© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey The Working Cell 1308 Ch 5 Notes

Biology and Society: Natural Nanotechnology Cells control their chemical environment using –Energy –Enzymes –The plasma membrane Cell-based nanotechnology may be used to power microscopic robots. Some Basic Concepts Energy makes the world go around. But what is energy? Conservation of energy © 2010 Pearson Education, Inc.

Conservation of Energy Energy is defined as the capacity to perform work. Kinetic energy is the energy of motion. Potential energy is stored energy. Machines and organisms can transform kinetic energy to potential energy and vice versa. In all such energy transformations, total energy is conserved. –Energy cannot be created or destroyed. –This is the principle of conservation of energy. Animation: Energy Concepts

Climbing the steps converts kinetic energy of muscle movement to potential energy. On the platform, the diver has more potential energy. Diving converts potential energy to kinetic energy. In the water, the diver has less potential energy. Figure 5.1

© 2010 Pearson Education, Inc. Entropy Every energy conversion releases some randomized energy in the form of heat. Heat is a –Type of kinetic energy –Product of all energy conversions Scientists use the term entropy as a measure of disorder, or randomness. All energy conversions increase the entropy of the universe.

© 2010 Pearson Education, Inc. Chemical Energy Molecules store varying amounts of potential energy in the arrangement of their atoms. Organic compounds are relatively rich in such chemical energy. Living cells and automobile engines use the same basic process to make chemical energy do work. Cellular respiration is the energy-releasing chemical breakdown of fuel molecules that provides energy for cells to do work. Humans convert about 40% of the energy in food to useful work, such as the contraction of muscles.

Fuel rich in chemical energy Energy conversion Waste products poor in chemical energy Gasoline  Oxygen Carbon dioxide  Water Energy conversion in a car Energy for cellular work Energy conversion in a cell Heat energy Heat energy Carbon dioxide  Water Food  Oxygen Combustion Cellular respiration Kinetic energy of movement ATP Figure 5.2

© 2010 Pearson Education, Inc. Food Calories A calorie is the amount of energy that raises the temperature of one gram of water by 1 degree Celsius. Food Calories are kilocalories, equal to 1,000 calories. The energy of calories in food is burned off by many activities.

(a) Food Calories (kilocalories) in various foods (b) Food Calories (kilocalories) we burn in various activities Cheeseburger Spaghetti with sauce (1 cup) Pizza with pepperoni (1 slice) Peanuts (1 ounce) Apple Bean burrito Fried chicken (drumstick) Garden salad (2 cups) Popcorn (plain, 1 cup) Broccoli (1 cup) Baked potato (plain, with skin) Food Calories Food Activity Food Calories consumed per hour by a 150-pound person* Running (7min/mi) Sitting (writing) Driving a car Playing the piano Dancing (slow) Walking (3 mph) Bicycling (10 mph) Swimming (2 mph) Dancing (fast) *Not including energy necessary for basic functions, such as breathing and heartbeat Figure 5.3

(a) Food Calories (kilocalories) in various foods Cheeseburger Spaghetti with sauce (1 cup) Pizza with pepperoni (1 slice) Peanuts (1 ounce) Apple Bean burrito Fried chicken (drumstick) Garden salad (2 cups) Popcorn (plain, 1 cup) Broccoli (1 cup) Baked potato (plain, with skin) Food CaloriesFood Figure 5.3a

(b) Food Calories (kilocalories) we burn in various activities ActivityFood Calories consumed per hour by a 150-pound person* Running (7min/mi) Sitting (writing) Driving a car Playing the piano Dancing (slow) Walking (3 mph) Bicycling (10 mph) Swimming (2 mph) Dancing (fast) *Not including energy necessary for basic functions, such as breathing and heartbeat Figure 5.3b

© 2010 Pearson Education, Inc. ATP AND CELLULAR WORK Chemical energy is –Released by the breakdown of organic molecules during cellular respiration –Used to generate molecules of ATP ATP –Acts like an energy shuttle –Stores energy obtained from food –Releases it later as needed

© 2010 Pearson Education, Inc. The Structure of ATP ATP (adenosine triphosphate) –Consists of adenosine plus a tail of three phosphate groups –Is broken down to ADP and a phosphate group, releasing energy ATP energizes other molecules by transferring phosphate groups. This energy helps cells perform –Mechanical work –Transport work –Chemical work Blast Animation: Structure of ATP

© 2010 Pearson Education, Inc. The ATP Cycle Cellular work spends ATP. ATP is recycled from ADP and a phosphate group through cellular respiration. A working muscle cell spends and recycles about 10 million ATP molecules per second. Blast Animation: ATP/ADP Cycle

Cellular respiration: chemical energy harvested from fuel molecules Energy for cellular work ATP ADP P Figure 5.6

© 2010 Pearson Education, Inc. ENZYMES Metabolism is the total of all chemical reactions in an organism. Most metabolic reactions require the assistance of enzymes, proteins that speed up chemical reactions. Every enzyme is very selective, catalyzing a specific reaction. Each enzyme recognizes a substrate, a specific reactant molecule. –The active site fits to the substrate, and the enzyme changes shape slightly. –This interaction is called induced fit.

© 2010 Pearson Education, Inc. Activation Energy Activation energy –Activates the reactants –Triggers a chemical reaction Enzymes lower the activation energy for chemical reactions. Blast Animation: How Enzymes Work: Activation Energy

The Process of Science: Can Enzymes Be Engineered? Observation: Genetic sequences suggest that many of our genes were formed through a type of molecular evolution. Question: Can laboratory methods form new enzymes through artificial selection? Hypothesis: An artificial process could modify the gene that codes for lactase into a new gene with a new function. Experiment: Many copies of the lactase gene were randomly mutated and tested for new activities. Results: Directed evolution produced a new enzyme with a novel function. © 2010 Pearson Education, Inc.

Enzymes can function over and over again, a key characteristic of enzymes. Animation: How Enzymes Work

(a) Enzyme and substrate binding normally Substrate Enzyme Active site Figure 5.10a

© 2010 Pearson Education, Inc. MEMBRANE FUNCTION Working cells must control the flow of materials to and from the environment. Membrane proteins perform many functions. Transport proteins –Are located in membranes –Regulate the passage of materials into and out of the cell Animation: Membrane Selectivity

© 2010 Pearson Education, Inc. Passive Transport: Diffusion across Membranes Molecules contain heat energy that causes them to vibrate and wander randomly. Diffusion is the tendency for molecules of any substance to spread out into the available space. Some substances do not cross membranes spontaneously. –These substances can be transported via facilitated diffusion. –Specific transport proteins act as selective corridors. –No energy input is needed.

© 2010 Pearson Education, Inc. Animation: Diffusion Blast Animation: Diffusion Passive transport is the diffusion of a substance across a membrane without the input of energy. Diffusion is an example of passive transport. Substances diffuse down their concentration gradient, a region in which the substance’s density changes. Osmosis and Water Balance The diffusion of water across a selectively permeable membrane is osmosis. Blast Animation: Passive Diffusion Across a Membrane

Hypotonic solutionHypertonic solution Sugar molecule Selectively permeable membrane Osmosis Figure

Hypotonic solutionHypertonic solution Sugar molecule Selectively permeable membrane Osmosis Isotonic solutions Osmosis Figure

© 2010 Pearson Education, Inc. A hypertonic solution has a higher concentration of solute. A hypotonic solution has a lower concentration of solute. An isotonic solution has an equal concentration of solute.

© 2010 Pearson Education, Inc. Plant have rigid cell walls. Plant cells require a hypotonic environment, which keeps these walled cells turgid. Water Balance in Plant Cells Video: Plasmolysis

Animal cell Plant cell Normal Flaccid (wilts) Lysing Turgid Shriveled Plasma membrane H2OH2O H2OH2O H2OH2OH2OH2O H2OH2O H2OH2O H2OH2O H2OH2O (a) Isotonic solution (b) Hypotonic solution (c) Hypertonic solution Figure 5.14

Animal cell Plant cell Normal Flaccid (wilts) H2OH2O H2OH2O H2OH2O H2OH2O (a) Isotonic solution Figure 5.14a

Lysing Turgid H2OH2O H2OH2O (b) Hypotonic solution Figure 5.14b

Shriveled Plasma membrane H2OH2O H2OH2O (c) Hypertonic solution Figure 5.14c

© 2010 Pearson Education, Inc. As a plant cell loses water, –It shrivels. –Its plasma membrane may pull away from the cell wall in the process of plasmolysis, which usually kills the cell. Video: Turgid Elodea

Figure 5.15

Active Transport: The Pumping of Molecules Across Membranes Active transport requires energy to move molecules across a membrane. © 2010 Pearson Education, Inc. Animation: Active Transport Blast Animation: Active Transport: Sodium-Potassium Pump

Exocytosis and Endocytosis: Traffic of Large Molecules Exocytosis is the secretion of large molecules within vesicles. © 2010 Pearson Education, Inc. Animation: Exocytosis Animation: Exocytosis and Endocytosis Introduction Blast Animation: Endocytosis and Exocytosis

© 2010 Pearson Education, Inc. Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane. Animation: Receptor-Mediated Endocytosis Animation: Pinocytosis Animation: Phagocytosis

© 2010 Pearson Education, Inc. There are three types of endocytosis: –Phagocytosis (“cellular eating”); a cell engulfs a particle and packages it within a food vacuole –Pinocytosis (“cellular drinking”); a cell “gulps” droplets of fluid by forming tiny vesicles –Receptor-mediated endocytosis; a cell takes in very specific molecules The plasma membrane helps convey signals between –Cells –Cells and their environment

Evolution Connection: The Origin of Membranes Phospholipids –Are key ingredients of membranes –Were probably among the first organic compounds that formed before life emerged –Self-assemble into simple membranes © 2010 Pearson Education, Inc.

Figure 5.20