BMicrobiology Ch. 4-6

Explain how ATP is recycled in cells

ATP is recycled through the electron transport chain. The chain replenishes ATP by converting ADP into ATP through the flowing of electrons down the chain. The cahin is fueled by products of the Krebs Cycle which are then used to create more ATP. in ATP stands for tri because it has three phophates. It can release a phosphate (creating ADP - di phosphate) to release energy. Visa-versa, ADP can pick up a phosphate and become ATP, storing the energy in the bond that locks the new phosphate on. ADP + P + energy --> ATP --> ADP + P + energy. When the cell needs energy, it takes the ATP, converts it to a ADP and phosphate and uses the energy. Rather than disguarding the ADP and phosphate, they travel back to the mitochondria where they are recycled in respiration to produce another ATP.

Distinguish between fermentation and cellular respiration.

Cellular respiration requires oxygen, fermentation does not. Cellular respiration produces much more ATP than fermentation. The purpose of the oxygen in cellular respiration is only to be the last acceptor of the hydrogen electrons from the electron transport chain, which does not occur in fermentation. The electron transport chain produces 32 ATP and has water as a byproduct (oxygen + hydrogen = water). Without enough oxygen present, fermentation must take place. Our cells use lactic acid fermentation, which is why in cases of extreme exercise your muscles may get sore due to the accumulation of lactic acid. Other cells such as yeast and bacteria use alcoholic fermentation, which produces ethyl alcohol and CO2 as byproducts.

Describe the process of chemiosmosis. Explain how the exergonic slide of electrons down the electron chain is coupled to the production of ATP by chemiosmosis using the roles of NADH, FAD2, Cytochromes, oxygen, and ATP synthesis

Chemiosmosis is the movement of ions across a semipermeable membrane. More specifically, it relates to the creation of ATP as hydrogen ions travel across the membranChemiosmosis involves the pumping of protons through specific passageways in the membranes of the mitochondria from the inner to the outer space. This creates the H+ proton gradient. This influences the H+ to diffuse across the gradient, thus providing energy as the proton is passed down. A hydrogen gradient awaits on either side of the inner mitochondrial membrane and as the H+ are moved through the ETC, energy is released, thus the exergonic reaction. Then when this energy is consumed by the ATP synthase, that would be the endergonic reaction.

Explain how membrane structure of the mitochondria is related to the membrane function chemiosmosis.

Chemiosmosis, the production of ATP due to the movement of ions, is made possible by the intermembrance space. Having a double membrane and this interim area allows for there to be a build up of hydrogen ions, thus causing a concentration gradient. Then they give up their energy to make ATP as they fall through ATP synthase.

Define glycolysis and include the products that are produced. Explain why ATP is required at the beginning of glycolysis.

Glycolysis is the metabolic breakdown of sugars and forms Pgal. Pgal contains 3C and since glucose has 6C it creates 2 Pgal. Pgal when it enters the mitochondria, then forms Pyruvate and NADH. The Pyruvate then forms Acetyal CoA, and CO2 and is put through the Krebs cycle, which forms 1 ATP, 3 NADH, and 1 FADH2. Then the NADH and FADH2 travels to the electron transport system and creates a concentration gradient by pumping out the H+ ions to the intermembrane space. Then oxidation phoshorylation takes place and with the gradient the H+ ion basically turns a turbine, which creates ATP. Glycolysis needs 2 ATP at first to get from the cytoplasm to the matrix of the mitochondria and the enzymes in the glycolysis pathways need energy to function and in the end you get Pyruvate.

Describe where cell respiration steps occurs in the cell. list the precursor metabolites required for each.

Glycolysis takes place in the cytoplasm for both proks and euks. The precursors are ATP and Glucose. The Krebs cycle happens in the mitochondria for euks and in the cytoplasm for proks. The precursors are 2 Acetyl- CoA. The ETC happens in the cytoplasm for proks and in the inner membrane, cristae, of mitochonria for euks. The precursors are 6NADH and 2FADH2. Fermentation occurs in the cytoplasm for both proks and euks. The precursor is 2 pyruvate.

Describe the reactions of Kreb's Cycle using roles of CoA, citric aacid,NAD+, and FAD. include the products that are produced in Krebs's Cycle.

In Krebs cycle, acetyl CoA is created from pyruvate where it joins with oxaloacetate to create citric acid. The citrate loses a CO2 molecule and the resulting compound is oxidized, reducing NAD+ to NADH, and this process repeats a second time for the compound, reducing NAD+ to NADH. Coenzyme A then attaches to the remaining molecule where CoA is displaced by a phosphate group, which is then transferred to GDP, forming GTP, and then to ADP, forming ATP. Two hydrogens are transferred to FAD from the resulting compound, forming FADH2. The addition of water rearranges bonds in the substrate and it is then oxidized, reducing NAD+ to NADH and regenerates oxaloacetate, repeating the cycle again.

Distinguish between substrate-level phosphorylation and oxidative phosphorylation. Give examples in cellular respiration of both types.

In oxidative phosphorylation it is the production of ATP using energy derived from the redox reactions of an electron transport chain, while substrate-level phosphorylation is the formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism. The citric acid cycle is an example from cellular respiration and the calvin cycle is an example for photosynthesis. Substrate-level phosphorylation: An enzyme transfers a phosphate group from a substrate molecule to ADP; no electron transport chain Oxidative phosphorylation:A process that includes electron transport and chemiosmosis, with electron transport chain.

Define oxidation and reduction. Explain how redox reactions are involved in energy exchanges. Explain the role of REDOX reactions in cellular respiration.

Oxidation is the loss of electrons, or the increase in oxidation state by a molecule. Reduction is the gain of electrons, or a decrease in oxidation by a molecule. Electrons contains the energy inside the molecules. Mostly, cellular respiration depend on the reduction of NAD+ to NADH and the oxidation of NADH to NAD+. The NADH are then used to fuel the proton pump and create a concentration gradient in the intermembrane space. In photosynthesis the oxidation of CO2 to glucose happens. Basically it's a cycle, in which cellular respiration oxidizes glucose to CO2 and oxygen to water, and photosynthesis oxidizes CO2 to glucose and water to oxygen.

What is the importance of electron transport chain seen in the cristae membranes of mitochondria?

The ETC in the cristae of mitochondria generates energy through the transport of electrons, to pump protons from the mitochonrial matrix to an intermediate space in the membranes of mitochondria. This creates a proton gradient across the cristae. It produces 10NADH and 6FADH2. O2 gets converted into H2O.

Summarize the net APT yield from the oxidation of a glucose molecule in aerobic respiration.

The energy investment stage of glycolysis uses 2 ATP to start glucose oxidation. In the next step, substrate- level phosphorylation, 4 ATP are made. Making a net of 2 ATP molecules. One cycle off the Krebs Cycle makes 1 ATP molecule through substrate-level phosphorylation. For every glucose consumed, 34 ATPs are produced in electron transport and oxidative phosphorylation. In total, 38 molecules of ATP are produced.

Describe where pyruvate is oxidized to acetyl CoA, what molecules are produced, and how this process links glycolysis to the Krebs cycle.

The two molecules of pyruvate left over from glycolysis enter the mitochondrion if oxygen is present. From there, it can then be used by the Krebs Cycle. When it enters the mitochondrion, a multienzyme complex catalyzes these reactions. Pyruvate's carboxyl group is removed and is given off as carbon dioxide, leaving a two-carbon fragment. This fragment is oxidized to make acetate. The extracted electrons are moved to NAD+ to make NADH that stores energy. Then, coenzyme A attaches to the acetate by an unstable bond, which makes the acetate (acetyl group) very reactive. Pyruvate has now been converted into acetyl coenzyme A (acetyl CoA). Acetyl CoA's acetate can be used by the Krebs Cycle for more oxidation.

If no oxygen is present in the cell, why must glycolysis continue to either lactic acid formation or alcoholic fermentation?

When there is no oxygen present, glycolysis must continue to alcohol fermentation to convert pyruvate to ethanol in two steps, the first being that it releases carbon dioxide from the pyruvate which is then converted to acetaldehyde, the acetaldyhyde is reduced by NADH to ethanol. This process regenerates the supply of NAD+ which is needed for the continuation of glycolysis. If needed glycolysis might also turn to lactic acid fermentation in which pyruvate is reduced directly by NADH to form lactate as an end product with no release of CO2, the human muscle cells make ATP by lactic acid fermentation when oxygen is scarce.