Exam II Study Guide NNNN oooo tttt eeee bbbb oooo oooo kkkk MCB 150 CCCCrrrreeee aaaatttt eeee dddd TTTT aaaagggg ssss UUUU RRRRLLLL 10 9 2012 11 14 PM MCB 150 Study Guide 9 17 2012 UUUU pppp dddd aaaatttt eeee dddd 10 15 2012 3 55 PM https www google com search q delta greek letter ie utf 8 oe utf 8 aq t rls Things to know Why does the cell do this Tools to do this What are we going to use this for Lecture Notes The energy needs of a cell are spectacularly high where does that energy come from METABOLISM the sum of all chemical activity in the cell thousands of individual reactions Catabolism takes MCs food and breaks them down releases energy G exergonic final products used as precursors for new MCs Biosynthesis takes precursors and makes macroMCs biosynthetic reactions require energy and get it from catabolic reactions HOW How do we get the energy from our food to use in biosynthesis The Carbon and Hydrogen in food molecules are not in most stable form which makes them reactive Most stable form of carbon is CO2 carbon dioxide BYPRODUCT OF METABOLISM Most stable form of hydrogen is H2O water So in a series of steps reactions large organic MCs glucose are broken down to CO2 and H2O by combining w O The C and H are OXIDIZED called an Oxidation Reaction very EXERGONIC process spread out over multiple reactions 20 to harness more of the energy so its not dissipated as heat each oxidation rx is controlled by a specific enzyme Oxidation reactions involve the REMOVAL of electrons electron are NOT lost instead they are transferred to a MC which is REDUCED OIL RIG Leo the Lion says Ger oxidation and reduction reactions must balance In bio most electrons transferred in redox reactions are in the form of 2 H atoms 2 e s and 2 protons ENERGY IS HELD IN THE TRANSFERRED ELECTRONS recipients of e s in redox reactions are often special molecules associated with enzymes called COFACTORS or COENZYMES UPS truck Molecular UPS trucks these coenzymes are only temporary carriers 2 main coenzymes in bio oxidation accepts 2H NAD reduced to NADH actually accepts 2 electrons and 1 H Nicotinamide Adenine Di Nucleotide FAD reduced to FADH2 accepts 2 H BOTH REDUCTION REACTIONS ARE REVERSIBLE So if cofactors don t keep the energy what happens to it Ultimately all the energy harnessed from the oxidation of food sources is used to make ATP ATP Adenosine Tri Phosphate most common energy currency for the cell Where does the energy in ATP come from Phosphate groups are unstable the NEGATIVE charges repel each other Hydrolysis of ATP to ADP Pi Energy ATP ADP Pi G 7 kcal mol Exergonic and Reversible Side notes 1 Energy currency MC 2 Put it in a growing RNA chain down w an RNA polymerase enzyme How does ATP drive energy requiring reactions ATP hydrolysis is COUPLED to the endergonic reaction The reaction that requires energy uses the energy provided upon hydrolysis of ATP one of them pays for the other A common ex Glucose Glucose 6 Phosphate G 3 ATP ADP Pi 7 Net of these coupled reactions G 4 whatever is left over is released as heat Coupled reactions often showed as insert lecture notes example here So how does the energy from food get to ATP CELLULAR RESPIRATION Breakdown of glucose to CO2 and H2O Multiple reactions in 3 distinct pathways phases Glycolysis Pyruvate Oxidation and the Krebs or Citric Acid Cycle Electron Transport Chain and Oxidative Phosphorylation Let s follow the path of energy and molecules from glucose to ATP 1 Glycolysis First pathway in breakdown of glucose glyco sugar lysis splitting 10 steps glucose 2 3carbon MCs pyruvates Pathway is actually ENDERGONIC up to production of first 3 Carbon MCs uses cell s store of ATP Occurs in the CYTOPLASM of all living cells essential and least different end goal MAKE ATP 2 steps are endergonic 3 steps are exergonic Net Result 2 ADP 2 ATP 4 ATP but net yield is 2 2 NAD 2 NADH Glucose 2 Pyruvate Energy from the first endergonic step harnessed by the transfer of e to NAD Energy not used to directly synthesize ATP but its saved and used later Energy from other exergonic reactions is in the form of Pi which is used to phosphorylate ADP SLP Substrate Level Phosphorylation Where s the source of Energy 1 Coupled reaction to a pathway reaction SUBSTRATE LEVEL PHOSPHORYLATION Stealing a Pi from this substrate to do it 2 Oxidative Phosphorylation Problems at the end of Glycolysis 1 Still aren t at lowest energy state 2 NAD is used up but not recycled and is still holding on to a lot of our energy Three things to think about 1 How is energy in pyruvate released 2 How is NAD replaced 3 How is energy in NADH transferred to ATP W Oxygen Aerobic Respiration W out Oxygen Anaerobic Respiration Fermentation Aerobic Respiration Carbon source 2 MCs of Pyruvate completely converted to CO2 only happens in the presence of oxygen pyruvate molecules are converted to acetyl CoA which then enters the Krebs or Citric Acid Cycle pyruvate shuttle all C H bonds converted to C O bonds 6 CO2 released energy transferred to NAD and FAD makes more NADH and FADH2 another SLP reaction in Krebs cycle GTP is ATP analog Where does aerobic respiration take place Eukaryote Mitochondria Prokaryotes Cytoplasm and Plasma Membrane Parts of the Mitochondria 2 membranes and 4 leaflets Levels of organization from outer to inner Outer Membrane typical protein lipid distribution about 50 50 PORINS a protein like a MC straw not selective Inter Membrane Space composition of ions and small MCs is same as cytoplasm Inner Membrane Principle site of ATP generation 70 protein ETC Electron Transport Chain proteins Impenetrable to ions small MCs except at transporters NO PORINS Cristae folds in the inner membrane Matrix Krebs Cycle enzymes Pyruvate gets brought into the matrix Where DNA is 5 10 small circular MC Mitochondrial DNA 2 Krebs Citric Acid Cycle 1 glucose 2 pyruvate 2 turns in the Krebs Cycle breaking off a C Carbon exergonic Substrate Level Phosphorylation SLP Net Result 6 CO2 8 NADH 2 FADH2 2 GTP which are equivalent in energy to 2 ATP insert lecture notes example here Problems with results of the Krebs Cycle 1 Still haven t replaced NAD in fact more NADH is made 2 Now you have FADH2 that needs to be re oxidized 3 Still haven t transferred energy carried by cofactors to ATP Also why is this dependent on oxygen Aerobic respiration requires oxygen but Krebs cycle itself does not B c Krebs cycle is COUPLED to the third pathway which DOES require Oxygen ETC 3 Electron Transport Chain ETC is a series of