Section 1 Answers Interest Grabber Answers 1. What are the benefits of having a bank account? To save money and earn interest. 2. What do you have to do if you need some of this money? Go to the bank and take out the money you need. 3. What might your body do when it has more energy than it needs to carry out its activities? Students will likely say that the body stores the energy. 4. What does your body do when it needs energy? Student answers may include that energy is gotten from food.

Go to Section: 8–1 Energy and Life A.Autotrophs and Heterotrophs The energy in most food comes from the sun. Plants and some other types of organisms are able to use light energy from the sun to produce food. Organisms such as plants, which make their own food, are called autotrophs. Other organisms, such as animals, cannot use the sun’s energy directly. These organisms, known as heterotrophs, obtain energy from the foods they consume. Section 8-1 Section Outline

Go to Section: 8–1 Energy and Life B.Chemical Energy and ATP The activities of the cell are powered by chemical fuels. One of the principal chemical compounds that living things use to store energy is adenosine triphosphate, abbreviated ATP. Adenosine diphosphate (ADP) has a structure that is similar to ATP but with one important difference: ADP has two phosphate groups instead of three. This difference is the key to the way in which cells store energy. When a cell has energy available, it can store small amounts of energy by adding a phosphate group to ADP molecules. In a way, ATP is like a fully charged battery, ready to power the machinery of the cell.

Go to Section: 8–1 Energy and Life C.Using Biochemical Energy –Cells use the energy provided by ATP in a number of ways. One way is active transport. Many cell membranes contain a sodium- potassium pump that moves sodium ions (Na+) out of the cell and potassium ions (K+) into it. This is an example of Active Transport. These are common in many cellular activities. –Most cells have only a small amount of ATP, enough to last for only a few seconds of activity. Why is this? –Even though ATP is very efficient at transferring energy, it is not very good for storing large amounts of energy over the long term. In fact, *a single molecule of the sugar glucose stores more than 90 times the chemical energy of a molecule of ATP.

Go to Section: AdenineRibose3 Phosphate groups Section 8-1 ATP

Go to Section: ADPATP Energy Adenosine diphosphate (ADP) + PhosphateAdenosine triphosphate (ATP) Partially charged battery Fully charged battery Section 8-1 Figure 8-3 Comparison of ADP and ATP to a Battery

Go to Section: ADPATP Energy Adenosine diphosphate (ADP) + PhosphateAdenosine triphosphate (ATP) Partially charged battery Fully charged battery Section 8-1 Figure 8-3 Comparison of ADP and ATP to a Battery

Go to Section: Trapping Energy Have you ever used a solar-powered calculator? No matter where you go, as long as you have a light source, the calculator works. You never have to put batteries in it. Section 8-2 Interest Grabber

Section 2 Answers Interest Grabber Answers 1. A solar-powered calculator uses solar cells that are found in rows along the top of the calculator. Into what kind of energy is the light energy converted so that the calculator works? They convert light energy into electrical energy. 2.Recall that plants use light energy from the sun to make food. Into what kind of energy is the light energy converted by plants? Plants convert light energy into chemical energy. 3.Most plants, no matter what size or shape they are, have some parts that are green. Which parts of a plant are usually green? Leaves are green, as are some stems. 4.What does the green color have to do with the plant’s ability to convert light energy into the energy found in the food it makes? The green color is the pigment chlorophyll, which absorbs light energy from the sun and converts it to chemical energy in the process of photosynthesis.

Go to Section: 8–2Photosynthesis: An Overview A.The study of energy capture and use begins with photosynthesis. In the process of photosynthesis, plants use the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy carbohydrates—sugars and starches. B.The Photosynthesis Equation Because photosynthesis usually produces 6-carbon sugars (C 6 H 12 O 6 ) as its final products, the overall equation for photosynthesis can be shown as follows: 6CO 2 + 6H 2 O Light C 6 H 12 O 6 + 6O 2 Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars, or carbohydrates. Section 8-2 Section Outline

Go to Section: 8–2Photosynthesis: An Overview C.Light and Pigments Photosynthesis takes place in a plant organelle called the chloroplast. In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in chloroplasts. Chloro.= Green

Go to Section: 8–2Photosynthesis: An Overview Plants gather the sun’s energy with light-absorbing molecules called pigments. The plants’ principal pigment is chlorophyll. There are two main types of chlorophyll: chlorophyll a and chlorophyll b Chlorophyll absorbs light very well in the blue and red regions of the visible spectrum. However, chlorophyll does not absorb light well in the green region of the spectrum, which is why plants are green.

Go to Section: Light Energy Chloroplast CO 2 + H 2 OSugars + O 2 Section 8-2 Photosynthesis: Reactants and Products

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A Look Into the Future It is 100 years in the future and you are a research scientist. An enormous volcanic eruption has recently sent huge quantities of dust and ash into the atmosphere. Working with a partner, make a list of how this event will affect each of the following: 1. photosynthesis 2. plant life 3. animal life 4. human societies Section 8-3 Interest Grabber

Section 3 Answers Interest Grabber Answers Working with a partner, make a list of how this event will affect each of the following: 1. The rate of photosynthesis will decrease due to reduced sunlight. 2. Plants will grow more slowly or die off due to decreased rate of photosynthesis. 3. Animal populations will decrease after a while due to fewer plants for herbivores to eat. Fewer herbivores will eventually result in fewer carnivores. Also, less oxygen will be available. 4. Human societies will have to adjust their eating habits as some food species die out.

Go to Section: Chloroplast Light O2O2 Sugars CO 2 Light- Dependent Reactions Calvin Cycle NADPH ATP ADP + P NADP + Chloroplast Section 8-3 Figure 8-7 Photosynthesis: An Overview