Water, Cells, Membranes and Cellular Transport

HOMEOSTASIS survival depends on the ability to maintain proper conditions maintaining balance is called homeostasis

The Cell Membrane selective permeability- the cell membrane allows some materials to enter/exit Fluid Mosaic Model- a “collage” of many different proteins and other molecules embedded in a fluid lipid bilayer

The Fluid Mosaic Model

Diffusion diffusion- movement of particles from an area of higher concentration to an area of lower concentration the cell membrane does not limit the diffusion of water

Example of Diffusion

Osmosis osmosis- the diffusion of water across a selectively permeable membrane concentration gradient- natural movement from high to low concentration the concentration gradient controls osmosis water will flow to the side of the membrane where water concentration is lower

Osmosis Prefixes iso- the same hypo- less hyper- more You have 3 types of solutions: isotonic, hypotonic, and hypertonic

Osmotic Solutions isotonic- same amount of water inside and outside the cell –water enters and exits at the same rate hypotonic- less water inside the cell –water enters the cell hypertonic- more water inside the cell –so water exits the cell

Now you know why it’s wrong to put salt on slugs….

Passive Transport Any type of transport that does NOT require energy (ATP) movement is with the concentration gradient i.e.- diffusion of water, facilitated diffusion

Passive Transport cont. facilitated diffusion- passive transport of materials across the membrane using transport proteins –transport proteins facilitate (assist) molecules across the membrane –movement is with the conc. grad.

Active Transport moves materials against a concentration gradient counteracts the force of diffusion requires energy from the cell transport proteins are involved

Transporting Large Particles endocytosis- a cell surrounds and takes in material from its environment –the material does not pass directly through the membrane exocytosis- reverse of endocytosis –materials are expelled from the cell

Endo- and Exocytosis