Let’s design a lab How can we demonstrate osmosis? What’s needed? Where can we get it? What do we need to do?

Let’s take a red blood cell Let’s take a red blood cell. If it is put into a hypertonic solution like sugar water or corn syrup where the [ ] of sugar is great outside the cell than inside the cell, water would leave the cell and it would shrivel. Take that same cell and place it in distilled water where the [ ] of solute is greater inside the cell and water will move into the cell causing the red blood cell to burst. The isotonic solution is where the [ ] outside the cell is the same as the concentration inside the cell. Water still moves in an out but at even rates and the cells are happy. Hypotonic solutions- Marine Plant cells can handle this because they have a rigid cell wall that only allows the central vacuole to get so big. Not so for us and animals. How do they handle this stress?

2 Important Strategies Osmoconformer- the organism allows its internal concentration of salts to change to match the salt concentration in the environment. Same osmolarity as the environment. Pretty handy but they are always adjusting.

Osmoregulator- organism regulates its internal concentration of salts. Brine shrimp and most bony fish. Regulate the amount of water in their bodies. They live say in the great salt lake. They live in a salt water environment. Think about which way the water will want to move. Will it move into them or out of them? It will flow out of them. Water is constantly lost so 30% of metabolism goes to regulating osmolarity.

What about fish. Let’s compare fresh water fish to salt water fish What about fish? Let’s compare fresh water fish to salt water fish. Fresh water fish live in water that has less solute that their cells. Water is constantly coming into the fish. They don’t drink water and their urine is very diluts. Salt water. Opposite problem. The water of the environment has more salt the inside the fish. Which way does the water want to flow? Out of the fish. They actually drink water and have very concentrated urine.

Think about the salmon. It spends part of its life in the salty ocean and part of its life in fresh water.. When a salmon is in salt water, then, the surrounding salinity is greater than the salinity inside its body and water will tend to leak out of its body by osmosis. The salmon has to overcome this water loss or die. When a salmon is in fresh water, however, the surrounding salinity is less than the salinity inside its body, and water will tend to enter its body by osmosis. So, just like we talked about before, while in the ocean, salmon constantlty drink seawater. The excessive salt is excreted in very concentrated urine and through special CHLORIDE CELLS found in the gills. When in fresh water, the salmon drinks very little and its kidneys produce lots of dilute urine thus eliminating the extra water.

http://www.youtube.com/watch?v=5DqjsWsY8-g

Question If a person survives a boating accident and is stranded on the ocean in a life boat, why can’t he drink the salt water?

Temperature Life in water happens at all different temperatures. Temperature affects metabolism. double in rate for every 10* C increase Organisms are designed to fit the temperature of the region in which they live. Enzymes begin to break down if temp goes to high or too low… therefore, orgain isms need to remain in specific temperature ranges in order to survive.