Biology Lab

Front 1

Concentration Gradient

Back 1

Diffusing molecules always move outward from an area of high concentration into areas of lower concentration. The difference in concentration levels between two locations (for example, inside the cell compared to outside the cell) is known as the concentration gradient. When molecules move from an area of high concentration to an area of lower concentration, we say they are moving with the concentration gradient.

Front 2

Solutions used by the cells have 2 main components: dissolved molecules and water.

Back 2

Dissolved molecules (called solutes) and water (the solvent). The cell membrane, which controls the movement of materials in and out of the cell, can't control the movement of all molecules.

Front 3

What are some examples of molecules that move passively through the cell membrane following the concentration gradient?

Back 3

Carbon dioxide, oxygen, and water

Front 4

Diffusion

Back 4

A type of transport method in cells across the cell membrane which occurs whenever dissolved particles move from an area of high concentration (more of them) to nearby areas where they are less concentrated.

Front 5

Osmosis

Back 5

A process similar to diffusion occurs with water molecules in the environment. water molecules disperse through a selectively permeable membrane from an area of high concentration to an area of low concentration.

Front 6

Selectively permeable membrane

Back 6

Cells are surrounded by a membrane that allows some substances to pass through, but not others.

Front 7

Describe the activity of the carmine particles in the water droplet

Back 7

Water droplets are randomly dancing and vibrating with carmine particles. The carmine particles are bouncing off of the water molecules.

Front 8

Since carmine particles are not alive, what is causing the carmine particles to move?

Back 8

Molecules of liquids (and gases) are always in motion. Water molecules everywhere are constantly moving and bumping into each other. As they move, they also collide with anything floating in the water, such as the carmine particles.

Front 9

If the carmine slide was warmed up a little bit, the rate of molecular motion would be fater. Why?

Back 9

Molecular motion in increased by heat.

Front 10

Bumper car model of diffusion is a good model of what happens when particles diffuse in the environment.

Back 10

In a bumper car ride, cars are moving quickly and often collide. The force of the collision sends the cars shooting outward into an empty area of the rink. The more an area is crowded with bumper cars, the more collisions occur. The cars are gradually dispersed from the crowded center of the rink (area of high concentration) to the emptier areas ( areas of lower concentration)

Front 11

We can demonstrate the process of diffusion and osmosis in an experiment using dialysis tubing. What does this represent?

Back 11

Dialysis tubing is an artificial membrane with many small pores. This represents a selectively permeable membrane.

Front 12

We tested a solution with 3 solutes. What were they?

Back 12

Sugar, salt, and starch

Front 13

What percent of the solution inside the dialysis tubing is solute and what percent is solvent?

Back 13

Solute makes up 15% of the solution (5% sugar, 5% salt, 5% starch). Solvent makes up 85% (water)

Front 14

If my dialysis tubing bag gains weight during the experiment, I'll know that water entered the bag.

Back 14

If my dialysis tubing loses weight during the experiment, I'll know that water exited the bag.

Front 15

Iodine Test

Back 15

Tests for the presence of starch. When added to a solution, iodine will tun black if starch is present. If no starch is present, iodine will remain redish-brown in color.

Front 16

Silver Nitrate Test

Back 16

Tests for the presence of chloride ions. When added to a solution that contains chloride ions, silver nitrate will change color from clear to cloudy white. Remember: salt is composed of sodium ions and chloride ions.

Front 17

Benedict's Test

Back 17

Test for simple sugars. When added to a solution that contains simple sugars, such as glucose, Benedict's solution will change color from turquoise blue to one of the following colors: green, yellow, orange, or red. Green indicates the smallest amount of simple sugar and red indicates the highest.

Front 18

It is important to remember that the starch, salt, and sugar are not changing in any way.

Back 18

It's the indicator chemicals that are changing color

Front 19

List the molecules that were able to diffuse out of the dialysis bag.

Back 19

Salt and sugar

Front 20

If molecules are expected to move from high concentration to low concentration why didn't all of the molecules leave the dialysis tubing bag?

Back 20

Starch molecule did not diffuse because they were too big to pass through the membrane (pores)

Front 21

Dialysis

Back 21

The ability to separate molecules from each other using a selectively permeable membrane.

Front 22

Elodea Cells in culture water

Back 22

Cells are in equilibrium. 98 or 99% water inside cell and 100% water outside of cell

Front 23

Elodea Cells in 20% saline solution

Back 23

Cells are not in equilibrium. 98% or 99% water inside cell and only 80% outside cell. Chloroplasts are pulled away from cell wall and in the center of the cell. Osmosis occured and the cell dehydrated.

Front 24

What cellular organelle present in leaf cells, but not in blood cells, prevented the elodea cells from shriveling or exploding during your experiment?

Back 24

Cell wall-- kept entire cell from shrinking

Front 25

A student performed the elodea cell experiment using human blood cells.

Back 25

When the student placed the blood cells in salt water, they shriveled up and died. When the student placed other blood cells in distilled water, they filled up, exploded, and died.