Chapter 14
14.1.e Recall how many mitochondria are present in a typical cell and how their numbers can change with the energy needs of the cell.
-1000 to 2000 mitochondria are present-numbers can vary depending on the cell type and can change with the energy needs of the cell-skeletal muscle cell: can divide until their numbers increase five to tenfold-marathon runners: twice as many in their legs as sedentary people
14.0.d Summarize the membrane-based processes involved in oxidative phosphorylation and photosynthesis.
-2 linked stages: one setting up an electrochemical proton gradient and the other uses that gradient to generate ATP -both stages being carried out by special protein complexes embedded in a membrane
14.1.r Express the ratio at which cells maintain the concentrations of ATP and ADP, and state how cyanide works to upset this balance.
-ATP in the cytosol must be kept about 10 times higher than that of ADP and when the activity is halted, ATP levels fall and the cell's battery runs down-cyanide blocks electron transport in the inner mitochondrial membrane causing cell death
14.2.g Compare the redox potentials of components in the electron transport chain and state which way electrons will flow.
-Goes from low electron affinity to high. The lower the redox potential, the lower the molecules' affinity for electrons-and the more likely they are to act as electron donors.-Redox potential are expressed in units of volts.-Electrons will move spontaneously from a redox pari with a lox redox potential (or low affinity for electrons), such as NADH/NAD+, to a redox pair with a high rex potential (or high affinity for electrons), such as O2/H2O
14.1.s Compare where electrons donated by NADH and FADH2 enter the respiratory chain, and relate how much ATP is ultimately produced by each activated carrier.
-NADH: NADH dehydrogenase complex (2.5 ATP)-FADH2: membrane-embedded mobile carrier ubiquinone (1.5 ATP)
14.2.c Relate redox potential to electron affinity and describe how the redox potentials of reduced/oxidized nicotinamide adenine dinucleotide and oxygen/water align with their functions in the respiratory chain.
-The redox potential goes from low to high with the lowest electron affinity in NADH passing its electrons to NADH dehydrogenase which has a slightly higher electron affinity, and so on and so forth with O2 having the highest electron affinity within the electron transport chain.-NADH is oxidized as it loses its e-
14.1.m Recall the direction in which protons are pumped across the inner mitochondrial membrane and describe the resulting pH difference in the mitochondrial matrix and intermembrane space.
-across the inner mitochondrial membrane from the matrix to the intermembrane space-the pH is .7 unit higher than it is in the intermembrane space
14.1.f Describe the structure of a mitochondrion and distinguish the functions and compositions of its different membranes and compartments.
-bounded by 2 specialized membranes (one inside the other)-called inner and outer mitochondrial membranes that crease 2 compartments: matrix and intermembrane space
14.1.j Distinguish the source of the high-energy electrons that power ATP production during cell respiration and photosynthesis.
-cell respiration: sugars and fats-photosynthesis: chlorophyll
14.1.l Compare the electron affinities of the components of the electron transport chain, and describe the change in energy of electrons as they move along the chain.
-energetically favorable: the electrons are passed from electron carriers with a weaker electron affinity to those with a stronger electron affinity until picked up by oxygen -energy released in the electron transport chain is captured as a proton gradient, which powers the production of ATP by a membrane protein called ATP synthase.
14.0.c Compare where the production of ATP by oxidative phosphorylation takes place in plant cells, animal cells, bacteria, and archaea.
-eukaryotes (plants and animals): inner mitochondrial membrane -bacteria and archaea: cytoplasm
14.1.d Compare where mitochondria are located in a heart muscle cell, sperm, and fibroblast.
-heart muscle: close to the contractile apparatus -sperm: wrapped tightly around the motile flagellum -fibroblast: by the RER due to excreted protein production
14.2.h Identify the metals that help give cytochrome c oxidase its high redox potential.
-heme group plus copper atoms-zinc-magnesium
14.2.fContrast the redox potentials of iron-sulfur clusters and iron atoms held in heme groups, and relate where proteins containing these metals are positioned along the electron transport chain.
-iron sulfur centers: low affinities for electrons and are prominent in the electron carriers that operate in the early part of the chain-iron atoms held in heme: used as electron carriers; give cytochromes their color-cytochrome proteins increase in redox potential the further down the mitochondrial ETC they are located
14.1.a State the percentage of the free energy available in a molecule of glucose that is captured during glycolysis, and relate that efficiency with that of a gasoline-powered engine.
-less than 10% less -gasoline engines operate at 10-20% efficiency
14.1.b Review the consequences of disrupting electron transport in mitochondria.
-mitochondrial dysfunction because you don't have ATP which will lead to...-an inherited disorder called myoclonic epilepsy and ragged red fiber disease (MERRF)-muscle and nerve cells need large amounts of ATP to function normally and w/o it can cause muscle weakness, heart problems, epilepsy, dementia
14.1.n Review the membrane potential and pH gradients across the inner mitochondrial membrane, and state in which direction it is energetically favorable for protons to flow.
-protons will flow in the direction towards the higher pH (less protons) and more negative membrane potential-matrix side becomes more (-) and intermembrane becomes more (+).-Its favorable to flow back to the matrix.
14.0.f List the evidence suggesting that both mitochondria and chloroplasts evolved from bacteria that were engulfed by ancestral cells.
-remarkable resemblance of the mechanism in prokaryotes and eukaryotes- both reproduce in a manner similar to that of most prokaryotes -both harbor bacterial-like biosynthetic machinery for making RNA and proteins, and possess DNA based genomes -membranes in both organelles contain the protein complexes involved in ATP production
14.1.g Review how pyruvate and fatty acids move from the cytosol to the mitochondrial matrix, and identify the metabolic intermediate into which both are converted before entering the citric acid cycle.
-they move through the porins in the outer mitochondrial membrane -fuel molecules are then transported across the inner mitochondrial membrane into the matrix where they are converted into acetyl CoA
14.1.p Describe the conditions under which ATP synthase will act as a proton pump and hydrolyze ATP.
-to go "uphill" against their electrochemical gradient-if the gradient is switched everything will be reversed. If reverse ATP synthase can turn into an ATP hydrolase, which means it will generate ADP and inorganic phosphate from ATP
14.1.k List the components of the electron transport chain in their order of operation, including mobile electron carriers, and describe the functions of each.
1.) NADH Dehydrogenase Complex: accepts NADH's e-, p+ pump2.) Ubiquinone(Mobile Carrier):Ferries e-; accepts FADH2's e-3.) Cytochrome c Reductase Complex: p+ pump4.) Cytochrome c(Mobile Carrier): Ferries e-5.) Cytochrome c Oxidase Complex: p+ pump
14.0.a Identify the molecule that serves as the main source of chemical energy in a cell.
ATP
14.0.b Differentiate between the mechanisms of ATP production by glycolysis and by oxidative phosphorylation.
Glycolysis breaks down glucose to produce ATP, whereas Oxidative phosphorylation uses proton gradient to synthesize ATP
14.1.h Recall the activated carriers, generated by the citric acid cycle, that will transfer high-energy electrons to the electron transport chain.
NADH & FADH2 transfer e-
14.1.i Outline the process that allows much of the energy contained in the high-energy electrons of activated carriers to be stored in the high-energy phosphate bonds of ATP.
NADH and FADH2 drop off their hi-energy electrons, the energy release is used for the phosphorylation of ATP through energy conversion processes in the inner mitochondrial membrane.
14.0.e Summarize the stages involved in generating ATP by oxidative phosphorylation.
Stage 1: high energy electrons (derived from oxidation of food, sunlight, or other chemical sources) are transferred along an ETC, embedded in a membrane. these electron transfers release energy used to pump protons, across the membrane and generate an electrochemical proton gradient Stage 2: protons flow back down their electrochemical gradient through a membrane-embedded protein complex (ATP synthase) which catalyzes the energy-requiring synthesis of ATP from ADP and inorganic phosphate. the enzyme functions as a turbine that couples the movement of protons across the membrane to the production of ATP
14.2.i Name the atoms or molecules that are oxidized or reduced by cytochrome c oxidase.
The mobile carrier cytochrome c is oxidized when Complex cytochrome c oxidase takes its e-
14.2.e Explain why NADH does not donate its electrons directly to molecular oxygen in living systems.
because of the huge drop in free energy, the reaction would proceed with almost explosive force and nearly all of the energy would be released as heat
14.1.q Outline how the electrochemical proton gradient is used to drive the transport of metabolites across the inner mitochondrial membrane in eukaryotic cells and to power the rotation of flagella in motile bacteria.
it is a source of usable energy in motile bacteria; the flow of protons into the cell drives the rapid rotations of the bacterial flagellum, which propels the bacterium along
14.2.m Summarize the effects that uncoupling agents such as dinitrophenol have on the proton motive force in intact mitochondria.
physical disruption of the inner mitochondrial membrane halts ATP synthesis in that organelle. Similarly dissipation of the proton gradient by a chemical "uncoupling" agent such as 2,4-dinitrophenol (DNP) also inhibits mitochondrial ATP production. Such gradient-busting chemicals carry H+ across the inner mitochondrial membrane forming a shuttle system for the movement of H+ that bypasses the ATP synthase. As a result of this short-circuiting the proton-motive force is dissipated completely and the organelle can no longer make ATP.
14.2.d Estimate the number of ATP molecules that could be synthesized from the energy released by the transfer of two electrons from NADH to molecular oxygen.
several (6)
14.2.j Summarize why cytochrome c oxidase must bind oxygen tightly.
the active site of cytochrome c oxidase therefore hold tightly to an oxygen until it receives all four of the electrons needed to convert two molecules of H2O. this retention is critical because it prevents superoxide radicals from attacking macromolecules throughout the cell--a type of damage that has been postulated to contribute to human aging. the evolution of cytochrome c oxidase allowed cells to use O2 as an electron acceptor and this protein complex is essential for all aerobic life.
14.2.b Summarize how electron carriers are able to transfer a proton from one side of the membrane to the other.
the electron carrier must be oriented in the membrane in such a way that it accepts an electron-along with a proton from water- on one side of the membrane and then releases a proton on the other side of the membrane when it passes an electron on to the next electron carrier molecule in the chain
14.1.o Explain how ATP synthase acts as a motor to convert the energy of protons flowing down an electrochemical gradient into the chemical bond energy in ATP.
the passage of proteins through the carrier causes the carrier and its stalk to spin rapidly (motor) and as the stalks rotate, it rubs against proteins in the enzymes stationary head, altering their conformation and causing them to produce ATP. a mechanical deformation gets converted into the chemical-bond energy of ATP
14.2.n Outline how investigators used an artificial system including bacteriorhodopsin and ATP synthase to demonstrate the role that a proton gradient plays in producing ATP.
this is where the ATP synthase comes in assemble an artificial ATP-generating system by combining an ATP synthase isolated from the mitochondria of cow heart muscle with a proton pump purified from the purple membrane of the archaean. Halobacterium halobium.-when bacteriorhodopsin alone was reconstituted into artificial lipid vesicles (liposomes), which showed that in the presence of light the protein pumps H+ into the vesicle, generating a proton gradient.
14.2.k Outline how conformational change in cytochrome c oxidase pumps protons across the inner mitochondrial membrane.
this pumping occurs because the transfer of electrons drives allosteric changes in the conformation of cytochrome c oxidase that causes protons to be ejected from the mitochondrial matrix
14.2.a Identify the main source of the protons that are pumped across the inner mitochondrial membrane by the electron transport chain.
water
14.2.l Explain how specialized carrier proteins in the inner mitochondrial membrane of brown fat cells allow those cells to oxidize fats to produce heat.
with oxidative phosphorylation, we use ATP synthase to make ATP from the protons flowing through it; in brown fat cells, there are uncouplers like thermogenin which also use proton flow to generate instead of ATP
