasm of the cell. • The carbohydrates are broken down into glucose molecules. • Each glucose molecule is broken down further into two simpler molecules.

13. Energy for Life 3 F. Breaking Down Carbohydrates 5. As the glucose molecules are broken down, energy is released. 6. The two simpler molecules are broken down again. This breakdown occurs in the mitochondria of the cells of plants, animals, fungi, and many other organisms. 7. This process uses oxygen, releases much more energy, and produces carbon dioxide and water as wastes.

14. Energy for Life 3 F. Breaking Down Carbohydrates 8. When you exhale you breathe out carbon dioxide and some of the water. 9. Respiration occurs in the cells of all living things.

15. Energy for Life 3 G. Fermentation • When cells do not have enough oxygen for respiration, they use a process called fermentationto release some of the energy stored in glucose molecules. • Like respiration, fermentation begins in the cytoplasm.

16. Energy for Life 3 G. Fermentation 3. Again, as the glucose molecules are broken down, energy is released. 4. But the simple molecules from the breakdown of glucose do not move into the mitochondria. 5. Instead, more chemical reactions occur in the cytoplasm.

17. Energy for Life 3 G. Fermentation 6. These reactions release some energy and produce wastes. 7. Depending on the type of cell, the wastes may be lactic acid, alcohol, and carbon dioxide. 8. The presence of lactic acid is why your muscle cells might feel stiff and sore after you exercise.

18. Energy for Life 3 H. Related Processes • During photosynthesis and respiration, what is produced in one is used in the other. • Photosynthesis produces sugars and oxygen, and respiration uses these products.

19. Section Check 3 Question 1 _______ is the total of all chemical reactions in an organism. Answer The answer is metabolism. All of the activities of an organism involve chemical reactions in some way.

20. Section Check 3 Question 2 Which does this equation represent? C. photosynthesis D. chemosynthesis A. respiration B. fermentation

21. Section Check 3 Answer The answer is C. During photosynthesis, plants take in carbon dioxide and water and combine it with light energy to make sugars, which they use for food.

22. Section Check 3 Question 3 _______ is the type of food molecules most easily broken down by cells. Answer The answer is carbohydrates. As carbohydrates are broken down, energy is released.

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