ENGL 224 Lecture Notes - Lecture 2: Long Term Ecological Research Network, Passive Transport, Facilitated Diffusion
Document Summary
Cellular activity requires materials input & output: Substances enter and edit cells by multiple methods. A cell"s interior is chemically different form its exterior. Solutes enter and exit cells by different methods; depending on 2 factors: 2. the chemical nature of the substance (polarity, charge and size) How cells transport substances across their membrane: passive transport: occurs when c. g. dissipate across a biological membrane. In simple diffusion, particles move from high concentration to low concentration that is, they move down their c. g. *smaller things can diffuse* - ex. ) oxygen molecule. Osmosis is the diffusion of water down it"s c. g. is also a type of passive transport. Passive transport does not require energy input. Water moves toward high solute concentration as it moves down its c. g. The fate of a cell relies on solute concentrations in the cellular movement. The hydrophobic tails of phospholipids repel hydrophilic substances. Ions and polar substances must pass thru a protein channel to cross the membrane.
