Photosynthesis How plants (and some algae and bacteria) make their own food video
Recall: • Plants use the energy of sunlight and the green pigment chlorophyll to convert carbon dioxide and water into the sugar glucose.
The Equation • What are the reactants or ingredients necessary to carry out photosynthesis? • Carbon Dioxide (CO2) • Water (H2O) • Solar energy (sun) • What are the products? • Glucose (C6H12O6) • Oxygen (O2) • So the formula is: CO2 + H2O + sun → C6H12O6 + O2 6 6 6 How can we balance this equation?
Heterotrophs vs. Autotrophs • Autotrophs • Create their own food from sun or inorganic chemicals • Photoautotrophs • obtain energy from sunlight • Chemoautotrophs • obtains its nourishment through the oxidation of inorganic chemical compounds as opposed to photosynthesis • Heterotrophs • They need to consume plants– or other animals that have consumed plants– in order to obtain products such as glucose
Photosynthesis is vital to life on Earth • Animals are not able to create their own food from inorganic compounds. • Animals EAT food, which is then broken down through cellular respiration (the breakdown of glucose to provide energy), which all living cells need to perform. • Cellular respiration produces carbon dioxide and water, which can be used for photosynthesis.
LIGHT DEPENDENT REACTION • The goal: • Pass the electrons of water to chlorophyll, and down the photosystems I and II to make Energy (ATP and NADPH) • Scene: • These reactions occur in the thylakoid membrane stacks (The Grana) Animation
The Players: • Photosystems (PS) II (most reactive at a wavelength of 680nm) & PhotosystemI (most reactive at a wavelength of 700nm) – • located in the thylakoidmembranes (grana) inside the chloroplast; • each photosystem contains a few hundred chlorophyll molecules. • Chlorophyll- • a green pigment, absorbs the red and blue wavelengths of sunlight and becomes photoexcitedto start photosynthesis.
Electrons- • When photoexcited by sunlight, they leave a chlorophyll molecule in PS II and travel through a series of proteins (called an electron transport chain) to PS I and its electron transport chain. • Water- • is split into oxygen, hydrogen, and electrons in a process called photolysis to replace the electrons lost from PS II. • This is where the oxygen we breathe comes from (a by-product of photosynthesis!) • water is the ultimate source of electrons for photosynthesis! Extra Info animation
Electron Transport Chain (ETC) • A group of compounds that pass electrons from one to another via redox reactions coupled with the transfer of protons across a membrane to create a proton gradient that drives ATP synthesis • Sort of like a bucket brigade • ATP– • Finally, the hydrogen ions (H+) inside the thylakoidform a proton gradient. • When there are more protons in the inner thylakoid space, they pass back to the stroma through ATP Synthase(an enzyme) which supplies the energy to produce ATP from ADP (this is called chemiosmosis).
ATP Synthase- • an enzyme that can synthesize ATP from ADP and inorganic phosphate by using a concentration gradient • NADPH— • Ferredoxin, the last electron acceptor in the second ETS, "hands" the electrons from PS I to NADP which then adds a H+ from the stroma to form NADPH. Animation- another overview of the process
Light Dependent Reaction Summed Up • Another animation