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Photosynthesis
Schreiber
Honors Biology
Who does it??• Photoautotrophs
• Plants• Algae• Protists• Bacteria
• **In Plants• Primarily Leaves• Mesophyll/
Parenchyma
Leaf Anatomy Review• Stomata
• Allow gas exchange
• Vein = Xylem and Phloem
Chloroplast Structure• Double Membrane
• Thylakoid – membrane bound compartment, site of the light dependent reactions of Photosynthesis
• Grana – Stacks of Thylakoids
• Stroma – Fluid surrounding thylakoids, site of light independent reactions
Light = electromagnetic wave made of photons (packets of energy)
Wavelength, Frequency, Energy
Light
Reflected
Transmitted
AbsorbedLight Granum
Absorption Spectrum of Chlorophyll
Light Absorbing Pigments• Chlorophylls are chemicals that have
lose electrons easily, so they provide energized electrons to other molecules. This is the fundamental process by which chlorophyll "captures" the energy of sunlight.
• There are several kinds of chlorophyll, the most important being chlorophyll "a". This is the molecule which makes photosynthesis possible, by passing its energized electrons on to molecules which will manufacture sugars. A second kind of chlorophyll is chlorophyll "b", which occurs only in "green algae" and in the plants.
Continued• Carotenoids are usually red,
orange, or yellow pigments, and include the familiar compound carotene, which gives carrots their color.
• Carotenoids cannot transfer sunlight energy directly to the photosynthetic pathway, but must pass their absorbed energy to chlorophyll. For this reason, they are called accessory pigments.
Hydrocarbon tailAnchors molecule to thylakoids
HYDROPHOBIC
Equation• Reactants = carbon dioxide and water
• Products = glucose, water, and oxygen
6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6 H2O
6 CO2 + 6 H2O C6H12O6 + 6 O2
6
Overview
6 CO2 12 H2O
C6H12O6 6 H2O 6 O2
• Water Split – Releasing O2
• Electrons and hydrogen ions transferred to carbon dioxide, reducing it to sugar
• Light Dependent Reactions
• Convert Solar Energy to Chemical Energy, Split Water, Release O2, Produce ATP + NADPH
• Calvin Cycle – Light Independent Reactions
• Incorporation of carbon into organic molecules (carbon fixation), uses ATP
Reactants
Products
ATP
Adenosine tri phosphate
Ribose
3 phosphates
Adenine
High energy bondCells recycle
ATP
ADP + Pi ↔ ATP
Light Dependent Reactions
Overview of Light Reactions
1. Light energy energizes electrons from chlorophyll.
2. The electron travels through Photosystem II and I losing energy, the energy is used to pump H+ into the thylakoid space.
3. NADP+ accepts the electron and is REDUCED to form NADPH (goes to Calvin Cycle).
4. Water is split in this process, replenishing the electron to chlorophyll, generating H+ ions and oxygen.
5. Some ATP made (photophosphorylation) (goes to CC)
6. No sugars produced
Light Reactions
• http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html
LE 10-14
ATP
Photosystem II
e–
e–
e–e–
Millmakes
ATP
e–
e–
e–
Ph
oto
n
Photosystem I
Ph
oto
n
NADPH
Overview of Calvin Cycle/Light Independent RXNs
1. Carbon dioxide is incorporated into organic molecules. This process is called carbon fixation
2. Compounds then reduced to sugars by adding electrons
3. Requires energy provided by light reactions (ATP& NADPH)
4. Sometimes called the dark reactions Careful!!! This only means that these reactions do not need light, but they still happen during the DAY!
Light Independent Reactions
• http://www.science.smith.edu/departments/Biology/Bio231/calvin.html
https://www.youtube.com/watch?v=sQK3Yr4Sc_k
www.youtube.com/watch?v=g78utcLQrJ4