BIO1113 Study Guide, Chapters 8-12
BIO1113 Study Guide, Chapters 8-12 1113
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Date Created: 09/29/16
Biology Midterm 2 study guide Chapter 8: Metabolism, Enzymes, and Energy Metabolism: the totality of organic reactions in the body that utilize enzymes in its pathway to reach an end goal o Catabolic pathways: breaking down of energy which release chemical energy (chemical potential energy) Cellular respiration o Anabolic pathway: building things by absorbing chemical energy Synthesis of amino acids The energy released from catabolic pathways are used to power the anabolic pathways which is referred to a method of energy coupling. The 1 law of thermodynamics states energy cannot be created or destroyed the 2ndlaw of thermodynamics, in relation to biology, is energy is lost during every reaction in order to increase the entropy (disorder) in the universe Cells cannot perform any kind of reactions if it is in order, therefore multiple processes go on at once to ensure disorder in the cell. The energy the cells uses flows in as light and leaves as heat. Free Energy & Metabolism Free energy: the portion of energy that can be when temperature and pressure is constant throughout the living cell. Symbolizes with a G o Delta G indicates whether a reaction is spontaneous or not. A negative value for delta G means it occurred spontaneously and didn’t require extra energy. A positive value for delta G means it was not spontaneous and required energy. Free energy increase as the cell moves away from equilibrium as when a cell at equilibrium, it cannot perform in cellular work. Hence, at equilibrium, delta G is the 0. Cellular respiration is a way in which it keeps the cell off or equilibrium. Exergonic: a release of free energy ie spontaneous Endergonic: absorbs free energy ie not spontaneous Cellular Work, ATP, & Energy coupling 3 types of cellular work 1. Chemical work: pushing endergonic reactions that do not occur spontaneously 2. Transport work: Pumping of substances across a cell membrane against the direction of spontaneously movement. 3. Mechanical Work: beating of cilia, muscle contractions, and cellular respiration Hydrolysis of ATP release a lot of energy to the surroundings by adding heat. ATP is the cell that gives the most energy. Phosphorylation: transfer of a phosphate group from ATP to some other molecule The phosphorylated intermediate is the recipient of that molecule with the phosphate group covalently added. o ATP hydrolysis changes shapes of molecules by a transport protein via phosphorylated intermediate ATP is regenerated by adding phosphate and ADP Enzymes Enzymes: macromolecules that speed up reactions without it, cell processes will be backed up Speed up reactions by lowering the activation barrier so that cell reaches the transition state faster. o Reactions are started by the reactants absorbing heat from the surroundings. Once enough energy is absorbed to put the cell in the , transition state, the reaction begins. The basic process of an enzyme is as follows: Enzyme + substrate to enzyme substrate complex to enzyme + products All reactions are reversible therefore the ‘to’ represents arrows facing opposite of itself to represent that the reaction can go either way Enzymes usually end in -ase Essentially, a substrate binds to the active site on an enzyme which the alters the shape of the enzyme. The binding of the two is referred to as an induced fit as they become closer together to enhance catalyzing reactions. Catalyzing of reactions is due to the substrate being held in the active site by weak interactions which start the reaction once R groups of amino acids catalyze the substrate. Enzymes work best in optimal conditions such as temperature and Ph which is usually the temp and ph of the body. There are two kinds of enzyme inhibitors: 1. Competitive inhibitors: competes with substrate to bind with the enzyme thus lowering the enzymes productivity. 2. Noncompetitive inhibitors: bind to somewhere on the enzyme other than the active site thus altering the shape of the enzyme which can cause the substrate not to fit in the active site. If the substrate happens to fit, the enzyme will not work efficiently. Cofactors: the inorganic non protein helper for catalytic activities. If an organic molecule, then called a coenzyme. Regulation of Enzyme activity Allosteric regulation: regulatory molecules change shape of enzyme and function by binding somewhere on the enzyme at a different site which affects the activity of another site. One kind deals with regulatory proteins attaching and another kind deals with substrates attaching to enzymes. Cooperativity: a mechanism that amplifies the response of enzymes. Steps of allosteric regulation: 1. Regulatory molecules bind to regulatory site a. Binding of an activator causes a shape with an active site. Binding of an inhibitor causes a shapes with an inactive shape. i. ATP is an inhibitor and ADP is a stimulator When ATP is running out, it send a signal to ADP to make more and when there is enough ATP, ADP attach to enzymes. Feedback inhibition: a metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathways Prevents the cells from using excess energy to make new products. Enzymes can be in fixed locations within cell like mitochondria or in multi enzyme complexes. Chapter 9: Cellular Respiration Chemical energy is stored in food which can be released when it is broken down either using aerobic respiration or anaerobic respiration Energy is harvested by having the electrons stripped from the glucose while traveling with hydrogen. Hydrogen is carried to oxygen using the electron carriers NAD+ (NADH reduced) There are three stages of cellular respiration: 1. Glycolysis a. Happens in the cytosol and it is when the glucose is split into 2 molecules of pyruvate. This whole process yields 2 ATP because it uses 2 ATP but puts out 4 ATP. 2. Pyruvate oxidation a. The 2 pyruvate molecules enter the mitochondria via active transport in which 3 more reactions take place i. COO- is removed thus becoming CO2 ii. Remaining 2 carbons is oxidized which forms NADH iii. Coenzyme A is added to form acetyl COA 3. Citric Cycle a. A series of 8 steps that occur the mitochondrial matrix (stroma) which produce: i. 2 CO2 ii. 1 GTPCATP ? iii. 3 NADH iv. 1 FADH2 It is important to remember that Acetyl COA (conenzyme) goes in and COA and oxaloacetate is recycled. Also that cellular respiration is used to follow the supply and demand of the cell, prevents cell from wasting energy, controls feedback, and makes more ATP. 4. Oxidative phosphorylation a. Generates ATP by adding Phosphate to ATP which occur in a series of 2 steps: i. Electron transport chain a. Electrons are dropped off by NADH and FADH2(the electron carriers) which switch between being oxidized and reduced to accept the electrons b. The final electron acceptor is oxygen which picks up 2H+ to form H20 ii. Chemiosmosis a. Chemiosmosis is the energy coupling mechanism that uses energy to stored in the H+ gradient to drive cellular work. It is also the exergonic (requires energy) flow of electrons to pump H+ across the membrane to created that H+ gradient b. ATP synthase uses the energy of the H+ gradient to power ATP synthesis which is located in the mitochondrial membrane. Hibernation happens due the uncoupling protein which allows H+ to flow down gradient without the need of regenerating ATP. This allows the oxidation of stored fuels without the build up of ATP Anaerobic respiration is different in that fact that it CO2 is the final electron acceptor instead of oxygen as seen in aerobic cellular respiration. a. Fermentation is the process of generating energy without using an electron transport chain or relying on oxygen being the final electron acceptor. This is like glycolysis as it glycolysis and a process to regenerate NAD+ There are two kinds of fermentation: o Alcohol fermentation Pyruvate is reduced to ethanol o Lactic acid Pyruvate is reduced by NADH to produce lactate which muscles cells use when the supply of oxygen cannot keep up with energy demand Biosynthesis: cells need building blocks to make their own molecules which is an anabolic process that uses the energy stores in the carbon skeletons in food. Chapter 10: Photosynthesis Photosynthesis is the process of converting light into chemical energy in the form of glucose. The pigments that absorb this light energy are called chlorophyll which reside in the thylakoid membrane. Redox reactions cause the split of H20, transferred into CO2, then going into sugar making this an endergonic process. Since light is a form of energy, it participates in light reactions to convert light energy to chemical energy which is: 1. H20 is split to provide electrons and H+ 2. NADHP is reduced to NADH 3. ATP is produced 4. O2 is given off The input of light reactions are light, water, ADP and NADHP+ which has an output of 02, ATP, NAPH The Calvin cycle(dark cycle) uses the chemical energy stored up chemical energy in ATP and NADPH to reduce CO2 to sugar (G3P).. It does this in two steps: 1. Carbon fixation a. Rubisco (RuBP carboxylase) attached to CO2 molecules to ribulose bisphosphate (RuBp) 2. Reduction a. The carbon intermediate received the phosphate group from ATP which is then reduced by NADH and loses the phosphate thus making sugar (G3P) 3. Regeneration of CO2 a. ATP is used to rearrange 5 molecules of G3P to regenerate 3 molecules of RuBP The inputs of the Calvin cycle are ATP, NADPH, & CO2 which put out G3P(sugar), ADP, and NADP+ The Calvin cycle occurs in the stroma and must be done 3x in order to get one G3P molecule. Chapter 11: cell communication Cell signaling is the release of receptors that cause a change in the cell that accepts the signal. Local signaling is when messenger molecules are released by signaling cell Paracrine signaling The ability to receive a growth factor signal from a signal in the vicinity. Synaptic signaling A signal causes a trigger of neurotransmitter which diffuse across the membrane. Long distance signaling is when hormones are used to pass a signal Endocrine signaling is when a cell releases hormones that travel through the circulatory system to reach certain target cells A type of local receptor is a growth hormones and a type of long distance receptor is plant growth hormone. The cells of cell signaling: 1. Reception a. The cell detects the signal but the actual reception happens when the signal binds to the receptor protein on the cell’s surface. 2. Transduction a. The binding of the signaling molecules changes the receptor protein in which it begins the signal transduction pathway. The molecules involved in that are relay proteins. 3. Response a. The transduced signal triggers a response which can either be gene expression or a protein.
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