Homeostasis and Transport

1. Homeostasis and Transport • Cells need to get materials in and out of the cell in order to maintain cellular processes • Some substances can move freely to and from the cell – Passive Transport • Others need assistance from cell – Active Transport

2. Homeostasis • Every cell seeks a state of equilibrium. • This is a balanced state where concentrations of chemicals are within a tolerable range. • This state of equilibrium is called Homeostasis • Homeo = Same Stasis = State

3. Passive Transport • Two types of Passive Transport • Diffusion • Osmosis

4. 1 4 2 3 Diffusion • Solute molecules moving from an area of high concentration to an area of low concentration • Random motion drives diffusion • Equilibrium is reached when there is an even distribution of solute molecules (water)

5. Diffusion across the Membrane • Some molecules that are soluble in lipids are able to cross the phospholipid membrane of the cell. • Because they do this on their own – the cell doesn’t expend any energy • Examples • Oxygen and Carbon Dioxide

7. Osmosis • Osmosis is a passive process in which water moves from areas of high concentration to low areas. • Water moves down its concentration gradient a crossed a semi-permeable membrane. • Like diffusion….it does not require cells to expend energy

8. Solutes are chemicals suspended in water. • Solvent is water.

9. Osmosis in Red Blood Cells

11. Cellulose in cell wall Osmosis in Living Cells

13. Active Transportation of Molecules • Passive Transport • Movement of molecules across a semi-permeable membrane • no energy required • Active Transport • Movement of molecules across a semi-permeable membrane against a concentration gradient with a protein • ENERGY – ATP • Facilitated Diffusion • Movement of molecules across a semi-permeable membrane with a protein • no energy required

14. Active Transport • Carrier proteins also assist cell in active transport. • In active transport these proteins act as “Membrane Pumps” to get ions out or into cell. • Cell has to expend energy (ATP) • Example • Sodium-Potassium Pump

16. Endocytosis and Exocytosis • Some substances are too large to pass through membrane – Macromolecules and food particles. • So cell develop another way to get these particles in and out using vesicles. • Vesicles are pinched off sacs created by the membrane.

17. Endocytosis • Endo = inside • Two type of endocytosis • Pinocytosis – Transportation of liquids • Phagocytosis – Transportation of Solids or whole cells • Some unicellular organisms use these processes to ingest food

19. Dealing with Visitors • Also used to capture bacteria and viruses from extra cellular fluid and destroy them with the help of the lysosomes. • Phagocytes

21. Exocytosis • Exo = Outside • Reverse of Endocytosis • Particles that come from golgi bodies or are free floating fuse with cell membrane. • Particles are enclosed in a membrane sac • Cell wall then opens the external side of the sac and particles is allowed to exit.

23. Animations Dialysis Bag Experiment • http://ccollege.hccs.cc.tx.us/instru/Biology/AllStudyPages/Diffusion_Osmosis/Baggif.swf Elodea Cell • http://ccollege.hccs.cc.tx.us/instru/Biology/AllStudyPages/Diffusion_Osmosis/Elodeagif.swf Osmosis • http://ull.chemistry.uakron.edu/genobc/animations/osmosis.mov