| Term | Definition |
|---|
| How much is substrate level phosphorylation used in respiration? | Only 4 of 38 ATP ultimately produced by respiration of glucose are produced by substrate-level phosphorylation.Two are produced during glycolysis, and 2 are produced during the citric acid cycle. |
| Majority of energy extracted from food | NADH and FADH2 account for the vast majority of the energy extracted from the food.These reduced coenzymes link glycolysis and the citric acid cycle to oxidative phosphorylation, which uses energy released by the electron transport chain to power ATP synthesis. |
| The electron transport chain | generates no atp directly. a collection of molecules embedded in the cristae, the folded inner membrane of the mitochondrion. The folding of the cristae increases its surface area, providing space for thousands of copies of the chain in each mitochondrion. Most components of the chain are proteins bound to prosthetic groups, nonprotein components essential for catalysis. Electrons drop in free energy as they pass down the electron transport chain. |
| Reduction/oxidation along the chain | During electron transport along the chain, electron carriers alternate between reduced and oxidized states as they accept and donate electrons. Each component of the chain becomes reduced when it accepts electrons from its "uphill" neighbor, which is less electronegative. It then returns to its oxidized form as it passes electrons to its more electronegative "downhill" neighbor. |
| Order of molecules of chain | first flavoprotein (named because it has a prosthetic group called flavin mononucleotide), then iron-sulfur protein, then ubiquinone (Q), only member of chain that is not a protein (mobile charier shuttles electrons and receives). Most of the remaining electron carriers between Q and oxygen are cytochroms |
| Cytochrome | protein, The prosthetic group of each cytochrome is a heme group with an iron atom that accepts and donates electrons.The last cytochrome of the chain, cyt a3, passes its electrons to oxygen, which is very electronegative. |
| Last step | after cyt a3 passes electrons, Each oxygen atom also picks up a pair of hydrogen ions from the aqueous solution to form water. For every two electron carriers (four electrons), one O2 molecule is reduced to two molecules of water. |
| The electrons carried by FADH2 | have lower free energy and are added at a lower energy level than those carried by NADH. The electron transport chain provides about one-third less energy for ATP synthesis when the electron donor is FADH2 rather than NADH. |
| Function of ETC | to break the large free energy drop from food to oxygen into a series of smaller steps that release energy in manageable amounts. |
| How does the mitochondrion couple electron transport and energy release to ATP synthesis? | The answer is a mechanism called chemiosmosis. |
| What is ATP synthase? | a protein complex in the cristae actually makes ATP from ADP and inorganic phosphate |
| How does the proton gradient play a part in ATP synthesis | The proton gradient develops between the intermembrane space and the matrix. It is produced by the movement of electrons along the ETC. The chain uses the exergonic flow of electrons to pump H+ from matrix to innermembrane space. Protons pass back to matrix through The protons pass back to the matrix through a channel in ATP synthase, using the exergonic flow of H+ to drive the phosphorylation of ADP. Thus, the energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis. |
| How does the flow of H+ through ATP synthase power ATP generation? | Protons flow down a narrow space between the stator and rotor, causing the rotor and its attached rod to rotate. The spinning rod causes conformational changes in the stationary knob, activating three catalytic sites in the knob where ADP and inorganic phosphate combine to make ATP. |
| main parts of ATP SYNTH | each made up of multiple polypeptides, A rotor in the inner mitochondrial membrane. A knob that protrudes into the mitochondrial matrix. An internal rod extending from the rotor into the knob. A stator, anchored next to the rotor, which holds the knob stationary. |
| How does the inner mitochondrial membrane generate and maintain the H+ gradient that drives ATP synthesis in the ATP synthase protein complex? | Creating the H+ gradient is the function of the electron transport chain. The ETC is an energy converter that uses the exergonic flow of electrons to pump H+ across the membrane from the mitochondrial matrix to the intermembrane space. The H+ has a tendency to diffuse down its gradient.The ATP synthase molecules are the only place that H+ can diffuse back to the matrix. The exergonic flow of H+ is used by the enzyme to generate ATP. |
| Chemiosmosis in respiration | coupling of the redox reactions of the electron transport chain to ATP synthesis |
| How does the electron transport chain pump protons? | Certain members of the electron transport chain accept and release H+ along with electrons. At certain steps along the chain, electron transfers cause H+ to be taken up and released into the surrounding solution. |
| Proton motive force | The electron carriers are spatially arranged in the membrane in such a way that protons are accepted from the mitochondrial matrix and deposited in the intermembrane space. The H+ gradient that results is the proton-motive force.The gradient has the capacity to do work. |
| Chemiosmosis definition and how it is used in plants and animals | an energy-coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work. In mitochondria, the energy for proton gradient formation comes from exergonic redox reactions, and ATP synthesis is the work performed. Chemiosmosis in chloroplasts also generates ATP, but light drives the electron flow down an electron transport chain and H+ gradient formation. |
| How do prokaryotes use the H+ gradient | Prokaryotes generate H+ gradients across their plasma membrane.They can use this proton-motive force not only to generate ATP, but also to pump nutrients and waste products across the membrane and to rotate their flagella. |
| Energy flow of cellular respiration | During cellular respiration, most energy flows from glucose → NADH → electron transport chain → proton-motive force → ATP. |
| the products generated when cellular respiration oxidizes a molecule of glucose to six CO2 molecules | Four ATP molecules are produced by substrate-level phosphorylation during glycolysis and the citric acid cycle. Many more ATP molecules are generated by oxidative phosphorylation. Each NADH from the citric acid cycle and the conversion of pyruvate contributes enough energy to the proton-motive force to generate a maximum of 3 ATP. The NADH from glycolysis may also yield 3 ATP. Each FADH2 from the citric acid cycle can be used to generate about 2 ATP. |
| Why is count of atp production inexact? | There are three reasons that we cannot state an exact number of ATP molecules generated by one molecule of glucose. 1. Phosphorylation and the redox reactions are not directly coupled to each other, so the ratio of number of NADH to number of ATP is not a whole number. One NADH results in 10 H+ being transported across the inner mitochondrial membrane. Between 3 and 4 H+ must reenter the mitochondrial matrix via ATP synthase to generate 1 ATP.Therefore, 1 NADH generates enough proton-motive force for synthesis of 2.5 to 3.3 ATP. We round off and say that 1 NADH generates 3 ATP. 2. The ATP yield varies slightly depending on the type of shuttle used to transport electrons from the cytosol into the mitochondrion. The mitochondrial inner membrane is impermeable to NADH, so the two electrons of the NADH produced in glycolysis must be conveyed into the mitochondrion by one of several electron shuttle systems. In some shuttle systems, the electrons are passed to NAD+, which generates 3 ATP. In others, the electrons are passed to FAD, which generates only 2 ATP. 3. The proton-motive force generated by the redox reactions of respiration may drive other kinds of work, such as mitochondrial uptake of pyruvate from the cytosol. If all the proton-motive force generated by the electron transport chain were used to drive ATP synthesis, one glucose molecule could generate a maximum of 34 ATP by oxidative phosphorylation plus 4 ATP (net) from substrate-level phosphorylation to give a total yield of 36–38 ATP (depending on the efficiency of the shuttle). |
| How efficient is respiration in generating ATP? | Complete oxidation of glucose releases 686 kcal/mol. Phosphorylation of ADP to form ATP requires at least 7.3 kcal/mol. Efficiency of respiration is 7.3 kcal/mol times 38 ATP/glucose divided by 686 kcal/mol glucose, which equals 0.4 or 40%. Approximately 60% of the energy from glucose is lost as heat. Some of that heat is used to maintain our high body temperature (37°C). Cellular respiration is remarkably efficient in energy conversion. |
| Why is oxygen necessary for the ETC? | Without electronegative oxygen to pull electrons down the transport chain, oxidative phosphorylation ceases. |
| Purpose of fermentation | provides a mechanism by which some cells can oxidize organic fuel and generate ATP without the use of oxygen. |
| Glycolysis ATP production and oxygen | In glycolysis, glucose is oxidized to two pyruvate molecules with NAD+ as the oxidizing agent. Glycolysis is exergonic and produces 2 ATP (net).If oxygen is present, additional ATP can be generated when NADH delivers its electrons to the electron transport chain. Glycolysis generates 2 ATP whether oxygen is present (aerobic) or not (anaerobic). |
| What does fermentation need? | Fermentation can generate ATP from glucose by substrate-level phosphorylation as long as there is a supply of NAD+ to accept electrons. If the NAD+ pool is exhausted, glycolysis shuts down. |
| What happens after glycolysis without oxygen? | Under aerobic conditions, NADH transfers its electrons to the electron transfer chain, recycling NAD+. Under anaerobic conditions, various fermentation pathways generate ATP by glycolysis and recycle NAD+ by transferring electrons from NADH to pyruvate or derivatives of pyruvate. |
| alcohol fermentation | pyruvate is converted to ethanol in two steps. First, pyruvate is converted to a two-carbon compound, acetaldehyde, by the removal of CO2. Second, acetaldehyde is reduced by NADH to ethanol. Alcohol fermentation by yeast is used in brewing and winemaking. |
| lactic acid fermentation | pyruvate is reduced directly by NADH to form lactate (the ionized form of lactic acid) without release of CO2. Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt.Human muscle cells switch from aerobic respiration to lactic acid fermentation to generate ATP when O2 is scarce. The waste product, lactate, may cause muscle fatigue, but ultimately it is converted back to pyruvate in the liver. |
| Similarities btwn cellular resp and ferm | Both use glycolysis to oxidize sugars to pyruvate with a net production of 2 ATP by substrate-level phosphorylation. Both use NAD+ as an oxidizing agent to accept electrons from food during glycolysis. |
| Ferm and cellular resp differ | in their mechanism for oxidizing NADH to NAD+ In fermentation, the electrons of NADH are passed to an organic molecule to regenerate NAD+. In respiration, the electrons of NADH are ultimately passed to O2, generating ATP by oxidative phosphorylation. |
| How is atp from pyruvate maximized? | More ATP is generated from the oxidation of pyruvate in the citric acid cycle.Without oxygen, the energy still stored in pyruvate is unavailable to the cell. Under aerobic respiration, a molecule of glucose yields 38 ATP, but the same molecule of glucose yields only 2 ATP under anaerobic respiration. |
| facultative anaerobes | ( Yeast and many bacteria) can survive using either fermentation or respiration. At a cellular level, human muscle cells can behave as facultative anaerobes.For facultative anaerobes, pyruvate is a fork in the metabolic road that leads to two alternative routes. Under aerobic conditions, pyruvate is converted to acetyl CoA and oxidation continues in the citric acid cycle. Under anaerobic conditions, pyruvate serves as an electron acceptor to recycle NAD+. Have to consume sugar faster if using ferm |
| what proves glycolysis has been going on for a while? | The fact that glycolysis is a ubiquitous metabolic pathway and occurs in the cytosol without membrane-enclosed organelles suggests that glycolysis evolved early in the history of life. |
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