4 1 Chemical Energy and ATP KEY CONCEPT

4. 1 Chemical Energy and ATP KEY CONCEPT All cells need chemical energy.

4. 1 Chemical Energy and ATP The chemical energy used for most cell processes is carried by ATP. • Molecules in food store chemical energy in their bonds. Starch molecule Glucose molecule

4. 1 Chemical Energy and ATP • ATP transfers energy from the breakdown of food molecules to cell functions. – Energy is released when a phosphate group is removed. – ADP is changed into ATP when a phosphate group is added. phosphate removed

4. 1 Chemical Energy and ATP Organisms break down carbon-based molecules to produce ATP. • Carbohydrates are the molecules most commonly broken down to make ATP. – not stored in large amounts – up to 36 ATP from one glucose molecule adenosine triphosphate tri=3 adenosine di=2 diphosphate

4. 1 Chemical Energy and ATP • Fats store the most energy. – 80 percent of the energy in your body – about 146 ATP from a triglyceride • Proteins are least likely to be broken down to make ATP. – amino acids not usually needed for energy – about the same amount of energy as a carbohydrate

4. 1 Chemical Energy and ATP A few types of organisms do not need sunlight and photosynthesis as a source of energy. • Some organisms live in places that never get sunlight. • In chemosynthesis, chemical energy is used to build carbon -based molecules. – similar to photosynthesis – uses chemical energy instead of light energy

4. 1 Chemical Energy and ATP Questions • What kind of molecule provides the most ATP when it is broken down? • Why do organisms need to digest food?

4. 2 Overview of Photosynthesis KEY CONCEPT The overall process of photosynthesis produces sugars that store chemical energy.

4. 2 Overview of Photosynthesis Photosynthetic organisms are producers. • Producers make their own source of chemical energy. • Plants use photosynthesis and are producers. • Photosynthesis captures energy from sunlight to make sugars.

4. 2 Overview of Photosynthesis • Chlorophyll is a molecule that absorbs light energy. chloroplast • In plants, chlorophyll is found in organelles called chloroplasts. leaf cell leaf

4. 2 Overview of Photosynthesis in plants occurs in chloroplasts. • Photosynthesis takes place in two parts of chloroplasts. – grana (thylakoids) – stroma grana (thylakoids) chloroplast stroma

4. 2 Overview of Photosynthesis • The light-dependent reactions capture energy from sunlight. – – take place in thylakoids water and sunlight are needed chlorophyll absorbs energy is transferred along thylakoid membrane then to light-independent reactions – oxygen is released

4. 2 Overview of Photosynthesis • The light-independent reactions make sugars. – take place in stroma – needs carbon dioxide from atmosphere – use energy to build a sugar in a cycle of chemical reactions

4. 2 Overview of Photosynthesis • The equation for the overall process is: 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 granum (stack of thylakoids) 1 chloroplast su nli gh t 6 H 2 O thylakoid 6 CO 2 3 6 O 2 2 energy stroma (fluid outside thylakoids) 1 six-carbon sugar 4 C 6 H 12 O 6

4. 2 Overview of Photosynthesis Questions • What is the role of chlorophyll in photosynthesis? • What is the overall purpose of photosynthesis? • Describe the overall process of photosynthesis using the equation to determine what information to include.

4. 3 Photosynthesis in Detail KEY CONCEPT Photosynthesis requires a series of chemical reactions.

4. 3 Photosynthesis in Detail The first stage of photosynthesis captures and transfers energy. • The light-dependent reactions include groups of molecules called photosystems.

4. 3 Photosynthesis in Detail • Photosystem II captures and transfers energy. – chlorophyll absorbs energy from sunlight – energized electrons enter electron transport chain – water molecules are split – oxygen is released as waste – hydrogen ions are transported across thylakoid membrane

4. 3 Photosynthesis in Detail • Photosystem I captures energy and produces energycarrying molecules. – chlorophyll absorbs energy from sunlight – energized electrons are used to make NADPH – NADPH is transferred to light-independent reactions

4. 3 Photosynthesis in Detail • The light-dependent reactions produce ATP. – hydrogen ions flow through a channel in the thylakoid membrane – ATP synthase attached to the channel makes ATP

4. 3 Photosynthesis in Detail The second stage of photosynthesis uses energy from the first stage to make sugars. • Light-independent reactions occur in the stroma and use CO 2 molecules.

4. 3 Photosynthesis in Detail • A molecule of glucose is formed as it stores some of the energy captured from sunlight. – carbon dioxide molecules enter the Calvin cycle – energy is added and carbon molecules are rearranged – a high-energy three-carbon molecule leaves the cycle

4. 3 Photosynthesis in Detail • A molecule of glucose is formed as it stores some of the energy captured from sunlight. – two three-carbon molecules bond to form a sugar – remaining molecules stay in the cycle

4. 3 Photosynthesis in Detail Questions • Describe a photosystem • When/where does water and oxygen play into this process • What is the ultimate product of photosystem? • What are the by products?

13. 3 Energy in Ecosystems KEY CONCEPT Life in an ecosystem requires a source of energy.

13. 3 Energy in Ecosystems Producers provide energy for other organisms in an ecosystem. • Producers get their energy from non-living resources. • Producers are also called autotrophs because they make their own food.

13. 3 Energy in Ecosystems Producers provide energy for other organisms in an ecosystem. • Consumers are organisms that get their energy by eating other living or once-living resources. • Consumers are also called heterotrophs because they feed off of different things.

13. 3 Energy in Ecosystems Almost all producers obtain energy from sunlight. • Photosynthesis in most producers uses sunlight as an energy source. • Chemosynthesis in prokaryote producers uses chemicals as an energy source. carbon dioxide + water + hydrogen sulfide + oxygen sugar + sulfuric acid

Chapter 6 Section 2 The Calvin Cycle Alternative Pathways • The C 4 Pathway – Some plants that evolved in hot, dry climates fix carbon through the C 4 pathway. These plants have their stomata partially closed during the hottest part of the day. – Certain cells in these plants have an enzyme that can fix CO 2 into four-carbon compounds even when the CO 2 level is low and the O 2 level is high. These compounds are then transported to other cells, where the Calvin cycle ensues. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6 Section 2 The Calvin Cycle Alternative Pathways, continued • The CAM Pathway – Some other plants that evolved in hot, dry climates fix carbon through the CAM pathway. These plants carry out carbon fixation at night and the Calvin cycle during the day to minimize water loss. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6 Section 2 The Calvin Cycle Factors That Affect Photosynthesis • Light Intensity – The rate of photosynthesis increases as light intensity increases, because more electrons are excited in both photosystems. – However, at some point all of the available electrons are excited, and the maximum rate of photosynthesis is reached. The rate then stays level regardless of further increases in light intensity. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6 Section 2 The Calvin Cycle Factors That Affect Photosynthesis, continued • Carbon Dioxide Levels – As with increasing light intensity, increasing levels of carbon dioxide also stimulate photosynthesis until the rate levels off. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6 Section 2 The Calvin Cycle Factors That Affect Photosynthesis, continued • Temperature – As temperature increases, the rate of photosynthesis increases to a maximum and then decreases with further rises in temperature. – The rate peaks at a certain temperature, at which many of the enzymes that catalyze the reactions become ineffective. Also, the stomata begin to close, limiting water loss and entry of carbon dioxide. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.