BIG IDEA IV Biological systems interact, and these systems and their interactions possess complex properties. Enduring Understanding 4.B Competition and cooperation are important aspects of biological systems. Essential Knowledge 4.B.1 Interactions between molecules affect their structure and function. PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Essential Knowledge 4.B.1: Interactions between molecules affect their structure and function. Learning Objectives: (4.17) The student is able to analyze data to identify how molecular interactions affect structure and function.
Change in the structure of a molecular system may result in a change of the function of the system. Consider the following molecular system: Signal transduction begins with the recognition of a chemical messenger, a ligand, by a receptor protein. A receptor protein recognizes signal molecules, causing the receptor protein to change shape, which initiates transduction. During transduction, the signal is converted to a cellular response whereby signaling cascades relay signals from receptors to cell targets. This generally involves protein modifications or phosphorylation cascades that lead to a cellular response within the cytosol or nucleus. A change in the structure of any part of this particular molecular system will change the function of the overall system.
The shape of enzymes, active sites and interaction with specific molecules are essential for basic functioning of the enzyme. http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html
A B C D Transition state A C B D E A Reactants A C B D G < O Products Progress of the reaction
Course of reaction without enzyme Reactants Course of reaction with enzyme E A without enzyme E A with enzyme is lower G is unaffected by enzyme Progress of the reaction Products
Substrate Specificity of Enzymes The reactant that an enzyme acts on is called the enzyme s substrate. The enzyme binds to its substrate, forming an enzyme-substrate complex. The active site is the region on the enzyme where the substrate binds. Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction.
Substrate Active site Enzyme Enzyme-substrate complex (a) (b)
1 Substrates enter active site; enzyme changes shape such that its active site enfolds the substrates (induced fit). 2 Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. Substrates Enzyme-substrate complex 3 Active site can lower E A and speed up a reaction. 6 Active site is available for two new substrate molecules. Enzyme 5 Products are released. 4 Substrates are converted to products. Products
Cofactors and coenzymes affect enzyme function. http://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter6/animations.html Cofactors are small molecules that bind either permanently or reversibly with enzymes and are necessary for enzyme function. They may be inorganic, such as various metal ions, or organic molecules called coenzymes. The interaction between enzymes and their cofactors relates to a structural change that alters the activity rate of the enzyme. The enzyme may only become active when all the appropriate cofactors or coenzymes are present and bind to the appropriate sites on the enzyme.
Cofactors and Coenzymes
Other molecules and the environment in which the enzyme acts can enhance or inhibit enzyme activity. Molecules can bind reversibly or irreversibly to the active or allosteric sites, changing the activity of the enzyme. Enzyme inhibitors selectively disrupt the action of enzymes. Competitive inhibitors compete with the substrate for the active site of the enzyme. Noncompetitive inhibitors bind to a part of the enzyme separate from the active site and change the shape of the enzyme, thus impeding it s action.
(b) Competitive Inhibition: Mimics the substrate and competes for the active site (c) Noncompetitive Inhibition: Binds to the enzyme at a location away from the active site, but alters the shape of the enzyme so that the active site is no longer fully functional.
Regulation of Enzyme Activity Helps Control Metabolism http://bcs.whfreeman.com/thelifewire/content/chp06/0602002.html Chemical chaos would result if a cell s metabolic pathways were not tightly regulated. A cell does this by switching on or off the genes that encode specific enzymes or by regulating the activity of enzymes. Allosteric regulation may either inhibit or stimulate an enzyme s activity. Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and affects the protein s function at another site.
Allosteric enzyme with four subunits Active site (one of four) Regulatory site (one of four) Active form Activator Stabilized active form Oscillation Nonfunctional active site Inactive form Inhibitor Stabilized inactive form (a) Allosteric activators and inhibitors
Cooperativity Cooperativity is a form of allosteric regulation that can amplify enzyme activity. In cooperativity, binding by a substrate to one active site stabilizes favorable conformational changes at all other subunits.
Initial substrate (threonine) Isoleucine used up by cell Isoleucine binds to allosteric site Feedback inhibition Active site available Active site of enzyme 1 no longer binds threonine; pathway is switched off. Intermediate A Enzyme 2 Intermediate B Enzyme 3 Intermediate C Enzyme 4 Intermediate D Enzyme 5 Threonine in active site Enzyme 1 (threonine deaminase) End product (isoleucine)
The change in function of an enzyme can be interpreted from data regarding the concentrations of product of substrate as a function of time. These representations demonstrate the relationship between an enzyme s activity, the disappearance of substrate, and/or the presence of a competitive inhibitor. An enzyme s activity can be affected by: General environmental factors, such as temperature, salinity and ph. Chemicals that specifically influence the enzyme. http://www.sumanasinc.com/webcontent/animations/content/protei nstructure.html
Rate of reaction Rate of reaction Optimal temperature for typical human enzyme Optimal temperature for enzyme of thermophilic (heat-tolerant) bacteria 0 20 40 60 80 100 Temperature (ºC) (a) Optimal temperature for two enzymes Optimal ph for pepsin (stomach enzyme) Optimal ph for trypsin (intestinal enzyme) 0 1 2 3 4 5 6 7 8 9 10 ph (b) Optimal ph for two enzymes
BIG IDEA IV Biological systems interact, and these systems and their interactions possess complex properties. PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Enduring Understanding 4.B Competition and cooperation are important aspects of biological systems. Essential Knowledge 4.B.2 Cooperative interactions within organisms promote Efficiency in the use of energy and matter. Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Essential Knowledge 4.B.2: Cooperative interactions within organisms promote efficiency in the use of energy and matter. Learning Objectives: (4.18) The student is able to use representations and models to analyze how cooperative interactions within organisms promote efficiency in the use of energy and matter.
Organisms have areas or compartments that perform a subset of functions related to energy and matter, and these parts contribute to the whole.
At the cellular level, the plasma membrane, cytoplasm and, for eukaryotes, the organelles contribute to the overall specialization and functioning of the cell. The Whole is Greater than the Sum of its Parts : Cells rely on the integration of structures and organelles in order to function. CELLULAR FUNCTIONS ARISE FROM CELLULAR ORDER the cell is a living unit greater than the sum of its parts!!!
Within multicellular organisms, specialization of organs contributes to the overall functioning of the organism. Illustrative examples include: Exchange of Gases: lungs, trachea, bronchi, diaphragm Digestion of Food: mouth, esophagus, stomach, small intestine, colon, rectum, anus Excretion of Wastes: kidneys, ureters, bladder, urethra For each system, consider the overall function of the system and how the organs are specialized to support that function.
Interactions in Unicellular Communities Interactions among cells of a population of unicellular organisms can be similar to those of multicellular organisms, and these interactions lead to increased efficiency and utilization of energy and matter. Illustrative examples include: Bacterial community in the rumen of animals
Bacterial Communities in the Rumen of Animals
BIG IDEA IV Biological systems interact, and these systems and their interactions possess complex properties. PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Enduring Understanding 4.B Competition and cooperation are important aspects of biological systems. Essential Knowledge 4.B.3 Interactions between and within populations influence patterns of species distribution and abundance. Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Essential Knowledge 4.B.3: Interactions between and within populations influence patters of species distribution and abundance. Learning Objectives: (4.19) The student is able to use data analysis to refine observations and measurements regarding the effect of population interactions on patterns of species distribution and abundance.
Interactions between and within populations influence patterns of species distribution and abundance. Competition, parasitism, predation, mutualism and commensalism can affect population dynamics. Relationships among interacting populations can be characterized by positive and negative effects, and can be modeled mathematically (predator/prey, invasive species). Many complex symbiotic relationships exist in an ecosystem, and feedback control mechanisms play a role in the functioning of the system. Read Articles: Population Interactions & Community Structure Community Structure & Interspecific Interactions
A population of organisms has properties that are different from those of the individuals that make up the population. The cooperation and competition between individuals contributes to these different properties.