DIFFUSION:
• High to low concentration until equilibrium reached
• hydrophobic (lipid – soluble) or small uncharged molecules
• through phospholipid bilayer
• passive, no energy required
FACILITATED DIFFUSION:
• high to low concentration until equilibrium reached
• hydrophilic molecules or ions
• through channel proteins or via carrier proteins that change shape
• passive, no energy required
OSMOSIS:
• a type of diffusion involving movement of free water molecules
• high to low concentration of free water molecules until equilibrium reached
• through phospholipid bilayer
• passive, no energy required
MOLECULES AND IONS MOVE ACROSS MEMBRANES BY:
• diffusion
• osmosis
• active transport
• exocytosis
• endocytosis
DIFFUSION: (OR PASSIVE TRANSPORT)
Diffusion is the net movement of molecules from a region where they are at a higher concentration to a region of their lower concentration. (diffusion continues until equilibrium)
FACILIATED DIFFUSION:
Is when molecules and ions that are larger than carbon dioxide cross the membrane with the aid of proteins. They diffuse through water-filled pores within channel proteins. Some proteins that help in this are called carrier proteins, the ion or molecule binds onto a specific site on the protein, the protein changes shape and then the ion or molecule can cross the membrane.
ACROSS CELL MEMBRANE
ACTIVE TRANSPORT:
against a concentration gradient, low to high concentration through carrier proteins that change shape requires energy
EXOCYTOSIS:
used for bulk transport of substances out of the cell vesicles fuse with the cell surface membrane, releasing their contents
ENDOCYTOSIS:
used for bulk transport of substances into the cell vesicles are created from the cell surface membrane, bringing their contents into the cell