Water, water everywhere and not a drop to drink…

-Samuel Taylor Coleridge

The Horse Latitudes

Why Are We Not Adivsed To Drink Seawater?

Water Balance

• Need appx. 3L/day

• Without water, no hydrolysis, temperature regulation, transport of materials

HYPONATREMIA

• 3 Gal/1hr = death due to loss of electrolytes (salts), causing nervous conductivity and muscle contraction to cease

Which organelles maintain water balance?

Why must the cell membrane maintain SELECTIVE PERMEABILITY?

Kinetic Molecular Theory

• Molecules are constantly in motion

• Molecules want to attain disordered state / fewer collisions

• Molecules will move until fewest number of collisions/least ordered state is reached

BROWNIAN MOTION

• Molecules are constantly moving as a result of their own vibrational/kinetic energy

• This movement can be observed as BROWNIAN MOTION

PASSIVE TRANSPORT

• As molecules are constantly in motion, they will move without requiring the expenditure of energy by the cell

Diffusion v. Osmosis

DIFFUSION

DIFFUSION

• Passive movement of solute molecules from high concentration to low

CONCENTRATION GRADIENT

• Molecules will tend to move from high concentration to low concentration on their own accord (using their own vibrational energy)

• Movement with the gradient is exergonic

OSMOSIS

• Passive movement of water molecules from high to low concentration

OSMOTIC POTENTIAL

• DEF: The difference between the concentration of water molecules inside and outside of cell

• The larger the size of this gradient, the greater the potential for water molecules to move

DYNAMIC EQUILIBRIUM

• No net passive movement of solute or solvent (water) due to an equal concentration

• No concentration gradient or osmotic potential

Factors Affecting Diffusion/Osmosis

• Tonicity of solution outside of cell• Selective Permeability of Membrane• Size of Particles• Weight of Particles• Charge of Particles• Temperature of Solvent

TONICITY

• Def: Relative measure of dissolved particles (solute) in the solution surrounding the cell membrane

• Measurement is always compared to interior/cytoplasm of cell

• Water does not have a tonic classification as it is invariably the solvent

ISOTONIC

• Concentration of solute outside of the cell is equal to the concentration of solute inside of the cell

• No net movement of particles

• DYNAMIC EQUILIBRIUM

HYPOTONICITY

• Concentration of particles outside of cell is lower than concentration inside of cells

• If permeable, solute will leave cell to establish equilibrium with outside concentration

HYPERTONIC

• Concentration of dissolved particles/solute is greater outside of cell than in its interior

• As a result, solute will attempt to enter the cell to establish equilibrium

CYTOLYSIS PLASMOLYSIS NORMAL

PLASMOLYSIS

• DEF: Loss of water and turgor due to placement of cell in HYPERTONIC environment

• Water leaves cell via osmosis, causing vacuole to shrink, or cytoplasm to lose volume (crenation)

CYTOLYSIS

• Def: Cells placed in HYPOTONIC environments may undergo cytolysis/cell rupture as water enters the cell

• Loss of the lipid bilayer ultimate causes cell death

TURGOR

• In plants, the cell wall resists cytolysis in hypotonic environments

• This turgor pressure allows the plant to resist gravity

Lab: Semipermeable Membranes and Osmosis

• Purpose: To analyze the movement of solutes and water across a selectively permeable membrane

• Method: Tracking movement of solutes and water achieved by use of organic indicators and qualitative description of turgor (rigidity of fluid filled container)

Dialysis

• Loss of kidney membrane permeability due to disease or damage requires dialysis

• Wastes are removed from body by passing blood through an artificial cell membrane

Protocol #1

• Fill beaker 2/3rds full with tap water• Add Lugol’s solution until mixture is amber• Test water with Tes-Tape to determine if glucose

is present in the bath

Protocol #2

• Open wet dialysis tube using fingers and glass rod. Tie one end off with string

• Using seral pipettes fill tube with starch and glucose solutions

• Tie off open end. Do NOT leave space for air• Trim the strings and excess tubing

Protocol #3

• Immerse “cell” in iodine-water bath• Allow to sit for 20 minutes while doing

Protocol #4• After 20 minutes, qualitatively assess color

of bath, cell and turgidity of cell• Retest water with Tes-Tape to check for

presence of Glucose

Protocol #4

• Observe Elodea cells in fresh water (pre-made slide) and sketch

• Make a 2nd slide using one Elodea leaf and a drop of 6% NaCl solution

• Sketch the 2nd slide, noting any changes between the fresh water and salt water

Did they or didn’t they…?

History of Cryogeny

Tonic Preserve: A Recipe

• At moment of death, sever head • Place head in hypertonic glycerol bath• Immerse glycerol-infused head into liquid

nitrogen bath.• Keep until the year ????• To thaw, remove head from liquid nitrogen• Place head in hypotonic bath until dynamic

equilibrium is reached• Enjoy