Unit 11: Homeostasis in Cells

Transcription

1 a Unit 11: Homeostasis in Cells Name: Period: Test Date: 1

2 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 Osmosis Practice 14 Plasmolysis Lab Transport Review 17 Freshwater Sharks Article Cell Membrane Images Review Homeostasis Stations Unit 11 Vocabulary 25 2

3 UNIT 10 WARM-UPS Question: Date: Answer: Question: Date: Answer: Question: Date: Answer: Question: Date: Answer: Question: Date: Answer: 3

4 Question: Date: Answer: Question: Date: Answer: Question: Date: Answer: Question: Date: Answer: Question: Date: Answer: 4

5 Word Definition Picture (letter)

6 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. Draw your phospholipid drawing here: 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 6

7 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 7

8 Passive Transport vs Active Transport Notes Passive Transport energy required Active Transport Requires energy = Moves the concentration gradient. Moves the concentration gradient. 8

9 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? 9

10 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? 10

11 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! 11

12 Think About It: OSMOSIS & TONICITY Notes 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 12

13 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.) WATER 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 WATER 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 13

14 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. 14

15 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 vacuole cell wall Cell membrane separating from the 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 15

16 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 Analysis: Onion Cells: Tap water Onion Cells: 10% salt solution Onion Cells: Distilled water 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? 16

17 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 Facilitated diffusion High to low concentration Against/up the concentration gradient Protein Pump Engulfs food particles into cell Movement of water Movement of particles Types of Transport 17

18 Freshwater Sharks: Big Fish Where You Least Expect Them Retrieved February 28, 2009, from Discovery Channel Web site: By Jennifer Viegas Placid lakes, rivers, estuaries and large streams make attractive vacation sites, but they can also attract nonhuman 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, 18

19 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. 19

20 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? 20

21 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 21

22 5. Describe the two cellular processes that allow cells to engulf food and excrete waste. Do these cellular processes require energy? 22

23 Homeostasis Stations My Starting Station: My Group Members: 23

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25 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 25