By: Diana Bivens Modified by: Kerri Shrestha CELLULAR TRANSPORT By: Diana Bivens Modified by: Kerri Shrestha

Plasma Membrane Plasma membrane: a selectively permeable membrane that surrounds all cells Maintains cellular homeostasis

Plasma Membrane Plasma Membrane Hydrophilic (water-loving) heads make up the outer layers of the bilayer Hydrophobic (water-hating) tails make up the inner layers of the bilayer

Plasma Membrane The structure ensures that water does NOT pass freely through it Water CAN pass through a process called osmosis “osmos”: pushing

Diffusion & Osmosis Diffusion: Osmosis: the diffusion of the movement of particles from an area of high concentration to an area of low concentration Osmosis: the diffusion of water across a selectively permeable membrane

How does osmosis work? Water will move across a selectively permeable membrane down a concentration gradient. animationl

Water will continue to move until the environment within the cell is in balance with the environment outside the cell Dynamic Equilibrium: When the solutions on both sides of the membrane are equal but water continues to move (no net change)

How does osmosis work? Cells and isotonic solutions Isotonic solution: the concentration of dissolved substances is the same on both sides of the cell membrane

Cells in isotonic solutions retain their shape

How does osmosis work? Cells in hypotonic solutions Hypotonic solution: the concentration of dissolved substances is lower outside the cell

Cells in hypotonic solutions cells try to maintain a balance with the solution outside. The cells will… SWELL

How does osmosis work? Cells in hypertonic solutions Hypertonic solutions: the concentration of dissolved particles is greater outside than inside the cell

Cells in hypertonic solutions Cells will try to maintain balance with their surroundings and they will… SHRINK!

Hypo or Hyper Hypo or Hyper

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Passive Transport Passive transport: When cellular energy is not required to move substances along a concentration gradient High concentration to low concentration

Passive Transport Facilitated diffusion Particles are too large to diffuse through the plasma membrane Uses the aid of transport proteins Sugars Amino acids facilitated diffusion animation

PASSIVE TRANSPORT Examples Osmosis Facilitated diffusion

Examples of Osmosis in Living Cells Turgor pressure in plants Death of bacterial cells as a result of the processes of food preservation Human red blood cells when the human body is dehydrated

How do cells regulate their amount of water uptake? The plant cell has a cell wall One celled organisms have a contractile vacuole that pumps out excess water Animals excrete water through urine and sweat

Active Transport Active transport: when a cell uses energy to move particles AGAINST a concentration gradient ______ concentration to ______concentration Low High

Active Transport carrier proteins bind to and transport the substance across the plasma membrane against the gradient

Active Transport of Large Molecules Endocytosis: cell surrounds a substance and engulfs it

Active Transport of Large Molecules Exocytosis: a cell expels or secretes a substance Expels waste Secretes hormones

Cell Size Why are cells so small? Diffusion is more efficient in a small cell DNA in the nucleus must support all protein needs of the cell in a timely manner A cell requires enough surface area to allow an adequate amount of substances to enter and exit the cell (as a cell grows, its surface area-to-volume ratio decreases drastically)