Campbell Biology: Concepts & Connections Chapter 5 PDF

Campbell Biology: Concepts & Connections Tenth Edition Chapter 5 The Working Cell Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Introduction The plasma membrane and its proteins enable cells to survive and functi...

Campbell Biology: Concepts & Connections Tenth Edition Chapter 5 The Working Cell Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Introduction The plasma membrane and its proteins enable cells to survive and function. This chapter addresses how working cells use – membranes, – energy, and – enzymes. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.0_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Membrane Structure and Function Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.1 Visualizing The Concept: Membranes Are Fluid Mosaics of Lipids and Proteins with Many Functions Biologists use the fluid mosaic model to describe a membrane’s structure—diverse protein molecules suspended in a fluid phospholipid bilayer. The plasma membrane exhibits selective permeability. The proteins perform various functions. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_9 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_3 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_4 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_5 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_6 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_7 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_8 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.1_9 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Signal Transduction Pathways Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.2 Evolution Connection: The Spontaneous Formation of Membranes Was a Critical Step in the Origin of Life Phospholipids spontaneously self-assemble into simple membranes. The formation of membrane-enclosed collections of molecules was a critical step in the evolution of the first cells. Checkpoint question In the origin of a cell, why would the formation of a simple lipid bilayer membrane not be sufficient? What else would have to be part of such a membrane? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.3 Passive Transport Is Diffusion Across a Membrane with No Energy Investment Diffusion is the tendency of particles to spread out evenly in an available space. Diffusion across a cell membrane does not require energy, so it is called passive transport. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.3b Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Diffusion video clip Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Membrane Selectivity Video clip Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Kidney Dialysis 5.4 Osmosis Is the Diffusion of Water Across a Membrane (1 of 2) The diffusion of water across a selectively permeable membrane is called osmosis. If a membrane, permeable to water but not to a solute, separates two solutions with different concentrations of solute, water will cross the membrane, moving down its own concentration gradient, until the solute concentration on both sides is equal. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.4 Osmosis Is the Diffusion of Water Across a Membrane (2 of 2) Checkpoint question Predict the net water movement between two solutions—a 0.5% sucrose solution and a 2% sucrose solution—separated by a membrane not permeable to sucrose. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.4 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Osmosis and water balance video clip Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.5 Water Balance Between Cells and Their Surroundings Is Crucial to Organisms (1 of 2) Tonicity is a term that describes the ability of a surrounding solution to cause a cell to gain or lose water. Cells shrink in a hypertonic solution. Cells swell in a hypotonic solution. In isotonic solutions, animal cells are normal, but plant cells are flaccid. Figure 5.5 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.5 Water Balance Between Cells and Their Surroundings Is Crucial to Organisms (2 of 2) Checkpoint question Explain the function of the contractile vacuoles in the freshwater Paramecium shown in Figure 4.11A in terms of what you have just learned about water balance in cells. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.6 Transport Proteins Can Facilitate Diffusion Across Membranes (1 of 2) Hydrophobic substances easily diffuse across a cell membrane. However, polar or charged substances do not easily cross cell membranes. Instead, polar or charged substances move across membranes with the help of specific transport proteins, called facilitated diffusion, which – does not require energy and – relies on the concentration gradient. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.6 Transport Proteins Can Facilitate Diffusion Across Membranes (2 of 2) Transport proteins help specific substances diffuse across the membrane down their concentration gradients and thus requires no input of energy. The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an aquaporin. Checkpoint question How do transport proteins contribute to a membrane’s selective permeability? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.6 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.7 Scientific Thinking: Research on Another Membrane Protein Led to the Discovery of Aquaporins Dr. Peter Agre received the 2003 Nobel Prize in Chemistry for his discovery of aquaporins. His research on the Rh protein used in blood typing led to this discovery. Checkpoint question Why did the researchers use frog eggs to test the function of this unknown protein? Why did they also monitor the behavior of control eggs in the hypotonic solution? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.7 Source: Adaptation of Figure 2A from “Appearance of water channels in Xenopus oocytes expressing red cell C H I P28 protein” by Gregory Preston et al., from Science, April 1992, Volume 256(5055). Copyright © 1992 by A A A S. Reprinted with permission. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.8 Cells Expend Energy in the Active Transport of a Solute In active transport, a cell must expend energy to move a solute against its concentration gradient. The energy molecule ATP supplies the energy for most active transport. The following figures show the four main stages of active transport. Checkpoint question Cells actively transport Ca2+ out of the cell. Is calcium more concentrated inside or outside of the cell? Explain. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.8_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.8_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.8_3 facilitated diffusion video clip Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Active Transport Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.9 Exocytosis and Endocytosis Transport Large Molecules Across Membranes (1 of 2) A cell uses two mechanisms to move large molecules across membranes. 1. Exocytosis is used to export bulky molecules, such as proteins or polysaccharides. 2. Endocytosis is used to take in large molecules. In both cases, material to be transported is packaged within a vesicle that fuses with the membrane. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.9 Exocytosis and Endocytosis Transport Large Molecules Across Membranes (2 of 2) There are three kinds of endocytosis. 1. Phagocytosis is the engulfment of a particle by the cell wrapping cell membrane around it, forming a vacuole. 2. Pinocytosis is the engulfment of liquids by forming a vacuole 3. Receptor-mediated endocytosis uses membrane receptors for specific solutes. In both cases, material to be transported is packaged within a vesicle that fuses with the membrane. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Endocytosis and exocytosis Figure 5.9_1 Phagocytosis Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Pinocytosis Figure 5.9_2 Receptor Mediated Endocytosis Copyright © 2020 Pearson Education, Inc. All Rights Reserved. LE 5-19c Three types of Endocytosis Pseudopodium of amoeba Food being ingested LM 230× Phagocytosis Plasma membrane Material bound to receptor proteins PIT TEM 54,000× TEM 96,500× Cytoplasm Pinocytosis Receptor-mediated endocytosis Animation: Exocytosis and Endocytosis Introduction video clip Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Review Video Energy and the Cell Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.10 Cells Transform Energy and Matter as They Perform Work (1 of 2) Energy is the capacity to cause change, ability to do work. Kinetic energy is the energy of motion. Potential energy is energy stored in the location or structure of matter and includes chemical energy. According to the laws of thermodynamics, – energy can change form but cannot be created or destroyed, and – energy transfers or transformations increase disorder, or entropy, with some energy being lost as heat. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. According to the laws of thermodynamics, 1st law: energy can change form but cannot be created or destroyed, and 2nd law:energy transfers or transformations increase disorder, or entropy, with some energy being lost as heat. Figure 5.10_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.10_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: Energy Concepts video clip Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.11 Chemical Reactions Either Release or Store Energy Exergonic reactions release energy. Endergonic reactions require energy and yield products rich in potential energy. Metabolism encompasses all of a cell’s chemical reactions. Catabolism and Anabolism. Catabolism is the breaking down of compounds to release energy. Anabolism is the building of compounds, which uses energy. People's body weight is a result of catabolism minus anabolism. Checkpoint question Remembering that energy must be conserved, what do you think becomes of the energy extracted from food during cellular respiration? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.11a Exergonic Reaction releases energy to the environment: spontaneous reaction Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.11b Endergonic Reaction Absorbs energy from the environment: not spontaneous Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.12 ATP Drives Cellular Work by Coupling Exergonic and Endergonic Reactions ATP powers nearly all forms of cellular work. Phosphorylation: The transfer of a phosphate group from ATP is involved in chemical, transport, and mechanical work. Checkpoint question Explain how ATP transfers energy from exergonic to endergonic processes in the cell. Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  ATP powers cellular work through coupled reactions – The bonds connecting the phosphate groups are broken by hydrolysis, an exergonic reaction – Hydrolysis is coupled to an endergonic reaction through phosphorylation A phosphate group is transferred from ATP to another molecule Figure 5.12a_2 video clip Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.12b Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  Cellular work can be sustained, because ATP is a renewable resource that cells regenerate – The ATP cycle involves continual phosphorylation and hydrolysis – ATP isn’t around for long so it constantly needs to be made by the cells. Figure 5.12c Energy Coupling in ATP video clip Phosphorylation Hydrolysis Copyright © 2020 Pearson Education, Inc. All Rights Reserved. REVIEW: How Enzymes Function Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.13 Enzymes Speed Up the Cell’s Chemical Reactions by Lowering Energy Barriers (1 of 2) Enzymes are catalysts that decrease the activation energy needed for a reaction to begin, without being consumed by the reaction. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.13_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.13_3 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.13_4 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.13 Enzymes Speed Up the Cell’s Chemical Reactions by Lowering Energy Barriers (2 of 2) Checkpoint question The graph below illustrates a reaction with and without an enzyme. Which curve represents the enzyme-catalyzed reaction? What do lines a, b, and c represent? Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Animation: How Enzymes Work Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.14 A Specific Enzyme Catalyzes Each Cellular Reaction (1 of 2) An enzyme’s substrate fits specifically in a region of the enzyme called the active site. The following figure illustrates the catalytic cycle of an enzyme. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.14_1 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.14_2 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.14_3 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.14_4 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.14 A Specific Enzyme Catalyzes Each Cellular Reaction (2 of 2) Cofactors: nonprotein helpers that bind to the active site and function in catalysis. Most are inorganic: iron, zinc, copper atoms If they are organic, they are called coenzymes: vitamins Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.15 Enzyme Inhibition Can Regulate Enzyme Activity in a Cell (1 of 2) A competitive inhibitor reduces an enzyme’s productivity by blocking substrate molecules from entering the active site. A noncompetitive inhibitor does not enter the active site. Instead, it binds to a site elsewhere on the enzyme, and its binding changes the enzyme’s shape so that the active site no longer fits the substrate. Feedback inhibition helps regulate metabolism. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.15a Allosteric site Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.15b Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.16 Connection: Many Drugs, Pesticides, and Poisons Are Enzyme Inhibitors (1 of 2) Many beneficial drugs act as enzyme inhibitors. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. 5.16 Connection: Many Drugs, Pesticides, and Poisons Are Enzyme Inhibitors (2 of 2) Enzyme inhibitors have also been developed as – pesticides and – deadly poisons for use in warfare. ARTICLE: Importance of enzyme inhibitors Copyright © 2020 Pearson Education, Inc. All Rights Reserved. You Should Now Be Able to (1 of 4) 1. Describe the fluid mosaic structure of cell membranes. 2. Describe the diverse functions of membrane proteins. 3. Relate the structure of phospholipid molecules to the structure and properties of cell membranes. 4. Define diffusion and describe the process of passive transport. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. You Should Now Be Able to (2 of 4) 5. Explain how osmosis can be defined as the diffusion of water across a membrane. 6. Distinguish between hypertonic, hypotonic, and isotonic solutions. 7. Explain how transport proteins facilitate diffusion. 8. Distinguish between exocytosis, endocytosis, phagocytosis, and receptor-mediated endocytosis. Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  You Should Now Be Able to (3 of 4) 9. Define and compare kinetic energy, potential energy, chemical energy, and heat. 10. Define the two laws of thermodynamics and explain how they relate to biological systems. 11. Define and compare endergonic and exergonic reactions. 12. Explain how cells use cellular respiration and energy coupling to survive. Copyright © 2020 Pearson Education, Inc. All Rights Reserved.  You Should Now Be Able to (4 of 4) 13. Explain how A T P functions as an energy shuttle. 14. Explain how enzymes speed up chemical reactions. 15. Explain how competitive and noncompetitive inhibitors alter an enzyme’s activity. 16. Explain how certain drugs, pesticides, and poisons can affect enzymes. Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.UN01 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.UN02 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.UN03 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.UN04 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Figure 5.UN05 Table A Reaction Rate and Enzyme Concentration Lactose concentration 10% 10% 10% 10% 10% Enzyme concentration 0% 1% 2% 4% 8% Reaction rate 0 25 50 100 200 Table B Reaction Rate and Substrate Concentration Lactose concentration 0% 5% 10% 20% 30% Enzyme concentration 2% 2% 2% 2% 2% Reaction rate 0 25 50 65 65 Copyright © 2020 Pearson Education, Inc. All Rights Reserved. Copyright This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching their courses and assessing student learning. Dissemination or sale of any part of this work (including on the World Wide Web) will destroy the integrity of the work and is not permitted. The work and materials from it should never be made available to students except by instructors using the accompanying text in their classes. All recipients of this work are expected to abide by these restrictions and to honor the intended pedagogical purposes and the needs of other instructors who rely on these materials./ Copyright © 2020 Pearson Education, Inc. All Rights Reserved.