Cellular Transport:

The movement of materials across the

cell membrane

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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

Isotonic

• Concentration inside the cell and outside the cell is the SAME

• equal flow both ways

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)

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

FLOWDiffusion 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

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Other Membrane Components

• Cholesterol

– helps with cell fluidity

• Carbohydrates

– help with cell recognition

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Hydrophilic Head

ProteinHydrophobic tail

Carbohydrate chains

Cholesterol

OUTSIDE OF CELL

INSIDE OF CELL