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) made of photons (packets of energy) Wavelength, Frequency, Energy

Light Reflected Transmitted Absorbed Light 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."green algae" 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 tail Anchors molecule to thylakoids HYDROPHOBIC

Equation Reactants = carbon dioxide and water Products = glucose, water, and oxygen 6 CO H 2 O  C 6 H 12 O O H 2 O 6 CO H 2 O  C 6 H 12 O O 2 6

Overview 6 CO 2 12 H 2 O C 6 H 12 O 6 6 H2O6 H2O6 O26 O2 Water Split – Releasing O 2 Electrons and hydrogen ions transferred to carbon dioxide, reducing it to sugar Light Dependent Reactions Convert Solar Energy to Chemical Energy, Split Water, Release O 2, 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 bond Cells recycle ATP ADP + P i ↔ 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 ts/Biology/Bio231/ltrxn.htmlhttp:// ts/Biology/Bio231/ltrxn.html

LE ATP Photosystem II e–e– e–e– e–e– e–e– Mill makes ATP e–e– e–e– e–e– Photon Photosystem I Photon NADPH

Overview of Calvin Cycle/Light Independent RXNs carbon fixation 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) do not need light 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 nts/Biology/Bio231/calvin.htmlhttp:// nts/Biology/Bio231/calvin.html