Glucose transporter as a sensor High glucose Glucose transporter as a sensor Low glucose Glucose - Glucose transporter RP VP RP R - Unphosphorylated transporter component VP R a The unphosphorylated form of the glucose transporter component indicates that glucose is available in the medium. This is because the phosphorylated transporter donates its phosphate group to glucose during the transport process. b The phosphorylated fom of the transporter component indicates that not much glucose is available in the medium. This is because the phosphorylated transporter cannot donate its phosphate during glucose transport. Inducer exclusion Positive regulation of the lac operon Low glucose High glucose АТР -Glucose Lactose- R P E. coli cell CAMP (inducer) + R Lactose transporter (permease) САР (inactive) Functional activator The unphosphorylated form of the glucose transporter component prevents the lactose transporter (permease) from functioning. Because lactose cannot be moved into the cell, the inducer (allolactose) cannot accumulate, so transcription will be blocked (see figure 7.23). c The phosphorylated form of the glucose transporter component activates the enzyme that produces CAMP, which binds to the activator (CAP). The complex of CAP and CAMP can then bind to the activator-binding site of the lac operon, allowing transcription. Note that lactose must be present for transcription to occur (see figure 7.23). FIGURE 7.25 Glucose and the lac Operon
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.
Why would it be advantageous for a cell to use glucose before lactose?
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