transport: passive and active. structure of cell membranes fluid not rigid selectively permeable...
TRANSCRIPT
Transport: Passive and Active
Structure of Cell membranes• Fluid not rigid• Selectively permeable• Made of a phospholipid bilayer• Embedded with proteins (4 kinds)
-cell surface markers-receptor proteins-enzymes- transport protein
Cell Membrane
Passive Transport
• Movement of substances from one side of the membrane to another WITHOUT the use of ENERGY
• Ex. Diffusion• Facilitated diffusion • osmosis
Diffusion• Process where particles move from an area of
high concentration to an area of lower concentration– Ex. Food coloring in water– Sugar in coffee– Spraying perfume
Facilitated Diffusion
• Membrane is a phospholipid bilayer. Substances that are non-polar tent to pass through easier than polar or large molecules…they need help.
• Proteins in cell membrane act as carriers and channels, helping (facilitating) molecules pass through.
• Ex. Glucose, Cl-
Osmosis
• Aquaporins – channel proteins that allow water to pass through membrane
• Osmosis – diffusion of WATER through a selectively permeable membrane
• Movement of water will occur until equilibrium is reached.
Effects of Osmosis in cells
Active transport
• Moving a substance against its concentration gradient, from a low to high concentration
• Requires energy via ATP
Sodium – Potassium Pump
• 3 Na+ ions out of the cell, 2 K+ ions in the cell
Vesicles• Used by substances too large to use carrier
proteins (ex. Proteins, polysaccharides)• Endocytosis – movement of substances into
cell by vesicle
• Pinocytosis• phagocytosis
Vesicles• Exocytosis – out of cell by vesicle (ex. proteins
packaged by golgi body!!)