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Chapter 8 Photosynthesis

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Presentation on theme: "Chapter 8 Photosynthesis"— Presentation transcript:

1 Chapter 8 Photosynthesis




5 Section 8-1 Energy and Life
Energy is the ability to do work Without energy, life would cease to exist The energy in most food comes from the sun

6 Autotrophs 1. Plants use sun energy to make food 2. Organisms that make their own food B. Heterotrophs 1. Obtain energy from the foods they consume 2. Some eat plants, some eat other animals, and some even get energy from decomposing matter

7 C. Chemical Energy and ATP
1. Energy comes in different forms a. light, heat, and electricity b. can also be stored in chemical compounds 2. ATP – adenosine triphosphate a. adenine, ribose, and 3 phosphate groups b. 3 phosphates – give the ability to store and release energy

8 i. Storing Energy - ADP – adenosine diphosphate - only has 2 phosphate groups - when energy is available it adds a phosphate group to store energy (full battery) ii. Releasing Energy - energy released by breaking the bond between the phosphate groups - basic energy source of all cells


10 D. Using Biochemical Energy (Using ATP)
1. Active Transport a. Sodium-Potassium Pump -membrane protein pumps Na+ out of the cell and K+ into the cell 2. Motor Proteins a. energy to move organelles 3. Synthesis of proteins and nucleic acids

11 E. ATP is a useful source of Energy, but it
E. ATP is a useful source of Energy, but it is not a good energy storage molecule Most cells only have a small amount of ATP One single molecule of glucose stores 90 times the chemical energy of an ATP molecule Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose

12 Section 8-2 Photosynthesis: An Overview
Photosynthesis – the key cellular process identified with energy production Plants use sunlight to convert water and carbon-dioxide into high energy carbohydrates and oxygen

13 A. Scientists Investigating Photosynthesis
Van Helmont a. concluded that trees gain most of their mass from water b. he did not account for the carbon part of the equation (CO2) 2. Priestley a. candle experiment – jar and the mint plant – release oxygen

14 3. Jan Ingenhousz -showed Priestley’s effect only occurred in the presence of light - light is necessary for plants to produce oxygen

15 B. Photosynthesis Equation
- Photosynthesis uses energy from sunlight to convert carbon dioxide and water into glucose and oxygen

16 C. Light and Pigments 1. photosynthesis requires light and chlorophyll – found in chloroplasts 2. Plants use pigments to gather the sun’s energy 3. Chlorophyll – plants key pigment - chlorophyll a - chlorophyll b



19 - Chlorophyll absorbs light in the blue-violet and the red regions of the visible spectrum
- Red and blue are absorbed and green is reflected (pg. 207)




23 Section 8-3 The Reactions of Photosynthesis
Inside a chloroplast a. Where photosynthesis takes place b. Structures i. Thylakoids – saclike photosynthetic membrane (pancakes) - proteins in the thylakoid organize chlorophyll into clusters called photosystems (light-collecting units) ii. Grana – Stacks of thylakoids iii. Stroma – region outside the thylakoid membrane (syrup)

24 2 reactions -Light-dependent- in the thylakoid membrane - Light-independent (Calvin Cycle) – in the stroma

25 2. Electron Carriers a. sunlight excites the electrons in chlorophyll – high in energy b. NADP+ - electron carrier - can accept a pair of high energy electrons and a hydrogen ion (H+) - this converts NADP+ to NADPH c. this makes up the ETC d. NADPH carries the electrons to Dark cycle

26 3. Light-Dependent Reactions
a. require light b. produce oxygen gas c. convert ADP and NADP+ into energy carriers ATP and NADPH


28 Light-Dependent Reactions
A. Photosystem II absorb light - electrons absorb energy - passed on to the ETC - thylakoid replaces electrons with electrons from broken apart H20 molecules - Oxygen is released into the air - H+ ions are released inside the thylakoid

29 B. e- go from PS II to PS I - energy from e- is used to pump the H+ ions from the stroma into the thylakoid membrane

30 C. Pigment in PS I use energy from light to reenergize the e-
- NADP+ then again turns to NADPH D. As the electrons pass to NADP+ more H+ ions are pumped across the membrane - outside of membrane (-) charged - inside of membrane (+) charged - this charge difference provides the energy needed to make ATP

31 E. ATP synthase – enzyme that allows the H+ ions to cross the membrane
- as H+ ions pass through the enzyme it rotates - as it rotates, ATP synthase binds the phosphate group to ADP making ATP - this produces not only high energy electrons but ATP as well

32 Calvin or Dark Cycle

33 American scientist Melvin Calvin
4. Light-Independent Reactions (Calvin Cycle)- American scientist Melvin Calvin - Uses ATP and NADPH to produce sugars (short term storage) - contain a lot of chemical energy - does not require light

34 Light Independent Reactions
A. 6 CO2 molecules – enter cycle from atmosphere - combine with (6) 5 Carbon molecules - produce (12) 3-Carbon molecules B. (12) 3-Carbon molecules are converted into high energy forms - energy for conversion comes from ATP and NADPH

35 C. (2) of the 3-Carbon molecules are removed from the cycle to produce molecules needed by the plant
D. The remaining (10) 3-Carbon molecules are converted back into (6) 5-Carbon molecules - These return to the beginning of the cycle to restart the next cycle.

36 Purpose of the Calvin Cycle
- It uses (6) CO2 molecules to make a single 6-carbon sugar molecule Light-dependent – Trap the energy from the sun in chemical form Light-independent – use the stored chemical energy to produce sugars

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