BI110 Lecture Notes - Lecture 34: Passive Transport, Glycerol, Atp Hydrolysis
Document Summary
Hydrophobic nature of membranes restricts free movement of many molecules and substances essential for life. Passive transport: movement of a substance across a membrane without need to expend chemical energy such as atp. Passive transport and diffusion: passive transport can be driven by diffusion, diffusion: net movement of a substance from a region of higher concentration to lower concentration. Primary mechanism of solute movement within a cell and between cellular compartments separated by a membrane. Rate of diffusion, in general, depends on the concentration difference on two sides of membrane, or concentration gradient. Energy is still required to get a substance to move across a membrane (in this case not. Atp); the gradient itself is a form of potential energy (bigger gradient more potential energy faster rate of diffusion: any molecule that"s dissolved is always in motion and has a little bit of kinetic energy. Higher temperature, greater the diffusion rate; at a given temperature, smaller molecules diffuse faster.