Cellular Transport South Carolina Biology Standard B2.5- Explain how active, passive, and facilitated transport serve to maintain the homeostasis of the cell

Homeostasis: Necessity of an organism to maintain constant or stable conditions. All organisms have processes and structures that respond to stimuli to keep conditions conducive for life Depends in part to movement of materials across the cell membrane

Homeostasis continued: Necessary materials must pass into cell to be utilized- example glucose and oxygen Waste materials must pass out of cell as produced Cell membrane regulates the passage of materials Each individual cell exists in a fluid environment Cell membrane is semi-permeable- some substances can pass/ others can’t

Transport of materials: Passive Transport- process by which substances move across the membrane without input of energy Diffusion- spreading of molecules across the membrane until equally concentrated; molecules move from an area of high concentration to an area of low concentration Moves down the concentration gradient

Passive transport contd: Osmosis- diffusion of water molecules through a selectively permeable membrane from an area of higher concentration to an area of lower concentration. Requires no energy

Hyper, hypo and isotonic

Passive transport contd: Facilitated diffusion- process by which a substance that is unable to just pass through the membrane is able to enter using a transport or channel protein Occurs along the concentration gradient so requires no input of energy Used when cell membrane isn’t permeable to the chemical structure of the material Example- glucose

Active Transport: Another way substances can move through a cell membrane Moves against the concentration gradient- from an area of low concentration to an area of higher concentration Requires energy

Types of Active Transport: Molecules are “pumped” across the membrane by specific transport proteins. This requires energy Because it is not diffusion, cells can use this process to concentrate molecules within the cell or remove waste Calcium, potassium, and sodium ions are examples of materials that use active transport

More active transport: Sometimes the molecules are too large to diffuse across the cell membrane. Requires use of vesicles to help it through membrane If large molecule is passing into the cell= endocytosis If large molecule is passing out of the cell= exocytosis