Chapter 3: Section 3

Chapter 3: Section 3 Energy for Life

Trapping and Using Energy • Where does energy for life come from? • The food we eat • All of the activities of an organism involve chemical reactions. • The total of all chemical reactions in an organism is called metabolism

Trapping and Using Energy • The chemical reactions of metabolism need enzymes. • Enzymes cause a change, but the enzyme is not changed and can be used again.

Trapping and Using Energy • Without the right enzyme, a chemical reaction in a cell cannot take place • Each chemical reaction in a cell requires a specific enzyme

Photosynthesis • All living thing are divided into two groups – producers and consumers – based on how they obtain their food. • Organisms that make their own food are called producers • Organisms that cannot make their own food are called consumers

Photosynthesis • Plants and many other kinds of producers can convert light energy into another kind of energy called chemical energy. • This process is called photosynthesis. • During photosynthesis, producers use light energy to make sugars, which can be used as food.

Producing Carbohydrates • Carbohydrates are organic molecules that supply energy for cell processes. • Producers that use photosynthesis are usually green because they contain a green pigment called chlorophyll. • Chlorophyll and other pigments are used in photosynthesis to capture light energy, these pigments are found in chloroplasts.

Producing Carbohydrates • The captured light energy powers chemical reactions that produce sugar and oxygen from the raw materials, carbon dioxide and water. • Some of the captured light energy is stored in the chemical bonds that hold the sugar molecules together.

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.

Storing Carbohydrates • Consumers take in food by eating producers or other consumers. • No matter what you eat, photosynthesis was involved directly or indirectly in its production

Respiration • To get energy, cells break down food. • Some of the energy from the food is used when you move and some of it becomes thermal energy (heat energy). • Most cells also need oxygen to break down food.

Respiration • During cellular respiration, chemical reactions occur that break down food molecules into simpler substances and release their stored energy.

Using Respiration to Break Down Carbohydrates • The food molecules most easily broken down by the cells are carbohydrates. • The carbohydrates are broken down into glucose molecules. • As glucose molecules are broken down, energy is released.

Using Respiration to Break Down Carbohydrates • The breakdown of energy occurs in the mitochondria of the cells of plants, animals, fungi, and many others. • This process uses oxygen , releases much more energy, produces carbondioxide, and water as waste.

Fermentation • When cells do not have enough oxygen for respiration, they use a process called fermentation. • Fermentation releases some of the energy stored in glucose molecules

Fermentation • Some microscopic organisms, such as bacteria, carry out fermentation and make lactic acid. • Some of these organisms are used to produce yogurt and some cheeses.

Related Processes • Some producers use photosynthesis to make food. • All living things use respiration or fermentation to release energy stored in food.

Related Processes • Photosynthesis and respiration are almost opposite of each other. • Photosynthesis produces sugars and oxygen, respiration uses these products. • Respiration produces carbon dioxide and water, photosynthesis uses these products.

Related Processes

Question 1 The total of all chemical reactions is __________. A. Respiration B. Metabolism C. Photosynthesis D. Enzyme

Question 2 Organisms that make their own food are consumers. A. True B. False

Question 3 In what organelle does photosynthesis take place? A. Chloroplast B. Mitochondria C. Nucleus D. Vacuole

Question 4 Food molecules most easily broken down by cells are _____________. A. Proteins B. Lipids C. Fats D. Carbohydrates

Question 5 Fermentation releases some of the energy stored in protein molecules. A. True B. False

Question 6 __________ produces sugars and oxygen, and ___________ uses these products. A. Respiration, photosynthesis B. Fermentation, respiration C. Photosynthesis, respiration D. Photosynthesis, fermentation

Chapter 3: Section 3

Chapter 3: Section 3

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