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Chapter 5 Test Membranes are composed of:____________________with embedded and attached proteins in a structure called a______________ In animal cell membranes, cholesterol helps: stabilize____________at warm temp, and keep_________________ at lower temperature Membrane proteins perform many functions: Some membrane proteins: -maintain cell shape through attachment to________________and ___________________ - function as____________for chemical messengers from other cells - function as__________ - Membrane glycoproteins are involved on the intercellular junctions that attach_____________to each other - Membranes may exhibit_______________, allowing some substances to cross more easily than others Phospholipids, the key ingredient of___________, spontaneously self-assemble into________________ The formation of membrane-enclosed collections of molecules was a critical step in the evolution of the ___________ _______________is diffusion across a membrane with no energy investment Diffusion –________________________________________________________________ This means that particles diffuse down their__________________________ Eventually the particles reach_________________where the concentration is the same throughout Diffusion across a cell membrane does not require__________so it is called passive transport The concentration gradient itself represents___________________for diffusion Osmosis- ____________________________________________________________________ If a membrane permeable to water (but not to a solute) separates 2 solutions with different concentrations of solute: - Water will cross the______________ Moving down its own_____________________________ Until the solute concentration on both sides is_________ 1 Water balance btwn cells and their surroundings is crucial to organisms Tonicity - ______________________________________________________________________ Tonicity mostly depends on concentration of a____________on both sides of the______________ Isotonic Solution – the concentration of solute is ________________of the membrane and cell volume ___________ change Hypotonic Solution – solute concentration is _________outside cell, water molecules move______ cell, and the cell will _______________ Hypertonic Solution – solute concentration is _________outside of cell, so water molecules move________of cell and the cell will __________ For an animal cell to survive in a hypotonic or hypertonic solution environment, it must engage in Osmoregulation- __________________________ Hydrophobic substances_________diffuse across membrane Polar or charged molecules do not easily cross cell membranes, and instead move across membranes with the help of________________in process called Facilitated Diffusion which: - Does not require_____________ And relies on the_____________ Channel Proteins: proteins that function by becoming a______________for passage of ions or other molecules Carrier proteins: proteins that __________________________________________________________ In both of these situations that protein is specific for the substrate which can be sugars, amino acids, ions, and even water Because water is________, its diffusion through a membrane’s hydrophobic interior is relatively_______ The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an_______________ Cells expend _________in the active transport of a ____________ In active transport, a cell: must expend _______to move a solute against its___________________ A cell uses 2 mechanisms to move large molecules across membranes Exocytosis – ______________________________________________________________________ Endocytosis – _____________________________________________________________________ 2 In both cases, material to be transported is packaged w/in a___________ that fuses with the membrane 3 kinds of endocytosis: Phagocytosis – engulfment of a particle by______________________________, forming a___________ Pinocytosis – is the same thing except that____________are taken into small vesicles Receptor –Mediated Endocytosis: uses___________in a receptor-coated pit to interact with a specific protein, initiating the formation of a_____________ Cells are small units, a chemical factory, housing thousands of chem reactions Cells use these chem reactions for: -Cell______________________ -Manufacture of________________ -And______ replication Energy- _________________________________________________________________ 2 kinds of energy:_________________and_________________________ Heat: type of__________energy; associated with random movement of_______________________ Light: type of_______________energy; can be harnessed to power___________________ Thermodynamics: study of energy______________________ that occur in____________ - Law 1: energy in universe is____________ Law 2: energy conversions increase___________of universe Entropy: measure of__________________ 5.11 chem reactions either release or store energy Cells use oxygen in reactions that____________ energy from fuel molecules In_________________________, the chemical energy stored in organic molecules is converted to a form that the cells can use to perform work Chemical reactions either: Release energy (________________Reactions) Require input of energy and store energy (____________________Reactions) 3 Exergonic Reactions: Release energy in _________________bonds of the____________________ - Burning wood releases energy in Glucose as _________ and ____________ Cellular Respiration : o Involves many steps o Releases energy__________ o Uses some of released energy to produce_____ Endergonic Reactions: Requires________________________; Yields products rich in __________________________ Begins with reactant molecules that contain little _______________________ End with products that contain more_________________________ Photosynthesis: Type of __________________________________process Energy-__________ reactants, ______ and H2O are used Energy is absorbed from ______________ Energy-rich _____________________________ are produced Energy-Coupling: Uses the: Energy released from exergonic reactions to drive_______________________________ Usually using energy stored in______________________ 5.12 ATP drives cellular work by coupling________________ and ___________________ reactions ATP (________________________) powers___________________ Consists of: - Nitrogenous base__________ - 5 Carbon sugar ___________and - 3 _________________ Hydrolysis of ATP releases energy by__________________________________________________to some other molecules in a process called Phosphorylation 4 Most cellular work depends on ATP energizing molecules by ______________________________ Is ATP renewable or non-renewable? List the 3 main types of cellular work:________________________________________________ What drives all three of these types of work? 5.13 enzymes speed up cell’s chem reactions by lowering _____________ Although biological molecules possess much__________energy, it is not released spontaneously An______________ must be overcome before a chem reaction can begin This energy is called the ____________________(EA) Enzymes Function as biological ___________ by lowering _______needed for reaction to begin Increase the __________________without being consumed by the reaction and Are usually____________, although some ___________molecules can function as enzymes An Enzyme: - Is very selective on the _______________it catalyzes Has a shape that determines enzyme’s ______________ The specific reactant that an enzyme acts on is called the enzyme’s __________ A (previous answer) __________fits into a region of the enzyme called the _______________ Enzymes are specific because their ______________fits only specific _________molecules (HINT: both blanks are previous answers) An enzyme’ optimal temp produces the ___________rate of contact btwn the reactants and enzyme’s ________________ The optimal pH for most enzymes is ________________________ Cofactors - ______________________________________________________________________ - Bind to _______________ Function in _______________ If a cofactor is an organic molecule, such as most______________, it is called a ________________ Inhibitor - ___________________________________________________________________ 5 Competitive Inhibitors - block substrates from entering _______________ - reduce enzyme’s _____________________ Non - Competitive Inhibitors - Bind to enzyme somewhere other than active site - Change _________ of active site - Prevent __________ from binding Chapter 5 Test Answers Membranes are composed of: a bilayer of phospholipids with embedded and attached proteins in a structure called a fluid mosaic In animal cell membranes, cholesterol helps: stabilize membranes at warm temp, and keep membrane fluid at lower temperature Membrane proteins perform many functions: Some membrane proteins: -maintain cell shape through attachment to cytoskeleton and extracellular matrix - function as receptors for chemical messengers from other cells - function as enzymes - Membrane glycoproteins are involved on the intercellular junctions that attach adjacent cells to each other - Membranes may exhibit selective permeability, allowing some substances to cross more easily than others Phospholipids, the key ingredient of biological membranes, 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 Passive Transport is diffusion across a membrane with no energy investment Diffusion – tendency of particles to spread out evenly in an available space This means that particles diffuse down their concentration gradient 6 Eventually the particles reach equilibrium where the concentration is the same throughout Diffusion across a cell membrane does not require energy so it is called passive transport The concentration gradient itself represents potential energy for diffusion osmosis- diffusion of water across a selectively permeable membrane If a membrane permeable to water (but not to a solute) separates 2 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 Water balance btwn cells and their surroundings is crucial to organisms Tonicity – term that describes the ability of a solution to cause a cell to gain or lose water Tonicity mostly depends on concentration of a solute on both sides of the membrane Isotonic Solution – the concentration of solute is the same on both sides of the membrane and cell volume won’t change Hypotonic Solution – solute concentration is lower outside cell, water molecules move into cell, and the cell will expand and may burst Hypertonic Solution – solute concentration is higher outside of cell, so water molecules move out of cell and the cell will shrink For an animal cell to survive in a hypotonic or hypertonic solution environment, it must engage in Osmoregulation- the control of water balance Hydrophobic substances easily diffuse across membrane Polar or charged molecules do not easily cross cell membranes, and instead move across membranes with the help of specific transport proteins in process called Facilitated Diffusion which: - Does not require energy - And relies on the concentration gradient Channel Proteins: proteins that function by becoming a hydrophilic tunnel for passage of ions or other molecules Carrier proteins: proteins that bind passenger, change shape, and release their passenger on other side 7 In both of these situations that protein is specific for the substrate which can be sugars, amino acids, ions, and even water Because water is polar, its diffusion through a membrane’s hydrophobic interior is relatively slow The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an aquaporin 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 A cell uses 2 mechanisms to move large molecules across membranes Exocytosis – used to export bulky molecules such as proteins or polysaccharides Endocytosis – used to import substances useful to the livelihood of the cell In both cases, material to be transported is packaged w/in a vesicle that fuses with the membrane 3 kinds of endocytosis: Phagocytosis – engulfment of a particle by wrapping cell membrane around it, forming a vacuole Pinocytosis – is the same thing except that fluids are taken into small vesicles Receptor –Mediated Endocytosis: uses receptors in a receptor-coated pit to interact with a specific protein, initiating the formation of a vesicle Cells are small units, a chemical factory, housing thousands of chem reactions Cells use these chem reactions for: -Cell maintenance -Manufacture of cellular parts -And cell replication Energy- capacity to cause change or to perform work 2 kinds of energy: kinetic and potential Heat: type of kinetic energy; associated with random movement of atoms or molecules Light: type of kinetic energy; can be harnessed to power photosynthesis Thermodynamics: study of energy transformation that occur in matter - Law 1: energy in universe is constant 8 - Law 2: energy conversions increase disorder of universe Entropy: measure of disorder or randomness 5.11 chem reactions either release or store energy Cells use oxygen in reactions that release energy from fuel molecules In cellular respiration, the chemical energy stored in organic molecules is converted to a form that the cells can use to perform work Chemical reactions either: Release energy (Exergonic Reactions) Require input of energy and store energy (Endergonic Reactions) Exergonic Reactions: Release energy in covalent bonds of the reactants - Burning wood releases energy in Glucose as heat and light - Cellular Respiration : o o o Involves many steps Releases energy slowly Uses some of released energy to produce ATP Endergonic Reactions: Requires input of energy; Yields products rich in potential energy Begins with reactant molecules that contain little potential energy End with products that contain more chemical energy Photosynthesis: Type of endergonic process Energy-poor reactants, CO2 and H2O are used Energy is absorbed from sunlight Energy-rich sugar molecules are produced Energy-Coupling: Uses the: Energy released from exergonic reactions to drive essential endergonic reactions 9 Usually using energy stored in ATP molecules 5.12 ATP drives cellular work by coupling exergonic and endergonic reactions ATP (adenosine triphosphate) powers nearly all forms of cellular work Consists of: - Nitrogenous base adenine - 5 Carbon sugar Ribose and - 3 Phosphate Groups Hydrolysis of ATP releases energy by transferring its 3rd phosphate from ATP to some other molecules in a process called Phosphorylation Most cellular work depends on ATP energizing molecules by phosphorylating them Is ATP renewable or non-renewable? Renewable List the 3 main types of cellular work: Chemical; Mechanical; Transport What drives all three of these types of work? ATP 5.13 enzymes speed up cell’s chem reactions by lowering energy barriers Although biological molecules possess much potential energy, it is not released spontaneously An energy barrier must be overcome before a chem reaction can begin This energy is called the activation energy (EA) Enzymes: Function as biological catalysts by lowering EA needed for reaction to begin Increase the rate of a reaction without being consumed by the reaction and Are usually proteins, although some RNA molecules can function as enzymes An Enzyme: -Is very selective on the reaction it catalyzes -Has a shape that determines enzyme’s specificity The specific reactant that an enzyme acts on is called the enzyme’s substrate A (previous answer) substrate fits into a region of the enzyme called the active site 10 Enzymes are specific because their active site fits only specific substrate molecules (HINT: both blanks are previous answers) An enzyme’ optimal temp produces the highest rate of contact btwn the reactants and enzyme’s active site The optimal pH for most enzymes is near neutrality Cofactors – non-protein helpers of enzymes - Bind to active site Function in catalysts If a cofactor is an organic molecule, such as most vitamins, it is called a coenzyme Inhibitor - A chemical that interferes with an enzyme’s activity Competitive Inhibitors - block substrates from entering active site - reduce enzyme’s productivity Non - Competitive Inhibitors - Bind to enzyme somewhere other than active site - Change shape of active site - Prevent substrate from binding 11