Anatomy Chapter 3 Passive and Active Transports

Passive Transport

* A process from a high concentration gradient to a low concentration gradient that does not require energy. 
* Examples include facilitated simple diffusion, diffusion, and osmosis.  

Active transport

* A process from a low concentration gradient to a high concentration gradient that does require cellular energy (ATP). 
* Examples include endocytosis and exocytosis.  

Diffusion

* Due to the random motion of molecules
* Going from a region of a higher concentration to a lower concentration
* Exchanges CO2 and O2 in the body
* effecting factors include distance, temperature, and concentration gradient
* Passive transport

Osmosis

* The diffusion of water
* The movement of water through a selectively permeable membrane from regions of higher to lower concentrations
* Water moves towards a higher concentration of solutes.  
* Passive transport

Hypertonic

* more solute, less water, water leaves the cell and shrivels


* Part of osmosis

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Hypotonic

* less solute, more water, water enters the cell and swells
* Part of osmosis

Isotonic

* equal solute concentration, same osmotic pressure, equilibrium, no net movement of water
* Part of osmosis

Osmotic pressure

* Ability of osmosis to generate enough pressure to move a volume of water
* Increases as the number of solute particles increases
* Part of osmosis

Facilitated diffusion

* Diffusion of molecules through a protein in the bi-layer
* A diffusion across a membrane with the help of a channel or carrier molecule
* Used for glucose and amino acids 
* Requires no energy
* Passive transport

Endocytosis

* The cell engulfs a substance by forming a vesicle around the substance


* Includes pinocytosis, phagocytosis and receptor-mediated cytosis
* Active transport

Pinocytosis

* Endocytosis where the substance is mostly water

Phagocytosis

Endocytosis where the substance is a solid

Receptor-mediated endocytosis

Endocytosis that requires the substance to bind to a membrane-bound receptor

Exocytosis

* When substances in a vesicle fuse with the cell membrane
* The contents are released outside the cell
* Neurotransmitters are released from nerve cells
* Active transport