1. Photosynthesis and Respiration: Defined *Photosynthesis and Respiration are both types of biochemical pathways. 1) They both involve a series of chemical reactions that involve REACTANTS (ingredients that used in a chemical reaction) and PRODUCTS (end result of a chemical reaction, such as compounds). 2) Both are responsible for creating energy for both plants and animals. *Photosynthesis and Respiration are very important to one another – each reaction makes products needed for the other reaction to occur.

2. Summary of Photosynthesis and Respiration Photosynthesis vs. Respiration Involves: Autotrophs Heterotrophs (any organism that (any organism that makes its own depends on other energy; contains living things to pigment) gain energy) Organism: Plants mostly Animals, roots of photosynthetic plants; some bacteria and bacteria protists Reactants: CO 2, Water, and Sugar (C 6 H 12 O 6 ) Sunlight and Oxygen (O 2 ) Products: Sugar (C 6 H 12 O 6 ) CO 2, Water, Heat and oxygen (O 2 ) Takes Place: Chloroplast Mitochondria

3. Chemical Reactions Respiration: C 6 H 12 O 6 + O 2 > CO 2 + H 2 O + Heat (glucose and oxygen creates carbon dioxide, water, and heat) Photosynthesis: CO 2 + H 2 O + sunlight > C 6 H 12 O 6 + O 2 (carbon dioxide, water, and sunlight creates glucose and oxygen)

4. Photosynthesis *Let’s Review... - involves mostly green parts of plants (also algae and photosynthetic bacteria). CO 2 + H 2 O + sunlight = C 6 H 12 O 6 + O 2 - takes place in the chloroplast of cells. *Two types of reactions involved in photosynthesis: light reactions and dark reactions

5. Light Reactions of Photosynthesis (aka “Light-Dependent” Reactions *The very beginning reactions of photosynthesis are called the light reactions, named so because sunlight is the initial signal that triggers the reaction (ultimately, sunlight is the very BEGINNING of photosynthesis).

6. *The light reactions take place in the chloroplasts (specifically, the thylakoids) of plant cells; the chloroplast contain pigments in the thylakoids that collect sunlight (similar to solar panels) used to “kick start” photosynthesis.

7. Types of Pigments 1) Chlorophyll A – main pigment; captures sunlight; green in color. 2) Chlorophyll B – called an “accessory pigment” because it helps chlorophyll A capture light; light green in color. 3) Carotenoids – accessory pigment; orange/yellow in color. 4) Anthocyanins – accessory pigment; reddish/brown color

8. *Many plants appear “green” even though they may contain a mixture of these pigments. *These pigments are influenced by the amount of sunlight present and outside temperatures. *Plants usually lose their main pigments (chlorophylls) first when fall approaches (decrease in sunlight and temps), which will expose the other pigment colors.

9. How Does Light Work? *The sun’s energy travels through space, to Earth in the form of electromagnetic radiation.  Electromagnetic radiation travels in waves through space and is a mixture of SEVEN different types of energy, including visible light.

10.  Each of the seven energies of the electromagnetic spectrum is categorized by the size of the wave, called a wavelength.  The smaller the wave, the more energy it carries. The size of these waves are measured in units called nanometers (nm), which is one-billionth of a meter. *Each unit of sunlight (or electromagnetic radiation) containing a mixture of these seven different types of energies is called a photon.

11. *Visible light is one of the seven energies that is either absorbed or reflected by plants. *Visible light contains ROYGBIV and the color is determined by the size of the wavelength. *Purple has the smallest wavelength and has the strongest amount of energy of all seven colors; red has the longest wavelength and has the least amount of energy of all seven colors.

12. *When light strikes an object, any of the seven colors can either be absorbed by that object, transmitted, or reflected. *Colors of objects are determined by whether light is absorbed or reflected; the actual color of an object is the color of light being reflected and all other colors being absorbed.

13. Examples: 1) An orange ball is orange because when light shines upon it, all colors EXCEPT orange is absorbed by the ball – only orange is reflected. 2) The leaves of plants appear green because all colors EXCEPT green is being absorbed by the chloroplast; green is being reflected. *Plant pigments CANNOT absorb the wavelength of light that is the same as their color; absorption of light works best with “opposite” colors. (see diagram in textbook, pg. 113)

14. What Happens During Light Reaction? *Sunlight and water are the only reactants used during light reactions. Oxygen is the only product made during the light reactions. *When the sun is absorbed by the pigments in the chloroplast, any water that is present is split into H+ and O 2. H 2 O + Sunlight  H+ and O 2.

15. *Oxygen is a WASTE product and immediately diffuses out of the chloroplast and into the atmosphere. *H+ ions left behind are used to fuel the remaining processes in the dark reactions. *At the end of the light reactions, the end products are the fuel (H+ and ATP molecules) that begins the dark reactions.

16. Summary of Light Reactions *The entire purpose of the light reactions is to create enough energy to keep photosynthesis going so that glucose (plant’s stored energy) can be made. H 2 O + Sunlight  H+, ATP, and O 2 (H+ and ATP are left behind and used to fuel dark reactions; O 2 is a waste product and is not needed).

17. The Dark Reactions (Light-Independent Reactions) *Dark reactions are called so not because they must occur in the dark – only that light is NOT required. *Dark reactions occurs 24 hrs./day. *Dark reactions use the ATP and high energy electrons (H+) from the light reactions to fuel the process.

18. *During the dark reactions, carbon dioxide is absorbed from the atmosphere and diffuses into the STROMA (liquid area) of the chloroplast. *Carbon dioxide (CO 2 ) is a reactant that is used in a series of chemical reactions called the Calvin Cycle. *The main purpose of the Calvin Cycle is to produce glucose from carbon dioxide. “Carbon Fixation” *The Calvin Cycle is cyclic because it repeats itself SIX times to form ONE molecule of glucose ( C 6 H 12 O 6 ). *Plants store their glucose in their vacuoles as STARCH.

19. Summary of the Dark Reactions H+, ATP, and CO 2  C 6 H 12 O 6