ap bio enzymes cellresp photosyn

cellular respiration

-Animals and other organisms obtain the energy available in carbohydrates through the process of cellular respiration. Cells take the carbohydrates into their cytoplasm, and through a complex series of metabolic processes, they break down the carbohydrates and release the energy. The energy is generally not needed immediately; rather it is used to combine adenosine diphosphate (ADP) with phosphate ions to form adenosine triphosphate (ATP) molecules. The ATP can then be used for processes in the cells that require energy, much as a battery powers a mechanical device. During the process of cellular respiration, carbon dioxide is given off. This carbon dioxide can be used by plant cells during photosynthesis to form new carbohydrates. Also in the process of cellular respiration, oxygen gas is required to serve as an acceptor of electrons. This oxygen is identical to the oxygen gas given off during photosynthesis. Thus, there is an interrelationship between the processes of photosynthesis and cellular respiration, namely the entrapment of energy available in sunlight and the provision of the energy for cellular processes in the form of ATP. The overall mechanism of cellular respiration involves four processes: glycolysis, in which glucose molecules are broken down to form pyruvic acid molecules; the Krebs cycle, in which pyruvic acid is further broken down and the energy in its molecule is used to form high‐energy compounds, such as nicotinamide adenine dinucleotide (NADH); the electron transport system, in which electrons are transported along a series of coenzymes and cytochromes and the energy in the electrons is released; and chemiosmosis, in which the energy given off by electrons pumps protons across a membrane and provides the energy for ATP synthesis. Glucose is converted to acetyl‐CoA in the cytoplasm, and then the Krebs cycle proceeds in the mitochondrion. Electron transport and chemiosmosis result in energy release and ATP synthesis. -Glycolysis is the process in which one glucose molecule is broken down to form two molecules of pyruvic acid. The glycolysis process is a multistep metabolic pathway that occurs in the cytoplasm of animal cells, plant cells, and the cells of microorganisms. At least six enzymes operate in the metabolic pathway. In the first and third steps of the pathway, ATP energizes the molecules. Thus, two ATP molecules must be expended in the process. Further along in the process, the six-carbon glucose molecule converts into intermediary compounds and then is split into two three-carbon compounds. The latter undergo additional conversions and eventually form pyruvic acid at the conclusion of the process. During the latter stages of glycolysis, four ATP molecules are synthesized using the energy given off during the chemical reactions. Thus, four ATP molecules are synthesized and two ATP molecules are used during glycolysis, for a net gain of two ATP molecules. Another reaction during glycolysis yields enough energy to convert NAD to NADH (plus a hydrogen ion). The reduced coenzyme (NADH) will later be used in the electron transport system, and its energy will be released. During glycolysis, two NADH molecules are produced. Because glycolysis does not use any oxygen, the process is considered to be anaerobic. For certain anaerobic organisms, such as some bacteria and fermentation yeasts, glycolysis is the sole source of energy. Glycolysis is a somewhat inefficient process because much of the cellular energy remains in the two molecules of pyruvic acid that are created. Interestingly, this process is somewhat similar to a reversal of photosynthesis. -Following glycolysis, the mechanism of cellular respiration involves another multistep process—the Krebs cycle, which is also called the citric acid cycle or the tricarboxylic acid cycle. The Krebs cycle uses the two molecules of pyruvic acid formed in glycolysis and yields high‐energy molecules of NADH and flavin adenine dinucleotide (FADH), as well as some ATP. The Krebs cycle occurs in the mitochondrion of a cell. This sausage-shaped organelle possesses inner and outer membranes and, therefore, an inner and outer compartment. The inner membrane is folded over itself many times; the folds are called cristae. They are somewhat similar to the thylakoid membranes in chloroplasts. Located along the cristae are the important enzymes necessary for the proton pump and for ATP production. Prior to entering the Krebs cycle, the pyruvic acid molecules are altered. Each three-carbon pyruvic acid molecule undergoes conversion to a substance called acetyl-coenzyme A, or acetyl-CoA. During the process, the pyruvic acid molecule is broken down by an enzyme, one carbon atom is released in the form of carbon dioxide, and the remaining two carbon atoms are combined with a coenzyme called coenzyme A. This combination forms acetyl-CoA. In the process, electrons and a hydrogen ion are transferred to NAD to form high-energy NADH. Acetyl-CoA now enters the Krebs cycle by combining with a four-carbon acid called oxaloacetic acid. The combination forms the six-carbon acid called citric acid. Citric acid undergoes a series of enzyme-catalyzed conversions. The conversions, which involve up to ten chemical reactions, are all brought about by enzymes. In many of the steps, high-energy electrons are released to NAD. The NAD molecule also acquires a hydrogen ion and becomes NADH. In one of the steps, FAD serves as the electron acceptor, and it acquires two hydrogen ions to become FADH2. Also, in one of the reactions, enough energy is released to synthesize a molecule of ATP. Because for each glucose molecule there are two pyruvic acid molecules entering the system, two ATP molecules are formed. Also during the Krebs cycle, the two carbon atoms of acetyl-CoA are released, and each forms a carbon dioxide molecule. Thus, for each acetyl-CoA entering the cycle, two carbon dioxide molecules are formed. Two acetyl-CoA molecules enter the cycle, and each has two carbon atoms, so four carbon dioxide molecules will form. Add these four molecules to the two carbon dioxide molecules formed in the conversion of pyruvic acid to acetyl-CoA, and it adds up to six carbon dioxide molecules. These six C02 molecules are given off as waste gas in the Krebs cycle. They represent the six carbons of glucose that originally entered the process of glycolysis. At the end of the Krebs cycle, the final product is oxaloacetic acid. This is identical to the oxaloacetic acid that begins the cycle. Now the molecule is ready to accept another acetyl-CoA molecule to begin another turn of the cycle. All told, the Krebs cycle forms (per two molecules of pyruvic acid) two ATP molecules, ten NADH molecules, and two FADH2 molecules. The NADH and the FADH2 will be used in the electron transport system. -The electron transport system occurs in the cristae of the mitochondria, where a series of cytochromes (cell pigments) and coenzymes exist. These cytochromes and coenzymes act as carrier molecules and transfer molecules. They accept high‐energy electrons and pass the electrons to the next molecule in the system. At key proton‐pumping sites, the energy of the electrons transports protons across the membrane into the outer compartment of the mitochondrion. Each NADH molecule is highly energetic, which accounts for the transfer of six protons into the outer compartment of the mitochondrion. Each FADH2 molecule accounts for the transfer of four protons. The flow of electrons is similar to that taking place in photosynthesis. Electrons pass from NAD to FAD, to other cytochromes and coenzymes, and eventually they lose much of their energy. In cellular respiration, the final electron acceptor is an oxygen atom. In their energy-depleted condition, the electrons unite with an oxygen atom. The electron-oxygen combination then reacts with two hydrogen ions (protons) to form a water molecule (H2O) The role of oxygen in cellular respiration is substantial. As a final electron receptor, it is responsible for removing electrons from the system. If oxygen were not available, electrons could not be passed among the coenzymes, the energy in electrons could not be released, the proton pump could not be established, and ATP could not be produced. In humans, breathing is the essential process that brings oxygen into the body for delivery to the cells to participate in cellular respiration. -The actual production of ATP in cellular respiration takes place through the process of chemiosmosis. Chemiosmosis involves the pumping of protons through special channels in the membranes of mitochondria from the inner to the outer compartment. The pumping establishes a proton gradient. After the gradient is established, protons pass down the gradient through particles designated F1. In these particles, the energy of the protons generates ATP, using ADP and phosphate ions as the starting points. The energy production of cellular respiration is substantial. Most biochemists agree that 36 molecules of ATP can be produced for each glucose molecule during cellular respiration as a result of the Krebs cycle reactions, the electron transport system, and chemiosmosis. Also, two ATP molecules are produced through glycolysis, so the grand total is 38 molecules of ATP. These ATP molecules may then be used in the cell for its needs. However, the ATP molecules cannot be stored for long periods of time, so cellular respiration must constantly continue in order to regenerate the ATP molecules as they are used. Each ATP molecule is capable of releasing 7.3 kilocalories of energy per mole. -Fermentation is an anaerobic process in which energy can be released from glucose even though oxygen is not available. Fermentation occurs in yeast cells, and a form of fermentation takes place in bacteria and in the muscle cells of animals. In yeast cells (the yeast used for baking and producing alcoholic beverages), glucose can be metabolized through cellular respiration as in other cells. When oxygen is lacking, however, glucose is still metabolized to pyruvic acid via glycolysis. The pyruvic acid is converted first to acetaldehyde and then to ethyl alcohol. The net gain of ATP to the yeast cell is two molecules—the two molecules of ATP normally produced in glycolysis. Yeasts are able to participate in fermentation because they have the necessary enzyme to convert pyruvic acid to ethyl alcohol. This process is essential because it removes electrons and hydrogen ions from NADH during glycolysis. The effect is to free the NAD so it can participate in future reactions of glycolysis. The net gain to the yeast cell of two ATP molecules permits it to remain alive for some time. However, when the percentage of ethyl alcohol reaches approximately 15 percent, the alcohol kills the yeast cells. Yeast is used both in bread and alcohol production. Alcohol fermentation is the process that yields beer, wine, and other spirits. The carbon dioxide given off during fermentation supplements the carbon dioxide given off during the Krebs cycle and causes bread to rise. In muscle cells, another form of fermentation takes place. When muscle cells contract too frequently (as in strenuous exercise), they rapidly use up their oxygen supply. As a result, the electron transport system and Krebs cycle slow considerably, and ATP production is slowed. However, muscle cells have the ability to produce a small amount of ATP through glycolysis in the absence of oxygen. The muscle cells convert glucose to pyruvic acid. Then an enzyme in the muscle cells converts the pyruvic acid to lactic acid. As in the yeast, this reaction frees up the NAD while providing the cells with two ATP molecules from glycolysis. Eventually, however, the lactic acid buildup causes intense fatigue, and the muscle cell stops contracting. -occurs in the mitochondria of an animal cell -C6H12O6 + 6O2 ------> 6CO2 + 6H2O + Energy -products: co2 and h2o and ATP -reactants: glucose and o2

photosynthesis

-The process of utilizing energy to synthesize carbohydrate molecules is referred to as photosynthesis. Photosynthesis is actually two separate processes. In the first process, energy‐rich electrons flow through a series of coenzymes and other molecules. This electron energy is trapped. During the trapping process, adenosine triphosphate (ATP) molecules and molecules of nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) are formed. Both ATP and NADPH are rich in energy. These molecules are used in the second half of the process, where carbon dioxide molecules are bound into carbohydrates to form organic substances such as glucose. -Energy-fixing reaction The energy‐fixing reaction of photosynthesis begins when light is absorbed in photosystem II in the thylakoid membranes. The energy of the sunlight, captured in the P680 reaction center, activates electrons to jump out of the chlorophyll molecules in the reaction center. These electrons pass through a series of cytochromes in the nearby electron‐transport system. After passing through the electron transport system, the energy‐rich electrons eventually enter photosystem 1. Some of the energy of the electron is lost as the electron moves along the chain of acceptors, but a portion of the energy pumps protons across the thylakoid membrane, and this pumping sets up the potential for chemiosmosis. The spent electrons from P680 enter the P700 reaction center in photosystem I. Sunlight now activates the electrons, which receive a second boost out of the chlorophyll molecules. There they reach a high energy level. Now the electrons progress through a second electron transport system, but this time there is no proton pumping. Rather, the energy reduces NADP. This reduction occurs as two electrons join NADP and energize the molecule. Because NADP acquires two negatively charged electrons, it attracts two positively charged protons to balance the charges. Consequently, the NADP molecule is reduced to NADPH, a molecule that contains much energy. Because electrons have flowed out of the P680 reaction center, the chlorophyll molecules are left without a certain number of electrons. Electrons secured from water molecules replace these electrons. Each split water molecule releases two electrons that enter the chlorophyll molecules to replace those lost. The split water molecules also release two protons that enter the cytoplasm near the thylakoid and are available to increase the chemiosmotic gradient. The third product of the disrupted water molecules is oxygen. Two oxygen atoms combine with one another to form molecular oxygen, which is given off as the byproduct of photosynthesis; it fills the atmosphere and is used by all oxygen‐breathing organisms, including plant and animal cells. What has been described above are the noncyclic energy‐fixing reactions (see Figure ). Certain plants are also known to participate in cyclic energy‐fixing reactions. These reactions involve only photosystem I and the P700 reaction center. Excited electrons leave the reaction center, pass through coenzymes of the electron transport system, and then follow a special pathway back to P700. Each electron powers the proton pump and encourages the transport of a proton across the thylakoid membrane. This process enriches the proton gradient and eventually leads to the generation of ATP. ATP production in the energy‐fixing reactions of photosynthesis occurs by the process of chemiosmosis. Essentially, this process consists of a rush of protons across a membrane (the thylakoid membrane, in this case), accompanied by the synthesis of ATP molecules. Biochemists have calculated that the proton concentration on one side of the thylakoid is 10,000 times that on the opposite side of the membrane. In photosynthesis, the protons pass back across the membranes through channels lying alongside sites where enzymes are located. As the protons pass through the channels, the energy of the protons is released to form high‐energy ATP bonds. ATP is formed in the energy‐fixing reactions along with the NADPH formed in the main reactions. Both ATP and NADPH provide the energy necessary for the synthesis of carbohydrates that occurs in the second major set of events in photosynthesis. Carbon-fixing reaction Glucose and other carbohydrates are synthesized in the carbon‐fixing reaction of photosynthesis, often called the Calvin cycle for Melvin Calvin, who performed much of the biochemical research (see Figure ). This phase of photosynthesis occurs in the stroma of the plant cell. In the carbon‐fixing reaction, an essential material is carbon dioxide, which is obtained from the atmosphere. The carbon dioxide is attached to a five‐carbon compound called ribulose diphosphate. Ribulose diphosphate carboxylase catalyzes this reaction. After carbon dioxide has been joined to ribulose diphosphate, a six‐carbon product forms, which immediately breaks into two three‐carbon molecules called phosphoglycerate. Each phosphoglycerate molecule converts to another organic compound, but only in the presence of ATP. The ATP used is the ATP synthesized in the energy‐fixing reaction. The organic compound formed converts to still another organic compound using the energy present in NADPH. Again, the energy‐fixing reaction provides the essential energy. The organic compounds that result each consist of three carbon atoms. Eventually, the compounds interact with one another and join to form a single molecule of six‐carbon glucose. This process also generates additional molecules of ribulose diphosphate to participate in further carbon‐fixing reactions. Glucose can be stored in plants in several ways. In some plants, the glucose molecules are joined to one another to form starch molecules. Potato plants, for example, store starch in tubers (underground stems). In some plants, glucose converts to fructose (fruit sugar), and the energy is stored in this form. In still other plants, fructose combines with glucose to form sucrose, commonly known as table sugar. The energy is stored in carbohydrates in this form. Plant cells obtain energy for their activities from these molecules. Animals use the same forms of glucose by consuming plants and delivering the molecules to their cells. All living things on earth depend in some way on photosynthesis. It is the main mechanism for bringing the energy of sunlight into living systems and making that energy available for the chemical reactions taking place in cells. -occurs in the chloroplast of a plant cell -6CO2 + 6H2O ------> C6H12O6 + 6O2 -reactants: co2 and h2o -products: glucose and o2

photorespiration

A metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry, bright days, when stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco.

C4 plants

A plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle.

CAM plants

A plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions. In this process, carbon dioxide entering open stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed.

C3 plants

A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.

chloroplast (photosynthesis)

Chloroplasts use light to generate ATP and sugars Plant cells and cells of other eukaryotic organisms that carry out photosynthesis typically contain from one to several hundred chloroplasts. Chloroplasts bestow an obvious advantage on the organisms that possess them: They can manufacture their own food. Chloroplasts contain the photosynthetic pigment chlorophyll that gives most plants their green color. The chloroplast, like the mitochondrion, is surrounded by two membranes (figure 4.17). However, chloroplasts are larger and more complex than mitochondria. In addition to the outer and inner membranes, which lie in close association with each other, chloroplasts have closed compartments of stacked membranes called grana (singular, granum), which lie inside the inner membrane. Chloroplast structure. The inner membrane of a chloroplast surrounds a... A chloroplast may contain a hundred or more grana, and each granum may contain from a few to several dozen disk-shaped structures called thylakoids. On the surface of the thylakoids are the light-capturing photosynthetic pigments, to be discussed in depth in chapter 8. Surrounding the thylakoid is a fluid matrix called the stroma. The enzymes used to synthesize glucose during photosynthesis are found in the stroma. Like mitochondria, chloroplasts contain DNA, but many of the genes that specify chloroplast components are also located in the nucleus. Some of the elements used in photosynthesis, including the specific protein components necessary to accomplish the reaction, are synthesized entirely within the chloroplast.

knwo the krebs cycle, where it occurs and when, main events in the process abd the products of the cycle

Following glycolysis, the mechanism of cellular respiration involves another multistep process—the Krebs cycle, which is also called the citric acid cycle or the tricarboxylic acid cycle. The Krebs cycle uses the two molecules of pyruvic acid formed in glycolysis and yields high‐energy molecules of NADH and flavin adenine dinucleotide (FADH), as well as some ATP. The Krebs cycle occurs in the mitochondrion of a cell. This sausage-shaped organelle possesses inner and outer membranes and, therefore, an inner and outer compartment. The inner membrane is folded over itself many times; the folds are called cristae. They are somewhat similar to the thylakoid membranes in chloroplasts. Located along the cristae are the important enzymes necessary for the proton pump and for ATP production. Prior to entering the Krebs cycle, the pyruvic acid molecules are altered. Each three-carbon pyruvic acid molecule undergoes conversion to a substance called acetyl-coenzyme A, or acetyl-CoA. During the process, the pyruvic acid molecule is broken down by an enzyme, one carbon atom is released in the form of carbon dioxide, and the remaining two carbon atoms are combined with a coenzyme called coenzyme A. This combination forms acetyl-CoA. In the process, electrons and a hydrogen ion are transferred to NAD to form high-energy NADH. Acetyl-CoA now enters the Krebs cycle by combining with a four-carbon acid called oxaloacetic acid. The combination forms the six-carbon acid called citric acid. Citric acid undergoes a series of enzyme-catalyzed conversions. The conversions, which involve up to ten chemical reactions, are all brought about by enzymes. In many of the steps, high-energy electrons are released to NAD. The NAD molecule also acquires a hydrogen ion and becomes NADH. In one of the steps, FAD serves as the electron acceptor, and it acquires two hydrogen ions to become FADH2. Also, in one of the reactions, enough energy is released to synthesize a molecule of ATP. Because for each glucose molecule there are two pyruvic acid molecules entering the system, two ATP molecules are formed. Also during the Krebs cycle, the two carbon atoms of acetyl-CoA are released, and each forms a carbon dioxide molecule. Thus, for each acetyl-CoA entering the cycle, two carbon dioxide molecules are formed. Two acetyl-CoA molecules enter the cycle, and each has two carbon atoms, so four carbon dioxide molecules will form. Add these four molecules to the two carbon dioxide molecules formed in the conversion of pyruvic acid to acetyl-CoA, and it adds up to six carbon dioxide molecules. These six C02 molecules are given off as waste gas in the Krebs cycle. They represent the six carbons of glucose that originally entered the process of glycolysis. At the end of the Krebs cycle, the final product is oxaloacetic acid. This is identical to the oxaloacetic acid that begins the cycle. Now the molecule is ready to accept another acetyl-CoA molecule to begin another turn of the cycle. All told, the Krebs cycle forms (per two molecules of pyruvic acid) two ATP molecules, ten NADH molecules, and two FADH2 molecules. The NADH and the FADH2 will be used in the electron transport system.

Mitochondria (cell respiration)

Mitochondria metabolize sugar to generate ATP Mitochondria (singular, mitochondrion) are typically tubular or sausage-shaped organelles about the size of bacteria that are found in all types of eukaryotic cells (figure 4.16). Mitochondria are bounded by two membranes: a smooth outer membrane, and an inner folded membrane with numerous contiguous layers called cristae (singular, crista). The inner membrane of a mitochondrion is shaped into folds called cristae... The cristae partition the mitochondrion into two compartments: a matrix, lying inside the inner membrane; and an outer compartment, or intermembrane space, lying between the two mitochondrial membranes. On the surface of the inner membrane, and also embedded within it, are proteins that carry out oxidative metabolism, the oxygen-requiring process by which energy in macromolecules is used to produce ATP (chapter 7). Mitochondria have their own DNA; this DNA contains several genes that produce proteins essential to the mitochondrion's role in oxidative metabolism. Thus, the mitochondrion, in many respects, acts as a cell within a cell, containing its own genetic information specifying proteins for its unique functions. The mitochondria are not fully autonomous, however, because most of the genes that encode the enzymes used in oxidative metabolism are located in the cell nucleus. A eukaryotic cell does not produce brand-new mitochondria each time the cell divides. Instead, the mitochondria themselves divide in two, doubling in number, and these are partitioned between the new cells. Most of the components required for mitochondrial division are encoded by genes in the nucleus and are translated into proteins by cytoplasmic ribosomes. Mitochondrial replication is, therefore, impossible without nuclear participation, and mitochondria thus cannot be grown in a cell-free culture.

the process f chemiosmosisin euk cell reps. comparison of process in plant and animal cells

Mitochondria: - electrons from organic substances - chemical energy transferred to ATP - electrons pumped from matrix to inner membrane space - ATP goes into matrix Chloroplast: - electrons from water - light energy transferred to ATP - protons pumped from stroma to lumen (thylakoid space) - ATP goes into stroma

know similarities and differences in metabolic pathways for photosynthesis and aerobic respiration

Photosynthesis and Cellular Respiration are very significant metabolic pathways because in these pathways we can see how energy enters the biosphere, how it is stored, how it is transferred from one molecule to another, and how it is used. There are countless other metabolic pathways, but these two are brought into focus because of their significance in energy. Metabolic pathways are called "pathways" because the reactions involve numerous steps, each a chemical reaction catalyzed by a specific enzyme. Each step involves "intermediates" - partially-constructed molecules. Anabolic pathways: When smaller molecules are built up into larger ones the metabolic pathway is anabolic. Photosynthesis is an anabolic pathway, because cells are "building" sugar molecules from carbon dioxide and water. Linking glucose molecules together to make starch is another anabolic process. Anabolic pathways are endergonic. Ever heard of anabolic steroids? What is being 'built up' with the help of anabolic steroids? Catabolic pathways: When large molecules are broken down and their energy is extracted, the pathway is catabolic. In aerobic cellular respiration, the energy contained in the bonds of sugars (and amino acids and fatty acids) is extracted by oxidation... all the way down to carbon dioxide. In digestion, polymers are hydrolyzed into their monomers. Both are examples of catabolism at different levels, and both are exergonic. The pathways of cellular respiration have the ultimate goal of extracting energy from food and transferring it to ATP. It is the same basic process in all life forms from bacteria to humans. Pretty much all of the enzymes involved are the same across all life, and that means that the genes (DNA) coding for those enzymes are also the same. As we will see, there is some wiggle room in the genes coding for the same protein/enzyme, so by analyzing the sequence of A, T, C, and G in the DNA coding for any specific gene, we can infer from accumulated changes (mutations) how distantly related any two organisms are. This topic will have to wait. Oxidation and Reduction: The energetics pathways involve many reactions that only occur together (they are 'coupled'). Oxidation involves the loss of one or more electrons and their energy. An oxidized molecule has less free energy than it had before it was oxidized. The electrons lost by one molecule must be picked up by another molecule. When a molecule receives electrons from another, it is reduced, and its free energy is increased. So whenever a molecule is oxidized, some other molecule is reduced, and vice versa. Because the two processes are inseparable, we often refer to such reactions as REDOX (oxidation/reduction) reactions. You "saw" a redox reaction when you tested reducing sugars with Benedict's reagent. A copper compound is reduced by a sugar molecule (that gets partially oxidized). So in that reaction, a sugar loses an electron (oxidized) and the copper compound in Benedict's reagent gains an electron (is reduced). That's why the test only works for 'reducing' sugars. (Even though the sugar gets oxidized, it was the source of the electrons that reduced the copper compound.... Thus "reducing sugar") There are molecules in both photosynthesis and cellular respiration that are so well-suited to being reduced, oxidized, reduced, oxidized - in an endless cycle, that they are referred to as electron carriers. NADH and FADH2 in cellular respiration, and NADPH in photosynthesis are the reduced forms of the electron carriers. The oxidized forms are NAD+, FAD++, and NADP+, respectively. All 3 are vitamins in the category of B vitamins. In addition to being "electron carriers" and vitamins, these molecules are also referred to as coenzymes, since they work with enzymes to catalyze reactions. Interestingly, all of these electron carriers are like little tiny pieces of DNA or RNA (as is ATP). NADH and NADPH are also chemically related to nicotine (the N stands for nicotinamide). Like the relatedness of organisms that appear to be so different, these related molecules that are found in every cell provide evidence for the common ancestry of all life. Phosphorylation: When a phosphate group (PO4) is bonded to a molecule, the bond is a high-energy bond and the free energy of the recipient is increased. Most commonly, "phosphorylation" refers to the bonding of the third phosphate group to ATP (ADP + P > ATP). The bond between the second and third phosphate groups is the source of most energy used by organisms to do work. Phosphorylation requires energy from food. However, in the light-dependent reactions of photosynthesis, ATP is phosphorylated by the energy from light (photophosphorylation). This ATP is primarily to make sugar, and then the plant can transport the sugar (not the ATP) to its roots, flowers, fruits, and other non-photosynthetic organs. In cyanobacteria (the term applied to all of the blue-green pigmented bacteria of which there are numerous species) the ATP from photosynthesis can be used for cellular work (some ATP) or to make sugar (most). Aerobic or anaerobic respiration: Phosphorylation of ATP in cellular respiration can occur with (aerobic) or without (anaerobic) oxygen. The yield of ATP is much greater in the aerobic pathways of respiration. If we go back to the very origin of life on Earth, we are fairly certain that there was little or no atmospheric or dissolved oxygen. Oxygen is simply too reactive to exist for a significant amount of time. Today, all atmospheric oxygen is constantly being regenerated by photosynthesis. So we can infer that phosphorylation of ATP was primarily anaerobic (w/o oxygen) in the very earliest life forms. On today's earth, we find microbes (bacteria and archaea) that live in oxygen-free environments, and that are in fact killed by oxygen - so both anaerobic and aerobic respiration occur today. At some point - evidence of photosynthetic bacteria dates back 3.8 billion years - the oxygen-producing (photosynthetic) life forms began to proliferate. Oxygen released into the water would react quickly. Anaerobes would be safe in their oxygen-free environments, and the oxygen level was generally very low and localized. Some organisms most likely evolved that could tolerate oxygen. And in fact, with oxygen the efficiency of making ATP from food molecules goes up dramatically. (We know that a single glucose molecule can phosphorylate 2 ATPs without oxygen, and 36 ATPs with oxygen.) For these oxygen-using and oxygen-tolerant microbes, an 18-fold increase in fuel efficiency would have created a significant advantage. Aerobic respiration is such an advantage that all of the multicellular life on the planet today is both oxygen-tolerant, and oxygen-dependent. As for the microbial world, we see today a full spectrum of organisms with regard to their need for oxygen and their ability to tolerate oxygen. Some microbes today are quickly killed by oxygen. These are anaerobic organisms, and as you might imagine, they are found in anoxic (zero oxygen) environments. Oxygen has its drawbacks, even with us. You hear about foods rich in "antioxidants" - and that's a good thing. Some vitamins have antioxidant properties. The reason we need antioxidants is that free radicals of oxygen can disrupt DNA and lead to cancer. So even though we must have oxygen to live, it is considered to be the #1 cause of cancer. Let's get back to oxidative (aerobic) respiration. Oxygen exerts a very strong pull on electrons, and it is the electrons moving through the electron transport system of cellular respiration that allows us to phosphorylate enough ATP to keep us alive. The process of producing ATP with oxygen is called oxidative phosphorylation. We can make a little extra ATP without oxygen, and this can help when we are pushing ourselves to the limit. The downside is that lactic acid is a byproduct of anaerobic respiration in muscles, and can build up in muscle tissue resulting in soreness that can last for days. In photosynthesis, electrons are driven off the chlorphyll molecules and pushed down an electron transport system. Eventually, they are pulled off the end of the line by NADPH (see above). The process of producing ATP in the light-dependent reactions of photosynthesis is called photophosphorylation. This ATP, along with the reduced NADPH is used to make sugar in the Calvin Cycle (light independent reactions). Chemiosmosis: There is an electron transport system in both photosynthesis (the light reactions) and aerobic cellular respiration (the electron transport system). They are amazingly similar. Both involve the movement of electrons through molecules embedded in cell membranes (thylakoid membranes in photosynthesis, and mitochondrial membranes in oxidative respiration). In both, the moving electrons provide the energy to pump protons (H+) across a membrane against their concentration gradient, and in both, these protons rush through an enzyme complex called ATP synthase. The rush of protons through ATP synthase provides the energy for phosphorylation of ATP. That's chemiosmosis. "Chemiosmotic phosphorylation" is also called photophosphorylation (in photosynthesis) and oxidative phosphorylation (in aerobic respiration).

photosystems, where they are found, purpose. their relation to production of Atp in Plants

Pigment molecules organized into photosystems capture sunlight in the chloroplast. Photosystems are clusters of light‐absorbing pigments with some associated molecules—proton (hydrogen ion) pumps, enzymes, coenzymes, and cytochromes. Each photosystem contains about 200 molecules of a green pigment called chlorophyll and about 50 molecules of another family of pigments called carotenoids. In the reaction center of the photosystem, the energy of sunlight is converted to chemical energy. The center is sometimes called a light‐harvesting antenna. There are two photosystems within the thylakoid membranes, designated photosystem I and photosystem II. The reaction centers of these photosystems are P700 and P680, respectively. The energy captured in these reaction centers drives chemiosmosis, and the energy of chemiosmosis stimulates ATP production in the chloroplasts.

aerobic respiration

The process in which glucose is converted into CO2 and H2O in the presence of oxygen, releasing large amounts of ATP. This process includes the krebs cycle, electron transport chain, and oxidative phosphorylation. Krebs Cycle, Cellular Respiration

anaerobic respiration

form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen. Glycolysis, Fermentation

know the part played by membranes in atp synthesis in photosynthesis and cellular respirtion and process involvedl know what sorts of processes in cells require atp and how they use it

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