1. Ocean County College BIOL 161 Lectures Photosynthesis ... Not like Chinese food, where you eat it and then you feel hungry an hour later. – Ray Liotta BIOL161_08 G. F. Barbato
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3. After 5 years, the tree had gained 74kg in weight but the soil had lost only 57g.
6. In a series of experiments Woodward measured the water consumed by plants. He observed that most of the water was “drawn off and conveyed through the pores of the leaves and exhaled into the atmosphere”.
15. In 1796, Ingenhousz suggested that this process of photosynthesis causes carbon dioxide to split into carbon and oxygen, and that the oxygen is released as a gas. ‘ Starch picture’ of Dr Jan Ingen-Housz on a geranium leaf (prepared by William Ruf and Howard Gest). The image of Ingen-Housz consists of photosynthetically-produced starch granules, which were ‘developed’ by staining with I2-KI. An engraving of Ingen-Housz (in Reed 1949) was photographed, and the negative placed in a slide projector. Light passing through the negative was focused on a geranium leaf (depleted of starch by prior incubation in darkness) for about one hour. After extraction of pigments from the leaf with boiling 80% alcohol, the blanched leaf was flooded with I2-KI solution to stain the starch granules. Within minutes, the details of the engraving dramatically appeared on the leaf. The inscription at the bottom refers to Dr Ingen-Housz’s fame as a ‘smallpox inoculator’. The ‘starch picture’ procedure was invented by Hans Molisch in 1914. (fromGest, Photosynthesis Research 53: 65–72, 1997)
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19. Chemoautotrophs : use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane
25. It ain't easy being green … Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).
26. Electromagnetic spectrum: Physical properties of light energy Gamma rays X-rays UV Infrared & Microwaves Radio waves Visible light Wavelength (nm)
30. Remember that the color we see is the light REFLECTED by the object – NOT the color absorbed!! Why are leaves green (again)? Light Reflected light Absorbed light Transmitted light Chloroplast
39. Photosynthesis road map Chloroplast Light Stack of thylakoids ADP + P NADP Stroma Light reactions Calvin cycle Sugar used for Cellular respiration Cellulose Starch Other organic compounds
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42. These electrons flow down an energy gradient and are picked up by chlorophyll in photosystem I – a reduction reaction.
43. The electrons lost from photosystem II are replaced by the splitting of water, forming electrons, H ions and releasing O 2 .
44. The H ion concentration builds in the thylakoid space and are used for ATP synthesis.
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48. How the Light Reactions Generate ATP and NADPH 2 H + 1 / 2 Water-splitting photosystem Reaction- center chlorophyll Light Primary electron acceptor Energy to make Electron transport chain Primary electron acceptor Primary electron acceptor NADPH-producing photosystem Light NADP 1 2 3
49. Production of ATP Thylakoid compartment (high H + ) Thylakoid membrane Stroma (low H + ) Light Antenna molecules Light ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
Two guard cells form the 'stomata' or 'stoma'. These cells allow for the transport of H2O, CO2 and O2 into the leaf – and through the cuticle. Note the 'green' cells. Anything that is green contains chlorophyll, which is located in the cell oranelles – chloroplasts.
Light is part of the electromagnetic spectrum. 'Wavelength' is the distance between the crests (or nadirs) of the wave. Light is made up of photons, which have properties of both waves AND particles!! (see Einstein... )
When molecules absorb photons of light, they absorb energy. Chlorophyll enters an excited, unstable state; to return to ground state, chlorophyll gives off heat and some photons (in the form of fluroescent light).
Photosystem I was so-named because it was discovered FIRST, not the order in which the systems operate, and were never renamed...
Photosysetm
The enzymes in the Calvin cycle are functionally equivalent to many enzymes used in other metabolic pathways but are found in the chloroplast stroma instead of the cell cytoplasm, separating the reactions. They are activated in the light (which is why the name "dark reaction" is misleading), and also by products of the light-dependent reaction. It should be noted that hexose (six-carbon) sugars are not a product of the Calvin cycle. Although many texts list a product of photosynthesis as C 6 H 12 O 6 , this is mainly a convenience to counter the equation of respiration, where six-carbon sugars are oxidized in mitochondria. The carbohydrate products of the Calvin Cycle are three-carbon sugar phosphate molecules, or "triose phosphates," to be specific, glyceraldehyde-3-phosphate Two G3P molecules (or one F6P molecule) that have exited the cycle are used to make larger carbohydrates. In simplified versions of the Calvin cycle, they may be converted to F6P or F5P after exit, but this conversion is also part of the cycle. Hexose isomerase converts about half of the F6P molecules in to glucose-6-phosphate. These are dephosphorylated and the glucose can be used to form starch, which is stored in, for example, potatoes, or cellulose used to build up cell walls. Glucose, with fructose, forms sucrose, a non-reducing sugar that, unlike glucose, is a stable storage sugar.
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