Photosynthesis and Cellular RespirationHonors Biology
Photosynthesis and respiration form a continuous cycle because the products of one process are the reactants for the other.
PhotosynthesisReactants: CO2, H2O, light
Products: Carbohydrate, O2
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Where do the reactants come from? How do they get into the plant?Water from rain through roots remember CAPILLARY ACTIONCO2 into leaves through stomata openings in the leafLight is trapped by chlorophyll in leaf cells
Stomata allow CO2 to enter and O2 and H2O to exit.Guard cells control the opening and closing of the stomata.
Cellular RespirationReactants: carbohydrates, O2
Products: CO2, H2O, and ATP for cell processes
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Energy is stored in organic molecules made by linking carbon atoms together. Excess carbohydrates produced by plants provide food for animals.
Before we startAn electron carrier is an energy carrier.NADPHNADHFADH2
Photosynthesis is the process that transforms light energy to chemical bond energy.
It takes place in the Chloroplast.Thylakoid membrane: internal membranes that trap energyGrana: stack of membranesStroma: liquid portion of chloroplast
Photosynthesis consists of two reactions: light reactions and Calvin Cycle.
LIGHT REACTIONS: the photo in photosynthesis
Electrons in chlorophyll absorb Energy: when enough is absorbed, electrons leave and release Energy along electron transport chains.
Chlorophyll FA new kind of chlorophyll that catches sunlight from just beyond the red end of the visible light spectrum has been discovered. The new pigment extends the known range of light that is usable by most photosynthetic organisms. Harnessing this pigments power could lead to biofuel-generating algae that are super-efficient, using a greater spread of sunlight than thought possible.
Chlorophyll picks up replacement electrons when water is split. Hydrogens electrons are taken, leaving H+.
Oxygen is released.
Energy from one ETC is stored as ATP.H+ are pumped into the thylakoid until the pressure increases and forces the H+ out through ATP synthetase channels into the stroma.
Energy from the other ETC is stored as NADPHExcited electrons combine with H+ and NADP (an electron acceptor)
NADPH and ATP are used in the Calvin Cycle.
REVIEW OF LIGHT REACTIONLight is absorbedWater is splitNADPH and ATP are producedOxygen is released
CALVIN CYCLE: the synthesis in photosynthesis
Carbon Dioxide Fixation: Carbon (in CO2) is added to a FIVE- Carbon organic compound (already in the cycle)Produces SIX-Carbon molecule (unstable)
IMMEDIATELYSIX-Carbon Unstable Molecule is split Produces 2 THREE-Carbon PGA molecules
2 THREE-Carbon PGA Added to NADPH and ATP (from light reaction) Produces 2 THREE-Carbon PGAL sugar
The 2 THREE-Carbon PGAL may combine to form glucose or another carbohydrate.Most are used to regenerate the original FIVE-Carbon compound to restart the cycle.
PGAPGALC6H12O6Original 5-C compound
Review of Calvin CycleCO2 usedNADPH and ATP from light reaction usedGlucose produced
Two StagesBreakdown of Glucose
Production of ATP
STAGE 1GLYCOLYSIS: to break up glucoseAnaerobic: does not require oxygenOccurs in the cytoplasm
STAGE 1 continuedRequires 2 ATPGlucose is broken down into 2 THREE-Carbon molecules of pyruvateProduces 2 NADH and 4 ATPNET gain of 2 ATP
After glycolysis, the remainder of the process is aerobic (requires oxygen).
STAGE 2Pyruvate enters mitochondriaConverted to a TWO Carbon Acetyl groupCO2 is releasedNADH is producedAcetyl group combines with coenzyme A to make Acetyl coA
STAGE 2 continuedAcetyl coA enters the Krebs cycle (Citric Acid Cycle)Acetyl coA combines with a FOUR-Carbon molecule already in the cycle to make a SIX-Carbon molecule (citric acid)coA is releasedCO2 is released from the SIX-Carbon molecule, leaving a FIVE-Carbon molecule (NADH made)CO2 is released again from the FIVE-Carbon molecule, leaving a FOUR-Carbon molecule (NADH and ATP made)
STAGE 2 continuedFOUR-Carbon compound is converted to a new FOUR-Carbon compound, making FADH2
New FOUR-Carbon compound is converted to the compound that started the cycle
NADH and FADH2 are used in the electron transport chain
The short version:
It produces ATP , NADH, and FADH2, and releases CO2
STAGE 2 continuedElectron Transport ChainNADH and FADH2 (from Krebs cycle) pass through the ETC in the inner membranes of mitochondriaLarge amounts of ATP produced as H+ are pumped through the membraneAt the end of the ETC, H+ and electrons combine with O2 to form H2O
The short version:It requires oxygen, uses NADH and FADH2, and it produces ATP for cell processes
When oxygen is not availableFermentation occurs in animals: e- from glycolysis are added to organic molecules to form Lactic Acid. Not very efficientonly 2 ATPAlcoholic fermentation occurs in fungi and plants: Bacteria and yeast can convert pyruvic acid into alcohol and carbon dioxide.