DO NOW What is the difference between an autotroph and a heterotroph? Why do plants need sunlight? What gases are exchanged between plants and animals?

Overview Of Photosynthesis

Objectives To be able to list the inputs and outputs of photosynthesis. To be able to identify the structures in a chloroplast. To be able to summarize light-dependent reactions.

Photosynthesis Light energy > chemical energy Used by autotrophs to produce food All of our energy starts as light energy! ◦ Plants use sunlight to make food  animals eat plants  other animals those animals

Photosynthetic Organisms Go through Photosynthesis to produce GLUCOSE… Autotrophs “Producers” in the food web Consist of plants, protists, cyanobacteria

Overall Chemical Equation

Phase Overview 1) Light dependent Reactions ◦ Light energy is absorbed and converted into chemical energy in the form of ATP and NADPH. (also produces Oxygen!) 2) Light Independent Reactions:(Calvin Cycle) ◦ CO 2 ATP and NADPH are used to make glucose. *Glucose is the basic building block for more complex sugars such as starch.*

Glucose

The Chloroplast

Structures within a chloroplast  Thylakoids:  flattened sac-like membranes arranged in stacks (stacks are called grana).  Light-dependent reactions take place here.  Electron transport occurs in the thylakoid membrane  Stroma:  Fluid filled space outside the grana.  Light-independent reactions take place here.

Light Dependent Reactions Step 1: Light energy reaches photosytem II causing the water molecule to split O H H H2OH2O H+H+ O2O2 + *H + is released to the electron transport system. * O 2 is given off as a byproduct.

Step 2:Light energy reaches photosystem I and electrons flow from photosystem II to photosystem I. (to replace the electrons lost)

Step 3: Hydrogen ions (protons) are pumped across the membrane as the electrons fall. (think of a hyper child losing energy)

Step 4: Electrons from photosystem I move to a protein called ferrodoxin. **Ferrodoxin = “helper” protein**

Step 5:Ferrodoxin transfers electrons to NADP+ forming NADPH. (We need this for the next part of photosynthesis!)

Step 6:Hydrogen ions move through the ATP Synthase because of the concentration gradient, creating ATP. (Chemiosmosis) To Calvin Cycle

Light Dependent Reactions Lets see it altogether now! Biology/Bio231/ltrxn.html

Review! What goes into a light dependent reaction? What is the goal of a light dependent reaction? What is given off as a byproduct? What is the name of the protein needed in a light dependent reaction?

Do Now In what part of the chloroplast do light reactions occur? What are the outputs of light-dependent reactions? What is the name of the cycle in light- independent reactions?

Objectives List the inputs and outputs of the Calvin Cycle Define chemiosmosis and it’s role in photosynthesis. Summarize light – independent reactions Perform chromatography to identify the pigments of green leaves.

Calvin Cycle Takes place in the stroma Uses NADPH and ATP from Phase I (light dependent reactions) Needs CO 2 !!! Produces GLUCOSE

Calvin Cycle Functions like a sugar factory within a chloroplast **Regenerates the starting material with each turn

Calvin Cycle Inputs - ATP - NADPH - CO 2 Outputs - Glucose

Calvin Cycle

Chemosynthesis Mechanism in which ATP is produced as a result from the flow of electrons down a concentration gradient. Ex: Light reactions (H + ions and ATP synthase)

Alternative Pathways Light and Water can limit the amount of photosynthesis a plant can perform. Some plants develop alternate pathways to maximize energy conservation. Ex: CAM and C 4 plants.

C 4 Plants These plants minimize water lost Turn CO 2 into a 4 carbon molecule instead of a 3 carbon molecule Keeps stomata (plant cell pores) closed during hot days Ex. Corn and Sugar Cane

CAM Plants Occurs in water-conserving plants that live in deserts, salt marshes, etc. CO 2 only enters leaves at night Turns CO 2 into a “storage molecule” until needed later Ex. Orchids, cacti, pineapples

Description CalvinC4C4 CAM 9. The second phase of photosynthesis, in which energy is stored in glucose 10. Pathway(s) that help(s) plants photosynthesize while minimizing water loss 11. Pathway that allows carbon dioxide to enter leaves only at night 12. Light-independent reactions 13. Uses the enzyme rubisco to convert carbon dioxide into molecules that can be used by the cell 14. Type of plant found in hot, dry environments

Animation s/Biology/Bio231/calvin.html s/Biology/Bio231/calvin.html

Do Now – True or False 1. The anaerobic pathway that follows glycolysis in the absence of oxygen is fermentation. 2. The hydrogen necessary in the electron transport chain comes from the splitting of carbon dioxide molecules. 3. Cellular respiration in eukaryotes is slightly more efficient than in prokaryotes. 4. The Krebs cycle is sometimes called the TCA cycle or the citric acid cycle. 5. Fermentation occurs in the mitochondria. 6. Skeletal muscle produces lactic acid when the body cannot supply enough oxygen. 7. Alcohol fermentation is found in some bacteria and in humans. 8. The two pyruvate molecules formed during glycolysis result in two Krebs cycles. 9. Electron transport is the first step in the breakdown of glucose.