Pre lab 6: Diffusion & Osmosis

The plasma membrane is _______

selectively permeable

Large molecules, polar molecules, and ions ______ cross the plasma membrane

cannot

T/F: small nonpolar molecules can cross the plasma membrane

true

oxygen, carbon dioxide, and water can cross the plasmsa membrane by ________

simple diffusion

the random movement of sustances down a concentration gradient (from a region of higher concentration to a region of lower concentration)

Diffusion

Glucose can cross the plasma membrane by ________

facilitated diffusion

diffusion that uses transport proteins within the membrane, a passive process that requires no expenditure of energy

Facilitated Diffusion

the movement of water acros a selectively permeable membrane

Osmosis

T/F: Water would move from a hypotonic solution towards the hypertonic solution until the concentrations on either side of the membrane are equal

True

low solute concentration

hypotonic

high solute concentration

hypertonic

solute concentration is equal

isotonic

The diffusion of molecules into and out of cells is affected by a variety of factors:

• concentration gradient

• temperature

• size of the diffusing molecules

• surface area to volume ratio of the cell

a difference in solute cocncetration between the contents of a cell and a surrounding fluid

Concentration Gradient

The rate of diffusion of molecules into and out of a cell ______ with steepness of the gradient, ______ in temperature, and ______ in surface area to volume ratio.

increases

The rate of diffusion of molecuels into and out of a cell ________ with an increase in the size of teh diffusing molecules

decreases

What is being examined in this lab?

• how a concentration gradient affects the diffuion of glucose from a sweet potato (Ipomoea batatas) core that is placed in distilled water

• how a cocnetration gradient affects the diffusion of glucose from a potato (Solanum tubersum) core that’s placed in distilled water

Glucose molecules move across the plasma membrane via _________

transport proteins

What indicator will be used to determine the amount of glucose diffusing from the cores into the distilled water?

a compound o-Dianisidine and peroxidase enzyme, the indicator turns yellow-orange in the presence of glucose

How will the color in the samples be measured?

the color in the samples will be measured using a spectrophotometer set to a wavelength of 450 nm

In Exercise’s 1 study, what time and temperature showed the greatest loss of glucose?

soaking in water for 70 minutes at a temperature of 50 degrees Celsius

The study also revealed that glucose loss was ______ after 70 minutes, but that the rate of glucose loss decreased significantly over time.

continous

What is being studied in Exercise 1?

the pattern of glucose diffusion from sweet potato and potato cores plaed in 50 degree C distilled water for 3 hours and the distilled water is sampled every 20 minutes