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Unit 11: Homeostasis in Cells

Name: _________________________________

Period: __________

Test Date: _______________________

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Table of Contents

Title of Page Page Number

Due Date

Unit 11 Warm Ups 3-4

Unit 11 Vocabulary Matching Activity 5

Cell Membrane Notes 6

Active vs. Passive Transport Notes 7-8

Osmosis through the Membrane of an

Egg 9-11

Osmosis & Tonicity Notes 12-13

Osmosis Practice 14

Plasmolysis Lab 15-16

Transport Review 17

Freshwater Sharks Article 18-19

Cell Membrane Images Review 20-22

Homeostasis Stations 23-24

Unit 11 Vocabulary 25

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UNIT 10 WARM-UPS

Question: Answer:

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Word Definition Picture (letter)

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4.

5.

6.

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8.

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10.

11.

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14.

15.

16.

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Cell Membrane Notes

What is the function of the cell membrane?

• Controls what __________________________________________ a cell (like a bouncer at a club)

• In doing this, it maintains ________________________________ in the cell.

Not everything could pass through the cell membrane to enter or exit the cell.

We call this _____________________________________.

What makes the cell membrane selectively permeable?

It is composed of a _________________________________________________that creates a barrier that only allows

_______________________________________ to pass through.

_____________________________________ are a special type of molecule that make up the cell membrane.

The phospholipids make up a ___________________________________.

Bi = 2…..So this means the cell membrane is two layers.

The phospholipids align so that the tails point in towards each other creating a

_______________________ center.

The current model of the cell membrane is called the ________________________________________.

______________________________- because individual phospholipids and proteins can move around freely within the

layer, like it’s a liquid.

____________________________- because of the pattern produced by the scattered protein molecules when the

membrane is viewed from above.

Selective Permeability is determined by…

1. The _________________________________ of the material

2. Polarity (________________________________________)

So what happens when we need a molecule in our cell that cannot pass through the cell membrane on its own?

___________________________________________________ to the Rescue!

• Some proteins act like ___________________________________ where materials can flow through

• Some act like _________________________________ to push material to the other side

Draw your phospholipid

drawing here:

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Passive and Active Transport Notes

What do you know about the cell membrane after completing the bubble demo?

__________________________________________________________________________________________________

__________________________________________________________________________________________________

Passive Transport &

Osmosis

Facilitated Diffusion

Active Transport (Protein Pumps)

Endocytosis &

Exocytosis

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Passive Transport vs Active Transport Notes

Passive Transport Active Transport

● ______ energy required ● Requires energy = ________

● Moves _________ the concentration ●Moves ___________ the

gradient. concentration gradient.

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Osmosis through the Membrane of an Egg

Osmosis is the movement of water across a semi-permeable membrane. The process by which osmosis occurs is when water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration. The direction of osmosis depends on the relative concentration of the solutes on the two sides. In osmosis, water can travel in three different ways. If the molecules outside the cell are lower than the concentration in the cytoplasm, the solution is said to be hypotonic to the cytoplasm, in this process, water diffuses into the cell until equilibrium is established. If the molecules outside the cell are higher than the concentration in the cytoplasm, the solution is said to be hypertonic to the cytoplasm, in this process, water diffuses out of the cell until equilibrium exists. If the molecules outside and inside the cell are equal, the solution is said to be isotonic to the cytoplasm, in this process, water diffuses into and out of the cell at equal rates, causing no net movement of water.

In this investigation we will use a fresh egg to determine what happens in osmosis. We are going to soak the egg in vinegar for 48 hours, corn syrup for 24 hours, and then soak the egg in water for another 24 hours. After all three “experiments”, we will take both quantitative measurements (in this case, mass of the egg) and qualitative measurements (what it looks like).

Materials:

raw egg three beakers 150 mL of vinegar 150 mL of corn syrup

water paper towels rubber band scale

Procedures: 1. Record the mass of the raw egg (with shell) and its appearance in your data table. 2. Add 150 mL of vinegar to a clean beaker and carefully place the egg into the beaker. Cover the beaker

tightly with a paper towel and rubber band. Wait 48 hours. 3. Carefully remove the egg (soaking in vinegar) and rinse. Record your observations and the mass of

the egg. 4. Add 150 mL of syrup to a clean beaker and carefully place the egg into the beaker. Cover the beaker

tightly. Wait 24 hours. 5. Carefully remove the egg (soaking in syrup) and rinse. Record your observations and the mass of the

egg. 6. Add 150 mL of water to a clean beaker and carefully place the egg into the beaker. Cover the beaker

tightly. Wait 24 hours. 7. Carefully remove the egg (soaking in water) and rinse. Record your observations and the mass of the

egg. 8. Clean up and answer all lab questions.

Predictions: 1. What will happen to the mass of the egg and its physical appearance when it is placed in vinegar?

______________________________________________________________________________________________________________________________________________________________________

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2. What will happen to the mass of the egg and its physical appearance when it is placed in syrup? ______________________________________________________________________________________________________________________________________________________________________

Data:

Solution Mass of the Egg Observations

Raw Egg (before start of

experiment)

Vinegar

Corn Syrup

Water

Analysis:

1. What did the vinegar do to the egg? Do you think vinegar is an acid or a base? ____________________________________________________________________________________________________________________________________________________________________________

2. Why did we cover the container each time we left it to soak? __________________________________

3. When the egg was placed in the syrup in which direction did the water molecules move? Sketch a quick picture showing the movement of water molecules.

4. When the egg was placed in the water, after being removed from the syrup, in which direction did the water move? Sketch a quick picture showing the movement of water molecules.

5. To what biological structure in the egg comparable? ______________ 6. What passive process of moving molecules is demonstrated in this lab? ____________________

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7. In which of the two liquids is the egg in a hypertonic solution? _____________________

a. How do you know? What is your evidence?

___________________________________________________________________________________

8. In which of the two liquids is the egg in a hypotonic solution? _______________________________

a. How do you know? What is your evidence?

___________________________________________________________________________________

9. How did your predictions compare with your actual results? _________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

10. Think about it: Why are vegetables sprinkled with water at the grocery store? Explain what happens in scientific terms!

___________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________

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OSMOSIS & TONICITY Notes

Think About It:

Make observations about the solution pictured. Is it in equilibrium? How do you know? ______________________________________________________________________________________________________________________________________________________

Can solutes diffuse across the membrane?__________________

How can the solution reach equilibrium? __________________________________________

OSMOSIS: Diffusion of __________________ across a membrane Moves from ______________ water potential (low solute) to _________ water potential (high solute) We label solutions as _____________________, ____________________, or _________________________ to help us understand the location of the highest solute concentration.

Salt SUCKS! Sugar SUCKS! Solutes SUCK! Solutes will ____________________________ water to balance out the solute concentration and reach equilibrium.

Not Equal Equal

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Hypotonic: HIPPO-HYPO: Think BIG! The cell will swell or get turgid in this type of solution.

_________________ concentration of solute in solution (Sugar, Salt, etc.) ______________________ ______________________

Isotonic: The cell will remain a “normal” size. Water will continue to move in and out of the cell at equal rates.

________________ concentration of solute in solution

Hypertonic: In this solution the cell will shrink. There is a hyper amount of solute on the outside of the cell that sucks the water out.

__________________ concentration of solute in solution _____________________ _____________________

WATER

WATER

WATER

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Predicting the Results of Diffusion & Osmosis

Scenario Diagram Explanation

Example:

A cell containing a 5% salt

solution is placed in a beaker

of 10 % salt solution.

The cell was in a

____________________

solution.

Use the word: hypotonic,

isotonic, or hypertonic.

Scenario 1:

A cell model containing a 2%

starch solution is placed in a

beaker of distilled water.

The cell was in a

____________________

solution.

Use the word: hypotonic,

isotonic, or hypertonic.

Scenario 2:

A cell model that contains

8% starch solution is placed

in a beaker that contains 3%

starch solution.

The cell was in a

____________________

solution.

Use the word: hypotonic,

isotonic, or hypertonic.

Scenario 3:

A cell model containing 98%

water is placed in a beaker

containing 92% water.

The cell was in a

____________________

solution.

Use the word: hypotonic,

isotonic, or hypertonic.

Scenario 4:

A cell model containing 5%

starch solution is placed in a

beaker of 10% starch

solution.

The cell was in a

____________________

solution.

Use the word: hypotonic,

isotonic, or hypertonic.

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Understanding Plasmolysis Lab

Background: Have you ever seen a plant with wilted leaves? Plant leaves wilt in response to water loss from individual cells.

When cells lose too much water, the cell membrane shrinks away from the cell wall in a process called plasmolysis. The leaf

appears wilted because the individual cells are flaccid, meaning their central vacuole is no longer filled with water. In a

healthy plant, the large central vacuole is filled with water creating an internal pressure, or turgor pressure, which helps keep

the cell membrane pressed against the cell wall. A plant cell with a water filled vacuole will be stiff or turgid (see figure 1.) A

plant cell whose central vacuole is not filled will have a lower internal turgor pressure and will be flaccid.

Large central Cell membrane

vacuole separating from the

cell wall

Cell wall

Turgid Vacuole begins Flaccid

to shrink

Water moves across the plasma membrane by osmosis from an area of high water concentration to an area of lower water

concentration. The movement of water affects cell homeostasis. Plant cells are homeostatic when the central vacuole is filled

with water. Plant cells placed in hypotonic solutions tend to exhibit turgidity while plant cells in hypertonic solutions will lose

water and become flaccid. Bacteria and fungus, which also have cell walls, will also experience plasmolysis in hypertonic

solutions. Plasmolysis can be observed in the laboratory by surrounding plant cells with hypertonic and hypotonic solutions

and observing the effects on the cell.

In this lab activity, you will observe the effects of plasmolysis.

Observing Plasmolysis

Problem: What will happen when onion cells are placed in a 10% salt solution?

Hypothesis: ______________________________________________________________________

Materials: 10% salt solution, red onion epidermal cells, dropper, paper towel, distilled water, slides, cover slips,

microscope, and forceps

Procedure:

1. Your teacher created a 10% salt solution by dissolving 1 gram of salt in 9 mL of water in a small beaker.

2. Using forceps, remove a small segment of epidermis from a piece of red onion. Prepare a wet mount slide by adding the

onion epidermis to a drop of tap water placed in the center of a clean glass slide. Cover with a cover slip.

3. Focus the slide under low power and then switch to high power. Adjust the microscope’s diaphragm to the amount of light

that allows you to visualize the cell wall and the vacuole of the cell. Make a labeled sketch of your observations on your

student answer sheet.

4. Leaving the slide on the microscope stage, place several drops of 10% salt solution on the left hand side of the slide. The

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drops should touch the side of the coverslip. Place a small piece of paper towel on the right hand side of the slide to draw the

salt water across the slide. This will expose the onion cells to the hypertonic salt solution.

5. Observe the effects of the salt solution on the onion cells. You may notice the movement of particles in the water as the

water is wicked to the opposite side of the slide. Do not let these particles distract your attention. Focus on what occurs

inside the onion cells. Notice any changes in color, size, or shape of the cell structures. Make a labeled sketch of your

observations in the space provided on your student answer sheet.

Problem: What will happen when onion cells are placed in distilled water?

Hypothesis: ______________________________________________________________________

6. Now flood the onion cells with a hypotonic solution by placing several drops of distilled water on the left hand side of the

slide. The drops should touch the edge of the coverslip. Place a small piece of paper towel on the right hand side of the slide

to draw the distilled water across the slide.

7. Observe the effects of distilled water on the onion cells. Make a labeled sketch of your observations in the space provided

on the student answer page.

Data and Observations:

Observing Plasmolysis

Onion Cells: Tap water Onion Cells: 10% salt solution Onion Cells: Distilled water

Analysis:

Which solution is hypertonic in relationship to the onion cell? _______________________________________________

Describe the effects of placing an onion cell in a hypertonic solution.

__________________________________________________________________________________________________

__________________________________________________________________________________________________

Which solution is hypotonic in relationship to the onion cell? ________________________________________________

Describe the effects of placing an onion cell in a hypotonic solution.

__________________________________________________________________________________________________

__________________________________________________________________________________________________

In which solution were the onion cells the most turgid? _____________________________________________________

In which solution were the onion cells the most flaccid? ____________________________________________________

Which type of solution is “best” for plant cells? ___________________________________________________________

Why? _____________________________________________________________________________________________

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Use the following terms/phrases to fill in the types of transport flowchart. Be sure to record your final answers in your student book.

Active Transport

Passive Transport

ATP

Exocytosis

Protein Pump

Engulfs food particles into cell

Movement of water

Movement of particles

Facilitated diffusion

High to low concentration

Against/up the concentration gradient

Types of Transport

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Freshwater Sharks: Big Fish Where You Least Expect Them

Retrieved February 28, 2009, from Discovery Channel Web site: http://dsc.discovery.com/sharks/freshwater-sharks.html

By Jennifer Viegas

Placid lakes, rivers, estuaries and large streams make attractive vacation sites, but they can also attract non-

human visitors, including sharks. The toothy elasmobranches may show up if the climate is tropical, warm or

temperate. Shark freshwater hot spots include places

like the Mississippi River in the U.S., the rivers of Natal

in South Africa, the Tigris River system of southern Iraq,

and multiple other freshwater bodies in India, China,

Indonesia, West Africa, New Guinea, the Philippines

and Australia. It’s unknown if any shark can live out its

entire life in fresh water, but the miracle is that they

can thrive at all under such conditions.

How Sharks Survive in Fresh Water

For most shark species, spending a day in fresh water would be like placing a human on the moon without a

spacesuit. It could not survive due to the inhospitable surrounding environment. A process called osmosis is

central to the problem. Osmosis is when a fluid moves through a semi-permeable membrane from a solution

with a low solute concentration to a solution with a higher solute concentration, until there is an equal

concentration of liquid on both sides of the membrane. The dissolved substances, in this case, primarily

involve sodium and chloride.

Since sharks evolved in salt water, they tend to have very salty bodies. Even sharks in fresh water contain

more than twice the amount of salt and chloride as more common freshwater fishes. In theory, they should

burst like an overfilled water balloon, given the osmosis effect, but they have come up with an effective

answer to the problem — they urinate a lot.

Ichthyologist Thomas Thorson studied bull sharks living in Lake Nicaragua and found these huge fish take in a

lot of extra water, as expected, but they excrete much of it as dilute urine, at a rate of over 20 times that of

typical saltwater sharks. That means their kidneys must work extra hard, utilizing additional energy. Like

people who become accustomed to life in low oxygen regions, however, sharks in fresh water appear to adapt

to what would seem to be formidable conditions.

Sharks Adapted for Fresh Water

Although a survey of freshwater sharks and rays in 1995 determined that 43 species of elasmobranches

penetrate freshwater environments, relatively few sharks spend substantial time in these areas. Sharks that do

frequent such regions include the river sharks and the aforementioned bull sharks, which, as their name

suggests, possess stocky bodies and an often aggressive, unpredictable nature to match.

The term “river sharks” refers to six rare species in the genus Glyphis. These include some of the world’s most

endangered sharks, such as the Ganges, speartooth, Irrawaddy River, Bizant River, Borneo River and New

Guinea River sharks. Aside from their pumped-up kidneys and other internal adaptations, these sharks tend to

additionally possess certain telltale exterior features. Their snouts are often short and broad, containing small,

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widely spaced nostrils. Broad, serrated teeth fill the upper jaw, while the lower contains teeth that menacingly

protrude, even when their mouths are fully shut. All of these characteristics likely help them to exist under

shallow conditions.

Why Freshwater Sharks Face Extinction

River shark populations are at dangerous lows now. Bull shark numbers are higher, since they can often move

between fresh- and saltwater environments. Species like the Ganges, though, which are more adapted to river

and lake life, are almost prisoners within their more land-locked environments, since they must withstand both

natural and human-induced problems. Natural problems include temperature, oxygen, mineral content and

turbidity changes that continue to be influenced by climate change. Human activities involve dam building,

modifications to water for irrigation and fisheries, and the introduction of pollutants into the water.

Adding to the problem is the “bad boy” image of sharks lurking in places where humans frequent. As apex

predators with no fear of being attacked by another animal, bull sharks have mistaken humans for prey over

the years, leading to unfortunate consequences. In fact, a series of bull shark attacks on the Jersey Shore in

1916 is said to have inspired the 1970s movie thriller Jaws, which wound up featuring a great white instead of

a bull shark. Humans are a much greater threat to sharks than they are to us, as evidenced by the 2006 ban

that the government of Nicaragua imposed on freshwater fishing of bull sharks. An alarming decline in the bull

shark population there prompted the ban.

The World Conservation Union’s Shark Specialist Group recently stated “biological data is urgently needed for

freshwater elasmobranches to make it possible to attempt management and conservation.” The scientists then

added a jolting statement: “At present, there is a vacuum of information, and elasmobranches can easily drop

to extinction without notice.” Time will only tell whether or not river sharks, which have been on Earth for

millions of years, can survive into the next decade, much less century.

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Cell Membrane Images Review

Look at each diagram and answer the questions using words from the word bank below. Words must be used more

than once.

Word Bank

Passive Transport Active Transport Diffusion

Osmosis Facilitated diffusion Endocytosis

Exocytosis Semipermeable membrane Hypotonic

Hypertonic Isotonic Cytolysis

Plasmolysis Channel protein Carrier protein

Vesicle Turgid Flaccid

against concentration gradient with concentration gradient

1. Why does the cell membrane allow this molecule to move into the cell?

2. What cellular process is occurring in this diagram? How do you know?

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3. What allows this molecule to pass through the cell membrane without using energy?

4. A sodium-potassium pump allows two potassium ions into the cell and removes three sodium ions. Complete

the sentence below:

This is ________ transport because _______________________________________

______________________________________________________________________________

_____________________________________________________________________________

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5. Describe the two cellular processes that allow cells to engulf food and excrete waste. Do these cellular processes

require energy?

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Homeostasis Stations

My Starting Station: ____ My Group Members: _____________________________________________________

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UNIT 11 VOCABULARY

1. Active transport – energy-requiring movement of molecules across a membrane from a region of lower concentration

to a region of higher concentration

2. ATP (adenosine triphosphate) – high-energy molecule that contains, within its bonds, energy that cells can use

3. Carrier protein – protein that must change shape or bond to a molecule to allow the molecule to pass through the

cell membrane

4. Channel protein – protein that forms a pore in the cell membrane that allows small molecules to pass through freely

5. Concentration gradient – difference in the concentration of a substance from one location to another

6. Diffusion – movement of dissolved molecules in a fluid or gas from a region of higher concentration to a region of

lower concentration; a type of passive transport

7. Endocytosis – uptake of liquids or large molecules into a cell by inward folding of the cell membrane; a type of active

transport

8. Equilibrium – condition in which the concentration of a substance is equal on both sides of a membrane

9. Exocytosis – release of substances out of a cell by the fusion of a vesicle with the membrane; a type of active

transport

10. Facilitated diffusion – diffusion of molecules assisted by protein channels that pierce a cell membrane

11. Hydrophilic – “water loving” – attracts water

12. Hydrophobic – “water fearing” – repels water

13. Hypertonic solution – solution that has a higher concentration of dissolved particles compared with another solution

14. Hypotonic solution – solution that has a lower concentration of dissolved particles compared with another solution

15. Isotonic solution – solution that has an equal concentration of dissolved particles with another solution

16. Osmosis – diffusion of water molecules across a semipermeable membrane from an area of higher water

concentration to an area of lower water concentration; a type of passive transport

17. Passive transport – movement of molecules across the cell membrane without energy input from the cell

18. Permeability – the state or quality of a material or membrane that causes it to allow liquids or gases to pass through

it.

19. Phospholipid bilayer – barrier around a cell that only allows certain molecules to pass through; composed of two

layers of phospholipids and proteins

20. Plasmolysis - the process in which cells lose water in a hypertonic solution

21. Protein pump – proteins that function to pump out or in solutes or ions from a low concentration region to high

concentration region with the use of ATP

22. Solute – substance that dissolves in a solvent and is present at a lower concentration than the solvent

23. Solvent – substance in which solutes dissolve and that is present in greatest concentration in a solution

24. Vacuole – organelle that is used to store materials, such as water, food, or enzymes, that are needed by the cell