Cells and Their Environment Chapter 4 p 74

Cells and Their Environment Chapter 4 p 74 -84

Homeostasis • A biological balance • Cells, tissues, organs, and organisms must maintain a balance. • Cells do so by controlling and regulating what gets into and out of the cell.

Membrane Structure & Function

Transport • Passive • Active • Transport that does not require chemical energy to occur • ie: diffusion and osmosis • The movement of any substance across a cell membrane with the use of chemical energy – ie: Na+/K+ pump

DIFFUSION • Process by which molecules spread from an area of high concentration to an area of low concentration • Concentration gradient: a difference in the concentration of a substance ***Molecules are in constant motion

Osmosis • Diffusion of water through a membrane from an area of high concentration to an area of low concentration. http: //highered. mcgrawhill. com/sites/0072495855/student_vie w 0/chapter 2/animation__how_osmosis _works. html

HYPOTONIC • Concentration of solute molecules in the environment outside of the cell is lower than that in the cell. • Water moves in

Red blood cell

Hypertonic • Concentration of solute molecules outside the cell is greater than that in the cell • Water moves out

Isotonic Concentration of solute molecules outside cell and inside are equal. **equilibrium

Think about it… What happened if you eat salty foods? Why do you gargle warm salt water if you have a sore throat? Why do athletes need to have electrolytes in their drinks? Grass wilts if you add too much fertilizer…WHY?

http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 14/animation__the_nerve_impulse. html

Requires Energy: ex. : thyroid gland concentrates Iodine glucose is completely absorbed by digestive tract

http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 2/a nimation__phagocytosis. html

Exocytosis

• Ex. LDL cholesterol (bad cholesterol) http: //highered. mcgrawhill. com/olc/dl/120068/bio 02. swf