are fluid mosaic, with protein molecules embeded in a phospholipid bilayer. Functions of membrane proteins include attatchement to the cytoskeleton and extracellular matrix, cell- cell regognition, intellecutural junctions, enzymatic activity, signal transduction, and transport. Phospholipids spontaneously form membranes, a necessary step in the evolution of life.
cells shrink in a hypertonic solution and swell in a hypotonic solution. In isotonic solutions, animal cells are normal, but plant cells are limp. The control of water balance is called osmoregulation.
water channels in cells with high water-transport needs
Exocytosis and Endocytosis
In moving large molecules across a membrane, a vesicle may fuse with the membrane and expel its contents )exocytosis), or the membrane may fold inward, enclosing material from the outside.
the capacity to perform work. Kinetic energy is the energy of motion. Potential energy is energy stored in the location or structure of matter. Chemical energy is potential energy stored in chemical bonds. According to the laws of thermodynamics, energy can change form but cannot be created or destroyed. Energy transformation increase disorder, or entropy, and some energy is lost at heart.
require energy and yiled products rich in potential energy
includes all of a cell's chemical reactions.
are protein catalysts that decrease the enrgy of activation (Ea) needed to begin a reaction. Each type of " "has a unique active site that binds specifically with its substrate. Temperature and pH influence enzyme activity.
competes with substrate for the active site
alters and enzymes function by changing its shape.