Lecture 15

• Some yeast cells perform alcohol fermentation.
• Fermentation is significantly less efficient than cellular respiration, only producing 2 ATP.
• If an organism can switch between fermentation and aerobic respiration this is called being a facultative anerobe.
• The glucose required in cellular respiration can come from either photosynthesis, making your own food (autotrophs), or eating other stuff (heterotrophs).
• Photosynthesis is the reduction of a carbon dioxide, and oxidation of water.
• Photosynthesis is the opposite of cellular respiration.
• Photosynthesis consists of 2 reactions, the light capturing reaction the Calvin cycle.
• The light capturing reaction produces O2 from H2O when its electrons are excited by light energy.
• The calvin cycle produces sugar from CO2.
• Photosynthesis takes place in the chloroplasts.
• Thylakoid membranes in chloroplasts contain laege quantities of pigments, which reflect green light.
• Pigments absorb only certain wavelengths of light.
• Chlorophylls absorb red and blue light, Carotenoids absorb blue and green light.
• Chlorophylls are the main pigments, as seasons change chlorophyll degrades and carotenoids absorb red and yellow wavelengths instead.
• Absorbed light promotes photosynthesis.
• photosystem 1 - energy is used to produce NADPH to produce ATP.
• photosystem 2 - energy is used to split water to produce oxygen.
• Carbon fixation is the addition of carbon atoms from inorganic CO2 to organic compound.
• Carbon fixation begins by making a five-carbon compound called RuBP (ribulose bisphosphate).
• The fixation of CO2 to RuBP is the most important chemical reaction on earth.
• Rubisco is a very slow and inefficient enzyme.
• Rubisco catalyzes the addition of either O2 or CO2 to RuBP
• Plants must control the levels of O2 and CO2 by opening and closing their stomata.
• The calvin cycle takes place in the stroma of chloroplasts.
• The primary product of the calvin cycle is G3P
• G3P molecules from Calvin cycle are used to make glucose and frucose.
• Glucose and fructose combine to make sucrose, and when sucrose is abundant glucose is polymerized to form starch.
• Every carbon prenest in organic molecules can be traced back to photosynthesis.