My AP Biology Thoughts  Unit 2 Cell Structure and Function

Welcome to My AP Biology Thoughts podcast, my name is Victoria and I am your host for episode #61 called Unit 2 Cell Structure and Function: Osmotic Pressure of Animal Cells. Today we will be discussing _the osmotic pressure of animal cells.

Segment 1: Introduction to Osmotic Pressure 

• What is osmosis? 
• The movement of a solvent/water through a semipermeable membrane from a low concentration or high water potential, where there is less solute to a higher concentration or low water potential, and it’s goal is to reach equilibrium of equal concentration of solute on the inside and out of the membrane/cell
• an example of passive transports as it does not require energy
•  What is osmotic pressure?
• Osmosis creates pressure 
• The pressure that must be applied to the solution side to stop fluid movement when a semipermeable membrane separates a solution from pure water.
• the pressure that would be required to stop water from diffusing through a barrier by osmosis. In other words, it refers to how hard the water would “push” to get through the barrier in order to diffuse to the other side.
• Determined by solute concentration, water will “try harder” to diffuse into an area with a high concentration of a solute, such as a salt, than into an area with a low concentration.

Segment 2: More About Osmotic Pressure of Animal Cells

• Water moves to hypertonic areas
• It can threaten the health of cells and organisms when there is too much or too little water in the extracellular environment compared to the inside of the cell.
• Animal cells lack a cell wall, and use active transport systems (especially the NA+ K+ ATPase that moves 3 NA+ out for each 2 K+ that move in) to move ions outside the cell reducing the osmotic pressure. 
• Most protozoa use a special contractile mechanism. Water collects in a vesicle, and microfilaments force a contraction that squeezes water back outside the cell. This pump mechanism protects the cell from osmotic pressure 

Segment 3: Connection to the Course

•  How does the osmotic pressure of animals connect back to cell structure and function?
• Without osmotic pressure the animal cells would not be able to move solvent/water through a semipermeable membrane from a low concentration to high concentration, and not reach equilibrium of equal concentration of solute on the inside and out of the membrane/cell
• This will collapse its structure and both will then lead the cell to death unable to perform its necessary functions 
• It is vital as the cell’s membrane is selective toward many of the solutes found in living organisms
• It determines the state/survival of the cell as well, like when it is placed in a hypotonic, isotonic, or hypertonic solutions

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Music Credits:

• “Ice Flow” Kevin MacLeod...