Chapter 5 membrane structure and function

Describe the fluid mosaic structure of cell membranes

The fluid mosaic model describes the structure of the plasma membrane as a mosaic of components —including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character.

Describe the diverse functions of membrane proteins

Receptor Proteins- Trigger cellular responses upon binding specific molecules, e.g. hormones, steroids, insulin

Recognition Proteins-Serve as identification tags on the surface of a cell

Enzymes-Promote chemical reactions that synthesize or break apart biological molecules

Attachment Proteins-Anchor the cell membrane to inner cytoskeleton, to proteins outside the cell, and to other cells

Transport Proteins-Include channel and carrier proteins

Regulate import/export of hydrophilic molecules

Relate the structure of phospholipid molecules to the structure and properties of cell membranes

Tails facing inward because its hydrophobic heads facing outwards because it's hydrophilic • 2 layers • hydrophobic materials can go through

Define diffusion and describe the process of passive transport

Diffusion- goes from high to low concentration

Passive transport-Substances move down their concentration gradients across a membrane

No energy is expended

Membrane proteins and phospholipids may limit which molecules can cross, but not the direction of movement

(Active needs energy (ATP) and goes against the gradient meaning low to high concentration)

Explain how osmosis can be defined as the diffusion of water across a membrane

Diffusion of water across a selectively permeable membrane from a region of high to low cocentration

Distinguish between hypertonic, hypotonic, and isotonic solutions

Hypertonic- water movement out of cell (shrivel up)

hypotonic- so much more water that causes the cell to swell- water moving into the cell

isotonic- example: saline solution equal amount going in as it goes out

Explain how transport proteins facilitate diffusion

protein that has a channel that has the ability to take molecule through membrane.

facilitated diffusion- diffusion of water, ions, or water soluble molecules through a membrane via a channel or carrier protein. (glucose)

Distinguish between exocytosis, endocytosis, phagocytosis, and receptor-mediated endocytosis

Exocytosis- movement of large particle out of the cell

endocytosis- movement of large particle into the cell

phagocytosis- "cell eating" moves large particles or whole organisms into the cell

receptor-mediated endocytosis- moves specific molecules into the cell