Chapter 7: Photosynthesis

Three questions about the chapter:
1.What process do plants use that eukaryote organisms do not, to get energy?
 Photosynthesis.
2.Where does photosynthesis occur?
It occurs in the chloroplasts in plant cells.
3.What are the two stages of photosynthesis?
The first one is the light reactions, and the second one is the Calvin cycle, or the dark reactions.

Five main facts from the reading:
1.Autotrophs are the producers of the biosphere.
2.Plants produce oxygen by splitting water.
3.Photosynthesis is a redox process,as is cellular respiration.
4.Photosynthesis uses light energy, carbon dioxide, and water to make food molecules.
5.Photosynthesis moderates global warming. 

Diagram:

 This diagram is a simple overview of the two stages of photosynthesis that take place in a chloroplast.
















Link: http://www.calpoly.edu/~mforte/dream/p3.html


Summary:
     In the introduction of the chapter, we learned that scientists are trying to use plant power as fuel source. Photosynthesis is one of the oldest energy pathways on the planet. In this process, green plants, algae, and certain bacteria transform light energy to chemical energy stored in the bonds of the sugar they make from carbon dioxide and water. After this we learned that autotrophs are the producers of the biosphere. Producers are the organisms that produce their own food supply. All organisms that produce organic molecules from inorganic molecules using the energy of light are called photoautotrophs. Photosynthesis occurs in the chloroplasts in plant cells. Plants' green color is from chlorophyll, a light-absorbing pigment in the chloroplasts that plays a central role in converting solar energy to chemical energy. Chloroplasts are concerned in the cells of the mesophyll, the green tissue in the interior of the leaf. Carbon dioxide enters the leaf, and oxygen exits, by way of tiny pores called stomata. Water absorbed by the roots is delivered tot he leaves in veins. An envelope of two membranes encloses an inner compartment in the chloroplast, which is filled with a thick fluid called stroma. Suspended in the stroma is a system of interconnected membranous sacs, called thylakoids. In some places thylakoids are concentrated in stacks called grana. Plants produce oxygen by splitting water. Photosynthesis is a redox process, as is cellular respiration. It has two stages and they are linked by ATP and NADPH. The light reactions include the steps that convert light energy to chemical energy and produce oxygen. The reactants in this process are water sunlight energy, ADP, and NADP+. The products are ATP, NADPH, and oxygen. This process takes place in the thylakoids in the chloroplast. The Calvin cycle occurs in the stroma of the chloroplast. It is a cyclic series of reactions that assembles sugar molecules using carbon dioxide and the energy-containing products of the light reactions. The reactants of this process are carbon dioxide, ATP, and NADPH. The products are NADP+, ADP, and sugar. The process takes place in the stroma in the chloroplast. Visible radiation drives the light reactions. An electromagnetic spectrum is the full range of electromagnetic wavelengths from the very short gamma rays to the very long-wavelength radio waves. The distance between the crests of two adjacent waves is called a wavelength. A photon is a fixed quantity of light energy. Photosystems capture solar power. A photosytem consists of a number of light-harvesting complexes surrounding a reaction center complex. The reaction center complex contains a pair of chlorophyll "a" molecules and a molecule called the primary electron acceptor, which is capable of acdpeting electrons and becoming reduced. There two photosystems in the light reactions process. Photosystem 2 (P680) and photosytem 1 (P700). The two photosystems are connected by an electron transport chain and generate ATP and NADPH. Chemiosmosis powers ATP synthesis in the light reactions. In photosynthesis the chemiosmotic production of ATP is called photophosphorylation. ATP and NADPH power sugar synthesis in the Calvin cycle. Adaptations that save water in hot, dry climates evolved in C4 and CAM plants. In most plants, initial fixation of carbon occurs when the enzyme rubisco adds carbon dioxide to RuBP. Such plants are called C3 plants because the first organic compound produced is the three-carbon compounds 3-PGA. In certain plant species, alternate modes of carbon fixation have evolved that save water without shuttling down photosynthesis. C4 plants are so named because they precede the Calvin cycle by first fixing CO2 into a four-carbon compound. When the weather is hot and dry, a C4 plant keeps its stomata mostly closed, thus conserving water. CAM plants are species adapted  to very dry climates. A CAM plant conserves water by opening its stomata and admitting carbon dioxide only at night. Photosynthesis moerates global warming.

Key Terms:
1.Autotrophs - organisms that make their own food and thus sustain themselves without consuming organic molecules derived from any other organisms.
2.Mesophyll - the green tissue in the interior of the leaf.
3.Stomata - tiny pores by which carbon dioxide enters the leaf, and oxygen exits.
4.Stroma - a thick fluid filled in an envelope of two membranes in the chloroplast.
5.Thylakoids - a system of interconnected membranous sacs suspended in the stroma.
6.Grana - stacks in which thylakoids are concentrated.
7.Light reactions - include the steps that convert light energy to chemical energy and produce oxygen.
8.Calvin cycle - occurs in the stroma of the chloroplast, and it is a cyclic series of reactions that assembles sugar molecules using carbon dioxide and the energy-containing products of the light reactions.
9.Photosystem - consists of a number of light-harvesting complexes surrounding a reaction center complex.
10.Photon - a fixed quantity of light energy.