Cellular Transport: The movement of materials across the cell membrane

2 Flow of substances across the cell membrane Membrane is selectively permeable: allows certain materials to cross through it to the inside of the cell Transport can be ACTIVE: with energy PASSIVE: without energy 9

Concentration and Equilibrium EVERYTHING FLOWS FROM HIGH TO LOW! Flow will occur in one direction until equilibrium is reached EQUILIBRIUM: The flow into and out of the cell is equal

Passive Transport – NO ENERGY is required by the cell to move substances across the cell membrane Osmosis Diffusion Facilitated Diffusion

Osmosis The passive transport of water across the cell membrane Based on concentration of things dissolved in the water (solutes) – Hypertonic – Hypotonic – Isotonic OSMOSIS ANIMATION

Hypertonic If the water surrounding the cell has a GREATER amount of dissolved materials than inside the cell... Water FLOWS OUT of the cell until equilibrium is achieved

Hypotonic Water surrounding the cell has a LOWER amount of dissolved materials than inside the cell Water flows INTO the cell

Isotonic Concentration inside the cell and outside the cell is the SAME equal flow both ways

Gummy Bear Osmosis Hypothesis: ________________________ DAYColorLengthWidth Thick- ness MassVolume 1 2

Gummy Bears Choose a gummy bear and write your name on a cup with sharpie Write a hypothesis about what you think will happen to a gummy bear if you leave it in water overnight. Measure and Weigh your gummy Calculate the Volume of your gummy Volume= length x width x thickness

Gummy Bears- Day 2 Re-measure your gummy...be REALLY careful, they are smooshy! Re-weigh your gummy bear. Weigh it on a paper towel so you don’t get gummy bear snot everywhere. Calculate the new Volume. Volume= length x width x thickness

Gummy Bear- Day 2 Was your hypothesis correct? Why or why not? Describe whether the gummy bear was placed in a hypotonic, hypertonic, or isotonic liquid. Explain why? Explain the change in volume of the gummy bear. (Volume is how much stuff there is in a given space)

Other types of cell transport

Diffusion DIFFUSION: Movement of particles from an area of high amount to an area of lower amount without the use of energy Occurs until Equilibrium is achieved, equal flow back and forth DIFFUSION ANIMATION

EQULIBRIUM: EQUAL FLOW Diffusion

Facilitated Diffusion Membrane Proteins act as a channel for particles to pass through some particles cannot go through membrane without help because membrane is selectively permeable FACILITATED DIFFUSION ANIMATION

Active Transport Can allow movement AGAINST the concentration gradient Cell uses energy (ATP from Mitochondria) to do active transport

Active Transport Transport proteins act as pumps to move particles across the membrane Example: Sodium/Potassium Pumps

SODIUM POTASSIUM ANIMATION

Transport of larger molecules by vesicles – Little spheres of cellular membrane that pinch off and contain particles – Allows movement into or out of the cell

Endocytosis and Exocytosis EXOcytosis – Releases materials to the outside of the cell from the inside of the cell ENDOcytosis – Brings materials into the cell from outside of the cell

Membrane Structure

Cellular Membranes Help regulate transport Made of proteins and phospholipids Selectively permeable – Allows certain things to diffuse passively across the membrane

Phospholipid Bilayer Made of phospholipids – Hydrophillic heads – Hydrophobic tails – Structure allows the membrane to function selectively

Membrane Hydrophilic sides facing towards the outside of the cell and the cytoplasm Hydrophobic sides face each other to avoid water

Fluid Membrane The membrane is fluid and the phospholipids can move around Proteins are embedded in the membrane between the phospholipids and can also move

Proteins embedded in the membrane Act as enzymes and carry out reactions Act as cell-to-cell recognition, like ID badges Act in chemical signaling, from cell to cell Act as transport helpers, move materials in and out

15 Other Membrane Components Cholesterol – helps with cell fluidity Carbohydrates – help with cell recognition 7

Hydrophilic Head Protein Hydrophobic tail Carbohydrate chains Cholesterol OUTSIDE OF CELL INSIDE OF CELL