cellular transport: the movement of materials across the cell membrane
Post on 18-Dec-2015
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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 energy9
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
Gummy Bear Osmosis
Hypothesis: ________________________
DAY Color Length Width Thick-ness
Mass Volume
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)
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
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
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
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
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Other Membrane Components
• Cholesterol
– helps with cell fluidity
• Carbohydrates
– help with cell recognition
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