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

1.Passive transport = movement of molecules across the membrane by using the molecules kinetic energy. The cell exerts NO energy!

2.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

A.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:

1. Solute – the substance that dissolves (salt, sugar)

2. 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

1. 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:

1. Pinocytosis – cell engulfs small particles such as fluids and solutes.

• Called “cellular drinking”

2. 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