Bio Lab 4 Quiz

Front 1

What is the external environment of a cell?

Back 1

A water solution that contains food molecules, waste products, gases, salts, and other substances that surrounds the cell.

Front 2

What is the purpose of a plasma membrane?

Back 2

To monitor/control what goes in and out of the cell.

Front 3

What does it mean to be selectively permeable?

Back 3

It means the cell's plasma membrane gets to decide which molecules enter and exit the cell via passive or active transport.

Front 4

Define passive transport.

Back 4

Passive transport is when no energy is required to pass through a plasma membrane/cell wall.

Front 5

What are two examples of passive transport?

Back 5

Diffusion and osmosis.

Front 6

Define diffusion.

Back 6

Diffusion is the net movement of molecules from an area of greater concentration to an area of lesser concentration.

Front 7

What kind of energy causes molecules in a gas, liquid, or solid to move?

Back 7

Kinetic energy.

Front 8

Define kinetic energy.

Back 8

Energy that a body possesses by virtue of being in motion.

Front 9

Describe the process of diffusion.

Back 9

Molecules are always moving, but not in a specific direction, they move wherever their collisions propel them to. When there are a lot of molecules tightly packed together, they run into each other over and over until they are more spread out, to the point where they reach equilibrium.

Front 10

Define equilibrium (in reference to cell diffusion).

Back 10

When molecules are uniformly distributed and the chances of collision are equal throughout an area. Does NOT mean they stop moving.

Front 11

Define concentration gradient.

Back 11

The measurement of how the concentration of an area shifts.

Front 12

Define osmosis.

Back 12

The net movement of solvent through a selectively permeable membrane, going from high concentration of water to low concentration of water, or from low concentration of solutes to high concentration of solutes.

Front 13

Define solution.

Back 13

Solution is the mixture of water and other molecules. The solution is defined by the solute dissolved into it (water + sugar=sugar solution).

Front 14

Define solvent.

Back 14

Water is the ultimate solvent. A solvent is something that acts to dissolve something else.

Front 15

Define solute.

Back 15

The substance that dissolved into the water.

Front 16

What did we compare in lab #1?

Back 16

We compared the rate of osmosis at three temperatures (hot, room, and cold).

Front 17

What were the "pseudo-cells" made of?

Back 17

Dialysis tube filled with sucrose.

Front 18

What was the percentage of water to sucrose in the sucrose solution?

Back 18

40% sucrose; 60% water

Front 19

How many ml of sucrose were used?

Back 19

9 ml of sucrose

Front 20

How long was the first experiment supposed to be in the water?

Back 20

30-40 minutes.

Front 21

What was the independent variable in the first experiment (measuring the rate of osmosis in different temperatures)?

Back 21

Water temperature

Front 22

What was the dependent variable in the first experiment (measuring the rate of osmosis in different temperatures)?

Back 22

The weight of the bag (mass).

Front 23

What were the standardized variables?

Back 23

The 40% sucrose solution and measuring 9 ml of it.

Front 24

What were the results of the first experiment (measuring the rate of osmosis at different temperatures)?

Back 24

The colder the water, the less mass is accrued. The warmer the water, the more mass is accrued.

Front 25

What is the formula for calculating the percentage of mass change?

Back 25

after weight - before weight / before weight x 100

=% change

Front 26

In the first experiment (measuring the rate of osmosis at different temperatures), what temperature was the rate of osmosis highest?

Back 26

39 degrees Celsius (the hottest temperature tested)

Front 27

What can you conclude about the affect of temperature on the rate of osmosis (in terms of molecular energy)?

Back 27

Molecular energy is increased in warmer temperatures, therefore the rate of osmosis is increased in warmer temperatures.

Front 28

Name at least two possible sources of error in the first experiment (measuring the rate of osmosis at different temperatures)?

Back 28

The timing wasn't specific enough (30-40 minutes)

Not a long enough time period to see if sucrose would have broken down and whether that would have changed anything.

Front 29

What was the second experiment objective?

Back 29

To measure the effects of concentration gradient on the rate of osmosis.

Front 30

Describe the experiment we came up with.

Back 30

Filled three pseudo cells with 9 ml of solution: 1 had 40% sucrose, 60% water; the second had 20% sucrose, 80% water; the third had 10% sucrose, 90% water. We colored each one differently and weighed them each. We placed them all in hot water for 20 minutes then weighed them again after drying them off.

Front 31

What is the formula for calculating the new sucrose percentage in a given solution when you start adding water to it?

Back 31

Assuming you start with the 40% sucrose solution and use 9 ml (as we did):

.40 x "new # of ml of sucrose used" / 9

Front 32

What is the independent variable of the second experiment (measuring the affect of concentration gradient on the rate of osmosis)?

Back 32

The sucrose concentration.

Front 33

What is the dependent variable of the second experiment (measuring the affect of concentration gradient on the rate of osmosis)?

Back 33

The weight/mass of the pseudo cell.

Front 34

What are the standardized variables in the second experiment (measuring the affect of concentration gradient on the rate of osmosis)?

Back 34

Water temperature, 9 ml of total solute (even if the concentration in each was varying), the "cell membrane".

Front 35

What were the results of the second experiment (measuring the affect of concentration gradient on the rate of osmosis)?

Back 35

The weight/mass of the pseudo cells increased with the higher concentration gradient, almost exponentially.

Front 36

In the second experiment, at which concentration was osmosis the highest?

Back 36

40%, our highest concentration.

Front 37

In what direction are water molecules capable of moving (consider molecular movement rather than net movement for this question)?

Back 37

Any direction; wherever they are propelled to once they collide.

Front 38

In a perfectly tied and unbroken pseudo cell, should we see evidence of sugar molecules passing through the "membrane"?

Back 38

No, sugar molecules are too big to pass through with differential permeability. We would have had to do a much longer experiment to see if the sugar molecules broke down to a size they could pass through.

Front 39

Was equilibrium reached in any of the demonstrations with the dialysis tubing? How do you know?

Back 39

No, there was no evidence of the molecules being dispersed equally throughout the container. Would have had to wait a lot longer to see what would happen after the sucrose broke down.

Front 40

Define hypotonic

Back 40

a solution with a comparatively lower concentration of solutes compared to another

Front 41

Define hypertonic

Back 41

a solution with a comparatively higher concentration of solutes compared to another

Front 42

Define isotonic

Back 42

a solution that is perfectly balanced/equal when compared to another

Front 43

What was the objective of the third experiment (osmosis in plant cells)?

Back 43

To see the affect of hypertonic solutions on plant cells.

Front 44

What was the results of the third experiment (osmosis in plant cells)?

Back 44

The cytoplasm shrunk and the chloroplasts moved away from the cell wall. When the external solution is hypertonic the chloroplasts fill the space occupied by the vacuole as the vacuole loses water to the external solution.

Front 45

What is the control in the third experiment (osmosis in plant cells)?

Back 45

The leaf; using forceps as opposed to fingers; dipping in fresh water first

Front 46

What is the independent variable in the third experiment (osmosis in plant cells)?

Back 46

The saline solution concentration

Front 47

What is the dependent variable?

Back 47

size and shape of cells

Front 48

Explain why you were asked to place the Elodea leaf in fresh water in the third experiment?

Back 48

To be sure they were controlled

Front 49

Explain the objective of the fourth experiment (osmosis is red blood cells).

Back 49

To observe how the outside environment affects osmosis in red blood cells.

Front 50

What were the three concentration gradients of saline solution used in the fourth experiment (osmosis in red blood cells)?

Back 50

.85%, .02%, 5.0%

Front 51

Which saline solution concentration is isotonic with red blood cells?

Back 51

.85%

Front 52

Which saline solution used in the fourth experiment is hypertonic with red blood cells?

Back 52

5.0%

Front 53

Which saline solution used in the fourth experiment is hypotonic with red blood cells?

Back 53

.02%

Front 54

What was the control in the fourth experiment (osmosis in red blood cells)?

Back 54

The .85% solution because it is isotonic with the cells.

Front 55

What was the independent variable in the fourth experiment (osmosis in red blood cells)?

Back 55

The saline solution concentrations.

Front 56

Describe the dependent variable in the fourth experiment (osmosis in red blood cells).

Back 56

The red blood cells reaction to the solutions.

Front 57

What happened to the red blood cells in 0.02% saline solution? Why?

Back 57

The cells ruptured because too much water was entering into them through osmosis.

Front 58

What happened to the red blood cells in 5.0% saline solution? Why?

Back 58

The cells shrunk and began to shrivel up because too much water was exiting the cell through reverse osmosis.

Front 59

What happens to lettuce leaves in a salad once the dressing is added?

Back 59

The leaves get soggy.

Front 60

Is salad dressing hypertonic, hypotonic, or isotonic to the lettuce in a salad?

Back 60

Hypertonic.

Front 61

Based on the experiments done, what is the FASTEST way to crisp-up wilted lettuce?

Back 61

Run it under some room temperature water.

Front 62

Explain why an intravenous feeding at the hospital should always be isotonic.

Back 62

So the patient's cells stay healthy and don't rupture or shrivel up.

Front 63

If you drank 3.56% salt water from the ocean, what would happen to your .9% solute-surrounded cells?

Back 63

Drinking too much ocean water will kill you because your cells will shrivel up and die from the hypertonicity.