F10. Mitokondrier og peroxisomer Flashcards
Essential concepts
- Mitochondria, chloroplasts, and many prokaryotes generate energy by a membrane-based mechanism known as chemiosmotic coupling, which involves using an electrochemical proton gradient to drive the synthesis of ATP.
- In animal cells, mitochondria produce most of the ATP, using energy derived from the oxidation of sugars and fatty acids.
- Mitochondria have an inner and an outer membrane. The inner membrane encloses the mitochondrial matrix; there, the citric acid cycle produces large amounts of NADH and FADH2 from the oxidation of acetyl CoA derived from sugars and fats.
- In the inner mitochondrial membrane, high-energy electrons donated by NADH and FADH2 move along an electron-transport chain and eventually combine with molecular oxygen (O2) to form water.
- Much of the energy released by electron transfers along the electrontransport chain is harnessed to pump protons (H+) out of the matrix, creating an electrochemical proton gradient. The proton pumping is carried out by three large respiratory enzyme complexes embedded in the inner membrane.
- The electrochemical proton gradient across the inner mitochondrial membrane is harnessed to make ATP when protons move back into the matrix through an ATP synthase located in the inner membrane.
- The electrochemical proton gradient also drives the active transport of selected metabolites into and out of the mitochondrial matrix.
- During photosynthesis in chloroplasts and photosynthetic bacteria, the energy of sunlight is captured by chlorophyll molecules embedded in large protein complexes known as photosystems; in plants, these photosystems are located in the thylakoid membranes of chloroplasts in leaf cells.
- Electron-transport chains associated with photosystems transfer
electrons from water to NADP+ to form NADPH, which produces O2 as a by-product.
• The photosynthetic electron-transport chains in chloroplasts also
generate a proton gradient across the thylakoid membrane, which
is used by an ATP synthase embedded in that membrane to generate ATP.
- The ATP and the NADPH made by photosynthesis are used within the chloroplast stroma to drive the carbon-fixation cycle, which produces carbohydrate from CO2 and water.
- Carbohydrate is exported from the stroma to the plant cell cytosol; there it provides the starting material used for the synthesis of many other organic molecules and for the production of the materials used by plant cell mitochondria to produce ATP.
- Both mitochondria and chloroplasts are thought to have evolved
from bacteria that were endocytosed by other cells. Each retains its own genome and divides by processes that resemble bacterial cell division.
• Chemiosmotic coupling mechanisms are of ancient origin. Modern microorganisms that live in environments similar to those thought to have been present on the early Earth also use chemiosmotic coupling to produce ATP.
Show how Acetyl CoA is produced in the mitochondria
Show how Activated carriers generated during the citric acid cycle power the production of ATP
As electrons are transferred from activated carriers to oxygen, protons are pumped across the inner mitochondrial membrane - explain.
Show how ATP synthase acts like a motor to convert the energy of protons down their electrochemical gradient to chemical-bond energy in ATP.
Show how ATP synthase is a reversible coupling device
Show how Cytochrome c oxidase is a finely tuned protein machine
Show how Electron transfers can cause the movement of entire hydrogen atoms, because protons are readily accepted from or donated to water
Show how Energy supplied by GTP hydrolysis drives nuclear transport.
Show how Experiments in which
bacteriorhodopsin and bovine
mitochondrial ATP synthase were
introduced into liposomes provided
direct evidence that proton gradients
can power ATP production.
Show how High-energy electrons are transferred through three respiratory enzyme complexes in the inner mitochondrial memranes
Show How redox potentials are measured
Show how Membrane-based mechanisms use the energy provided by food or sunlight to generate ATP
Show how Membrane-based systems use the energy stored in an electrochemichal proton gradient to synthesize ATP
Show how Mitochondria and chloroplasts share many of the features of their bacterial ancestors
Show how Mitochondria are located near sites of high ATP utilization. A mitochondrion is organized into four separate compartments.
Show how Mitochondria are thoguh to have originated when an aerobic bacterium was engulfed by a larger anaerobic eukaryotic cell
Show how Mitochondria often form elongated, tubular networks, which can extend throughout the cytoplasm
Show how Mitochondrial precursor proteins are unfolded during import
Show how NADH donates its high-energy electrons to an electrontransport chain
Show how Nuclear memranes and the ER may have evolved through invagination of the plasma membrane
Show how Product yields from glucose oxidation
Show how Proton pumping is coupled to electron transport
Show how Quinones carry electrons within the lipid bilayer
Show how Redox potential increases along the mitochondial electron transport chain.
Show how The electrochemical H+ gradient across the inner mitochondrial membrane includes a large force due to the membrane potential (ΔV ) and a smaller force due to the H+ concentration gradient—that is, the pH gradient (ΔpH).
Show how The electrochemical proton gradient across the inner mitochondrial membrane is used to drive some coupled transport processes
Show how The endoplasmic reticulum is the most extensive membrane network in eukaryotic cells
Show how The iron in a heme group can serve as an electron acceptor
Show how The orientation of a membrane-embedded electron carrier allows electron tranfer to drive proton pumping
Show how To produce ATP, mitochondira catalyze a major conversion of energy
Show how Uncoupling agents are H+ carriers that can insert into the inner mitochondrial membrane
