Ch.7 Photosynthesis: Using Light to Make Food

WHAT IS RUBISCO?
Rubisco is used from the beginning of the calvin cycle. From the second that CO2 is taken in by the plants, Rubisco starts the process. Starting with phase 1; carbon fixation which is where ATP, and NADPH are produced. The second phase; reduction, is where glucose is produced. In the final cycle, regeneration of CO2 acceptor, ribulose bisphosphate is produced. And the the calvin cycle continues all over again, producing more and more ATP and glucose. The reason that Rubisco is so important to our world is that it acts as a catalyst for the Calvin Cycle, therefore making sure that the cycle can metabolize ATP from glucose (sugar). This also makes it the most abdunent protein on earth.

HOW IS PHOTOSYNTHESIS RELATED TO CELLULAR RESPIRATION?
In photosynthesis, plants use the sun's energy as light to transform carbon dioxide and water into glucose. In cellular respiration, glucose is ultimately broken down to yield carbon dioxide and water, and the energy from this process is stored as ATP molecules. They are the opposite process of each other. Animals need oxygen to breathe in order to perform cellular respiration, and plants need CO2 to perform photosynthesis. If those process didn't happen, there would be no living things in universe.

HOW DOES PHOTOSYNTHESIS AFFECT GLOBAL WARMING?
Photosynthesis reduces the amount of carbon dioxide in the air. This is the difference between plants and animals. The carbon dioxide is stored in the plants until they decompose or they are burned. For example, each fall when the trees lose their leaves and the plants die the level of carbon in the atmosphere goes up. The rest of the tree, bark etc.., does not continue to absorb carbon. Plants only take in carbon so long as they are growing and not after they have reached their natural height. Planting trees and other plants is one component of the solution to global warming, but the number of plants we have now cannot consume more carbon than they already do, and there is some evidence that warmer temperatures make photosynthesis more difficult.

SUMMARY:
Photosynthesis is a totally opposite process of cellular respiration. Plants produce a simple sugar and oxygen, using water and carbon dioxide.
Formula of Photosynthesis:
6CO2 + 6 H2O --(light energy)--> C6H12O6 + 6O2
The most important organelle in photosynthesis is chloroplast. It is consisting of photosynthetic pigments, enzymes, and other molecules grouped together in membranes. Stomata are tiny pores in the leaf that allow carbon dioxide to enter and oxygen to exit. Photosynthesis occurs in thylakoids, which segregates the stroma from another compartment. Photosynthesis is a redox process. Light energy is converted to chemical energy, which is stored in the chemical bonds of sugar molecules, as a result of this process. There are two stages in photosynthesis, light reactions and calvin cycle.
In the light reactions, light energy is converted in thylakoid membranes to chemical energy and O2. Water is split to provide the O2 as well as electrons. Reactants are water, light, NADP+ and ADP. Products are ATP, NADPH, and O2. Light and water go into the second photo system. While that is happening, they excite electrons and electrons move because of electron transport until first photo system Once they get to this point, light comes through to excite the electrons to produce NADPH. The hydrogen gradient is inside the membrane. Hydrogens move through ATP synthase to produce ATP.
In Calvin cycle, which occurs in the stroma of the chloroplast, it builds sugar molecules from CO2 and the products of the light reactions. Reactants are CO2, ATP, and NADPH. Products are glucose, NADP+, and ADP. CO2 bonds with rubisco to form two 3-carbons. ATP and NADPH are oxidized which reduces two 3-carbons. One of them leaves the cycle and the other five form rubisco.
The light behaves as photons. Chloroplasts contain several different pigments all absorb light of different wavelengths. For example, chlorophyll is a absorbs blue violet and red light and reflects green. Chlorophyll b absorbs blue and orange and reflects yellow-green. The carotenoids absorb mainly blue-green light and reflect yellow and orange. Also they are responsible for absorbing photons, capturing solar power in another words, causing release of electrons.
Within the photosystem, the energy is passed from molecule to molecule. At the end, it reaches the reaction center where a primary electron acceptor accepts these electrons and consequently becomes reduced. There are two types of photosystems. Photosystem I(P700) and photosystem II(P680). II is the first one because its pigment absorbs light with a wavelength of 680 nm.  I is the second one because it absorbs light with a wavelength of 700 nm. During the light reactions, light energy is transformed into the chemical energy of ATP and NADPH. Electrons are removed from water pass from photosystem II to I and are accepted by NADP+. Electron transport chain works as a bridge between I and II.

KEY TERMS:
1) Autotrophs: living things that can make their own food without using organic molecules derived from any other living things
2) Chlorophyll: important light absorbing pigment in chloroplasts. Responsible for the green color of plants.
3) Electromagnetic spectrum: the full range of electromagnetic wavelengths
4) Photon: a fixed quantity of light energy, and the shorter the wavelength, the greater the energy.
5) Photosystems: light harvesting complexes surrounding a reaction center complex.
6) Photophosphorylation: the chemiosmotic production of ATP in photosynthesis.
7) Photorespiration: a process that rubisco adds oxygen instead of carbon dioxide to RuBP and produces a two-carbon compound.
8) C4 plants: the plants that first fix carbon dioxide into a four-carbon compound
9) CAM plants: the plants that conserve water by opening their stomata and admitting CO2 only at night
10) Carbon fixation: a process that during the calvin cycle, CO2 is incorporated into organic compounds.

http://www.youtube.com/watch?v=hj_WKgnL6MI
Light reaction produces ADP and Pi from ATP, using light from the sun. It occurs in chloroplast. It has photo system I and II. They excite electrons to produce ATP. NADPH is produced by NADP+ bonding with hydrogen, which are in hydrogen gradient. It is simpler than cellular respiration.

5 FACTS:
1) The products of the light reactions are NADPH, ATP, and O2.
2) There are two stages in photosynthesis, the light reactions, and Calvin cycle.
3) There are two types of photosystems, photosystem I and photosystem II. Photosystem II comes first and I comes the next.
4) Photosysthesis is a opposite process of cellular respiration. It produces sugar and O2, using CO2 and light and water.
5) Chrolophyll is responsible for the color of the leaves. Green color is represented by them.