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.

Ch.6 How Cells Harvest Chemical Energy

WHAT ARE THE DIFFERENCES BETWEEN FAST AND SLOW TWITCH MUSCLE FIBERS?
Because fast fibers use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However they get tired more quickly. Fast fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire faster. Having more fast fibers can be an asset to a sprinter since she needs to quickly generate a lot of force. Olympic sprinters are supposed to have about 80 % fast fibers, while those who excel in marathons tend to have 80% slow fibers. Slow fibers are more continuous and are able to keep making ATP since they take oxygen more. They are smaller in diameter, red in color, they depend on oxidative phosphorylation for their ATP supply, they have better blood supply, they have more mitochondria, and more myoglobin.

HOW DOES ATP WORK IN THE BODY?
ATP is stored in chemical bonds and is released when the last phosphate is lost and ATP becomes ADP. It is used to do work in the cell by a reaction that removes one of the phosphate-oxygen groups, leaving ADP. When ATP converts to ADP, the ATP is spent. Then the ADP is usually immediately recycled in the mitochondria where it is recharged and comes out again as ATP. The total human body content of ATP is only about 50 grams, which must be constantly recycled everyday. The ultimate source of energy for constructing ATP is food. ATP is the carrier and regulation-storage unit of energy. The average daily intake of 2500 food calories translates into a turnover of a whopping 180 kilograms of ATP.

WHAT IS THE RELATIONSHIP BETWEEN GLUCOSE, NADH AND FADH2?
Glucose has the most energy and during cellular respiration, it is broken down. The energy that is in glucose is stored in many molecules of NADH and a few of FADH2. NADH is able to store more energy than FADH2. This is why it is more abundant electron carrier. Also NADH can be synthesized from scratch or from tryphtophan. FADH2 has accommodation for two hydrogens while NAD accepts one hydrogen molecule. In NAD, an electron pair one hydrogen are transferred, with a second hydrogen released into the medium. Electron transfer by FADH2 produces less ATP than by NADH.

SUMMARY:
This chapter discusses about how ATP is produced, and how cells work for the process. There are two types of muscle fibers, slow and fast. Slow fibers such as marathoners make ATP using oxygen, aerobically. Fast fibers, such as sprinters, make ATP without oxygen anaerobically. Energy is essential for life processes. Photosynthesis make glucose from CO2 and H2O and releases O2. Other organisms need O2 and energy and release CO2 and H2O. Animals perform cellular respiration and plants perform both photosynthesis and cellular respiration since they have mitochondria. Breathing is the key of cellular respiration. The equation of cellular respiration is; C6H12O6 + 6O2 --> 6CO2 + energy. This tells that the atoms of the starting molecules glucose and O2 regroup to form the products CO2 and H2O. In this exergonic process, the chemical energy of the bonds in glucose is transferred and stored (banked). Cellular respiration can produce up to 38 ATP molecules for each glucose molecule. During cellular respiration, carbon-hydrogen bonds of glucose get broken, and electrons will be transferred to oxygen. Dehydrogenase (enzymes) remove hydrogen from an organic molecules. They also use NAD+ to shuttle electrons. NADH will be formed by transferring electrons to NAD+.
There are 3 stages in order to produce ATP in cellular respiration.
1) Glycolysis: Begins respiration by breaking glucose, a six carbon molecule, into two molecules of a three-carbon compound called pyruvate. It occurs in cytoplasm.
2) The citric acid cycle: Breaks down pyruvate into carbon dioxide and supplies the third stage with electrons. It occurs in mitochondria.
3) Oxidative phosphorylation: Electrons are shuttled through the electron transport chain. ATP is generated through oxidative phosphorylation associated with chemiosmosis. It occurs in inner mitochondrion membrane.
In glycolysis, glucose will be cut in half to produce two molecules of pyruvate. Two NAD+ are reduced to two NADH. At the same time, two ATP are produced by substrate-level phosphorylation. The pyruvate formed in glycolysis is transported the mitochondria, where it is prepared for entry into the next level. With the help of CoA, the acetyl enters the citric acid cycle. Oxidative phosphorylation requires the involvement of electron transport and chemiosmosis and also adequate supply of oxygen. NADH and FADH2 are involved as well.
There are three different categories of cellular poisons that affect cellular respiration.
1) Blocking of the electron transport chain, such as cyanide and carbon monoxide.
2) Inhibiting ATP synthase, such as oligomycin
3) Production of the membrane leaky to hydrogen ions, such as dinitrophenol
Muscles are able to oxidize NADH through lactic acid fermentation. NADH is oxidized to NAD+ when pyruvate is reduced to lactate. Pyruvate is serving as an electron sink, a place to dispose of the electrons generated by oxidation reactions in glycolysis.



KEY TERMS:
-kilocalorie: the quantity of heat required to raise the temperature of 1 kilogram of water by 1C.
-redox reaction: the movement of electrons from one molecule to another. Oxidation-reduction reaction.
-chemiosmosis: process that the potential energy of this concentration gradient is used to make ATP
-substrate-level phosphorylation: process that an enzyme transfers a phosphate group from a substrate molecule to ADP, forming ATP
-fermentation: an anaerobic energy-generating process taking advantages of glycolysis, which is producing two ATP and reducing NAD+ to NADH
-yeasts: single-called fungi that not only can use respiration for energy but can ferment under anaerobic conditions
-dehydrogenase: an enzyme that is used in the process of oxidizing glucose
-intermediates: compounds that form between the initial reactant, glucose, and the final product, pyruvate
-obligate anaerobes: prokaryotes that live in stagnant ponds and deep in the soil.
-facultative anaerobe: process that is able to make ATP either by fermentation or by oxidative phosphorylation, depending on whether O2 is available.

http://www.youtube.com/watch?v=iXmw3fR8fh0

Glycolysis produces 2 ATP molecules by substrate level phosphorylation. Also it makes 2 pyruvate. In energy investment phase, it starts with one molecule of glucose and hexopkinase breaks down the bonds.  Then in this stage, dihydroxyacetone phosphate and G3P are produced, but isomerase converts them into two G3P. Next payoff phase, NADH is made and at the end, pyruvate will be made and 4 ATP produced at the same time. It happens in the cytoplasm.
In the citric acid cycle, reactants are acetyl CoA. ATP and NADH and FADH2 are produced. 2 molecules are created in net amount and 6 molecules of NADH and 2 molecules of FADH2 are produced as well. CO2, oxaloacetate, as if combines with acetyl in the first step. It occurs in the mitochondria.
In oxidative phosphorylation, NADH and FAOH2, which give away their electrons to the electron transport chain as reactants. The reactants of chemiosmosis are ADP and phosphate, which form ATP as the products. They produce water molecules in the electron transport chain. Oxygen and hydrogen are two important molecules as are the mulriprote, complexes in the energy transport chain. 32 to 34 molecules of ATP are produced while no new NADH or FADH2 are formed. It happens in the inner membrane of the mitochondria.

5 FACTS:
1) Although glucose is considered to be the source of sugar for respiration, carbohydrates, proteins, and fats are the actual three sources for generation of ATP
2) Glycolysis is the universal energy-harvesting process of living organisms
3) The statement "plants perform photosynthesis and animals perform cellular respiration." is wrong, because plants do perform cellular respiration with mitochondria as well.
4) There are three stages of producing ATP, glycolysis, the citric acid cycle, and oxidative phosphorylation.
5) The total number of ATP molecules per a glucose molecule produced are 32 to 34. This is about 40% of a glucose molecule potential energy.