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General Biology Chapter 4 Cellular Transport

General Biology Chapter 4 Cellular Transport. Cells and Their Environment. Cellular Transports Two Major Types. Passive Transport Diffusion Osmosis Facilitated Diffusion Active Transport Sodium Potassium Pumps Endocytosis Exocytosis. CELL MEMBRANE.

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General Biology Chapter 4 Cellular Transport

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  1. General BiologyChapter 4Cellular Transport Cells and Their Environment

  2. Cellular TransportsTwo Major Types • Passive Transport • Diffusion • Osmosis • Facilitated Diffusion • Active Transport • Sodium Potassium Pumps • Endocytosis • Exocytosis

  3. CELL MEMBRANE • Membranes are selectively permeable and allow only certain substances to move across them. • The interior portion of a cell membrane forms a nonpolar zone that prevents ions and most large molecules from passing through the membrane. • Membranes have ion channel gates that close the pores of some ion channels in response to • Stretching of the cell membrane • Change in electrical charge • The binding of specific molecules to the channel

  4. PASSIVE TRANSPORT • Passive Transport - requires NO ENERGY does NOT use ATP to move molecules • Diffusion = random dispersion of molecules from an area of HIGH concentration to an area of LOW concentration. (Molecules down the concentration gradient) • Osmosis = is the diffusion of WATER molecules from an area of HIGH concentration to an area of LOW concentration (water down the concentration gradient) • Facilitated Diffusion = Uses CARRIER PROTEINS to transport specific subs. (sugar/amino acids) down a concentration gradient.

  5. Diffusion-PASSIVE • As a result of diffusion, the concentration of many types of substances eventually become balanced on both sides of a membrane. • Dispersal of ink or sugar in a beaker of water is an example of diffusion. • Cell does not expend energy (no energy used) • Substances always flow from an are of high concentration to an area of LOW concentration.

  6. Facilitated Diffusion-PASSIVE • Use of transport proteins called carrier proteins that bind to a specific subs. Carry the subs. across the membrane and then release the subs. • Amino acids and Sugars cross the membrane in this manner • NO energy is required to transport the subs.

  7. OSMOSIS-PASSIVE • Diffusion of WATER into or out of a cell • Is a type of PASSIVE transport. • Diffusion of water down the concentration gradient. (from HIGH to LOW) • Three water concentrations. • Hypertonic • Hypotonic • Isotonic

  8. PASSIVE- Hypertonic • A solution that causes a cell to shrink • More solute than water • If a cell is placed into a hypertonic solution water will flow out of the cell • When a plant cell shrinks it loses Turgor pressure. • A strong salt solution = hypertonic solution/more salt than water. Therefore the cell would shrink.

  9. PASSIVE -Hypotonic • When water diffuses into the cell and the cell swells. • If a cell is placed into a hypotonic solution the cell will swell and may burst. • When the concentration of water molecules is higher outside a cell than inside the cell, water will diffuse into the cell

  10. PASSIVE -ISOTONIC • No net water movement. • Water diffuses into and out of the cell at the same rate. • Fluid inside and outside is the same. • The cell stays the same – equilibrium

  11. ACTIVE TRANSPORT • USES ENERGY USES ATP • Moves against the concentration gradient. • Moves molecules from an area of LOW to HIGH concentration • Energy is required to move a substance across a cell membrane • Unlike passive active REQUIRES ENERGY

  12. ACTIVE TRANSPORTThree types • Sodium Potassium Pumps • Endocytosis • Exocytosis • Cell will use energy supplied by ATP

  13. ENDOCYTOSIS-ACTIVE • Transports molecules that are to large to be moved through the membrane can be transported into the cell by Endocytosis • Requires Energy to carry out Endocytosis. Usually supplied by ATP • Endocytosis is a process that uses vesicles to capture substances and bring them into the cell • Endocytosis the cell membrane extends to engulf substances that are too big to pass through the cell membrane

  14. EXOCYTOSIS - ACTIVE • Ridding the cell of materials by discharging the materials in vesicles • Helps rid the cell of waste • Molecules that are to large to be moved across the cell membrane can be removed by Exocytosis • Exocytosis requires ENERGY to expel proteins and other materials from the cell

  15. Paramecium Unicellular aquatic organisms • Paramecia are aquatic (live in water) unicellular protists. • They have a number of characteristics also found in animals • Need to ingest food in order to obtain energy (Heterotrophs) • NO cell wall. • Surrounded by a cell membrane • Have some of the same organelles as animals ( nucleus/mitochondria/ribosomes/cilia) • In addition – paramecium have CONTRACTILE VACUOLES • Contractile vacuoles expel excess water. • Contractile vacuoles are found in unicellular aquatic organisms.

  16. Question A • How can you explain the observed relationship between the salt concentration and the rate of contractile vacuole concentration?

  17. Answer A • When there is less salt there is more water causing the contractile vacuoles pump faster.

  18. Question B • If something happened to a paramecium that caused its contractile vacuole to stop contracting, what would you expect to happen?

  19. Answer B • The water would build up inside the paramecium causing it to swell and then burst resulting in death.

  20. Question C • Would this result occur more quickly if the paramecium was in water with a high salt concentration or in water with a low salt concentration? Why?

  21. Answer C • LOW concentration Because if the salt content is low then the water content is high and water accumulates more rapidly.

  22. Homework • Pp. 88 #’s 1-6; 8; 10 • Pp 89 #’s 1-3; 5 & 6 • Define Key Terms pp. 87 • Pp. 80 Section 1 Review #’s 4 & 5 • Pp. 86 Section 2 Review # 6

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