Homeostasis, Osmosis, and Diffusion

Homeostasis I. Homeostasis – biological balance between a cell or organism and its external environment. A. In multicellular organisms, you can have homeostasis on the cellular level or on the organism level. B. Homeostasis is maintained by the cell controlling what enters and exits

C. Good Stuff 1. CHO 2. Lipids 3. Proteins 4. Nucleic Acid 5. Water 6. Various chemicals D. Bad Stuff 1. Waste 2. Extra Water

E. Cells can exist in a broad range of environment, but there are limits. F. Ways a cell maintains homeostasis 1. Diffusion 2. Osmosis 3. Facilitated Diffusion 4. Gated Channels 5. Active Transport 6. Endocytosis 7. Exocytosis

Diffusion II. Diffusion – movement of molecules from areas of HIGH concentration to LOW concentration.

A. Equilibrium – point where the concentration of a substance is equal throughout the solution B. In a cell, many small molecules such as water will diffuse across the cell membrane through protein channels 1. Diagram

2. Each protein channel or pore is sepcific to a certain type of molecule 3. Each cell may have thousands of each type of protein channels

Osmosis III. Osmosis – the process by which water molecules diffuse across a selectively permeable membrane A. Diagram

B. Direction of Osmosis 1. Hypotonic Solution – solute is less on the outside of the cell than the inside; water is greater on the outside. *Cell Swells

2. Hypertonic solution – solute is more on the outside than the inside; water is less on the outside *Cell Shrinks

3. Isotonic solution – solute is equal on the inside and outside of the cell a) Cell is in homeostasis

C. Examples 1. Hypotonic Solution a) Jellyfish in Lake Norman

2. Hypertonic Solution a) Goldfish in the Atlantic Ocean

3. Isotonic Solution a) Jellyfish in the Atlantic Ocean

D. Roles of Osmosis 1. Kidneys use it to maintain water levels in the blood 2. Turgor pressure – water pressure in plant cells a) help maintain support 3. Plasmolysis – occurs when a ell is in a hypertonic solution and shrinks due to water leaving 4. Cytolysis – occurs when a cell is in a hypotonic solution and it bursts due to water rushing into the cell.

Types of Diffusion

Facilitated Diffusion IV. Facilitated Diffusion – diffusion of molecules across the cell membrane with the help of carrier proteins A. Carrier Protein – protein which carries molecules across the cell membrane B. Carries large molecules such as starch, sucrose, lipids, and proteins C. Each carrier protein is specific to a type of molecule

Facilitated Diffusion continued..

Active Transport V. Active Transport – movement of molecules from areas of low concentration to areas of high concentration with the use of ATP and a carrier protein A. goes against diffusion B. uses ATP to power it

Gated Channels VI. Gated Channels – protein that can be opened or closed to allow molecules to enter or leave the cell wall A. works by diffusion B. diagram

Endocytosis VII. Endocytosis – process where large molecules are taken into the cell A. Two types 1. Phagocytosis – takes in solids 2. Pinocytosis – takes in liquids B. diagram

Exocytosis VIII. Exocytosis – getting rid of large molecules A. diagram

B. Ex) Sodium-Potassium Pump 1. used to carry nerve signals 2. steps