Chapter 5 Homeostasis and Cell Transport

Transcription

1 Chapter 5 Homeostasis and Cell Transport

2 Palabra Palooza! Role #1: The Definer says: The word can be explained as Role #2: The Re-stater says: Then I understand (word) to mean Words: Passive transport Diffusion Equilibrium Osmosis Facilitated diffusion

3 Finger Vote! How many people can define all five terms?

4 Human Matching Passive transport Diffusion Equilibrium Osmosis Facilitated diffusion 1. concentration of molecules is the same throughout the space 2. diffusion of substances across a cell membrane with the aid of carrier proteins 3. movement of substances across a cell membrane without the use of energy 4. the diffusion of water molecules from an area of higher concentration to an area of lower concentration 5. movement of molecules from an area of higher concentration to an area of lower concentration

5 What is homeostasis? Homeostasis is the ability to maintain normal internal conditions. This means maintain a state of balance in living things. Cells must maintain homeostasis

6 What is homeostasis?

7 What structure does a cell have to help it maintain homeostasis? Cells are enclosed in a phospholipid bilayer called a cell (plasma) membrane that regulates their interactions with their surrounding environment. A cell membrane has a specific structure that allows it to be semipermeable.

8 What structure does a cell have to help it maintain homeostasis?

9 What is the cell membrane s structure and function? 1. Semi/Selectively permeable (controls what substances enters and leaves the cell) 2. Helps organisms maintain homeostasis

10 What is selectively permeable? Selectively permeable means that the membrane will allow some substances to pass through and will not allow other substances to pass through.

11 What is permeable and impermeable? If a membrane allows a substance to pass through, it is said to be permeable to that substance. If a membrane does not allow a substance to pass through, it is said to be impermeable to that substance.

12 How does a cell maintain homeostasis? Through the movement of different molecules through the cell membrane by: 1. Passive transport or 2. Active transport

13 2. What is passive The movement of substances across a cell membrane without the use of energy by the cell. transport?

14 2. What is passive transport?

15 3. What is diffusion? The simplest type of passive transport. The movement of molecules from an area of higher concentration to an area of lower concentration. Molecules move on their own kinetic energy. Examples: When you add a sugar cube to water Aroma (smell) of microwave popcorn

16 3. What is diffusion?

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18 What does it mean by kinetic energy? Molecules are in constant motion because they have kinetic energy Molecules move randomly in a straight line until they hit another molecule, then bounce off and move in the opposite direction. Molecules have the tendency to move from high to low concentration.

19 4. What is equilibrium? When the concentration of molecules of a substance is the same throughout a space. Even at equilibrium there is a random movement of molecules.

20 4. What is equilibrium?

21 CHECK IT: Stand Up BRING YOUR NOTES! Find one partner that is wearing the same color as you!

22 CHECK IT Partner #1: Explain the structure of a cell membrane and the term semipermeable. Sentence starters: The cell membrane is made up of Semi or selectively permeable means

23 CHECK IT Partner #2: Describe the term diffusion. Be sure to include the term passive transport in your answer. Sentence Starter: Diffusion is

24 5. What is a solution? A solution is composed of a solute dissolved in a solvent. Example: Salt water Salt is the solute Water is the solvent In the case of cells, the solutes are organic* and inorganic compounds, and water is the solvent. *Carbohydrates, Proteins, Lipids

25 5. What is a solution?

26 6. What is osmosis? Osmosis is the movement of water across a cell membrane from an area of higher concentration to an area of lower concentration. ****Because water is moving from an area of higher concentration to an area of lower concentration, osmosis does not require cells to expend energy. *****Therefore, osmosis is a type of passive transport!!!!!

27 6. What is osmosis?

28 What s wrong with this picture?

29 7. What determines the direction of the water? The relative concentration of water and solute on the two sides of the cell membrane.

30 8. Some Definitions Hypertonic-higher concentration of solutes Isotonic-even concentration of solutes Hypotonic-lower concentration of solutes I&index=4&list=PL3iRMx--LNd2uOzNRHwToHkd0mu2SmTjg

31 If the outside fluid is Isotonic Hypotonic Hypertonic Then the fluid 8. Some outside the Definitions cell has Equal conc. of H 2 O and solutes Lower conc. of solutes (higher conc. of water) Higher conc. of solutes (lower conc. of water) Water diffuses Into & out of cell at the same rate Into the cell Out of the cell Effect on the cell Cell is normal (shape and size) Cell will swell and burst (cytolysis) Cell will shrink (plasmolysis or crenation)

32 In living systems, the point of reference is always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower concentration of solutes than the cell cytoplasm. It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell. In this situation, water will follow its concentration gradient and enter the cell, causing the cell to expand.

33 9. What happens to the cells of a freshwater fish when it is in a saltwater tank? Fish-- Animal Cells No Cell Walls Salt

34 9. What happens to the cells of a freshwater fish when it is in a saltwater tank? Salt Outside solution is hypertonic Plasmolysis / crenation occurs H 2 O leaves fish s cells and fish will die

35 10. What happens to the cells of a saltwater fish when it is in a freshwater tank? Fish-- Animal Cells No Cell Walls Salt

36 10. What happens to the cells of a saltwater fish when it is in a freshwater tank? Salt Outside solution is hypotonic Cytolysis occurs H 2 O enters fish s cells and fish will die

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38 11. How do plant cells deal with osmosis? Plant cells have cell wall and most live a hypotonic environment. This moves water into the cells by osmosis. These cells swell as they fill with water until the cell membrane is pressed against the inside of the cell wall. The water exerts of pressure against the cell wall called turgor pressure.

39 11. How do plant cells deal with osmosis? In a hypertonic environment, water leaves the cells through osmosis. As the water leaves the central water vacuole, the cells shrink away from the cell walls, and turgor pressure is lost. This condition is called plasmolysis, and is the reason that plants wilt if they don t receive enough water.

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41 Some of them, such as the paramecia have structures called contractile vacuole which remove the excess water by pumping it out of the cell. =vk5nfsvp8ly 12. How do unicellular organisms deal with osmosis? Because most of them live in a hypotonic environment, water is constantly entering the cells, so they must rid themselves of the excess water.

42 13. What is selectively permeable? Selectively permeable means that the membrane will allow some substances to pass through and will not allow other substances to pass through.

43 13. What is selectively permeable? YW-xs

44 13. What is selectively permeable? If a membrane allows a substance to pass through, it is said to be permeable to that substance If a membrane does not allow a substance to pass through, it is said to be impermeable to that substance.

45 14. What is facilitated diffusion? Another type of passive transport in which molecules that cannot readily diffuse across a membrane are assisted by carrier proteins in the membrane.» Example: glucose diffusing across a cell membrane through the protein

46 Check your knowledge We have talked about three types of passive transport. Take a minute to quietly look through your notes and refresh you memory on the three types of passive transport. Circle the three types of passive transport in your notes!!!

47 Check your knowledge With your table partner discuss the following: Partner 1: Explain the term passive transport. Passive transport is the movement of molecules from and area of Partner 2: Explain diffusion. What types of substances diffuse through our cells. Diffusion is the movement of from an area of

48 Check your knowledge Partner 1. Explain osmosis. What substance is moved in our cells through osmosis? Osmosis is the movement of from an area of Partner 2. Explain facilitated diffusion. What substance is moved in our cells using facilitated diffusion. Facilitated Diffusion is the movement of from an area of

49 15. What is active transport? The movement of substances, usually across a cell membrane, against (up) a concentration gradient which requires cells to use energy.

50 16. What does against a concentration gradient mean? When cells move substances from an area of lower concentration to an area of higher concentration.

51 17. How are carrier proteins involved in active transport? Carrier proteins in animal cells are involved in an active transport process called the sodium-potassium pump. In humans this process occurs in muscle cells and liver cells. Cells have to expend energy to pump Potassium (K + ) ions into the cells and to pump Sodium (Na + ) ions out of cells.

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53 18. How do macromolecules that are too large to pass through the cell membrane by the other process get in and out of the cells? 1) Endocytosis - the process by which cells ingest external fluid, macromolecules, and large particles, including other cells.

54 18. How do macromolecules that are too large to pass through the cell membrane by the other process get in and out of the cells?

55 Endocytosis Two types: a) Pinocytosis -involves the transport of solutes or fluids b) Phagocytosis -involves the transport of large solid particles or whole cells. Example: White blood cells engulfing bacteria or amoeba engulfing a paramecium

56 Endocytosis

57 2) Exocytosis- the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out of the cell. Cells use exocytosis to release large molecules such as proteins, waste products, or toxins that would damage the cell if they were released within the cytosol. KEY

58 Exocytosis