Section Objectives Explain how the processes of diffusion, passive transport, and active transport occur and why they are important to cells. Predict the effect of a hypotonic, hypertonic, or isotonic solution on a cell.

Molecules move from high to low Diffusion – move from HIGH to LOW concentration

Diffusion Move from HIGH to LOW concentration – passive transport – no energy needed diffusionosmosis diffusion of water

Simple Diffusion Move from HIGH to LOW inside cell outside cell Which way will fat move? fat LOW HIGH

Movement through the channel Why do molecules move through membrane if you give them a channel? ? ? HIGH LOW

Facilitated Diffusion Move from HIGH to LOW through a channel inside cell outside cell sugar Which way will sugar move? sugar LOW HIGH

Diffusion Move from HIGH to LOW concentration – directly through membrane simple diffusion no energy needed – help through a protein channel facilitated diffusion (with help) no energy needed HIGH LOW

Simple vs. facilitated diffusion inside cell outside cell lipid inside cell outside cell H2OH2O simple diffusionfacilitated diffusion H2OH2O protein channel

Passive Transport Requires no energy from cell Movement down the concentration gradient

Facilitated Diffusion Cellular Structure and Function  Movement of materials across the plasma membrane using protein channels.

Osmosis Cellular Structure and Function  Diffusion of water across a selectively permeable membrane  Aquaporins are water channel proteins that allow water to pass through cell membrane through facilitated diffusion.

Dynamic equilibrium is reached when the concentration

Osmosis is the passive transport of water In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentration –Hypertonic: [hyper=above, over] Solutions in which more solute present (concentrated solution) –Hypotonic: [hypo= below, under] Solutions in which less solute is present (dilute solution) –Isotonic: [ iso= equal] Solutions have equal concentrations of substances

Blood Cell Plant Cell Isotonic Solution Cellular Structure and Function  Water and dissolved substances diffuse into and out of the cell at the same rate. 11,397x

Blood Cell Hypotonic Solution Cellular Structure and Function  Solute concentration is higher inside the cell.  Water diffuses into the cell. Plant Cell 13,000x

Plant Cell Hypertonic Solution Cellular Structure and Function  Solute concentration is higher outside the cell.  Water diffuses out of the cell. Blood Cell 13,000x

Water balance between cells and their surroundings is crucial to organisms Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution –The control of water balance (osmoregulation) is essential for organisms ISOTONIC SOLUTION HYPOTONIC SOLUTION HYPERTONIC SOLUTION ANIMAL CELL PLANT CELL

Active transport [ATP]Requires the cell to spend energy [ATP] Transport proteins can move solutes across a membrane against [up] a concentration gradient

Active Transport Cellular Structure and Function  Movement of particles across the cell membrane using energy Active Transport Using Carrier Proteins

Active Transport active transport :Movement of materials through a membrane against a concentration gradient and requires energy from the cell. ATP Concentration gradient Plasma membrane Carrier proteins Cellular energy

Active transport Cells may need molecules to move against concentration “hill” – need to pump “uphill” from LOW to HIGH using energy – protein pump – requires energy ATP

Exocytosis and endocytosis transport large molecules 1. Exocytosis [ exo = outside] movement of large materials OUT of the cell ~a vesicle may fuse with the membrane and expel its contents CYTOPLASM FLUID OUTSIDE CELL

2. Endocytosis [ endo = inside] movement of large materials to INSIDE of the cell ~membrane may fold inward, trapping materials from the outside