Membranes are a fluid mosaic of phospholipids and proteinsMembrane proteins have specific functionsMembranes form spontaneously, a critical step in the origin of lifePassive transport is diffusion across a membrane with no energy investmentOsmosis is the diffusion of water across a membraneWater balance between cells and its surroundings is crucial to organismsTransport proteins may facilitate diffusion across membranesCells expend energy in the active transport of a solute against its concentration gradientExocytosis and endocytosis transport large molecules across membranesCells transform energy as they perform workTwo laws govern energy transformations• First law of thermodynamics: Energy can be transferred and transformed, but it cannot be created or destroyed.• Second law of thermodynamics: Energy conversions increase the Entropy of the universe.• Entropy: A measure of disorderChemical reactions either release or store energyExergonic reactionEndergonic reactionATP shuttles chemical energy and drives cellular workATP powers cellular workPhosphorylationEnzymes speed up the cell’s chemical reactions by lowering energy barriersA specific enzyme catalyzes each cellular reactionEnzyme inhibitors block enzyme action and can regulate enzyme activity in a
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