Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter Presentation Transparencies Standardized Test Prep Visual Concepts Resources

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Homeostasis and Cell Transport Plasma Membrane Table of Contents Section 1 Passive Transport Section 2 Active Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Objectives Explain how an equilibrium is established as a result of diffusion. Distinguish between diffusion and osmosis. Explain how substances cross the cell membrane through facilitated diffusion. Explain how ion channels assist the diffusion of ions across the cell membrane.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Passive Transport When a cell uses no energy to move particles across a membrane passive transport occurs. Concentration gradient Plasma membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Click below to watch the Visual Concept. Visual Concept Concentration Gradient Passive Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Diffusion Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration, driven by the molecules’ kinetic energy until equilibrium is reached. Diffusion Across Membranes –Molecules can diffuse across a cell membrane by dissolving in the phospholipid bilayer or by passing through pores in the membrane.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Diffusion Passive Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Osmosis Osmosis is the diffusion of water across a membrane. In a cell, water always moves to reach an equal concentration on both sides of the membrane. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Click below to watch the Visual Concept. Visual Concept Osmosis Passive Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. What controls osmosis? What controls osmosis? Before Osmosis After Osmosis Water molecule Sugar molecule Selectively permeable membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Direction of Osmosis –The net direction of osmosis is determined by the relative solute concentrations on the two sides of the membrane. Solute: in a solution, the substance that is dissolved in the solvent –i.e. Sugar in sugar water

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Osmosis

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Hypertonic, Hypotonic, Isotonic Solutions Passive Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Direction of Osmosis - hypertonic –When the solute concentration outside the cell is higher than inside the cell, the solution outside is hypertonic to the inside of the cell, and water will diffuse out of the cell.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Cells in a hypertonic solution In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink. H2O Water Molecule Dissolved Molecule

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Direction of Osmosis - isotonic –When the solute concentrations outside and inside the cell are equal, the solution outside is isotonic, and there will be no net movement of water.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions. Cells in an isotonic solution H2O Water Molecule Dissolved Molecule

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Cells in an isotonic solution In an isotonic solution, the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell. H2O Water Molecule Dissolved Molecule

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Cells in an isotonic solution In an isotonic solution, water molecules move into and out of the cell at the same rate, and cells retain their normal shape.*** H2O Water Molecule Dissolved Molecule

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Cells in a hypotonic solution In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. H2O Water Molecule Dissolved Molecule

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Cells in a hypotonic solution Plant cells swell beyond their normal size as pressure increases.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Click below to watch the Visual Concept. Visual Concept Comparing Hypertonic, Isotonic, and Hypotonic Conditions Passive Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane How Cells Deal With Osmosis –Contractile vacuoles are organelles that regulate water levels in paramecia.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Facilitated Diffusion – carrier proteins In facilitated diffusion, a molecule binds to a carrier protein on one side of the cell membrane. The carrier protein then changes its shape and transports the molecule down its concentration gradient to the other side of the membrane.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Passive Transport by proteins Plasma membrane Channel proteins Concentration gradient

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Passive Transport by proteins Some transport proteins, called carrier proteins, form channels that allow specific molecules to flow through. Plasma membrane Channel proteins Concentration gradient

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Passive transport by proteins The movement is with the concentration gradient, and requires no energy input from the cell. Concentration gradient Plasma membrane Step 1Step 2 Carrier proteins

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Passive transport by proteins Carrier proteins change shape to allow a substance to pass through the plasma membrane. Concentration gradient Plasma membrane Step 1Step 2 Carrier proteins

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Passive transport by proteins In facilitated diffusion by carrier protein, the movement is with the concentration gradient and requires no energy input from the cell. Plasma membrane Step 1Step 2 Carrier proteins Concentration gradient

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Passive Transport: Facilitated Diffusion Passive Transport Facilitated diffusion movdiffusion

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Facilitated Diffusion Passive Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Passive Transport Plasma Membrane Diffusion Through Ion Channels Ion channels are proteins, or groups of proteins, that provide small passageways across the cell membrane through which specific ions can diffuse.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Ion Channels Passive Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Diffusion Through Ion Channels Passive Transport Ion Channels movChannels

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Active Transport Plasma Membrane Objectives Distinguish between passive transport and active transport. Explain how the sodium-potassium pump operates. Compare endocytosis and exocytosis.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Active Transport Plasma Membrane Active transport moves molecules across the cell membrane from an area of lower concentration to an area of higher concentration, moving against the concentration gradient. Unlike passive transport, active transport requires cells to expend energy. Active Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Active Transport Movement of materials through a membrane against a concentration gradient is called active transport and requires energy from the cell. Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Active Transport Plasma Membrane Cell Membrane Pumps Some types of active transport are performed by carrier proteins called cell membrane pumps.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages How active transport occurs In active transport, a carrier protein called a cell membrane pump first binds with a particle of the substance to be transported. Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages How active transport occurs Each type of carrier protein has a shape that fits a specific molecule or ion. Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages How active transport occurs When the proper molecule binds with the protein, chemical energy allows the cell to change the shape of the carrier protein so that the particle to be moved is released on the other side of the membrane. Step 1Step 2 Carrier proteins Cellular energy Plasma membrane Concentration gradient

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages How active transport occurs Once the particle is released, the protein’s original shape is restored. Step 1Step 2 Carrier proteins Cellular energy Plasma membrane Concentration gradient Active transport allows particle movement into or out of a cell against a concentration gradient.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages How active transport occurs Click image to view movie.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages How active transport occurs Click image to view movie.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Active Transport Plasma Membrane Cell Membrane Pumps Sodium-Potassium Pump –The sodium-potassium pump moves three Na + ions into the cell’s external environment for every two K + ions it moves into the cytosol. –ATP supplies the energy that drives the pump.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Sodium-Potassium Pump Active Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Sodium-Potassium Pump Active Transport Sodium-PotassiumSodium-Potassium pump mov

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Active Transport Plasma Membrane Movement in Vesicles Endocytosis –In endocytosis, cells ingest external materials by folding around them and forming a pouch. –The pouch then pinches off and becomes a membrane-bound organelle called a vesicle.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Transport of Large Particles Endocytosis is a process by which a cell surrounds and takes in material from its environment. EndocytosisExocytosis Digestion Nucleus Wastes

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Active Transport Plasma Membrane Movement in Vesicles Endocytosis –Endocytosis includes pinocytosis, in which the vesicle contains solutes or fluids, and phagocytosis, in which the vesicle contains large particles or cells.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Transport of Large Particles - Endocytosis The material is engulfed and enclosed by a portion of the cell’s plasma membrane. Exocytosis Digestion Nucleus Wastes Endocytosis

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Transport of Large Particles - Endocytosis The resulting vacuole with its contents moves to the inside of the cell. Exocytosis Digestion Nucleus Wastes Endocytosis

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Click below to watch the Visual Concept. Visual Concept Endocytosis Active Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Active Transport Plasma Membrane Movement in Vesicles Exocytosis –In exocytosis, vesicles made by the cell fuse with the cell membrane, releasing their contents into the external environment.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Click below to watch the Visual Concept. Visual Concept Exocytosis Active Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Transport of Large Particles - Exocytosis Exocytosis is the expulsion or secretion of materials from a cell. Endocytosis Exocytosis Digestion Nucleus Wastes

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 8.1 Summary – pages Transport of Large Particles - Exocytosis Endocytosis and exocytosis both move masses of material and both require energy. EndocytosisExocytosis Digestion Nucleus Wastes

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma Membrane Endocytosis and Exocytosis Active Transport

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Check Question 1 B. Endocytosis C. exocytosis D. osmosis A. active transport The diffusion of water across a selectively permeable membrane is called __________. Water molecule Sugar molecule Selectively permeable membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Check The answer is D, osmosis. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within the cell. Water molecule Sugar molecule Selectively permeable membrane Before osmosis After osmosis

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Check What is the expected result of having an animal cell in a hypertonic solution? Question 2 D. The cell retains its normal shape. C. The cell swells up. A. The cell shrivels up. B. The plasma membrane shrinks away from the cell wall.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Check The answer is A. In a hypertonic solution, cells experience osmosis of water out of the cell. Animal cells shrivel because of decreased pressure in the cells. H2O Water molecule Sugar molecule

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Check A grocer mists the celery display with water to keep it looking fresh. What type of solution is the celery now in? Question 3 D. exotonic C. hypertonic B. hypotonic A. isotonic

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Check The answer is B. Plant cells contain a rigid cell wall and do not burst even in a hypotonic solution.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Plasma membr ane Section 1 Check Transport of materials across the plasma membrane that does not require energy from the cell but does use transport proteins is called __________. Question 4 B. Simple diffusion C. Facilitated diffusion D. Active transport A. osmosis Concentr ation gradient Channel proteins

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Check The answer is C. Facilitated diffusion is a type of passive transport and requires no energy from the cell. Plasma membr ane Concentr ation gradient Channel proteins

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 1. During diffusion, molecules tend to move in what direction? A. the molecules involved in diffusion never move B. in a direction that doesn’t depend on the concentration gradient C. from an area of lower concentration to an area of higher concentration D. from an area of higher concentration to an area of lower concentration Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 1. During diffusion, molecules tend to move in what direction? A. the molecules involved in diffusion never move B. in a direction that doesn’t depend on the concentration gradient C. from an area of lower concentration to an area of higher concentration D. from an area of higher concentration to an area of lower concentration Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 2. Ion channels aid the movement of which substances? F. ions across a cell membrane G. water across a cell membrane H. molecules up a concentration gradient J. carrier proteins within the lipid bilayer Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 2. Ion channels aid the movement of which substances? F. ions across a cell membrane G. water across a cell membrane H. molecules up a concentration gradient J. carrier proteins within the lipid bilayer Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 3. The sodium-potassium pump transports which of the following? A. both Na + and K + into the cell B. both Na + and K + out of the cell C. Na + into the cell and K + out of the cell D. Na + out of the cell and K + into the cell Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 3. The sodium-potassium pump transports which of the following? A. both Na + and K + into the cell B. both Na + and K + out of the cell C. Na + into the cell and K + out of the cell D. Na + out of the cell and K + into the cell Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 4. Which process do some animal cells use to engulf, digest, and destroy invading bacteria? F. exocytosis G. pinocytosis H. phagocytosis J. All of the above Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 4. Which process do some animal cells use to engulf, digest, and destroy invading bacteria? F. exocytosis G. pinocytosis H. phagocytosis J. All of the above Standardized Test Prep Plasma Membrane

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 5. Which line represents the diffusion of glucose through the lipid bilayer? A. line X B. line Y C. both lines X and Y D. neither line X nor Y Plasma Membrane The graph below shows the rate of glucose transport across a cell membrane versus the concentration gradient. Use the graph that follows to answer the question. Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 5. Which line represents the diffusion of glucose through the lipid bilayer? A. line X B. line Y C. both lines X and Y D. neither line X nor Y Plasma Membrane The graph below shows the rate of glucose transport across a cell membrane versus the concentration gradient. Use the graph that follows to answer the question. Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 6. passive transport : osmosis :: active transport : F. cytolysis G. diffusion H. ion channel J. endocytosis Plasma Membrane Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 6. passive transport : osmosis :: active transport : F. cytolysis G. diffusion H. ion channel J. endocytosis Plasma Membrane Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 7. What form of cellular transport is being illustrated in the diagram? A. osmosis B. exocytosis C. facilitated diffusion D. a cell membrane pump Plasma Membrane The diagram below shows one form of cellular transport. Use the diagram to answer the question that follows. Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 7. What form of cellular transport is being illustrated in the diagram? A. osmosis B. exocytosis C. facilitated diffusion D. a cell membrane pump Plasma Membrane The diagram below shows one form of cellular transport. Use the diagram to answer the question that follows. Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Short Response When a cell takes in substances through endocytosis, the outside of the cell membrane becomes the inside of the vesicle. What might this suggest about the structure of the cell membrane? Plasma Membrane Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Short Response, continued When a cell takes in substances through endocytosis, the outside of the cell membrane becomes the inside of the vesicle. What might this suggest about the structure of the cell membrane? Answer: This suggests that the cell membrane’s inner and outer layers have essentially the same structure and are, therefore, interchangeable. Plasma Membrane Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Extended Response Some cells have carrier proteins that transport sugar molecules and hydrogen ions into the cytosol at the same time. These proteins move sugar up their gradient as hydrogen ions move down their gradient. Part A How would the transport of sugar into these cells affect the pH of the cells’ external environment? Part B What would happen to the transport of sugar if hydrogen ions were removed from the external environment? Plasma Membrane Standardized Test Prep

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Extended Response, continued Answer: Part A Because H + ions move into the cells with the sugar molecules, the transport of sugar into the cells would lower the concentration of H + ions in the external environment, raising the pH. Part B Removing H + ions from the external environment would stop the entry of sugar into the cells by this mechanism. Plasma Membrane Standardized Test Prep