Cellular Transport

Cellular Transport All particles move and have kinetic energy (energy of motion). Movement is random and usually in a water solution. Cells are mostly made of water and there is a constant flow of ions and particles.

IV. 2 Types of Cellular Transport Passive transport = movement of molecules across the membrane by using the molecules kinetic energy. The cell exerts NO energy! Active transport = transport of materials against the concentration gradient and requires cellular energy.

V. Passive Transport 3 types of passive transport: 1. Diffusion = the net movement of particles from an area of HIGHER concentration of particles to an area of LOWER concentration of particles.

Diffusion… Molecules move randomly until they are equally distributed. Diffusion continues until the concentration of substances is uniform throughout.

Diffusion… Dynamic equilibrium – continual movement but no overall change in the concentration; Movement of materials into and out of the cell at equal rates maintaining dynamic equilibrium with its environment.

Diffusion… Diffusion depends on the concentration gradient. Concentration gradient is the difference between the concentration of a particular molecule in one area and the concentration in an adjacent area. Ex: gas exchange in the lungs (oxygen from air to blood and carbon dioxide from blood to air).

V. Passive Transport 2. Facilitated Diffusion = type of passive transport that increases the rate of diffusion with the use of carrier proteins. Ex: Facilitated diffusion of glucose.

Facilitated Diffusion

How facilitated diffusion works http://www.youtube.com/watch?v=I4123hUU8xo

V. Passive Transport 3. Osmosis = the diffusion of water molecules from an area of HIGH water concentration to an area of LOW water concentration.

V. Passive Transport: OSMOSIS Occurs in response to the concentration of solutes dissolved in water! Solutes are dissolved substances in a solution. Cytoplasm is mostly water containing many dissolved solutes.

V. Passive Transport: OSMOSIS Because no TWO molecules can occupy the same space at the same time, the MORE solutes there are in a certain volume of water; the FEWER water molecules there can be in the same water.

V. Passive Transport: OSMOSIS Plant and animal cells behave differently because plant cells have a large water vacuole and a cell wall.

How OSMOSIS works http://www.youtube.com/watch?v=w3_8FSrqc-I

V. Passive Transport: OSMOSIS Ex: Osmosis occurring in a slug (animal) cell.

V. Passive Transport: OSMOSIS Isotonic solution = a solution in which the concentration of dissolved substances (solutes) is the SAME as the concentration of solutes inside the cell. Osmosis DOES NOT occur since a concentration gradient is not established.

What happens to cells when placed in an isotonic solution? Plant cell – becomes flaccid (limp) Plant wilts because no net tendency for water to enter Animal cell - normal

Animal cell Plant cell

V. Passive Transport: OSMOSIS B. Hypotonic solution = a solution in which the concentration of solutes is LOWER than the concentration of solutes inside the cell.

What happens to cells when placed in a hypotonic solution? Animal cell – water will move thru plasma membrane into the cell. This causes the cell to swell and the internal pressure increases. Cell lyses (bursts)!

What happens to cells when placed in a hypotonic solution? Plant cell – normal The vacuole and cytoplasm increase in volume The cell membrane is pushed harder against the cell wall causing it to stretch a little. The plant tissue becomes stiffer (turgid).

V. Passive Transport: OSMOSIS C. Hypertonic solution = a solution in which the concentration of dissolved substances is HIGHER than the concentration inside the cell.

What happens to cells when placed in a hypertonic solution? Animal cell – will shrivel because of decreased turgor pressure.

What happens to cells when placed in a hypertonic solution? Plant cell – will lose water from vacuole and a decrease in turgor pressure will occur; so it is plasmolyzed. Turgor pressure = internal pressure of a cell due to water held there by osmotic pressure Plasmolysis = the loss of turgor pressure causing the plasma membrane to pull away from the cell wall Causes the plant to wilt

D. Summary of Cell Behavior in Different Environments:

OSMOSIS PROBLEMS First we need to understand 2 vocab words: Solute – the substance that dissolves (salt, sugar) Solvent – the substance in which the solute dissolves (water)

How to work osmosis problems https://www.youtube.com/watch?v=7E_qjzvCtNA

OSMOSIS PROBLEMS Cell: 5% salt (solute) Environment: 0% salt (solute)

OSMOSIS PROBLEMS Cell: 25% salt (solute) Environment: 30% salt (solute)

OSMOSIS PROBLEMS Cell: 45% salt (solute) Environment: 45% salt(solute)

VI. Active Transport Movement of molecules from an area of LOW to an area of HIGH concentration. (opposite of passive transport!) REQUIRES cellular energy! Moves large, complex molecules such as proteins across the cell membranes.

How active transport works http://www.youtube.com/watch?v=yz7EHJFDEJs

VI. Active Transport Large molecules, food, or fluid droplets are packaged in membrane-bound sacs called vesicles.

2 types of active transport Endocytosis = process in which a cell surrounds and takes in material from its environment Used by ameba to feed and white blood cells to kill bacteria

2 types of active transport 2. Exocytosis = expels materials out of the cell, reverse of endocytosis Used to remove wastes, mucus, and cell products Proteins made by ribosomes in a cell are packaged into transport vesicles by the golgi apparatus Transport vesicles fuse with the cell membrane and then the proteins are secreted out of the cell (ex: insulin)

Exocytosis

How endocytosis and exocytosis works http://www.youtube.com/watch?v=DuDmvlbpjHQ

Identify the following….

Two types of endocytosis: Pinocytosis – cell engulfs small particles such as fluids and solutes. Called “cellular drinking” Phagocytosis – cell engulfs large particles such as bacteria, viruses, and other cells. Called “cellular eating” Our white blood cells perform phagocytosis

Sodium Potassium Pump Form of active transport that uses a protein and energy to pump 3 Na+ out of the cell and 2 K+ into the cell against the concentration gradient.

Review video Watch the video and fill out the worksheet! http://www.bozemanscience.com/016-transport- across-cell-membranes