Exam 2 Study Guide Energy and the laws of thermodynamics Metabolism all of an organism s chemical reactions emergent property o Bioenergetics the study of how organisms manage their energy resources o Metabolic pathways alteration of molecules in steps Catabolic pathways breakdown of complex molecules into simpler ones release energy Anabolic pathways build complex molecules from simpler ones consume energy Energy the capacity to do work the energy released by catabolic pathways drives anabolic pathways o Chemical energy form of potential energy in molecules because of the arrangement of atoms Thermodynamics study of energy transformations o First law of thermodynamics energy can be transferred or transformed but can not be created or destroyed o Second law of thermodynamics every energy transfer or transformation increases entropy of the universe Entropy a measure of disorder or randomness the more Free energy measure of the amount of work that can be extracted random the greater the entropy from a system to preform work o Free energy change portion of a system s energy that is able Exergonic reaction chemical reaction where energy is released Endergonic reaction reactions that absorbs energy from the surroundings to proceed Adenosine triphosphate energy of the cell made up of adenine ribose 3 phosphate groups Energy coupling the use of exergonic process to drive an endergonic process o Phosphorylated intermediate recipient molecule that receives a phosphate from ATP making it more reactive than the original molecule Enzymes and catalysis Catalyst chemical agent that changes reaction rate without being consumed by the reaction changed o Activation energy energy required to break bonds in the reactant molecules and start a reaction o Enzyme a catalytic RNA protein encoded by genes Substrate the reactant an enzyme acts on Product what the substrate is converted to Active site region of the enzyme where the substrate binds to enzymes catalytic center Conformational change alteration in the shape usually the tertiary structure of a protein or the binding of a ligand to a receptor or binding of substrate to an enzyme Evolution changed in genes lead to changes in amino acid composition of an enzyme and may result in novel enzyme activity or altered substrate specificity under new environmental conditions a novel form of an enzyme might be favored Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and affects the protein s function at another site may inhibit or stim Feedback inhibition a method of metabolic control in which a product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway Negative feedback homeostasis is the consequence of self regulating control system that operates the mechanism Positive feedback a process that causes movement from the normal state stimulate still other changes Cooperativity binding of a substrate to one polypeptide of a protein triggers a favorable conformational change to all other subunits of the enzyme Passive membrane transport Diffusion molecules tend to spread out in available space due to kinetic energy the rate depends on the concentration gradient and molecular size o Concentration gradient what a substance diffuses down to in the absence of other forces substance diffuses from regions of high concentration to low concentration Selective permeability allows certain molecules or ions to pass through it by means of active or passive transport Passive transport a movement of biochemical and other atomic or molecular substances across cell membranes without need of energy input Osmosis diffusion of water across a selectively permeable membrane that continues until solutions are isotonic special case of passive transport o Hypertonic higher solute concentration o Hypotonic lower solute concentration o Isotonic solutions with equal solute concentrations Facilitated diffusion the process of spontaneous passive transport as opposed to active transport of molecules or ions across a biological membrane via specific transmembrane integral proteins Active Membrane transport Active transport uses energy to move molecules and ions across the plasma membranes against the concentration gradient Sodium potassium pump a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into it Proton pump integral membrane protein that is capable of moving protons across a biological membrane Electrogenic pump transports ions across membrane generates unequal distribution of cations and anions Membrane potential cells maintain a voltage across plasma membrane Electrochemical gradient driving force for passive transport of ions across cell membrane sum of concentration gradient and membrane potential o Cotransport coupling of the downhill diffusion of one substance to the uphill transport of an other against its own concentration gradient Bulk transport The movement of macromolecules such as proteins or polysaccharides into or out of the cell o Vesicle a small structure within a cell consisting of fluid enclosed by a lipid bilayer o Exocytosis secretion export from cell where vesicles are moved to the plasma membrane and lipid bilayers fuse and spill contents of vesicle to the outside o Endocytosis cell imports from macromolecules etc by forming a pocket which pinches in to form new vesicles from the plasma membrane Phagocytosis a type of endocytosis where the cell engulfs a particle by extending pseudopodia around it and packaging it in a large vacuole and then the contents of a vacuole are digested non specific process Pinocytosis second type of endocytosis where the cell creates a vesicle around a droplet of extracellular fluid non specific process Receptor mediated endocytosis triggered when specific extracellular molecules ligands bind to receptor molecules proteins on membrane surface where the ligand binding triggers the formation of a vesicle very specific process Receptor protein molecule that receives chemical signals from outside a cell Ligand a molecule that binds specifically to another molecule or receptor cite Cell Structure and Organization Cytoplasm a thick solution that fills each cell and is enclosed by the o Cytosol semifluid aqueous substance of the cytoplasm Ribosome protein synthesis machinery instructions are in genes Prokaryotic cell small simple cell organisms with DNA in the cell membrane nucleoid o Domains Bacteria
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