transport: passive and active. structure of cell membranes fluid not rigid selectively permeable...

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!!)