Section 8.1 Energy and Life Name: Biology Date: Period ...

Section 8.1 Energy and Life

Name:

Biology

Date:

Period:

Lesson Objectives Describe the role of ATP in cellular activities. Explain where plants get the energy they need to produce food.

Lesson Summary Chemical Energy and ATP Energy is the ability to do work. Organisms need energy to stay alive.

Adenosine triphosphate (ATP) is a chemical compound cells use to store and release energy. o An ATP molecule consists of adenine, the sugar ribose, and three phosphate groups. o Cells store energy by adding a phosphate group to adenosine diphosphate (ADP) molecules. o Cells release energy from ATP molecules by removing a phosphate group.

Energy provided by ATP is used in active transport, to contract muscles, to make proteins, and in many other ways.

Cells contain only a small amount of ATP at any one time. They regenerate it from ADP as they need it, using energy stored in food.

Heterotrophs and Autotrophs The energy to make ATP from ADP comes from food. Organisms get food in one of two ways.

Heterotrophs get food by consuming (eating) other organisms. Autotrophs use the energy in sunlight to make their own food. Photosynthesis is the process that uses light energy to produce food molecules.

Chemical Energy and ATP For Questions 1?6, complete each statement by writing the correct word or words.

1.

is the ability to do work.

2. The main chemical compound cells use for energy is

(ATP).

3.

is a 5-carbon sugar molecule that is part of an ATP molecule.

4. The

of ATP are the key to its ability to store and supply energy.

5. ATP releases energy when it

bonds between its phosphate groups.

6. Most cells only store enough ATP for

of activity.

7. Label each part of the diagram of an ATP molecule below.

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8. In the visual analogy, what chemical is represented by the low battery? 9. What are two ways in which the diagram shows an increase in energy? 10. Describe the concepts shown in the diagram.

11. What are two ways in which cells use the energy temporarily stored in ATP?

12. Energy is needed to add a third phosphate group to ADP to make ATP. What is a cell's source of this energy?

Heterotrophs and Autotrophs - For Questions 13?17, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true.

_________________13. All heterotrophs must eat food to get energy. _________________14. Autotrophs do not need to eat food because they make food. _________________15. The energy in food originally came from ATP. _________________16. The term photosynthesis means "pulling apart with light" in Greek. _________________17. The energy of sunlight is stored in the chemical bonds of carbohydrates.

18. Complete the table comparing two types of organisms.

Autotrophs and Heterotrophs

Type

Description

Examples

Autotrophs

Heterotrophs

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Why are Plants Green?

Biology 6.0

Introduction A pigment is a molecule that absorbs light. The leaves of most plants are rich in pigments. These pigments absorb light and convert it into chemical energy to fuel the production of sugars. The primary photosynthetic pigment is chlorophyll a and chlorophyll b. Other pigments such as carotenoids and xanthophyll are referred to as accessory pigments. These accessory pigments absorb light in other regions of the spectrum making the plant more efficient in absorbing sunlight and photosynthesis.

Different types of pigments absorb different types (wavelengths) of light. Some pigments might absorb blue light better than other wavelengths of light for example. A spectrophotometer is a machine used by scientists to measure the absorbance of light by substances. The better a pigment absorbs a color (wavelength) of light, the higher percent of absorbance reading. The data in Table 1 gives a possible spectrophotometer absorbance reading for the two plant chlorophylls a and b. Graph the data for chlorophyll a and chlorophyll b on the same graph. The line for each is an approximation of the absorption spectrum for that molecule.

Table 1:

Wavelength nanometers (nm)

400 425 450 475 500 525 550 575 600 625 650 675 700

Chlorophyll a % Absorption

32 60 10 3 0 0 4 2 4 3 21 44 12

Chlorophyll b % Absorption

8 29 62 51 8 0 3 4 2 20 29 4 0

Carotenoids % Absorption

22 23 49 43 55 34 0 0 0 0 0 0 0

Analysis 1. Color code your graph in a way that clearly shows the color range between 400 and 700 nanometers.

400-425: Violet 575: Green-yellow 675-700: Red

450-475: Blue 600: Yellow

500: Blue-Green 625: Orange

525-550: Green 650: Orange-red

2. Based on the data and your graphs, what can you conclude about the two chlorophylls and their absorption spectra? In what ways are the two similar? Different?

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3. Chlorophylls are the predominant pigments in leaves. Based on the data and your graph, give a possible explanation for why plants are green.

4. If some wavelengths (colors) of light are absorbed by chlorophylls, what happens to the other wavelengths that are not absorbed?

5. Based on your graph, which type of light is most important to plants for photosynthesis? Explain.

The yellow-orange carotenoids in leaves absorb wavelengths of light that chlorophyll a and chlorophyll b cannot. The energy collected by carotenoids through light absorption is channeled to chlorophyll a in photosynthesis. Use the data from Table 1 to make an absorption spectrum graph for carotenoids, as you have done previously for chlorophyll a and b. Put the data for the carotenoids on the same graph as the chlorophylls.

6. What color corresponds with the carotenoids? Explain using evidence from your graph.

7. What is the adaptive value of accessory pigments like carotenoids? That is, what advantage do they provide the plants?

8. Leaves of many North American trees change color in the fall or before a dry season. Explain why and relate your answer to carotenoids.

Why Leaves Change Color

- The Splendor of Autumn Every autumn we revel in the beauty of the fall colors. The mixture of red, purple, orange and yellow is the result of

chemical processes that take place in the tree as the seasons change from summer to winter. During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch. Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot. Most of the year these colors are present but they are masked by great amounts of green coloring. Chlorophyll Breaks Down - But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their foodmaking process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor. At the same time other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange. The autumn foliage of some trees show only yellow colors. Others, like many oaks, display mostly browns. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season. Weather Affects Color Intensity - Temperature, light, and water supply have an influence on the degree and the duration of fall color. Low temperatures above freezing will favor anthocyanin formation producing bright reds in maples. However, early frost will weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall colors. The best time to enjoy the autumn color would be on a clear, dry, and cool (not freezing) day. Enjoy the color, it only occurs for a brief period each fall.

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Section 8.3 Review

Biology 6.0

The Light-Dependent Reactions: Generating ATP and NADPH (page 235) For Questions 1?5, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true.

1. Photosystems are clusters of chlorophyll and proteins. 2. The light-dependent reactions begin when photosystem I absorbs light. 3. Electrons from water molecules replace the ones lost by photosystem II. 4. ATP is the product of photosystem I. 5. ATP and NADPH are two types of protein carriers.

6. How does ATP synthase produce ATP?

7. When sunlight excites electrons in chlorophyll, how do the electrons change?

8. Where do the light-dependent reactions take place?

9. Complete the table by summarizing what happens in each phase of the light-dependent reactions of

photosynthesis.

Light-Dependent Reactions

Description

Photosystem II

Electron Transport Chain

Photosystem I Hydrogen ion movement and ATP Formation

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