NOTE SHEET 8 – Transport Through The Cell Membrane

What is cell transport? Cell Transport – when substances move into or out of cells In order to get into or out of the cell, substances must pass through the cell membrane

What is cell transport? Substances in a living thing naturally move from areas of high concentration (where there is a lot of that substance) to areas of low concentration (where there is less of that substance)

What are the 2 types of cell transport? Passive Transport – When substances move in or out of cells from areas of high concentration to areas of low concentration

Passive Transport The cell uses NO ENERGY in this process, it happens naturally Osmosis – the movement of water from high to low concentration Diffusion – the movement of any substance besides water from high to low concentration Osmosis and diffusion happen in opposite directions

Passive Transport EX. If there is a lot of sodium outside of a cell, the sodium moves into the cell by diffusion and water moves out of the cell by osmosis

The Rime of the Ancient Mariner By Samuel Taylor Coleridge (written in 1797-98) Water, water, every where, And all the boards did shrink; Nor any drop to drink.

Salt-Cured Meat Meat or fish preserved or cured with salt The only widely available method of preserving food until the 19th century Salt prevents the growth of bacteria by drawing water out of bacteria cells by osmosis Salted meat was a staple of the mariner's diet in the Age of Sail. It was stored in barrels, and often had to last for months spent out of sight of land.

What are the 2 types of cell transport? Active Transport – When the cell uses energy to move substances in or out from an area of low concentration to an area of high concentration

Active Transport The cell must USE ENERGY because substances do not naturally move from low concentration to high concentration The cell must also use energy to move very large particles into or out of the cell (endocytosis and exocytosis)

Another way to look at it…

Two Solutions Are Separated By A Selectively Permeable Membrane Solution A has a high concentration of solute compared to solution B Solution B has a high concentration of water compared to Solution A So what happens?

Two Solutions Are Separated By A Selectively Permeable Membrane Solute moves through the membrane from Solution A to Solution B (Diffusion) Solution A becomes less concentrated, Solution B becomes more concentrated

Two Solutions Are Separated By A Selectively Permeable Membrane Water moves through the membrane from Solution B to Solution A (Osmosis) Solution B becomes more concentrated, Solution A becomes less concentrated

Two Solutions Are Separated By A Selectively Permeable Membrane Dynamic equilibrium is reached Solute and Water move back and forth equally

What are the effects of passive transport on cells? As the cell’s external environment changes, passive transport causes water and other substances to continuously move into and out of cells Turgor Pressure – pressure in a cell caused by water Plant cells need the correct amount of turgor pressure to stay rigid

Elodea Cells Before and After Placement in a Hypertonic Solution

What happens if there is a lower concentration of substances outside the cell?

What happens if there is a lower concentration of substances outside the cell?

What happens if there is a lower concentration of substances outside the cell? Type of Solution Hypotonic Turgor Pressure High Cell Shape Swollen

Plant Cell - Hypotonic

What happens if the concentration of substances outside of the cell is equal to the cytoplasm

What happens if the concentration of substances outside of the cell is equal to the cytoplasm

What happens if the concentration of substances outside of the cell is equal to the cytoplasm Type of Solution Isotonic Turgor Pressure Normal Cell Shape Normal

Plant Cell - Isotonic

What happens if there is a higher concentration of substances outside of the cell?

What happens if there is a higher concentration of substances outside of the cell?

What happens if there is a higher concentration of substances outside of the cell? Type of Solution Hypertonic Turgor Pressure Low Cell Shape Shriveled

Plant Cell - Hypertonic

Animal Cells in Different Solutions

How do I figure out the direction of passive transport? Look at the solution outside of the cell. Compared to the cytoplasm, is the concentration of substances higher, lower, or equal? Diffusion – Which way will the substances move? (into cell, out of cell, in or out equally) Osmosis – Which way will water move? (into cell, out of cell, in or out equally)

To sum up… If there is a lot of substance outside a cell, substance moves in (diffusion), water moves out (osmosis) and the cell shrivels If there is a lot of substance inside a cell, substance moves out (diffusion), water moves in (osmosis) and the cell swells These processes happen naturally (passive transport), if the cell wants the opposite to happen, it must use energy (active transport)

Cells need a steady supply of energy for active transport otherwise they would not be able to adjust to their environment

Cell Transport Animations http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.swf