Homeostasis & Transport

Chapter 7 Section 7.3 & 7.4

Two Main Types of Transport

Passive Transport:Does not need energy

Active Transport: Needs energy

Like floating down a river, passive transport does NOT need energy to occur

Passive TransportDiffusion – molecules move across a given space without the use of energy from High concentration to low concentration

Osmosis-specifically water moving across a membrane without the use of energy from HC LC

Facilitated Transport- No energy, “help” moving from HC LC (channel, carrier proteins)

Substances move until they are balanced throughout a space; until the inside of the cell and outside of the cell are equal. This is called a state of equilibrium; homeostasis.

Osmosis : Three solutionsWater will move from an area of high concentration to an area of low concentration until equilibrium is reached.

1. Hypotonic –water moves into the cell (cell can “pop”) Example: Distilled water.

Cytolysis – cell bursting (animal cells may burst but plant cells won’t because they have a cell wall)

2. Isotonic – no movement; equal concentration of water on each side of the membrane. Ex. Tap water, spring water, purified water

3. Hypertonic – water moves out of the cell (cell shrinks- called plasmolysis) Ex. Salt water,sugar water. http://www.youtube.com/watch?v=gWkcFU-hHUk

Plant cellWatering a Plant (Think of blowing up a balloon)

Turgor Pressure -as water enters the plant cell. The cell wall is strong enough to resist the pressure exerted by the water inside the expanding cell. The pressure that water molecules exert against the cell wall is Turgor Pressure.

Plasmolysis- Cell shrinks away from the cell wall, turgor pressure is lost. Plant begins to Wilt

Solute concentration –particles inside and outside the cell, effecting whether water moves INTO the cell, or OUT of the cell.

More solutes less room for water

Less Solutes More room for water

Think of two beakers same size and shape, filled with water.

Now drop rocks into one of the beakers. Which beaker has more water in it?

Which one has Less?We can see the results of that demo but sometimes you can’t see the solute. Ex salt

More Sugar (solute) Less room for water. Therefore, this is the Low Concentration

Lab

• Elodea

• Red onion

• Potato

• Dialysis tubing

Elodea:http://www.youtube.com/watch?v=VK-_YHakvhoOnionhttp://www.youtube.com/watch?v=JaCCKPyE6I4&feature=related

BioRocks!

Like paddling upstream, active transport requires a lot of

energy!

Endocytosis- process where the cell membrane extends outward and envelops food particles.

1. Phagocytosis-if the material taken in is organic matter

2. Pinocytosis-takes in liquids

http://www.youtube.com/watch?v=4gLtk8Yc1Zc&NR=1

Exocytosis-

Discharge of materials from vesicles at the cell surface.

Protists contractile vacuole discharge waste, water.

Animal cells- provide a mechanism for secreting many hormones, neurotransmitters, digestive enzymes, tears and other substances.

Excretion: CO2, sweat, urine

http://www.youtube.com/watch?v=K7yku3sa4Y8&feature=related

Active Transport

Usually form Pumps

Used to move independent of gradient LC HCCells that perform a lot of active transport, require a lot of Mitochondria.Nerve and Muscle cells (both perform a lot of active transport)

Two Main Types of Pumps

• Almost all of the active transport in animal cells is carried out by only two kinds of pumps:

1. The sodium-potassium pump and

2. The proton pumps.

1/3 of the body’s energy is used to work this pump!

• This flow of ions is vital for restoring a

balance needed to keep a nerve cell functioning.

Na+/K+ pump: Very Important !1. Carrier protein has a shape that allows 3 Na + to enter

2. ATP splits, phosphate attaches to carrier (split by enzyme in carrier)

3. Change in shape allows 3 Na +’s to be dumped outside cell

4. New Shape allows 2 K+’s to enter carrier protein

5. Phosphate group is released (conformational change)

6. Carrier protein changes back to original shape, releasing 2 K +’s inside the cell.

http://www.youtube.com/watch?v=9CBoBewdS3U

Na+/K+ pump continued

Pump results in concentration gradient and electrical gradient across the cell.

3 Na+’s outside cell, 2 K+ inside cell.

Outside is more positive than the inside of the cell.

Na+ via diffusion, 300 Na per sec per carrier

Cl- are attracted to the positive Na, they diffuse through the channel

For Robin: http://www.youtube.com/watch?v=6v5o9AzjH6Q

Membrane potential. . . Charge difference between the inside and outside of the membrane.

The charge difference is due to the difference of concentrations of ions on either side of the cell

membrane.Inside the membrane is negative and the outside is

positive. This is due to the permeability of ions. There are more Na+ ions in the extracellular fluid and more K+ ions in the intracellular fluid. The membrane is more permeable to K+ which leaks

out to the outside of the membrane giving it a positive charge.

http://www.youtube.com/watch?v=iA-Gdkje6pg&feature=related

Cystic Fibrosis

Inherited disorder, caused by a faulty Cl- ion channel Thick mucous collects in airways (respiratory system) and in pancreatic and liver ducts. (digestive system)

(high solute concentration out of the cell, watery mucous) No Cl- can enter the cell.

Liver ducts-clogged, liver becomes cirrhotic less working liver tissue-liver transplant

Age about 28-30 with meds, liver trans,gene therapy works in mice not humans (yet)

http://www.pbs.org/wgbh/nova/genome/media/2809_q056_09.html