Chapter Five Notes September 24th 2012 Biology 108 Test II Notes Defined as the capacity to perform work Kinetic is the energy of motion Potential energy is stored energy What is energy Energy can be changed from one form to another However it cannot be created or destroyed This is the conservation of energy principle Heat is a type of kinetic energy and is a 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 Entropy Chemical Energy Is a form of potential energy Is found in food gasoline and other fuels Living cells and automobile engines use the same basic process to make chemical energy do work Figure 5 3 A and B Food Calories A calorie is the amount of energy that raises the temperature of one gram of water by one degree Celsius Calories are very small units of energy not practical for measuring the energy in food A food calorie C is actually a kilocalorie 1 000 calories The Calories in Food Foods with the most C H bonds Store the most potential energy Have the most calories Make the most ATP Cellular Respiration Is the energy releasing chemical breakdown of fuel molecules Provides energy for the cell to do work A series of energy transferring chemical reactions The chemical bonds in food are broken down The energy in those bonds is shifted to the bonds in ATP ATP is the energy currency in all cells adenosine triphosphate About 40 of the energy in food is transferred to ATP the remainder becomes heat Figure 5 4 KNOW THESE EXAMPLES Motor protein performing mechanical work Transport protein performing chemical work Chemical reactants performing chemical work The ATP Cycle Cellular work spends on ATP ATP is recycled from ADP and phosphate through cellular respiration ATP functions in what is called energy coupling or ATP cycle Figure 5 6 September 26 2012 Metabolism is the sum total of all chemical reactions that occur in organisms Few metabolic reactions occur without the assistance of enzymes Enzymes Activation Energy The energy that activates the reactants in a chemical reaction Triggers a chemical reaction to proceed Enzymes lower the activation energy for chemical reactions Each enzyme is very selective It catalyzes specific reactions Each enzyme recognizes a specific substrate Induced Fit The active site fits to the substrate and the enzyme changes shape slightly The interaction is called induced fit Enzymes can function over and over again This is key characteristic of enzymes Sucrase can accept a molecule of its substrate Substrate binds to the enzyme Enzyme Inhibitors Can inhibit a metabolic reaction Some bind to the active site as substrate imposters Bind at a remote site changing the enzyme s shape The flow of energy The pace of chemical reactions The flow of materials to and from the environment Cells Control Importing nutrients Exporting wastes Working cells must control the flow of materials to and from the environment Membrane proteins help with this task Membrane proteins perform a variety of functions Membrane Function Passive Transport Diffusion Across Membranes Molecules contain heat energy They vibrate and wander randomly Diffusion is one result of the movement of molecules Molecules tend to spread into the available space Diffusion is passive transport no energy is needed Know passive transport and diffusion September 28th 2012 Molecules want to be in equilibrium Another type of passive transport is facilitated diffusion the transport of some substances by specific transport proteins that act as selective corridors Osmosis and Water Balance in Cells Osmosis is the passive transport of water across a selectively permeable membrane Figure 5 13 the word tonic refers to solute 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 Water Balance in Animal Cells The survival of a cell depends on it s ability to balance water uptake and loss In animal cells Normal water concentration is normal hypotonic is lysing and hypertonic is shriveled In plant cells Normal is flaccid hypotonic is turgid and hypertonic is shriveled Control of water balance in animals Osmoregulation Water balance in plant cells is different they have rigid cell walls and are at the mercy of their environment Active Transport The Pumping of Molecules Across Membranes Active transport requires energy to move molecules across a membrane Figure 5 16 Exocytosis and Endocytosis Traffic of Large Molecules Exocytosis secretes substances outside of the cell Endocytosis takes material into the cell Figure 5 17 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 is triggered by the binding of external molecules to membrane proteins Figure 5 19 The Role of Membranes in Cell Signaling Cellular communication begins with the reception of an extracellular signal The signal transduction pathway consists of proteins and other molecules that relay the signal Chapter Six October 1st 2012 Energy Flow and Chemical Cycling in the Biosphere Animals depend on pants to convert solar energy to Chemical energy of sugars Other molecules we consume as food Photosynthesis organic molecules Uses light energy from the sun to power a chemical process that makes Plants and other autotrophs self feeders Make their own organic matter from inorganic nutrients Producers and Consumers Heterotrophs other feeders Include humans and other animals that cannot make organic molecules from inorganic ones Autotrophs are producers because ecosystems depend upon them for food Heterotrophs are consumers because they eat plants or other animals Know the definitions of producers and consumers Glucose Oxygen Carbon Dioxide Water ATP The Metabolic Pathway of Cellular Respiration Carbon Dioxide Water Light Energy Glucose Oxygen Gas The Overall Equation for Photosynthesis Notice that they are the opposite of each other Chemical Cycling between Photosynthesis and Cellular Respiration The ingredients for photosynthesis are carbon dioxide and water CO2 is obtained from the air by a plant s leaves H2O is obtained from the damp soil by a plant s roots Chloroplasts in the cells leave Use light energy to rearrange the atoms Co2 and H2O which produces Sugars such as glucose