Chapter 5 Miss Colabelli

Cell Transportmaintaining homeostasis

Passive Transport

Does NOT require any ATP or energy

Happens automatically

Channels may be used in cell membrane

Passive Transport

This type of transport moves from an area of high concentration to low concentration

Passive Transport

• Three types of passive transport

• Simple diffusion

• Osmosis

• Facilitated Diffusion

• These processes DO NOT REQUIRE ENERGY

Diffusion

Type of passive transport

When molecules move from an area of higher concentration to an area of lower concentration until equilibrium is met

http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP1903

What affects the rate of diffusion?

Concentration of the solution

Temperature of the solution

Pressure also speeds up particle motion

Concentration

The amount of dissolved solute in a solution

Molecules will move to an area less concentrated

Molecules diffuse through the cell membrane of cells

Concentration gradient

The difference in concentration in a solution between a cell and its surroundings

Concentration Gradient

No gradient - even distribution

Concentration to the right

Increase Rate of Diffusion

Temperature

Molecules move faster in higher temperatures

Pressure

Increasing pressure also increases rate of diffusion

EquilibriumThis occurs when there is no longer a concentration gradient

Molecules are evenly dispersed but still continue to move randomly

Cell Membrane

Movement through membrane

Cell membrane is surrounded by water

Phospholipid bilayer

Cell Membrane

Forms by itself in water

Proteins imbedded

Markers

Receptors

Channels

Diffusion in cells

Small molecules diffuse in and out of the cell to reach equilibrium on both side of the membrane

OsmosisDiffusion of water across a biological membrane

From an area of high concentration to low concentration of WATER

Comparing concentrations

Osmosis in Cells

Cells are surrounded and filled with water

Water can move freely through the membrane

http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP11003

Direction of Osmosis

Hypertonic

Outside cell is more concentrated than the cell

ex:

The solution with 20% salt is hypertonic compared to the 10% salt solution

20% salt solution outside the cell

10% salt solution inside the cell

Hypotonic

Outside the cell is less concentrated than cell

ex:

The solution with 10% salt is hypotonic compared to the 20% salt solution

10% salt solution outside the cell

20% salt solution inside the cell

Isotonic

Equal concentrations

ex:

Equilibrium is reached

10% salt solution outside the cell

10% salt solution inside the cell

Osmotic Pressure

Net movement of water into cells

Determined by solute concentration

Osmosis - hypertonic

Higher solute concentration in solution

Ex: a cell in salt water

When molecules are too large to fit through cell membrane or protein channels

Water will diffuse OUT of the cell to reach equilibrium

Cell shrinks

Osmosis - hypotonic

Lower solute concentration in solution

Ex: a cell in pure water

If molecules are too large to fit through cell membrane or protein channels

Water will diffuse INTO the cell to reach equilibrium

Cell swells - may burst!

Osmosis - IsotonicEqual concentration in solution

If molecules are too large to fit through cell membrane or protein channels

Water will diffuse IN AND OUT of the cell to maintain equilibrium

Osmosis in Plant Cells

Turgor Pressure

Pressure on the walls of the plant cells due to vacuole filling

Increase in turgor pressure is due to an increase of water to cell

Plasmolysis

When a cell shrinks due to lack of water

Red Onion Cells - Isotonic

Red Onion Cells - Hypertonic

Red Onion Cells - Hypotonic

Facilitated DiffusionWhen the cell membrane has protein channels (carrier proteins) where materials are transported in or out of cell

NO energy needed for this process

http://www.youtube.com/watch?v=-Ul2oJ_TkNw

Active Transport

Against concentration gradient

From an area of low concentration to an area of high concentration

Requires cell energy (ATP) because you’re going AGAINST concentration gradient

3 types of active transport

Three types of active transport

Active transport

Endocytosis

Exocytosis

These processes REQUIRE ENERGY

Active Transport

Protein channels embedded in cell membrane

Gated channels

Need energy to open

Protein changes shape when energy is used

Sodium/Potassium Pump

Step 1: 3 sodium ions bind to carrier protein

Step 2: ATP binds to carrier protein and changes shape allowing Na+ to move out of the cell

Step 3: 2 potassium ions move into carrier protein

Step 4: ATP binds to carrier protein and changes shape allowing K+ to move into the cell

http://www.youtube.com/watch?v=GTHWig1vOnY

Sodium/Potassium Pump

Sodium Potassium Pump

Movement in Vesicles

Endocytosis - INTO the cell

Cell membrane is used to create a vesicle around particles

Phagocytosis

Particle ingestion

Pinocytosis

Liquid ingestion

Movement in Vesicles

Exocytosis - OUT of the cell

Vesicles created in the cell fuse with cell membrane and release particles/liquids

Known as bulk transport