Study Guide Chapter 3.3-3.4

Chapter 3.3 Key Concept: The cell membrane is a barrier that separates a cell
from the external environment

Vocabulary words for this section that you need to know:

cell membrane
selective permeability
phospholipid
receptor
Fluid Mosaic Model

Much of this section is a review from Chapter 2 when we studied lipids as a carbon molecule. The first part of the section should be review for you.

Cell membrane has two major functions: 1) forms a boundary between the inside
and outside of the cell; and 2) controls passage of materials in and out of the
cell

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The cell membrane is made of a phospholipid bilayer. Label its three parts: 1) charged phosphate group or head, 2) glycerol, and 3) the two fatty acid chains or tails. Mark the end that is polar (likes water) and the end that is nonpolar (doesn't like water). This is all review from Chapter 2.

There are other molecules embedded in the membrane. The Fluid Mosaic Model
describes the arrangement of these molecules and the fluidity of the membrane
(meaning that these molecules move around in the membrane - they are not
stationary).

Fluid Mosaic Model - abt 2 1/2 mins

3

List the function of each of the main three molecules that are found in the cell membrane.

1

Some molecules can cross the membrane while others cannot. What term describes this property: __(type the name of the term on the figure below)

Receptors detect a signal from a molecule and perform an action in response.
There are two types of receptors: 1) intracellular and 2) membrane.

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Figure A above is the Intracellular Receptor that is located inside the cell and it is able to bind to a molecule to cross the membrane Figure B above is the Membrane Receptor that is located in the membrane and the molecule binds to it, causing a change of shape that transmits the molecule across the membrane

Chapter Section 3.4 Key Concept: Materials move across membranes because of a
concentration gradient (i.e., a difference in concentrations)

Vocabulary words that you need to be familiar with are:

passive transport
facilitated diffusion
diffusion
osmosis
concentration gradient
hypotonic
hypertonic
isotonic
plasmolysis
tonicity

1

A concentration gradient means there is a difference in the concentration of a substance in one location compared to another location.

1

Describe what is meant by a molecule moving down a concentration gradient.

Diffusion (A) and Osmosis (B) are both forms of Passive Transport - this means
that no energy is required to cause the movement. They both have movement from a
higher concentration to a lower concentration. The difference is that diffusion
is the movement of substances, and osmosis is the movement of water.

1

The higher the concentration of dissolved particles in a solution, means that the concentration of water molecules in that solution is _______________.

Facilitated Diffusion uses a transport protein to move molecules from a higher
concentration to a lower concentration across a cell membrane. It doesn't
require energy.

1

Facilitated diffusion differs from simple diffusion because it requires a transport protein to move it across the membrane.

1

In facilitated diffusion, do molecules move down a concentration gradient or against a concentration gradient?

Let's practice with some problems to solidify your understanding of diffusion and osmosis.

Remember: With diffusion, solutes move from an area of high concentration to an area of lower concentration.

Remember: With osmosis wherever more solutes are, water follows! Or, water also goes from an area of high amount of water to an area of lower amount of water.

You will put your answers in the multiple choice questions that follow. Your choices will be "move to inside", "move to outside", "no movement", and "equal movement",

DIFFUSION	OSMOSIS
Does the SOLUTE move inside or outside the cell?	Does WATER move inside or outside the cell?	Intracellular fluid (inside the cell)	Extracellular fluid (outside of the cell)
1	2	5% salt	10% salt
3	4	10% salt	10% salt
5	6	3% glucose	1% glucose
7	8	2% protein	1% protein
9	10	9% salt	9% salt
11	12	13% water	25% water
13	14	59% water	45% water
15	16	90% water	92% water
17	18	74% glucose	87% glucose

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 5% salt inside the cell 10% salt outside the cell. The answer to #1 and #2 in the Table is (remember column 1 will be diffusion of solutes; and column 2 will be osmosis of water):

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 10% salt inside 10% salt outside. The answer to #3 and #4 in the Table is:

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 3% glucose inside 1% glucose outside. The answer to #5 and #6 in the Table is:

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 2% protein inside 1% protein outside. The answer to #7 and #8 in the Table is:

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 9% salt inside cell 9% salt outside cell. The answer to #9 and #10 in the Table is:

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 13% water inside cell 25% water outside cell. The answer to #11 and #12 in the Table is:

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 59% water inside cell 45% water outside cell. The answer to #13 and #14 in the Table is:

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 90% water inside cell 92% water outside cell. The answer to #15 and #16 in the Table is:

1

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 74% glucose inside cell 87% glucose outside cell. The answer to #17 and #18 in the Table is:

Try some scenarios of conditions that affect the rate of diffusion. Each diagram
shows substances at different concentrations separated by a cell membrane. The
green squares represent glucose.

1

Refer to figure above

Another scenario of conditions that affect the rate of diffusion. Each diagram
shows substances at different concentrations separated by a cell membrane. The
green squares represent glucose.

1

Use Figure above

Last scenario of conditions that affect the rate of diffusion. Each diagram
shows substances at different concentrations separated by a cell membrane. The
green squares represent glucose.

1

Use Figure above

The experiments below show visking osmometers, which are used to measure
osmosis. Visking tubes are partially permeable. The experiments have different
solutions in each. They were left for a day. The water level at the start of the
day is shown. Go t

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Experiment A. There was no change in the level of water in the visking tube or beaker after a 24 hour period, because the glucose concentrations inside and outside the visking tubing were the same.

1

Experiment B. Water moved out of the visking tube into the beaker, so the water level in the beaker rose higher and the water level in the glass tubing went down.

One last concept to learn about diffusion and osmosis. There are three types of
solutions cells can be placed in 1) isotonic, 2) hypertonic, and 3) hypotonic
and cells react differently in each.

Watch the video on Tonicity to see how the solutions affect cells.

1

You become so dehydrated on a hot summer day that you go into shock and are taken to an emergency room at a hospital. They start you on an IV of saline solution to get you rehydrated. Why can't they give you an IV with just water in it?

The cell membrane is made of a phospholipid bilayer. Label its three parts: 1) charged phosphate group or head, 2) glycerol, and 3) the two fatty acid chains or tails. Mark the end that is polar (likes water) and the end that is nonpolar (doesn't like water). This is all review from Chapter 2.

List the function of each of the main three molecules that are found in the cell membrane.

Some molecules can cross the membrane while others cannot. What term describes this property: ________________ __________________(type the name of the term on the figure below)

A concentration gradient means there is a difference in the concentration of a substance in one location compared to another location.

Describe what is meant by a molecule moving down a concentration gradient.

The higher the concentration of dissolved particles in a solution, means that the concentration of water molecules in that solution is _______________.

Facilitated diffusion differs from simple diffusion because it requires a transport protein to move it across the membrane.

In facilitated diffusion, do molecules move down a concentration gradient or against a concentration gradient?

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​10% salt inside​ 10% salt outside. The answer to #3 and #4 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​3% glucose inside​ 1% glucose outside. The answer to #5 and #6 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​2% protein inside​ 1% protein outside. The answer to #7 and #8 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​9% salt inside cell​ 9% salt outside cell. The answer to #9 and #10 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​13% water inside cell​ 25% water outside cell. The answer to #11 and #12 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​59% water inside cell ​45% water outside cell. The answer to #13 and #14 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​90% water inside cell​ 92% water outside cell. The answer to #15 and #16 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. ​74% glucose inside cell​ 87% glucose outside cell. The answer to #17 and #18 in the Table is:

Refer to figure above

Use Figure above

Use Figure above

Experiment A. There was no change in the level of water in the visking tube or beaker after a 24 hour period, because the glucose concentrations inside and outside the visking tubing were the same.

Experiment B. Water moved out of the visking tube into the beaker, so the water level in the beaker rose higher and the water level in the glass tubing went down.

You become so dehydrated on a hot summer day that you go into shock and are taken to an emergency room at a hospital. They start you on an IV of saline solution to get you rehydrated. Why can't they give you an IV with just water in it?

Some molecules can cross the membrane while others cannot. What term describes this property: __(type the name of the term on the figure below)

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 10% salt inside 10% salt outside. The answer to #3 and #4 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 3% glucose inside 1% glucose outside. The answer to #5 and #6 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 2% protein inside 1% protein outside. The answer to #7 and #8 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 9% salt inside cell 9% salt outside cell. The answer to #9 and #10 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 13% water inside cell 25% water outside cell. The answer to #11 and #12 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 59% water inside cell 45% water outside cell. The answer to #13 and #14 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 90% water inside cell 92% water outside cell. The answer to #15 and #16 in the Table is:

Use the Table above with the cell conditions in Columns 3 and 4 to determine movement of solutes and water for each condition. 74% glucose inside cell 87% glucose outside cell. The answer to #17 and #18 in the Table is: