Homeostasis and The Plasma Membrane

Honors Agriculture Biology

The Effects of Solutions on Cells

Osmosis- the diffusion of water Diffusion of water molecules

through a selectively permeable membrane from high concentration to low concentration (passive transport)

Cell will lose or gain water by osmosis depending on the water concentration outside of the cell versus inside of the cell

Osmosis in Action

Osmosis in Action

Process of Diffusion

Diffusion - Movement of particles from higher concentration to low concentration (people move from big city to country for more space!!)

Drops of color into a beaker; high conc. of color (drop) to low conc., eventually the beaker will be evenly distributed with color

Equilibrium

Diffusion is due to random movement of particles

Colored ions evenly distributed in beaker, but ions still move and collide

Dynamic Equilibrium- (movement balanced) – continuous movement but no overall change in concentrations in beaker

What happened here? Diffusion in action!

Diffusion

Fertile eggs are injected at day 19 with pure dye into the opposite end of the air cell.

The dye then diffuses into the yolk sac which is absorbed by the chick and becomes systemic.

When they hatch…voila…Easter Chicks!! Who needs to dye eggs when you have

dyed chicks!

Concentration Gradients

Diffusion cannot occur unless a substance is of higher concentration in one region than another

Oxygen diffuses into capillaries of lungs because there is greater conc. of oxygen in lungs than in capillaries

Difference in concentration of substance is concentration gradient

Isotonic Solutions

Concentrations of dissolved substances and water are equal on both sides of cell (inside and out)

Water molecules still move into and out of cell, but no osmosis occurs

Most solutions injected into body are isotonic so cells are not damaged by loss or gain of water

Hypotonic Solutions

Concentration of dissolved substances (glucose or salt) lower outside cell than concentration of substances inside cell

Osmosis causes water to move into cell when in hypotonic solutions

Cells swells and pressure increases (turgor pressure)

Plants have cell walls so they can swell well; animals cells usually burst in hypotonic solutions

Hypertonic Solutions

Concentration of dissolved substances is higher outside than inside cell (salt water)

Osmosis causes water to leave cell in hypertonic solution

Animal cells shrivel (don’t salt meat before cooking) and plasma membrane shrinks away from cell wall (plants wilt)

Effects on Agriculture: Why is this important?

The floral industry relies on osmosis to help carry dye up the stems of carnations and roses

Growing plants, both ornamental and crops, is a science itself. Making sure that plants are irrigated properly will ensure more product which equals=====$$$$$$$

If the livestock and pet industries do not provide adequate fresh water for animals what happens to the cells? They shrink! This can be detrimental to the livestock industry with regards to “shrinkage” when selling cattle, etc.