(Section 6.2 in book)
The cell membrane is the edge of life; it is the boundary that separates the living cell from its nonliving surroundings. A remarkable film only about 8 micrometers thick, the membrane surrounds the cell and controls the traffic of substances into and out of the cell. As we have seen repeatedly in our study so far, cellular structure fits function. Therefore, to understand how membranes work we will begin by examining their structures and characteristics.
SELECTIVE PERMEABILITY
The MOST IMPORTANT characteristic of the cell membrane is its ability to maintain homeostasis within the cell by regulating the passage of materials in and out of the cell. In other words, it is very "picky" about what gets in or out. This important quality is called selective permeability.
1.
Cell membrane: ___________________________________________________________________
_______________________________________________________________________________
2.
Define selective permeability:_______________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3.
Label the parts of the phospholipid with these four terms: head, tail, hydrophobic, & hydrophilic
4.
Rank the molecules according to their speed to cross the cell membrane from fastest to slowest….
Explain why you ranked them in that order. a. b. c. d. _____________________________________
______________________________________________________________________________________
______________________________________________________________________________
5.
Name the scientists who discovered the structure of the cell membrane.______________________
6.
What did they call their model? _____________________________________________________
7.
What characteristic does mosaic refer to?______________________________________________
8.
What characteristic does fluid refer to? _______________________________________________

a) Phospholipids: are arranged in a double layer and are the most numerous part of the membrane, they have round heads and 2 squiggly tails b) Protein: each one looks like a potato c) Cholesterol: are the dark colored chains in between the phospholipids d) Carbohydrates: chains on the outside of the membrane that look like antennae e) Cytoskeleton: thin structures inside the cell
THE CONNECTION BETWEEN STRUCTURE AND FUNCTION
The main job of the cell membrane is to maintain cellular _____________________________.
The main characteristic that allows it to do this is its ________________________________________.
Other parts / characteristics of the membrane help it do its job >
1.
The phospholipids are a great barrier because they are _______________________________ which means that they will NOT mix with water, while their ‘heads’ are ________________, which means they will mix with water. This helps the cell membrane keep the water on the inside of the cell separate from the water on the outside of the cell.
2.
It is ________________________ so it won’t rupture easily. If it did break easily, the cell membrane would not be the great boundary that it is! In addition, the membrane contains
__________________________ which adds strength and stability.
3.
Most importantly, the membrane contains gates and channels (which are the
___________________________________) which help regulate what goes in and out.

TYPES OF PROTEINS IN THE MEMBRANE
Although the basic structure of a cell membrane is a lipid bilayer, most of the functions of the membrane are carried out by proteins. Proteins can function as enzymes. So far, we have seen that enzymes in the mitochondrial membrane are responsible for allowing cellular respiration to occur.
Likewise, proteins in the membranes of chloroplasts allow photosynthesis to happen. When our cells need glucose, the cell membrane proteins are signaled to start breaking down a larger molecule (called glycogen) into smaller glucose molecules. Some proteins allow one cell to recognize another. For example, when our white blood cells are roaming around our body looking for invaders, they check every cell. Cell membrane proteins allow them to determine whether another cell is a cell of our body or a germ. These proteins are called marker proteins. Other proteins receive signals from hormones. These proteins are called receptor proteins. An example of this is when insulin is released from the pancreas, it travels to all the cells of the body and joins with membrane protein receptors. The receptors then open the gate that allows glucose to get into the cell. Lastly, many proteins work to transport substances either into or out of cells. Our nerve cells conduct signals by transporting sodium and potassium into and out of the cell. This happens through transport proteins.
For each type of cell membrane protein, give an example of how it works in our body.
1.
Enzyme: _________________________________________________________________
________________________________________________________________________
2.
Cell recognition: ___________________________________________________________
________________________________________________________________________
3.
Transport: _______________________________________________________________
________________________________________________________________________
4.
Signaling / Receptor: ________________________________________________________
________________________________________________________________________

Our blood type is directly determined by the proteins present in the membranes of our red blood cells. We’re going to explore the concept of blood typing by going to the following site, reading the content and answering the questions.
(Once in awhile this web address does not work. If it doesn’t work, please google blood typing and nobel prize to get to the website.)
Please use the information in this chart to help you with the website:
BLOOD TYPE ANTIGENS ANTIBODIES PICTURE OF RBC & PLASMA
A
B antibodies
B
AB
A antibodies
None
O
A & B antibodies

1.
Who discovered blood groups? When? _________________________________________________
2.
If incompatible blood is mixed, agglutination occurs. What is agglutination? Why is this bad?
_____________________________________________________________________________
_____________________________________________________________________________
3.
With the discovery of blood groups, what was made possible? _______________________________
4.
What are the four parts of blood and what is the job of each? ______________________________
_____________________________________________________________________________
5.
The differences in human blood are due to the presence or absence of certain protein molecules called
_________________________________ and ________________________________________.
6.
Where are antigens located? _______________________________________________________
7.
Where are antibodies located? _____________________________________________________
8.
If you have the Rh factor protein on your red blood cells, you are called ____________. If this protein is absent, you are referred to as ___________.
9.
An Rh- person can develop Rh ___________________________ if they get blood from an Rh+ person.
10.
But an Rh____ person can receive blood from an Rh____ person without any problems.
11.
Play the agglutination animation. (you will need to know this information to help you play the game)
12.
How can you tell what blood type someone has? __________________________________________
_____________________________________________________________________________
13.
What results from agglutination? ____________________________________________________
_____________________________________________________________________________
14.
What blood type is the universal donor (meaning it can be given to all blood types without causing a reaction)?
____________
15.
What blood type is the universal recipient (meaning it can receive all blood types without having a reaction)?
____________

PLAY THE BLOOD TYPING GAME AT THE BOTTOM. Fill in this chart as you play the game.
*Hint: When you find the blood type of the patient, notice you are putting their blood into 3 testtubes.
The testtubes are filled with ANTIBODIES, not bloodtypes. Use the chart from the beginning of this activity to help you.
Patient description Blood type Which blood type can the patient receive (it may be more than one!)
17. How many mistakes did you make during the simulation? (It will tell you at the end of the game, if it does not tell you, you made too many mistakes, and you should re-read the information & play it again)
_____________________________________________________________

THE CELL MEMBRANE PROTEINS CAN RECEIVE SIGNALS FROM HORMONES
Glucagon is a hormone that works with insulin to maintain sugar balance in the blood. When glucose is needed in between meals, the hormone glucagon is used to release stored glucose. Glucagon is produced in the pancreas
(just like insulin). It travels through the bloodstream and binds to receptor proteins located in the cell membranes of liver and muscle cells. When glucagon molecules bind to receptor proteins, the receptor proteins change shape and cause enzyme proteins in the membrane to produce a molecule called cyclic
AMP (which is related to ATP and ADP). Cyclic
AMP relays the first message (from the hormone) into the cell. The cyclic AMP molecules activate a series of enzymes that break down a larger molecule (called glycogen) into glucose for the cell to use.
On the other hand, after we eat, insulin is released from the pancreas. The insulin hormone attaches to cell membrane receptor proteins on each cell in our body. This causes the cell to open transport protein tunnels so glucose can enter the cell. Once inside the cell, glucose is used for cellular respiration.
Remember? 

Based on your reading and class work, answer the following questions to demonstrate your understanding of why and how the membrane is important in the body.
1.
____ Each type of RED blood cell has a different ____ in its cell membrane. a.
antigen b. antibody
2.
____ A person with O blood has a.
O antibodies b. A antibodies c. B antibodies d. A & B antibodies
3.
____ If a person with type A blood receives blood from an AB person their blood will a.
be okay b. will agglutinate (clump)
4.
____ The hormone that is released in-between meals and breaks down glycogen to release glucose is called a.
glucagon b. insulin
5.
____ Both glucagon and insulin are hormones that bind to _______ proteins in the cell membrane. a.
transport b. enzyme c. marker d. receptor
6.
____ Insulin is to glucose like a.
key is to a person b.
door is to a window c.
window is to a fly
Summarize how cell membrane proteins are essential to each of the following processes.
7.
blood type and transfusions
________________________________________________________________________
________________________________________________________________________
_______________________________________________________________________
8.
hormones working to maintain sugar balance
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________

Now that you have a picture of the plasma membrane and its structure, think about its role as a gatekeeper of the cell. Keep in mind that it is selectively permeable. In an effort to maintain homeostasis, the cell membrane must determine what enters and leaves the cell. Some substances that are either entering or leaving the cell are oxygen, carbon dioxide, water, ions, glucose, amino acids, and protein. Each of these molecules moves into or out of cells in different ways.
MOLECULAR MOTION
All molecules are constantly in motion… bumping into one another. This random motion of molecules is called Brownian motion. As molecules randomly bump into the cell membrane, there is a chance that the molecule will go through the cell membrane.
1.
Brownian Motion: ___________________________________________________________
WHERE SUBSTANCES CROSS THE MEMBRANE
Substances cross the membrane in different ways based on their SIZE and CHARGE. Smaller molecules such as water (8 um), oxygen (5 um) and carbon dioxide (9 um) can fit through these small pores and therefore pass directly through the lipid bilayer. Charged atoms or molecules (ions such as Na+, K+, Cl-,
Mg+) pass through the proteins in the membrane because they are charged. Other larger molecules such as glucose (20 um) and amino acids (25 um) must travel across the membrane through a protein tunnel because they are too big to fit through the bilayer.
2.
What two characteristics determine where a molecule will pass through the membrane?
________________________________________________________________________
3.
What type of molecules pass through the bilayer? Give examples.
________________________________________________________________________
4.
What type of molecules pass through the proteins? Give examples.
________________________________________________________________________

5.
If the size of the protein tunnels are 25 um, then would glycogen (60 um) and protein (150 um) be able to fit through the cell membrane? YES / NO
Well, if they can’t fit THROUGH the membrane, then how do they enter and leave the cell? The answer to that question is the cell membrane will actually open up and let them in or out!
HOW SUBSTANCES CROSS THE MEMBRANE: TWO GENERAL TYPES OF TRANSPORT
There are two types of transport across the membrane – passive transport and active transport. Passive transport relies on Brownian motion to automatically cause molecules to spread out without the use of any cellular energy. The three types of passive transport that we will be studying are diffusion, facilitated diffusion and osmosis. Active transport (as its name suggests) is when the cell membrane proteins use energy to actually grab molecules and pump them in or out.
6.
Describe passive transport: ___________________________________________________
________________________________________________________________________
________________________________________________________________________
7.
Describe active transport: ___________________________________________________
________________________________________________________________________
________________________________________________________________________ http://www.biologymad.com/resources/DiffusionRevision.pdf

Substances in and around the cell are evenly distributed among water molecules. All of these particles move randomly, colliding with each other. Random collisions would tend to scatter the molecules of the substance until it was evenly mixed with the water molecules. Diffusion refers to this net movement of particles from an area of higher concentration to an area of lower concentration.
1.
Diffusion: ________________________________________________________________________
________________________________________________________________________________
2.
OBSERVATION: Add a drop of dye to a beaker of water. Keep an eye on its progress while
reading the rest of this section. This demonstrates what you are reading about!
Concentration refers to the amount of substance in a given area. The difference in concentration of a substance across space (or a membrane) is called a concentration gradient. Because ions and molecules diffuse from areas of higher concentration to areas of lower concentration, they are said to move with a gradient. If no other processes interfere, diffusion will continue until there is no concentration gradient (all molecules are evenly spread out). At this point, the solution is said to be in dynamic equilibrium. When the molecules are evenly spread out they continue to move around but there is no overall change in the concentration. Maintaining dynamic equilibrium is one of the characteristics of homeostasis.
3.
Concentration:_____________________________________________________________________
________________________________________________________________________________
4.
Gradient:_________________________________________________________________________
________________________________________________________________________________
5.
Concentration Gradient: ______________________________________________________________ a.
Draw 8 X’s on the left side of the diagram and 4 X’s on the right to illustrate a concentration gradient of molecules. b.
Draw an arrow to indicate the direction the molecules will move across the membrane by diffusion.
6.
Dynamic equilibrium:_________________________________________________________________
________________________________________________________________________________ a.
Draw a diagram showing the molecules of X in dynamic equilibrium.
7.
Reexamine the beaker with the dye. Discuss what happened in the beaker incorporating what you know about diffusion.________________________________________________________________
________________________________________________________________________________

PART A: Use during-reading strategies (such as highlighting) to learn about how diffusion of oxygen and carbon dioxide is seen in red blood cells.
The cell obtains and excretes a variety of atoms and molecules by the process of diffusion across the membrane.
Molecules of oxygen and carbon dioxide are two of these molecules. Let’s examine how they diffuse into and out of red blood cells.
OXYGEN TRANSPORT: When we take a breath, oxygen is MORE concentrated in our lungs and LESS concentrated in our red blood cells (RBCs). Therefore oxygen will diffuse from the lungs into RBCs. Inside the
RBC, the protein hemoglobin soaks up this oxygen. The RBCs take this oxygen to the cells of the body. Since the oxygen is MORE concentrated in the RBC and LESS concentrated in our body cells, the oxygen diffuses out of the
RBC and into the body cell.
In tissues, the presence of carbon dioxide produced by cellular respiration makes the blood more acidic and causes the hemoglobin molecules to change shape, releasing oxygen more easily. So the tissues that are working the hardest (and therefore releasing the most carbon dioxide) are the tissues that will get more oxygen. The effect of carbon dioxide on the rate of oxygen unloading is called the Bohr effect.
CARBON DIOXIDE TRANSPORT: At the same time that the red blood cells are unloading oxygen to tissues, they are also absorbing carbon dioxide. Only 7% of the carbon dioxide that the blood carries is dissolved in plasma
(about 7%). About 23 percent is carried by the hemoglobin molecules inside red blood cells. The remaining 70 percent is carried within the cytoplasm of red blood cells.
How do the red blood cells manage to keep all of this carbon dioxide inside their cytoplasm? Why doesn’t it simply diffuse back into the plasma, where carbon dioxide levels are lower? And then back into the cells where there is also a lower amount of carbon dioxide? An enzyme within the red blood cells, called carbonic anhydrase, combines carbon dioxide molecules with water to form carbonic acid which breaks apart into bicarbonate ions. Ions have a harder time passing through the cell membrane – that’s how the carbon dioxide is kept in the RBC on its journey back to the lungs.
Once the RBC gets back to the lungs, the opposite process occurs and the ions are converted back to carbon dioxide.
Hemoglobin likes oxygen more than carbon dioxide.
Therefore, the hemoglobin releases its bound carbon dioxide and takes up oxygen instead. The red blood cells, with their newly bound oxygen, then start their next journey back to the body’s tissues.
PART B: Answer these questions based on information from the reading.

1.
Which two molecules move across the membrane by diffusion?____________________________
2.
Where do they cross (through lipid bilayer or protein channel)? Why? ______________________
___________________________________________________________________________
3.
Once in the body cells, what process uses this oxygen? _________________________________
4.
What is the protein that carries O
2
and CO
2
in red blood cells?___________________________
5.
When we take a breath, oxygen diffuses from our _______________ to our ________________ and then to our ___________________________.
6.
As carbon dioxide builds up in the body (as a result of cell respiration) it makes the blood more
_______________________. This causes the ________________________ of the hemoglobin molecule to change. This INCREASES / DECREASES the speed at which oxygen is released from hemoglobin.
7.
The condition where hemoglobin will release oxygen quicker as a result of acidic conditions to the tissues that need it the most is called ___________________________________________
8.
As oxygen is released, the RBCs pick up carbon dioxide which is mainly carried in the
9.
_________________________ of the red blood cell but hemoglobin helps.
What enzyme converts carbon dioxide into carbonic acid? _____________________________
10.
The carbonic acid then breaks apart into __________________.
11.
How does this help carbon dioxide stay highly concentrated in RBCs until they get to the lungs?
_________________________________________________________________
12.
Hemoglobin likes _______________________________ better than
____________________ and therefore releases carbon dioxide when it gets back to the lungs.

1.
_____ Which of the following substances moves across the membrane by simple diffusion? a.
starch b. carbon dioxide c. glucose d. ions
2.
_____ Where does oxygen cross the membrane? a.
bilayer b. protein channels c. protein pumps
3.
_____ What is the name of the protein that carries oxygen in red blood cells? a.
fibrinogen b. collagen c. hemoglobin d. enzymes
4.
_____ When you take a breath, where is there a higher concentration of oxygen? a.
in the lungs b. in red blood cells c. in body cells
5.
_____ When carbon dioxide builds up in the blood, it makes the blood more a.
basic b. acidic c. neutral d. has no effect
6.
_____ Which of the following is an effect of change in pH on hemoglobin? a.
changes its shape causing it release oxygen quicker b.
changes its shape causing it to release oxygen slower c.
causes it to become completely denatured
7.
_____ Which of the following is a part of the Bohr effect? a.
lots of oxygen builds up in tissues b.
oxygen is unloaded to tissues that need it quicker c.
carbon dioxide is unloaded to tissues that need it quicker d.
helps cells that undergo a low rate of cell respiration
8.
_____ Where is MOST carbon dioxide carried? a.
in plasma b. by hemoglobin c. in the cytoplasm of red blood cells
9.
_____ If lots of carbon dioxide is in red blood cells, what will it have the tendency to do? a.
change to oxygen b. diffuse out c. kill the red blood cell
10.
_____ What is the name of the enzyme that converts carbon dioxide into carbonic acid? a.
luciferase b. carbonic anhydrase c. carbonic peroxidase
11.
_____ What does carbonic acid break apart into? a.
bicarbonate ions b. sodium ions c. carbon ions
12.
_____ What is the permeability of the cell membrane to ions? a.
they easily diffuse in and out b.
they need to go through the proteins because of their charge c.
they have a difficult time getting across the membrane d.
b and c
13.
_____ If given the choice, which substance would hemoglobin rather bind to? a. oxygen b. carbon dioxide

In a typical cell, a few molecules (primarily oxygen, carbon dioxide and water) diffuse freely through the plasma membrane. But many larger molecules or those with a charge have restricted access. For example, sugars, amino acids and ions do not pass easily through the phospholipid bilayer. The traffic of such substances can only occur by way of transport proteins. In this process, known as facilitated diffusion, transport proteins provide a pathway for certain molecules to pass. (The word facilitate means
"to help.") Specific proteins allow the passive transport of different substances.
1.
COMPARE diffusion and facilitated diffusion using the diagram/information.
List 3 similarities.__________________________________________________________
________________________________________________________________________
_________________________________________________________________________
_____________________
2.
CONTRAST diffusion and facilitated diffusion using the diagram/information.
List 2 differences.__________________________________________________________
________________________________________________________________________
________________________________________________________________________

1.
_____ What is the random motion of molecules called? a) Brownian Motion b) Darwinian Motion c) Magic
2.
_____ Diffusion and facilitated diffusion are types of _________ transport a) active b) passive
3.
_____ When a teaspoon of sugar is dropped into a beaker of water, the sugar ions will a) move from low to high concentration b) form a covalent bond c) start to diffuse d) remain on the bottom of the beaker
4.
The amount of material in a given space refers to _________________________________.
5.
_____ When materials pass into and out of the cell at equal rates, there is no net change in concentration inside the cell. The cell is in a state of a) dynamic equilibrium b) imbalance c) inertia d) concentration
6.
_____ The difference in concentration from one region to another is called a) equilibrium b) gradient c) homeostasis
7.
_____ Molecules of the following will NOT directly diffuse across the lipid bilayer a) amino acids b) carbon dioxide c) water d) oxygen
8.
_____ Facilitated diffusion occurs through a) phospholipid bilayer b) transport protein channels
9.
_____ Which of the following molecules moves into the cell by facilitated diffusion? a) sodium (Na+) b) water c) glucose d) a and c
10.
_____ Both facilitated diffusion and diffusion a) use energy to move substances across the membrane b) happen directly through the phospholipids in the membrane c) move larger molecules and ions across the cell membrane d) involve molecules moving from higher concentration to lower concentration
How many did you get right? _______ / 10
9 - 10 correct: Star student!! Keep up the excellent work!
7-8 correct:
6/less correct:
You are doing a great job!
Quick! Check for a pulse!

The diffusion of water molecules into and out of cells is so common that the process is given its own name, osmosis.
Osmosis is the diffusion of water molecules through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration. This process MUST occur through a selectively permeable membrane! This is one way in which it is different from other types of diffusion.
1.
Define osmosis:_____________________________________________________________________
________________________________________________________________________________
2.
Which molecule crosses the membrane by osmosis?__________________________________________
3.
Does this molecule cross through the proteins or the bilayer?__________________________________
4.
OBSERVATION: Place a few raisins in warm water and watch what happens.
When you are trying to explain how osmosis works, remember that water will always follow another substance, such as salt or sugar, because where there is more substance, there is less water. So remember… Wherever there is a higher concentration of a solute such as sugar or salt, there is a lower concentration of water and vice versa. For example, a strong sugar solution has a high concentration of sugar but a low concentration of water. If the sugar and water solutions are separated with a selectively permeable membrane that has holes big enough to let water through but not sugar, osmosis would occur. The water molecules would diffuse across the membrane toward the concentrated sugar solution (because there would be less water there).
5.
Before osmosis, where is there more water, less sugar? INSIDE / OUTSIDE the bag
6.
Which direction did the water move? Why?_______________________________________________
________________________________________________________________________________
________________________________________________________________________________
7.
Why do you think sugar didn’t move across the membrane? ___________________________________
________________________________________________________________________________
8.
Examine the raisins. Explain what happened.___________________________________________
________________________________________________________________________________
________________________________________________________________________________

Since the body consists of roughly 2/3 water, osmosis is in action throughout the body and can have severe effects on cells! Most cells, whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions. Depending on the concentration of the water surrounding the cell, the cell will either shrink, expand or stay in balance. There are three different types of solutions that a cell can be exposed to: hypotonic solutions, hypertonic solutions, and isotonic solutions.
If more solute is IN the cell (meaning there is less water IN the cell), then water will diffuse INTO the cell because it is moving from high concentration OUTside the cell to lower concentration INside the cell. This causes the water pressure inside a cell, called osmotic pressure, to increase. In plants, osmotic pressure is referred to as turgor pressure. When plants are put in a hypotonic solution, water fills their vacuole and cytoplasm, thus giving shape and support to the plant. When a plant cell is full of water, it is referred to as being turgid. Plant cells have strong cell walls which can resist the turgor pressure caused by osmosis so they won’t burst. Animal cells, however, lack cell walls. If they are put in a hypotonic solution, they will swell and may even burst. An animal cell that has burst scientifically can be referred to as lysed.
If a cell is placed in an isotonic solution, water molecules still move into and out of the cell at random, but there will be no overall change in the concentration of water inside the cell. Therefore, no osmosis occurs. The cell is in dynamic equilibrium with the surrounding liquid. Animal cells in an isotonic solution have their normal shape. Plant cells in an isotonic solution are slightly wilted.
Organisms that live in salty water have the opposite problem. A hypertonic solution is a solution in which the concentration of dissolved substances OUTside a cell is higher than the concentration inside a cell. If a cell is placed in a hypertonic solution, osmosis will cause water to LEAVE the cell. Animal cells placed in a hypertonic solution will shrivel because of decreased pressure in the cells. An animal cell that shrinks is referred to as crenated. If a plant cell is placed in a hypertonic environment, it will lose water, mainly from its central vacuole. The plasma membrane and cytoplasm will shrink away from the cell wall.
This causes the plant to be severely wilted.

Water ______________
Water ______________
Animal Cell Plant Cell

1.
_____ Osmosis requires a permeable membrane to occur. a) true b) false
2.
_____ The concentration of water is lower outside the cell than inside the cell. a) hypertonic solution b) hypotonic solution c) isotonic solution
3.
_____ When a cell is placed in this solution, water will enter the cell by osmosis. a) hypertonic solution b) hypotonic solution c) isotonic solution
4.
_____ The concentration of water is equal on both sides of the cell membrane. a) hypertonic solution b) hypotonic solution c) isotonic solution
5.
_____ The concentration of water is higher outside the cell than inside the cell. a) hypertonic solution b) hypotonic solution c) isotonic solution
6.
_____ When injected into the body, it will not cause cellular damage because no osmosis occurs a) hypertonic solution b) hypotonic solution c) isotonic solution
7.
_____ Putting a plant cell in this type of solution will cause the plant to wilt a) hypertonic solution b) hypotonic solution c) isotonic solution
8.
_____ Which of the following describes a animal cell that has burst? a) crenated b) lysed c) plasmolyzed d) turgid
9.
_____ If a cell is put into a hypertonic solution, what happens? a) shrinks b) swells c) stays the same
10.
_____ Turgor pressure is osmotic pressure in animal cells. a) true b) false
How many did you get right?
9-10 correct:
7-8 correct:
6 or less correct:
_____ / 10 points
You are Superbiohuman!! Congratulations!
Give yourself a HIGH 5! Good job!
Are you awake?? e) flaccid

PROTEIN PUMPS
In active transport, energy is used to transport substances into or out of a cell. The substances that are transported this way include charged particles (ions) or larger substances (glucose and amino acids). These substances move through a transport protein called a protein pump. First, the molecule enters the protein pump. Then ATP is used to change the shape of the protein so that the particle is “pumped” to the other side of the membrane. Usually, molecules transported this way are moved AGAINST the gradient – meaning they move from low concentration to high concentration across the membrane.
1.
What TYPE of molecules does the cell pump across the membrane? Give specific examples.
___________________________________________________________________________________
2.
What type of protein is involved in active transport?___________________________________________
3.
Do molecules move WITH (hi>lo) or AGAINST (lo>hi) the gradient? ________________________________
ENDOCYTOSIS & EXOCYTOSIS
Some cells can take in HUGE molecules, groups of molecules, or even whole cells! They do this NOT by transporting them through the membrane – the membrane completely opens up instead! Endocytosis is a process in which a cell “swallows” huge molecules…bringing them into the cell. The swallowed substance is contained within a vacuole made by a piece of the membrane breaking off. The reverse process of endocytosis is exocytosis. Cells use exocytosis to get rid of wastes. They also use this method to secrete substances produced by the cell, such as proteins (remember the vesicles that break off the Golgi bodies?). Because endocytosis and exocytosis both move material across the membrane, they both require energy and are therefore classified as active transport.
4.
LABEL each diagram (on the right above) as either endocytosis or exocytosis.
5.
What do you think white blood cells “swallow” using endocytosis? __________________________________
6.
What do you think amoeba (unicellular pond organisms) take in by endocytosis?
_______________________
When the proteins and lipids are packaged by the Golgi bodies in a cell… they are put into vesicles. These vesicles travel to the cell membrane. When they get there, what process is seen as they release HUGE protein and lipid molecules?______________________________________________________________

Diffusion Lab:
Using an indicator to determine if starch or iodine will cross a selectively permeable membrane
Observation: Cells need to obtain certain substances and get rid of others.
Question: Will starch or iodine move across a selectively permeable membrane?
Background Knowledge:
1.
Dialysis tubing selectively permeable. Why are we using it to represent the plasma membrane?
2.
Describe passive transport:
3.
Describe diffusion:
4.
What is meant by concentration gradient?
5.
What is the indicator for starch?
6.
What two factors affect the passage of materials across a selectively permeable membrane?
Hypotheses:
Propose a hypothesis for the question asked in the beginning of the lab. The hypothesis should include reference to both the independent and dependent variables. It should state what will happen. Be certain to use "if" and "then".
Materials:
Approximately 4” piece of dialysis tubing
Starch solution
Iodine
Methods:
1.
Obtain dialysis tubing. Wet it. Rub it back and forth between your thumb and forefinger to open the tube. Be
2.
patient! Seal the bottom of the dialysis tube by twisting the bag and tying it tightly.
Fill the dialysis tube with starch solution (starch dissolved in water) OR Iodine solution (this can be made by adding
3.
a couple drops of iodine to water that you put in the tubing). MAKE SURE THE BAG IS FLEXIBLE, NOT
COMPLETELY FILLED. Tie off the other end. Rinse the outside of the bag well . The filled dialysis bag represents a cell.
Note and record the color of the solution inside the dialysis cell.

4.
5.
6.
7.
Fill a small beaker with water…about 100-150 ml.
Add whatever substance that was NOT added to the tubing. (If you used iodine in the tubing, put starch in the beaker!)
Place the bag into the beaker. Observe and record what is occurring.
After the experiment is completed, throw the bag away and clean the beaker.
Draw a picture of the results:
__________________________________________________________________________________________________
Discussion:
1.
Answer the lab question IN DETAIL using your notes and background information.
Clearly explain ALL observations as you define and apply the following terms: passive transport, diffusion, concentration gradient, equilibrium, selective permeability (or selectively permeable), size comparison of starch to iodine.
2.
Examine the hypothesis. Was it correct, incorrect and why?

1.
Prepare a wet mount slide of an Elodea (or celery) leaf
2.
Observe an “normal” cell in tap water
3.
Observe plasmolysis in the cell as salt solution is added to the wet mount.
4.
Observe the reversal of plasmolysis as the salt solution is diluted.
5.
Compare and diagram normal cells in tap water with plasmolyzed cells in salt solution.
Microscope
Tap water coverslip microscope slide distilled water elodea/celery droppers paper towel Salt solution
1.
Prepare a wet mount slide of an elodea/celery leaf using
.
2.
Observe the leaf under both low and high powers. Note the location of the chloroplasts in relation to the cell wall.
3.
Draw a normal cell at 400x in the space provided for you.
4.
Label chloroplast, cell wall and cell membrane.
5.
Prepare a wet mount slide of an elodea leaf using
. Allow the slide to sit for a couple of minutes.
6.
Observe the leaf under both low and high powers. Again, note the location of the chloroplasts in relation to the cell wall.
7.
Draw a plasmolyzed cell at 400x in the space provided for you.
8.
Label chloroplast, cell wall and cell membrane.
9.
Use a clean dropper to add
along the edge of the coverslip. Place a piece of paper towel along the opposite edge of the coverslip. The paper towel will “pull” the distilled water under the cover slip and across the elodea leave (changing the type of solution the cell is in).
10.
Note any changes from the plasmolyzed cell and draw the cell at 400x in the space provided for you.
11.
Label chloroplast, cell wall and cell membrane.
12.
Clean up slide, put microscope away and answer the analysis questions.

Tap Water/ 400X
Distilled Water/400x
Salt/ 400X
1.
Describe the chloroplasts, cell wall and plasma membrane of the elodea in the tap water.
2.
Why does the cell look like this…in terms of osmosis.

3.
What type of solution is this?
4.
Describe the chloroplasts, cell wall and plasma membrane of the elodea in the salt water solution.
5.
What happened to the water inside the cell after it was put in the salt water?
6.
What type of solution is this?
7.
What happened to the cell when you placed the elodea in distilled water? (If nothing happened…what
happened in more time?)
8.
What type of solution is this?