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Enzymes: “Helper” Protein molecules Regents Biology 2009-2010 Flow of energy through life Life is built on chemical reactions Regents Biology Chemical reactions of life Processes of life building molecules synthesis + breaking down molecules digestion Regents Biology + Nothing works without enzymes! How important are enzymes? all chemical reactions in living organisms require enzymes to work building molecules synthesis enzymes enzyme + breaking down molecules digestive enzymes We can’t live without enzymes! enzymes speed up reactions “catalysts” Regents Biology enzyme + Examples synthesis + enzyme digestion enzyme Regents Biology + Enzymes are proteins Each enzyme is the specific helper to a specific reaction each enzyme needs to be the right shape for the job enzymes are named for the reaction they help Oh, I get it! They end in -ase sucrase breaks down sucrose proteases breakdown proteins lipases breakdown lipids DNA polymerase builds DNA Regents Biology Enzymes aren’t used up Enzymes are not changed by the reaction used only temporarily re-used again for the same reaction with other molecules very little enzyme needed to help in many reactions substrate active site Regents Biology product enzyme It’s shape that matters! Lock & Key model shape of protein allows enzyme & substrate to fit specific enzyme for each specific reaction Regents Biology 2 1 3 Regents Biology Enzyme vocabulary Enzyme helper protein molecule Substrate molecule that enzymes work on Products what the enzyme helps produce from the reaction Active site part of enzyme that substrate molecule fits into Regents Biology What affects enzyme action Correct protein structure correct order of amino acids why? enzyme has to be right shape Temperature why? enzyme has to be right shape pH (acids & bases) why? enzyme has to be right shape Regents Biology Temperature Effect on rates of enzyme activity Optimum temperature greatest number of collisions between enzyme & substrate human enzymes 35°- 40°C (body temp = 37°C) Raise temperature (boiling) denature protein = unfold = lose shape Lower temperature T° molecules move slower fewer collisions between enzyme & Regents Biology substrate Temperature reaction rate human enzymes 37° temperature Regents Biology What’s happening here?! How do cold-blooded creatures do it? Regents Biology pH Effect on rates of enzyme activity changes in pH changes protein shape most human enzymes = pH 6-8 depends on where in body pepsin (stomach) = pH 3 trypsin (small intestines) = pH 8 Regents Biology pH intestines trypsin What’s happening here?! reaction rate stomach pepsin 0 1 2 3 4 5 6 pH Regents Biology 7 8 9 10 11 12 13 14 For enzymes… What matters? SHAPE! Regents Biology 2009-2010 Phospholipids Structure Glycerol + 2 fatty acids + phosphate group Functions Component of cell membranes Lipid transport as part of lipoproteins Emulsifiers Phosphatidylcholine Food sources Egg yolks, liver, soybeans, Regents Biology Cell membranes are phospholipid bilayers Regents Biology The basic structural unit of biological membranes is a lipid bilayer Regents Biology Regents Biology Energy. The Cell: Mitochondria & Chloroplasts Regents Biology 2005-2006 Overview Mitochondria & chloroplasts are the organelles that convert energy to forms that cells can use for work mitochondria: from glucose to ATP ATP chloroplasts: from sunlight to ATP & carbohydrates ATP = active energy carbohydrates = stored energy ATP Regents Biology + 2005-2006 Mitochondria & Chloroplasts Important to see the similarities transform energy generate ATP double membranes = 2 membranes semi-autonomous organelles move, change shape, divide internal ribosomes, DNA & enzymes Regents Biology 2005-2006 Mitochondria Function cellular respiration generate ATP from breakdown of sugars, fats & other fuels in the presence of oxygen break down larger molecules into smaller to generate energy = catabolism generate energy in presence of O2 = aerobic respiration Regents Biology 2005-2006 Mitochondria Structure 2 membranes smooth outer membrane highly folded inner membrane the cristae fluid-filled space between 2 membranes internal fluid-filled space mitochondrial matrix DNA, ribosomes & enzymes Why 2 membranes? increase surface area for membranebound enzymes that synthesize ATP Regents Biology 2005-2006 Mitochondria Regents Biology 2005-2006 Membrane-bound Enzymes Regents Biology 2005-2006 Dividing Mitochondria Who else divides like that? Regents Biology What does this tell us about the evolution of 2005-2006 eukaryotes? Mitochondria Almost all eukaryotic cells have mitochondria there may be 1 very large mitochondrion or 100s to 1000s of individual mitochondria number of mitochondria is correlated with aerobic metabolic activity more activity = more energy needed = more mitochondria What cells would have a lot of mitochondria? active cells: • muscle cells Regents Biology • nerve cells 2005-2006 Regents Biology 2005-2006 Regents Biology 2005-2006 Chloroplasts Chloroplasts are plant organelles class of plant structures = plastids amyloplasts store starch in roots & tubers chromoplasts store pigments for fruits & flowers chloroplasts store chlorophyll & function in photosynthesis in leaves, other green structures of plants & in eukaryotic algae Regents Biology 2005-2006 Chloroplasts Structure 2 membranes outer membrane inner membrane internal fluid-filled space = stroma DNA, ribosomes & enzymes thylakoids = membranous sacs where ATP is made grana = stacks of thylakoids Why internal sac membranes? increase surface area for membrane-bound enzymes synthesize ATP Regentsthat Biology 2005-2006 Membrane-bound Enzymes Regents Biology 2005-2006 Chloroplasts Function photosynthesis generate ATP & synthesize sugars transform solar energy into chemical energy produce sugars from CO2 & H2O Semi-autonomous moving, changing shape & dividing can reproduce by pinching in two Who else divides like that? Regents Biology bacteria! 2005-2006 Chloroplasts Why are chloroplasts green? Regents Biology 2005-2006 Regents Biology 2005-2006 Mitochondria & chloroplasts are different Organelles not part of endomembrane system Grow & reproduce semi-autonomous organelles Proteins primarily from free ribosomes in cytosol & a few from their own ribosomes Own circular chromosome directs synthesis of proteins produced by own internal ribosomes Who else has a circular chromosome no bound within a nucleus? bacteria Regents Biology 2005-2006 1981 | ?? Endosymbiosis theory Mitochondria & chloroplasts were once free living bacteria engulfed by ancestral eukaryote Endosymbiont cell that lives within another cell (host) as a partnership evolutionary advantage for both one supplies energy the other supplies raw materials & protection Regents Biology 2005-2006 Endosymbiosis theory Evolution of eukaryotes Regents Biology 2005-2006 Any Questions?? Regents Biology 2005-2006