Transport in the Cell

In a way a cell is like a miniature version of you. It requires nutrients and, in the process of breaking down the nutrients, the cell produces wastes. So there has to be a way to get nutrients in and wastes out.

One particular part of the cell plays a huge role in controlling what enters and leaves the cell, so this organelle is in charge of CELLULAR TRANSPORT.

Cell Membrane  Phospholipids  Phospholipids – main component of the cell membrane  Cholesterol  Cholesterol – prevents close packing of the lipids  Proteins  Proteins – transport ions through the membrane

General Terms Concentration Gradient – The unequal distribution of particles

Concentrations

Cell Transport 2 Main Types of Transport: Passive Transport Active Transport No Energy Needed Molecules naturally want to reach a balance on either side of a membrane moving from high to low concentration “Homeostasis” The cell’s version of energy is needed - ATP It moves molecules from low concentration to high concentration.

Cell Transport PASSIVE TRANSPORT DIFFUSION The movement of molecules from a HIGH to LOW concentration ashanimat/transport/diffusion.swf

Cell Transport PASSIVE TRANSPORT OSMOSIS the diffusion of water ni/flashanimat/transport/osmosis.sw f

Cell Transport PASSIVE TRANSPORT FACILITATED DIFFUSION “needs a passageway”

More General Terms  Osmotic Pressure  Osmotic Pressure – the water pressure in cells  Turgor pressure  Turgor pressure – the water pressure in plant cells  Plasmolysis  Plasmolysis – Process where the cell membrane pulls away from the cell wall due to water loss

Solutions

Passive Transport 0 % solutes 75% solutes Solutes: Dissolved substances like salt and sugar. 1.Where is the concentration of solutes the greatest? 2.Where is the concentration of water the greatest? 3.Which molecule would be easier to move – the solute or the water?

Passive Transport 0 % solutes 75% solutes As a result, the smaller molecule, water, will move into the cell causing the cell to expand. 75% solutes

Passive Transport 0 % solutes 75% solutes Since the concentration of the solutes OUTSIDE of the cell is lower, then the solution is considered to be HYPOTONIC.

Outside the cell Solutes

Passive Transport 50 % solutes As a result, the smaller molecule, water, will move into and out of the cell at an equal rate causing the cell to remain the same size.

Passive Transport 50 % solutes Since the concentration of the solutes OUTSIDE of the cell is EQUAL or the SAME, then the solution is considered to be ISOTONIC.

Outside the cell Solutes

Passive Transport 70 % solutes 20% solutes out As a result, the smaller molecule, water, will move out of the cell causing the cell to shrivel. 20%

Passive Transport 70 % solutes 20% solutes Since the concentration of the solutes OUTSIDE of the cell is HIGHER or ABOVE, then the solution is considered to be HYPERTONIC.

Outside the cell Solutes

Everyday examples of solutions  Hypertonic: Alcohol, Caffeine, Ocean water, Epson Salt bath  Hypotonic: Distilled water  Isotonic: Blood

Cell Transport Active transport It moves molecules from low concentration to high concentration.

Cell Transport Why does active transport need energy? against Because the molecules are moving against the CONCENTRATION GRADIENT.

Cell Transport Sometimes a substance that a cell needs to transport in is too large to fit through the cell membrane, so the membrane moves around the substance. Endocytosis - the cell membrane engulfs a substance by surrounding it and forming a “vessicle.”

Exocytosis – The cell needs to rid the cell of a waste or substance so it forms a “vessicle” around it and releases the substance at the cell membrane. Cell Transport

50 % solutes

0% solutes

50 % solutes 100% solutes

80 % solutes 90% solutes

100 % solutes 10% solutes