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Electron Transport Chain
The electron transport chain, also known as the electron transport system, is a group of proteins that transfer electrons through a membrane within mitochondria to create a gradient of protons that drives adenosine triphosphate (ATP)synthesis. The cell uses ATP as an energy source for metabolic processes and cellular functions. ETC involves series of reactions that convert redox energy from NADH (nicotinamide adenine dinucleotide (NAD) + hydrogen (H)) and FADH2(flavin adenine dinucleotide (FAD)) oxidation into proton-motive force(PMF), which is then used to synthesize ATP through conformational changes in the ATP synthase complex, a process known as oxidative phosphorylation.
Metabolism
Picture a campfire. It keeps the body warm on a cold night and provides light. To ensure that the fire keeps burning, fuel needs to be added(pieces of wood in this case). When a small piece is added, the fire burns bright for a bit and then dies down unless more wood is added. But, if too many pieces are placed at a time, the fire escalates and burns for a longer time, without actually burning away all the pieces that have been added. Many of them, especially the larger chunks or damp pieces, remain unburnt.
Cellular Respiration
Cellular respiration is the cellular process involved in the generation of adenosine triphosphate (ATP) molecules from the organic nutritional source obtained from the diet. It is a universal process observed in all types of life forms. The glucose (chemical formula C6H12O6) molecules are the preferred raw material for cell respiration as it possesses a simple structure and is highly efficient in nature.
Biochemists working with isolated mitochondria recognize five energy
“states” of mitochondria, depending on the presence or absence of essential substrates for respiration—O2, ADP, oxidizable substrates, and so forth. The characteristics of each state are:
state 1: mitochondria alone (in buffer containing Pi)
state 2: mitochondria + substrate, but respiration low due to lack of ADP
state 3: mitochondria + substrate + limited amount of ADP, allowing
rapid respiration
state 4: mitochondria + substrate, but all ADP converted to ATP, so
respiration slows
state 5: mitochondria + substrate + ADP, but all O2 used up (anoxia),
so respiration stops
(a) On the graph, identify the state that might predominate in each stage of the trace indicated with a letter.
(b) To determine whether isolated mitochondria exhibit respiratory control,
one determines the ratio of rates of oxygen uptake in two different states.
Which states?
(c) Which state probably predominates in vivo in skeletal muscle fatigued
from a long and strenuous workout?
(d) Which state probably predominates in resting skeletal muscle of a wellnourished animal?
(e) Which state probably predominates in heart muscle most of the time?
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