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I. Sunlight and SurvivalA. Autotrophs = self-nourishing
B. Photoautotrophs = sunlight captured to drive metabolic reactions
• Photosynthesis
• Light Energy Chemical Energy
C. Heterotrophs = other organisms as source of energy
D. Chemosynthesis = energy from inorganic molecules
• Hydrothermal Vents
E. Light Energy- has characteristics of both waves and bundles (photons)
- Waves – the electromagnetic spectrum
A. Chloroplast structure 20 to 100/photosynthetic plant cell
1. Inner and outer membranes2. Intermembrane space3. Stroma4. Granum (grana is plural) = stack of
membrane bound sacs called thylakoidsa. Thylakoids - Thylakoid membrane - Thylakoid space
B. Three major steps of photosynthesis
1. Absorb light energy (photosynthetic pigments)2. Convert light energy to unstable chemical bonds (ATP and NADPH)
3. Convert unstable chemical bonds to stable chemical bonds (G3P and glucose) (Calvin Cycle)
These are light dependent reactions that take place in the thylakoids
These are the light independent reactions that take place in the stroma
C. Key Concepts: Photosynthesis is the pathway by which
carbon and energy enter the web of life
In plants, photosynthesis takes place in
chloroplasts
Photosynthesis is summarized this way
12H20 + 6CO2 ---> 602 + C6H12O6 + 6H2O
ATP supplies energy for reactions which synthesize glucose from CO2 and water
D. Photosynthetic pigments1. Absorption spectrum vs. Action spectrum (absorbed wavelengths) (performance)
3. Englemann’s Observational Test Oxygen-requiring bacteria congregated
where oxygen was being produced by algae
4. Accessory pigments Purpose = to transfer energy to chlorophyll a
1. Chlorophyll b 3. Phycobilins2. Carotenoids 4. Anthocyanins
5. Chlorophyll structurea. Porphyrin ring with Mg++ at center
-absorbs light energyb. Hydrocarbon chain tail
-anchors molecules in thylakoid membrane
6. Role of chlorophyll a
Chl a
Chl* Chl+
Excited state
Ground state
Charged state
light energy
electrons to NADP+
H2O electrons
2 H+
½ O2
V. Calvin-Benson Cycle Occurs in the stroma Called “light-independent reactions” Called “carbon fixation” Forms stable bonds from energy in
NADPH and ATP
IX. Other forms of carbon fixationA. Photorespiration
1. Under hot,dry conditions stomata close to prevent dehydration
2. In C3 plants the CO2 levels drop, causing rubisco to use O2
3. No ATP produced, 2-carbon compounds wasted
B. C4 plants have a way to overcome photorespiration1. Calvin cycle in bundle-sheath cells
2. CO2 pumped into bundle-sheath cells from mesophyll cells at a cost of ATP3. Corn, sugarcane, crab grass
C. CAM plants1. Plants living in arid conditions (desert)2. Stomata are closed during day to prevent water loss3. Therefore during the night, CO2 is taken in and used to make organic acids, malate (R-COOH)4. During day CO2 is released from organic acid to supply Calvin cycle for carbon fixation5. Cactus, pineapple
1) PHOTOSYNTHESIS ESSAY
Membranes are important structural features of cells. (a) Describe how membrane structure is related to the
transport of materials across a membrane. (b) Describe the role of membranes in the synthesis of ATP in
either respiration or photosynthesis.
Or
2) ENZYME QUESTION
Enzymes are biological catalysts.a. Relate the chemical structure of an enzyme to its
specificity and catalytic activity.b. Design a quantitative experiment to investigate the
influence of pH or temperature on the activity of an enzyme.
c. Describe what information concerning the structure of an enzyme could be inferred from your experiment.