Chapter 5 Key Terms

• Made up a phospholipid bilayer
• Must be fluid to function properly
• Switch from fluid to solid state as temperatures cool
• Rich in unsaturated fatty acids

Allow hydrophilic molecules to cross the membrane

Tendency for molecules to spread out evenly into an available space

Determine the direction of diffusion, and this requires no work

Diffusion of water across a selectively permeable membrane

Diffuses across a membrane from the region of low concentration to the region of higher solute concentration

Uses transport proteins to speed up the passive movement of molecules across the plasma membrane

Proteins, such as "Channel Proteins" and "Carrier Proteins" that are involved in facilitated diffusion

Provide a pore that allows a molecule to cross the membrane

Proteins that undergo a change in shape to translocate solute-binding sites across the membrane

• Moves substances against their gradients and requires energy (ATP)
• Allows cells to maintain concentration gradients that differ from their surroundings

The voltage difference across a membrane

Created by differences in the distribution of positive and negative ions across a membrane

• Principle property that drives the diffusion of ions across a membrane
• Determine by two forces: Chemical force and Electrical Force

Transport proteins that generate voltage across a membrane and stores energy that can be used for cellular work