Unit 6 Energy in Ecosystems

Photosynthesis “making from light” Photosynthesis Cellular Respiration

Photosynthesis takes place in chloroplasts

Leaf Structure Waxy cuticle –water resistant barrier against disease Epidermis –Outermost layer of cells Mesophyll –Palisade is denser and loaded with chloroplasts –Spongy is less dense- allows for gas exchange Stoma –Opening on the underside of the leaf –Guard cells control the opening and closing of the stoma (full of water = open, empty = closed) Vein –Xylem- water up –Phloem- sugars out Structural Advantages? Waxy on top Palisade layer on top Stoma on underside

Chloroplast Structure Inner and outer membranes surround the chloroplast The thylakoids are the site of the Light Reactions Stacks of thylakoids are called granum stacks The stroma is the site of the Calvin Cycle

The Electromagnetic Spectrum The range of types of electromagnetic energy Sunlight is a form of electromagnetic energy Visible light are those wavelengths that your eyes see as different colors

Pigments and Colors Color is due to chemical compounds called pigments. Pigments in chloroplasts absorb blue-violet and red- orange light, but do not absorb green light well Leaves look green because the green light is not absorbed

Chemical formula for Photosynthesis From the atmosphere through the stoma Absorbed by roots in soil

Photosynthesis

The Light Reactions The light reactions convert light energy into the chemical energy of ATP and NADPH Two photosystems are involved in the light reactions

The first photosystem is the "water-splitting photosystem” –Oxygen is released as a waste product –Hydrogen electrons travel to the second photosystem (pumping H + across the membrane) –H + ions power ATP production

The second photosystem is the "NADPH-producing photosystem." –excited electrons are accepted by NADP+

The Light Reactions Reactants sunlight water Products ATP NADPH O 2 (by-product)

The Calvin Cycle It is called a cycle because the starting material (RuBP) is regenerated each time the process occurs This is the sugar producing stage of photosynthesis

Inputs are –carbon dioxide from the air Source of carbon –ATP and NADPH produced by the light reactions Source of energy and electrons

Output is –an energy-rich sugar molecule called G3P. The plant cell uses G3P as the raw material to make glucose and other organic molecules it needs.

Factors that Affect Photosynthesis 1.Amount of sunlight 2.Amount of water 3.Amount of CO 2 4.Nutrients 5.Temperature

Photosynthesis

Food Stores Chemical Energy Chemical Energy –Potential energy stored in the bonds of chemical compounds

Living things require energy for work Types of Work –Chemical Building or breaking molecules –Mechanical Movement –Transport Pumping substances across membranes

Breathing and Cellular Respiration Cellular respiration is an aerobic process –it requires O 2 Breathing delivers O 2 and releases CO 2

Adenosine TriPhosphate Bond energy between the last two phosphates provides the cell with energy when it is broken

Site of Photosynthesis Site of Cellular Respiration Where does this all take place?

Structure of the Mitochondria The highly folded inner membrane allows for many reaction sites. The matrix contains enzymes and other molecules.

Stages of Cellular Respiration

How does Cellular Respiration work? Oxygen is an electron grabber. This causes carbon and hydrogen atoms to change partners and bond with oxygen atoms instead. –They are replaced by carbon-oxygen (CO 2 ) and hydrogen-oxygen (H 2 O) bonds. As the electrons of these bonds "fall" toward oxygen, energy is released.

Glycolysis “Splitting of sugar” Anaerobic- O 2 is not required Location: cytoplasm of the cell Reactants: glucose, 2 ATP Products: 2 pyruvic acid, 2 NADH, 4 ATP (Net 2ATP)

Kreb’s Cycle Aerobic- O 2 is required Location: matrix of the mitochondria Reactants: 2 Acetyl CoA Products: 6 CO 2, 2 ATP, 6 NADH, 2 FADH 2

Electron Transport Chain NADH and FADH 2 pass the electrons on in a series of transfers called an electron transport chain- each carrier holds the electrons more strongly than the one before it. Each transfer releases a small amount of energy used to pump hydrogen ions across the membrane to where they are more concentrated. Hydrogen ions rush back "downhill" through the ATP synthase converting ADP to ATP. At the end of the chain, oxygen—the electron grabber—pulls electrons from the final carrier molecule and joins them with hydrogen ions, forming water. Aerobic- O2 is required Location: inner membrane Reactants: electrons carried by NADH and FADH2 Products: 34 ATP, 6 H2O

Stages of Cellular Respiration

Fermentation Anaerobic cellular respiration results in fermentation. Fermentation in humans results in Lactic Acid production…… sore muscles. Fermentation in bacteria and yeasts results in the production of alcohol. 1