Passive process - when is substances do not require energy to move up to concentration gradient. Example diffusion, facilitated diffusion and osmosis
Active transport - substances require energy to move up their concentration gradient
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A symport allows two substances to pass through at the same time
An antiport allows substances to move in opposite directions.
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passive movement
- diffusion - movement of molecules or ions from an area of high concentration to an area of low concentration. Molecules such as oxygen and carbon dioxide move freely through the phospholipid bilayer
- facilitated diffusion - movement of molecules or ions from an area of high concentration to low concentration through a channel protein. The protein can change shape allowing the molecules to open or close. It only allows specific ions or molecules to pass through eg chloride ions. Symports and antiports are involved in facilitated diffusion.
- Osmosis - movement of water molecules down their water potential gradient through a partially permeable membrane. water molecules move freely across the bilayer or can move through permanently open aquaporins.
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active movement (requires ATP)
- Active transport - breakdown of ATP allows the direct transporter/ carrier protein to change shape and allow ions to move. Example sodium potassium pump where 3 sodium ions move out and 2 potassium ions move in. This is an example of antiport.
- Endocytosis - the movement of bulk liquids into a cell. The cell spreads around an object or area of solution outside the cell. The area enclosed becomes a vesicle and the contents of the vesicle is then absorbed into cytoplasm.
- Exocytosis - the movement of bulk liquids or solids out of a cell. The substances to be released from the cell is enclosed in tiny membrane bound vesicles. The vesicles are moved toward the plasma membrane. The membrane of vesicle joins with plasma membrane and empty vesicle content release out of the cell
