Lesson 8.1 - Energy & Life

• Energy

  • Energy comes from food

  • All living things need energy to live

  • Food gets its energy from the sun

  • Some organisms use light to create energy

  • Organims that make their own food are called autotrophs

  • Organims that consume their energy are called heterothrophs

• Chemical Energy + ATP

  • Energy can come from light, heat, and electricity

  • Can be stored in chemical compounds

  • Cells store and use ATP

  • ATP is made of:

    • Adenine

    • Ribose (5-sugar molecule)

    • 3 phosphate groups

  • The phosphate groups are the key to ATP use and recycling

• Storing Energy

  • ADP has 2 phosphate groups instead of 3

  • A cell can store a small amount of energy by adding one phosphate

• Releasing Energy

  • Energy is released by breaking one phosphate bond

  • This bond must be between the second and third bond

• Cellular Activites

  • Can be used for:

    • Active transport across cell membranes

    • Protein synthesis

    • Muscle contraction

  • Most cells don’t store a lot of ATP because it is not able to store large amounts of energy

  • Cells can regulate ATP from ADP as needed by using the energy in foods like glucose

Lesson 8.2 - Photosynthesis Overview

• The Photosynthsis Equation

  • Process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbs and oxygen

  • 6CO2 + 6H2O → C6H12O6 + 6O2

• Lights + Pigments

  • Photosynthesis also requires light and chlorophyll

  • Plants absorb the sun’s energy with pigments

    • Pigments are light-absobing

  • The main pigment in plants is chlorophyll

  • Two main types of chlorophyll:

    • chlorophyll a

    • chlorophyll b

  • Chlorophyll absorbs light very well in the blue-violet and red regions

    • This means that these colors are not visible to the naked eye on trees

  • Chlorophyll does not absorb light very well in the green and yellow regions

    • This means that these colors are visible to the naked eye on trees

  • Light is a form of energy, so when light is absorbed, so is energy

  • When light is absorbed, much of the energy is moved directly to the electrons in the molecule, raising the energy levels of these electrons

    • These electrons are what make photosynthesis work

    • Electrons are excited by light

• Factors Affecting Photosynthesis

  • Factors Affecting The Rate of Photosynthesis:

    • Water

    • Carbon D

    • Temp

    • Intensity of Light

    • Ur Mom and Wooster The Rooster

  • Enzymes do the physical work of making photosynthesis occur

  • More reactants, more enzymes, more work done

  • You need more than just light for photosynthesis to be successful

Lesson 8.3 - Reactions of Photosynthesis

• Inside a Chloroplast

  • Photosynthsis occurs inside chloroplasts

  • Chloroplasts contain thylakoids

    • These are saclike photosynthetic membranes

  • Thylakoids are arranged in stacks known as grana

    • A singular stack is called a granum

  • Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems

    • These are light-collecting units of the chloroplast

• Steps to Photosynthesis

  • There are 2 steps to Photosynthesis:

  • Light-dependent reactions

    • These take place in the thylakoid membranes

  • Light-independent reaction (also known as the Calvin Cycle)

    • These take place in the stroma, which is the cytoplasm part of the chloroplast

• Electron Carriers

  • When electrons in chlorophyll absorb sunlight, the electrons gain a great deal of energy

  • Cells use electron carriers to transport these high-energy electrons to other molecules

  • One carrier is called NADP+

    • Transports 2 high-energy electrons along with a hydrogen ion (the parent)

    • Convert NADP+ into NADPH

  • NADPH can store some of the energy from sunlight in chemical form

  • The energy stored in NADPH can be used to build a variety of molecules including glucose (sugars) and carbs

• Light-Dependent Reactions

  • Require light

  • Produce oxygen gas and convert ADP and NADP+ into the energy carries ATP and NADPH

• Inside A Thylakoid Processes:

1. Photosynthesis begins when pigments in photosystem II absorb light, increasing their energy level

2. These high-energy electrons are passed on to the electron transport chain

3. Enzymes on the thylakoid membrane break water molecules into:

   hydrogen ions

   oxygen atoms

   energized electrons

4. The energized electrons from water replace the high-energy electrons that chlorophyll lost to the electron transport chain

5. As plants remove electrons from water, oxygen is left behind and is released into the air

6. The hydrogen ions left behind when water is broken apart are released inside the thylakoid membrane

7. Energy from the electrons moving down the electron transport chain (ETC) is used to transport H+ ions from the stroma into the inner thylakoid space

8. High-energy electrons move through the electron transport chain from photosystem II to photosystem I

9. Pigments in photosystem I use energy from light to re-energize the electrons

10. NADP+ then picks up these high-energy electrons, along with H+ ions, and becomes NADPH

11. As electrons are passed from chlorophyll to NADP+, more H+ ions are pumped across the membrane causing a concentration gradient

12. The inside of the membrane has a high concentration of positively charged hydrogen ions, which makes the outside of the membrane negatively charged

13. The difference in charges across the membrane provides the energy to make ATP

14. H+ ions cannot cross the membrane directly, so the cell membrane contains a protein called ATP synthase that allows H+ ions to pass through it

15. As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP

16. Because of this system, light-dependent electron transport produces not only high-energy electrons but ATP as well

• Summary of Light-Dependent Reaction

  • Light-dependent reaction use water, ADP, and NADP+

  • Produce: Oxygen, ATP, and NADPH

  • These provide the energy to build sugars from low-energy compounds

• Calvin Cycle

  • ATP and NADPH have a lot of chemical energy but are unstable to store energy for longer than a moment

  • During this cycle, plants use the ATP and NADPH to build high-energy compounds that can be stored for a long time

  • Uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars

  • These reactions are called light-independent

• Summary:

  • Two sets of photosynthetic reactions work together

  • Light-dependent reactions trap sunlight in chemical form

  • They use this energy to create stable, high-energy sugars from carbon and water