DO NOWDO NOWWhat is the difference between

an autotroph and a heterotroph?

Why do plants need sunlight?

What gases are exchanged between plants and animals?

Overview Of PhotosynthesisOverview Of Photosynthesis

ObjectivesObjectivesTo 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.

PhotosynthesisPhotosynthesisLight 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 OrganismsPhotosynthetic OrganismsGo through Photosynthesis to

produce GLUCOSE…Autotrophs “Producers” in the food webConsist of plants, protists,

cyanobacteria

Overall Chemical EquationOverall Chemical Equation

Phase OverviewPhase Overview1) 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)◦CO2 ATP and NADPH are used to make

glucose. *Glucose is the basic building block for more complex sugars such as starch.*

Glucose

The ChloroplastThe Chloroplast

Structures within a Structures within a chloroplastchloroplast

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 Light Dependent ReactionsReactions

Step 1: Light energy reaches photosytem II causing the water molecule to split

OHH

H2O

H+

O2+

*H+ is released to the electron transport system.* O2 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 Light Dependent ReactionsReactions

Lets see it altogether now!

http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html

Review!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 NowDo 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?

ObjectivesObjectives

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 CycleCalvin Cycle

Takes place in the stromaUses NADPH and ATP from Phase

I (light dependent reactions)Needs CO2!!!Produces GLUCOSE

Calvin CycleCalvin Cycle

Functions like a sugar factory within a chloroplast

**Regenerates the starting material with each turn

Calvin CycleCalvin Cycle

Inputs

- ATP- NADPH- CO2

Outputs

- Glucose

Calvin CycleCalvin Cycle

ChemosynthesisChemosynthesis

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 PathwaysAlternative 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 C4 plants.

CC44 Plants PlantsThese plants minimize water lostTurn CO2 into a 4 carbon molecule

instead of a 3 carbon moleculeKeeps stomata (plant cell pores)

closed during hot daysEx. Corn and Sugar Cane

CAM PlantsCAM PlantsOccurs in water-conserving

plants that live in deserts, salt marshes, etc.

CO2 only enters leaves at nightTurns CO2 into a “storage

molecule” until needed laterEx. Orchids, cacti, pineapples

Description Calvin C4 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

AnimationAnimation

http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

Do Now – True or FalseDo 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.