- WELCOME TO CARBOHYDRATES PART FIVE.
IN THIS TUTORIAL, WE'LL START TO LOOK AT THE BREAKDOWN OF SUGARS.
SO, LET'S GET STARTED.
BECAUSE WE'RE TALKING ABOUT THE BREAKDOWN,
WE RECOGNIZE THAT'S CATABOLISM, RIGHT?
WE ALWAYS THINK WHEN WE HEAR THAT WORD WE THINK BREAKDOWN,
RIGHT?
WE CAN THINK EXOTHERMIC, RIGHT?
WHICH LETS US KNOW THAT THIS IS GOING TO BE ENERGY RELEASED,
RIGHT?
SO, WE BREAKDOWN OUR FOOD TO GET ENERGY. OKAY.
SO, THE FIRST STAGE IS HYDROLYSIS.
AND THAT'S BASICALLY LIKE THE OPPOSITE
OF WHAT WE'VE BEEN PRACTICING IN THE EARLIER TUTORIALS.
WE WERE LOOKING AT HOW WE TAKE SIMPLE SUGARS
AND HOOK THEM TOGETHER THROUGH GLYCOSIDIC BONDS
TO MAKE BIGGER AND BIGGER SUGARS.
WELL NOW, WE'RE NOW GOING TO GO THE OTHER WAY.
WE'RE GOING TO BREAK THEM APART.
ONCE WE HAVE THEM INTO GLUCOSE, THEN GLYCOLYSIS HAPPENS.
SO, LET'S LOOK A LITTLE BIT MORE CLOSELY AT THIS CONCEPTUALLY
BEFORE WE DIG IN TO THE CHEMISTRY, RIGHT?
SO, THE FIRST STAGE OF CARBOHYDRATE CATABOLISM
IS DIGESTION.
WE HAVE TO BREAK THE SUGARS INTO SMALLER MOLECULES
FOR ENERGY PRODUCTION.
WITH CARBOHYDRATES, IT'S VERY INTERESTING. WHEN--
YOU KNOW, WHEN WE'VE BEEN NAGGED TO CHEW OUR FOOD
THERE'S A REALLY GOOD REASON FOR THAT.
THE DIGESTION OF CARBOHYDRATES BEGINS IN OUR MOUTH,
NOT ONLY WITH THE PHYSICAL GRINDING AND SOFTENING
THAT OUR SALIVA HAS ALPHA-AMYLASE IN IT,
AN ENZYME, RIGHT?
SO, WHEN WE SEE ASE,
WE RECOGNIZE THAT AS AN ENZYME AND THE ALPHA,
THAT MAKES SENSE, RIGHT?
SO, IT'S GOING TO CLEAVE THOSE ALPHA-GLYCOSIDIC BONDS, RIGHT?
BUT THE INTERESTING THING IS,
AS SOON AS WE SWALLOW THAT MOUTHFUL OF FOOD
AND IT GOES INTO OUR STOMACH,
THE STOMACH ACID DENATURES THE AMYLASE.
SO, INSIDE OUR STOMACHS, CARBOHYDRATES,
NOTHING REALLY HAPPENS THERE.
WE HAVE TO WAIT UNTIL THE CARBOHYDRATES ARE MOVED
ON TO OUR SMALL INTESTINE.
AND THEN, ADDITIONAL RESOURCES OF ALPHA-AMYLASE
AND OTHER ENZYMES ARE SECRETED BY THE, WELL, AMYLASE
FROM THE PANCREAS.
AND THEN, THE SMALL INTESTINE BRINGS IN MALTASE AND SUCRASE
AND LACTASE
TO CONTINUE THE HYDROLYSIS OF THE DISACCHARIDES.
SO, HOPEFULLY THIS WILL--
IT ALWAYS REMINDS ME TO CHEW CAREFULLY.
SO, IN THIS TUTORIAL
WE WILL LOOK AT THE HYDROLYSIS REACTIONS.
AND THEN, WE WILL LOOK MORE CLOSELY AT GLYCOLYSIS.
SO, BASICALLY, THE WHOLE POINT OF HYDROLYSIS IS
TO GET TO GLUCOSE.
TAKING THOSE POLYSACCHARIDES AND BREAKING THEM DOWN INTO GLUCOSE.
ONCE WE HAVE GLUCOSE THEN, WE CAN USE THE GLYCOLYSIS PATHWAY
TO PRODUCE PYRUVATE.
AND THEN, WE'LL SEE THAT PYRUVATE CAN BE CONVERTED
INTO ACETYL-COA
AND IT ENTERS THE CITRIC ACID CYCLE TO PRODUCE CO2
AND REDUCE COENZYMES.
SO, THIS IS A PATHWAY THAT WE WILL BE LOOKING AT MORE CLOSELY
WHEN WE GET TO OUR BIOENERGETICS CHAPTER.
SO, FOR NOW, WE'LL FOCUS ON THE PART UNIQUE TO CARBOHYDRATES,
THE HYDROLYSIS OF CARBOHYDRATES AND GLYCOLYSIS.
THE STAGE THREE IS SHARED BY PROTEINS, CARBOHYDRATES,
AND LIPIDS.
SO, WE'LL WAIT UNTIL WE'VE WORKED THROUGH
ALL OF THESE BIOMOLECULES.
AND THEN, WE'LL LOOK AT THE BIOENERGETICS.
SO, WHERE IS ALL THIS HAPPENING? ALL RIGHT.
WELL, THE HYDROLYSIS, WE'VE ALREADY TALKED ABOUT,
IT'S HAPPENING THROUGH OUR DIGESTIVE SYSTEM.
BUT AT THE CELLULAR LEVEL, GLYCOLYSIS, RIGHT,
GLYCOLYSIS WILL HAPPEN IN THE CYTOPLASM,
SPECIFICALLY IN THE CYTOSOL OF THE CELL.
AND SO, GLYCOLYSIS IS REALLY IMPORTANT
BECAUSE IT'S HAPPENING JUST IN THE FLUID PORTION.
SO, THERE--WE DO HAVE CELLS THAT DON'T HAVE MITOCHONDRIA.
AND WE WILL LEARN THAT MITOCHONDRIA,
THAT IS WHERE STAGE THREE TAKES PLACE.
SO, FOR THE CELLS IN OUR BODY THAT DON'T HAVE MITOCHONDRIA,
GLYCOLYSIS IS A BIG DEAL
BECAUSE THAT IS THE PRIMARY PATHWAY FOR ENERGY PRODUCTION
INSIDE THAT CELL. ALL RIGHT.
SO, WE'VE LOOKED AT CATABOLISM IN TERMS OF WHERE IT'S HAPPENING
IN THE CELLULAR STRUCTURE.
AND TO BE MORE SPECIFIC, TO MAKE SURE EVERYONE KNOWS,
THE MITOCHONDRIA IS RIGHT THERE, SO THAT'S STAGE THREE.
ALL RIGHTY, SO, STEP ONE, WHERE IS THIS HAPPENING IN THE CELL?
STEP TWO, LET'S THINK ABOUT THIS
IN TERMS OF THE BIOCHEMICAL PATHWAYS, RIGHT?
SO, THE CARBOHYDRATES,
WE CAN THINK OF THOSE AS THE POLYSACCHARIDES, RIGHT?
AND SO, STAGE ONE THEN HERE WILL BE THE HYDROLYSIS, RIGHT?
PRODUCING THE MONOSACCHARIDES AND IN PARTICULAR, GLUCOSE.
NOW, WE'RE GOING TO BE TALKING A LOT ABOUT GLUCOSE,
SO IT'S GOING TO BE VERY HANDY JUST TO SYMBOLIZE IT WITH A G.
ALL RIGHT.
SO, THERE IS STAGE ONE.
AND SO, WE'LL TALK ABOUT HYDROLYSIS IN THIS TUTORIAL.
AND THEN, WE'LL LOOK AT GLYCOLYSIS, WHICH IS STAGE TWO.
AND THEN, THE END RESULT OF GLYCOLYSIS, RIGHT,
IS THE PYRUVATE. SO, THAT'S--RIGHT.
AND THEN, WHAT WE SEE, RIGHT, IS--SO, THERE IS CARBOHYDRATES
AND THEN, NOTICE LIPIDS CAN PRODUCE PYRUVATE
OR THEY CAN GO STRAIGHT TO ACETYL-COA.
AND PROTEINS CAN ALSO BE BROKEN DOWN TO PRODUCE PYRUVATE
OR ACETYL-COA.
SO THEN, THAT WILL LEAD US TO THE BIOENERGETICS CHAPTER
WHERE WE'LL FOCUS ON STAGE THREE.
SO, STAY TUNED FOR BIOENERGETICS.
AND FOR STAGE TWO, JUST TO REALLY REINFORCE, RIGHT,
GLYCOLYSIS IS STAGE TWO.
AND WE WILL LOOK AT IT--
WE'LL LOOK AT THE ENTIRE PATHWAY BECAUSE THERE'S 10 STEPS, RIGHT?
SO, THE 10 STEPS, SOMETIMES THEY ARE REALLY OVERWHELMING.
SO, AT A VERY FUNDAMENTAL LEVEL,
JUST KEEP IN MIND GLYCOLYSIS IS D-GLUCOSE TO PYRUVATE
AND ENERGY. ALL RIGHT. OKAY.
SO NOW, LET'S TAKE SOME TIME TO LOOK AT STAGE ONE, HYDROLYSIS.
SO, REMEMBERING, RIGHT, SO, OUR POLYSACCHARIDES
AND KEEP IN MIND, RIGHT, THAT IF WE'RE LOOKING AT STARCH
AND THINGS,
WE'RE LOOKING AT THOSE ALPHA-- THE ALPHA LINKAGES.
THOSE ARE THE ONES THAT WE CAN DIGEST.
AND SO, HERE'S AMYLOSE, A POLYMER.
AMYLASE THE ENZYME, RIGHT, WITH--
AND THIS IS A HYDROLYSIS REACTION.
SO, THERE IS OUR ENZYME. ALL RIGHT.
HERE'S OUR POLYSACCHARIDE.
AND THEN, OF COURSE, OUR WATER BECAUSE THIS IS HYDROLYSIS.
AND SO, WE START TO BREAK APART THE POLYSACCHARIDES
INTO MONOSACCHARIDES, DISACCHARIDES, OLIGOSACCHARIDES,
DEXTRINS.
SO, LET'S PRACTICE THIS.
SO, IN OUR PREVIOUS TUTORIALS, WE LINKED THEM TOGETHER.
NOW, LET'S PRACTICE TAKING THEM APART.
SO, WHENEVER WE'RE WORKING WITH SUGARS,
IT'S ALWAYS A GOOD IDEA TO FIND THE ANOMERIC CARBONS.
THEY HELP US KEEP OUR BEARINGS.
SO, WE LOOK FOR THE CARBONS BONDED TO TWO OXYGENS.
AND THEN, WHEN WE'RE FOCUSING ON THE LEFT, RIGHT,
THINK OF THE ANOMERIC CARBON WAS ALSO THE CARBONYL CARBON,
SO WE CAN TREAT IT THE SAME WAY WE'RE GOING TO BREAK RIGHT HERE,
RIGHT?
SO, HERE'S OUR GLYCOSIDIC BOND
COMING OFF OF THE ANOMERIC CARBON.
AND WE'RE GOING TO BREAK IT RIGHT THERE. OKAY.
SO NOW, IT'S JUST A MATTER OF NOT LOSING ANYBODY. ALL RIGHT.
SO, WE REWRITE THE SUGAR ON THE LEFT,
MAKING SURE WE INCLUDE ALL OF ITS CARBONS.
AND THEN, THERE IS OUR ANOMERIC CARBON.
AND SINCE IT WAS POINTING DOWN,
WE'LL GO AHEAD AND POINT IT DOWN.
AND THEN, WE'LL JUST MAKE SURE THAT WE DON'T LOSE ANY ATOMS.
AND WE MAINTAIN THE STRUCTURE OF THE R GROUP.
NOW HERE, WE BRING IN THE MOLECULE ON THE RIGHT.
AND WE'LL JUST KEEP THE CONFIGURATION THERE.
THERE'S OUR OTHER ANOMERIC CARBON.
HERE IS OUR FLAGPOLE.
AND NOW, JUST--RIGHT, SO CARBON TWO IS DOWN, UP, AND DOWN.
ALL RIGHTY. OKAY.
SO, WE CAN LOOK HERE AND WE SEE,
SO, THIS IS--HOPEFULLY BY NOW, YOU RECOGNIZE THIS AS MALTOSE.
AND WE SEE THAT MALTOSE AND THEN, THESE MONOSACCHARIDES,
BY NOW, YOU SHOULD RECOGNIZE THEM
THAT THEY ARE BOTH D-GLUCOSE.
SO, MALTOSE IS A DISACCHARIDE OF TWO GLUCOSE MOLECULES
AND RECOGNIZING THAT WHEN THE WATER CAME IN--
THINK ABOUT THE WATER.
MAYBE WE SHOULD WRITE THAT OUT, RIGHT?
SO, WATER--IT'S HELPFUL TO THINK OF WATER AS HOH.
SO, HERE WAS THE OH GROUP OF THE WATER.
AND THERE WAS THE HYDROGEN OF THE WATER.
SO, THE WATER CAME IN AND SPLIT APART THE MALTOSE
AND JUST LIKE WITH--SO, THE ANOMERIC CARBON ON THE LEFT,
JUST TAKE ALL YOUR KNOWLEDGE OF CARBONYL CARBONS
AND PUT THE OH WITH THE ANOMERIC CARBON. ALL RIGHTY.
NOW, WE'RE ON FOR A CHALLENGE.
LET'S DO THE HYDROLYSIS OF SUCROSE.
SO, TEST YOUR KNOWLEDGE. CAN YOU DRAW SUCROSE RIGHT NOW?
IF NOT, YOU'LL WANT TO BE ABLE TO BY THE EXAM.
SO, LET'S GO AHEAD AND DRAW IT OUT. ALL RIGHTY.
SO, REMEMBERING THE-- IT'S A-ALPHA, RIGHT?
SO, IF WE THINK ABOUT SUCROSE WRITE IT TO ALPHA ONE, TWO.
SO, THERE IS OUR--RIGHT.
SO, ALPHA ENDS ARE ON THE GROUND.
WE'LL GO AHEAD AND MAKE SURE WE KEEP ALL OUR CARBONS.
NO SENSE LOSING POINTS FOR LOST CARBONS.
AND THEN, WE GO TO THE SECOND CARBON.
AND BY NOW, YOU SHOULD REMEMBER THAT'S FRUCTOSE.
SO, FRUCTOSE IS KIND OF FUNNY
BECAUSE IT HAS THE TWO FLAGPOLES. ALL RIGHTY.
SO, WITH SUCROSE, RIGHT? WE HAVE A GLUCOSE MOLECULE.
SO, DOWN, UP, DOWN.
AND THEN, WE HAVE OUR FRUCTOSE, UP, DOWN. ALL RIGHT.
SO, WE'RE GOING TO BRING WATER IN.
AND WE WOULD HAVE--OUR ENZYME WOULD BE SUCRASE, RIGHT,
THE ASE ENDING TELLS US IT'S AN ENZYME, RIGHT?
SO, WE THINK ABOUT WATER.
REMEMBERING THAT THE HYDROXYL GROUP
WILL GO TO THE FIRST ANOMERIC CARBON
AND THEN, THE SECOND H,
WILL COME OVER HERE TO BOND WITH THE ALCOHOL, RIGHT?
SO, WHEN WE LOOK AT THE BOTTOM CARBOHYDRATE,
IT'S JUST A VERY FANCY ALCOHOL.
SO, THERE'S THE R GROUP. OKAY.
SO, NOW, LET'S--SO, WHEN WE SPLIT THIS APART, RIGHT,
JUST LIKE CARBONYLS,
WE JUST GO IMMEDIATELY TO THE RIGHT OF THE ANOMERIC CARBON.
AND NOW, WE REWRITE THE MOLECULES.
OKAY, SO, HERE, RIGHT AT THIS ANOMERIC CARBON,
THIS IS WHERE THE WATER COMES IN
AND THE HYDROXYL PORTION OF THE WATER
GOES TO THE ANOMERIC CARBON.
FOR THE OTHER MONOMER, GET OUR CARBON SKELETON IN, RIGHT?
SO, WE'RE RIGHT HERE, RIGHT?
SO, THE OXYGEN WAS AN ORIGINAL PART OF THE SUGAR.
AND IT'S THE HYDROGEN FROM THE WATER THAT GOES IN.
AND NOW, WE'LL JUST MAKE SURE THAT WE HAVEN'T FORGOTTEN
ANY OF THE DETAILS. THERE WE GO. OKAY.
SO, WE'VE JUST SHOWN THE HYDROLYSIS
OF A SUCROSE MOLECULE.
SO--AND WE COULD NAME THE PRODUCTS.
WE--BY NOW, WE SHOULD BE ABLE TO RECOGNIZE GOING DOWN,
SO THIS WOULD BE ALPHA D-GLUCOSE.
AND THEN, HERE'S THE OH GROUP IS POINTING UP,
SO THIS WOULD BE BETA D-FRUCTOSE. ALL RIGHTY.
SO, THAT'S STAGE ONE.
SO, STAGE ONE IS THE HYDROLYSIS OF GLYCOSIDIC BONDS.
AND SO, WE PRACTICE THAT SYNTHESIZING THOSE
AND REVERSING THEM.
NOW, WE'LL GO ON TO STAGE TWO OF CARBOHYDRATE CATABOLISM.
AND THAT WILL BE GLYCOLYSIS.
SO, REMEMBER, RIGHT,
THAT WE'RE GOING TO LOOK AT ALL 10 STEPS NOW.
SO, IT CAN BE PRETTY OVERWHELMING BUT IN A NUTSHELL,
IT'S GLUCOSE TO PYRUVATE, RIGHT, PLUS ENERGY, ALL RIGHT.
SO, THAT'S THE BIG PICTURE. NOW, LET'S LOOK AT THE DETAILS.
SO, HERE WE GO. HERE IS OUR BUDDY GLUCOSE.
NOTICE THAT INITIALLY, WE TALKED ABOUT HOW WE GET ENERGY OUT,
BUT INITIALLY WE'RE ACTUALLY HAVING TO USE SOME ATP.
SO, IN THE EARLY STAGES OF GLYCOLYSIS,
WE TALK ABOUT THAT BEING IN ENERGY INVESTMENT PHASE.
BECAUSE WE'RE USING ATP,
SO WE'RE TAKING SOME OF OUR ENERGETIC MOLECULES
AND CONSUMING THEM.
WHAT IS HAPPENING DURING THIS FIRST STEP?
WELL, IF YOU LOOK AT GLUCOSE,
AND WE LOOK AT THE NEXT MOLECULE IN THE PATHWAY,
WE SEE GLUCOSE 6-PHOSPHATE, RIGHT?
SO, GLUCOSE 6-PHOSPHATE, SO WHAT HAPPENED, RIGHT?
WE LOOK AT CARBON 6
AND WE SEE WHAT HAPPENED THAT THE PHOSPHATE GROUP FROM THE ATP
WAS TRANSFERRED TO GLUCOSE.
SO, WE HAD A PHOSPHATE TRANSFER.
NOW, THIS STEP IS NEEDED
BECAUSE GLUCOSE HAS THE ABILITY TO SLIDE IN AND OUT OF THE CELLS
THROUGH THE CELL MEMBRANE.
SO, BY PUTTING ON A PHOSPHATE GROUP, WE ADD CHARGE.
IN OUR NEXT CHAPTER, WE'LL LEARN THAT CELL MEMBRANES
ARE VERY NON-POLAR.
SO, ONCE WE PUT THAT PHOSPHATE GROUP ON THE GLUCOSE MOLECULE,
IT TRAPS THE GLUCOSE IN THE CELL, RIGHT?
SO, NOW, IT'S TRAPPED IN THE CELL.
AND THIS IS GOOD FOR THE CELL
BECAUSE IF THE MOLECULES ARE JUST GOING IN AND OUT AT WILL,
IT'S HARD FOR THE CELL TO, YOU KNOW, KEEP AN INVENTORY.
SO--AND THE TYPE OF--SO, WHAT TYPE OF ENZYME WOULD THIS BE?
THE PHOSPHATE GROUP STARTED HERE AND ENDED HERE.
SO, THIS FIRST REACTION IS A TRANSFERASE REACTION.
SO, WE WOULD NEED A TRANSFERASE ENZYME.
NOW, LET'S LOOK AT STEP TWO, WHAT'S CHANGING THERE?
WELL WE'VE--HERE WE HAVE GLUCOSE 6-PHOSPHATE.
AND NOW, WE HAVE FRUCTOSE 6-PHOSPHATE.
SO, WE KNOW THE RELATIONSHIP BETWEEN GLUCOSE AND FRUCTOSE.
WE SAW THAT EARLIER.
THOSE ARE STRUCTURAL ISOMERS.
SO, BASICALLY, WHAT'S HAPPENED IN STEP TWO
IS WE HAVE DONE AN ISOMERIZATION.
SO, WE WOULD NEED AN ISOMERASE ENZYME
TO CONVERT GLUCOSE 6-PHOSPHATE INTO FRUCTOSE 6-PHOSPHATE.
NOW, WE BRING IN A LITTLE BIT MORE ENERGY
BECAUSE WE ARE USING ATP MOLECULES.
AND SO, WHAT HAPPENS HERE?
NOTICE WE HAVE AN ALCOHOL TO A SECOND PHOSPHATE GROUP.
WE WOULD DESCRIBE THIS AS FRUCTOSE 1, 6-BISPHOSPHATE.
ALL RIGHT, SO, WE DID--WHAT DID WE DO? WE TRANSFERRED, RIGHT?
WE DID ANOTHER PHOSPHATE TRANSFER.
SO, THAT'S GOING TO REQUIRE A TRANSFERASE ENZYME. ALL RIGHTY.
NOW, IN STEP FOUR,
WE ARE GOING TO TAKE THIS VERY LARGE FRUCTOSE
1, 6-BISPHOSPHATE MOLECULE AND WE'RE GOING TO SPLIT IT APART.
NOTICE WHAT HAPPENS HERE. THIS--
IT GET SPLIT INTO A GLYCERALDEHYDE
AND THEN, DIHYDROXYACETONE COMPOUND. ALL RIGHTY.
NOTICE THAT HERE WE HAVE PRETTY MUCH ALL--
AND IF YOU LOOK AT THE CARBON SKELETON AND EVERYTHING,
WE SEE A LOT OF ALCOHOL GROUPS.
NOTICE THAT WE GET THE FORMATION OF CARBONYLS.
SO, IN THIS STEP,
WE SPLIT A LARGE MOLECULE INTO SMALLER MOLECULES
AND WE CREATED DOUBLE BONDS.
SO, THAT'S OUR CLUE THAT WE WOULD NEED A LYASE ENZYME.
WE DIDN'T NEED ANY ATP HERE. AND WATER IS NOT INVOLVED.
THERE'S NO OXIDATION OR REDUCTION.
IT'S ALMOST BY DEFAULT YOU CAN RECOGNIZE
THAT WE WOULD NEED THE LYASE ENZYME HERE
AND THE CARBONYL BOND FORMATION IS THE CLUE. ALL RIGHTY.
NOW, IT'S VERY INTERESTING BUT THESE TWO--
THE TWO PRODUCTS OF THE SPLITTING
OF THE FRUCTOSE MOLECULE,
IF YOU COUNT UP THE ATOMS HERE,
YOU WILL DISCOVER THAT THESE ARE STRUCTURAL ISOMERS.
AND SO, STEP FIVE IS THAT THE GLYCERALDEHYDE 3-PHOSPHATE
IS ABLE TO CONTINUE ON THE GLYCOLYSIS PATHWAY.
SO, STEP FIVE, WE NEED AN ISOMERASE ENZYME
TO CONVERT THE DIHYDROXYACETONE PHOSPHATE
INTO THE GLYCERALDEHYDE 3-PHOSPHATE,
SO THAT GLYCOLYSIS CAN CONTINUE.
THE OTHER CONSEQUENCE HERE IS NOW, ALL OF A SUDDEN,
YOU'LL START TO NOTICE ALL THESE TWO'S IN FRONT OF EVERYTHING,
RIGHT?
BECAUSE WE TOOK ONE BIG MOLECULE,
WE SPLIT IT IN HALF, AND THEN ISOMERIZE.
SO, NOW, WE HAVE TWO GLYCERALDEHYDES.
SO, NOW, EVERYTHING IS DOUBLED.
SO, WE JUST SHOW IT ONCE,
BUT IT'S IMPORTANT TO RECOGNIZE THAT THE PROCESS IS HAPPENING
TO TWO SEPARATE MOLECULES.
SO, WHAT WE CAN NOTE THEN IS, IS THAT FOR EVERY GLUCOSE,
WE'RE GOING TO GET TWO PYRUVATE MOLECULES. ALL RIGHTY.
SO, LET'S GO ON WITH OUR GLYCOLYSIS PATHWAY. OKAY.
SO, IN STEP SIX, WHAT HAS CHANGED?
GLYCERALDEHYDE HERE.
WHAT DO WE HAVE? LET'S SEE HERE.
OH, OKAY.
SO, HERE, WE HAVE AN ALDEHYDE AND YOU'LL NOTICE HERE,
WE HAVE A--WE HAVE A--SOME SORT OF PHOSPHATE ESTER CARBONYL.
AND WE SEE WE HAVE COENZYMES.
SO, OUR COENZYMES ARE REDUCING AND OUR CARBON IS OXIDIZING.
SO, WE WOULD NEED AN OXIDOREDUCTASE ENZYME.
AND THEN, IF WE CONTINUE LOOKING AT THE CHANGES,
NOW WE CAN SEE THAT WE'RE PRODUCING ATP, RIGHT?
SO, THIS IS WHERE WE GET THE ENERGY PAYOFF.
NOW, WE PUT IN ONE,
BUT WE'RE GOING TO GET BACK TWO HERE
BECAUSE WHAT DO WE SEE?
WE HAVE RIGHT THERE THE PHOSPHATE GROUP
IS GETTING TRANSFERRED TO THE ADP.
SO, THIS WOULD BE ANOTHER TRANSFERASE ENZYME.
AND THEN, IF WE LOOK AT STEP EIGHT, WHAT'S HAPPENING THERE?
WE LOOK FOR CHANGES IN THE MOLECULE,
AND WHAT DO WE SEE HERE?
HMM, THIS GROUP IS THE SAME. BASICALLY, WE SWAPPED, RIGHT?
THE ALCOHOL AND THE PHOSPHATE GROUP SWAPPED FROM BEING INSIDE
AND ON THE TERMINAL EDGE.
SO, ANOTHER ISOMERASE ENZYME IS NEEDED.
AND THEN, WE GET--WHAT HAPPENS HERE IS WE GET THE FORMATION.
IF WE LOOK RIGHT HERE, WE HAVE THE ALCOHOL IN A SINGLE BOND.
AND THEN, NOTICE THAT WE FORMED A DOUBLE BOND AND WE LOST WATER,
RIGHT, DEHYDRATION, RIGHT,
WITH CARBON, CARBON DOUBLE BOND FORMATION.
SO, THAT IS A CLUE THAT WE WOULD NEED A LYASE ENZYME.
AND THEN, FOR OUR LAST STEP, WE PRODUCE MORE ATP,
AND IF WE LOOK AT THE CHANGE FROM THE TWO PHOSPHOENOLPYRUVATE
WE SEE WHAT HAPPENED, RIGHT?
WE LOST, RIGHT, WE LOST OUR PHOSPHATE GROUP.
IT GOT TRANSFERRED, RIGHT?
SO, TRANSFERRED TO ADP, RIGHT, TO PRODUCE ATP.
SO, WE GET MORE, RIGHT, SO WE GET MORE ENERGY BACK,
SO ONE LAST TRANSFERASE. ALL RIGHTY. OKAY.
SO, WE'VE GONE THROUGH THE GLYCOLYSIS PATHWAY
IN A LOT OF DETAIL.
AND I'VE HIGHLIGHTED ALL THE IMPORTANT POINTS
THAT I WANT YOU TO KNOW FOR QUIZZES AND TESTS.
AND NOW, WE'LL JUST DO A LITTLE WRAP UP
TO SEE WHAT HAPPENS TO PYRUVATE, RIGHT?
SO, STAGE TWO IS DONE.
BUT WE HAVE THIS LITTLE TRANSITION, RIGHT,
BECAUSE THE PYRUVATE DOESN'T ENTER THE CITRIC ACID CYCLE
DIRECTLY.
SO, LET'S LOOK AT THE FATE OF PYRUVATE.
THERE ARE TWO POSSIBILITIES.
IN ANAEROBIC, OF COURSE, THERE IS NO OXYGEN,
IN AEROBIC, THERE IS.
SO, UNDER AEROBIC CONDITIONS,
THE PYRUVATE WILL FORM ACETYL-COA.
SO, WE CAN LOOK HERE AND WE CAN SEE THAT THIS CARBOXYLATE GROUP,
RIGHT, IS OXIDIZED TO CO2.
SO, THERE'S OUR OXIDATION.
AND IN THE PROCESS WE GET ACETYL-COA
WHICH CAN ENTER THE CITRIC ACID CYCLE, RIGHT?
SO, I'VE DESCRIBED IT TO YOU.
AND THEN, HERE IT IS, PARAPHRASED.
IT TALKS ABOUT RIGHT WHERE IT'S HAPPENING IN THE CELL
AND THAT SORT OF THING, RIGHT?
SO, IN THE MITOCHONDRIAL MATRIX, THE PYRUVATE IS OXIDIZED TO CO2
AND THE ACETYL GROUP GOES TO IT THAT MAY FORM ACETYL-COA.
AND THEN, IT HAS TO DIFFUSE INTO THE MITOCHONDRIA
FROM THE CYTOSOL.
AND THEN, ON THE MITOCHONDRIAL MATRIX,
THAT'S WHERE THE CITRIC ACID CYCLE WILL OCCUR.
AND THAT'S WHAT HAPPENS, RIGHT, WHAT HAPPENS TO THE ACETYL-COA,
IT ENTERS THE CITRIC ACID CYCLE. OKAY.
AND SO, THIS IS WHERE WE'LL GET TO, RIGHT?
SO, THIS WILL ALL BE STAGE THREE.
AND WE'LL TALK ABOUT THAT IN OUR BIOENERGETICS CHAPTER.
SO, THAT--WE'LL GO INTO THAT IN A LOT MORE DETAIL.
IT'S THE ANAEROBIC PART
THAT WE'RE REALLY ONLY GOING TO TALK ABOUT ON THIS PAGE.
AND THEN, IT'S DONE.
SO, IT'S REALLY IMPORTANT TO UNDERSTAND THE FATE OF PYRUVATE.
SO, UNDER ANAEROBIC CONDITIONS, RIGHT,
WE THINK ABOUT THAT AS A REDUCING.
SO, IF WE LOOK OVER HERE, WE HAVE A KETONE, RIGHT?
IT REDUCES TO AN ALCOHOL.
SO, THERE'S OUR REDUCTION REACTION.
AND THAT FORMS LACTATE.
SO, THAT'S WHAT HAPPENS, RIGHT,
IF WE'RE EXERCISING AND WE CAN'T GET ENOUGH OXYGEN
TO OUR MUSCLES, RIGHT,
THE GLYCOLYSIS PRODUCES THE PYRUVATE TO GIVE US ENERGY.
AND IF THERE'S NOT ENOUGH ENERGY AND OXYGEN IN OUR BODY,
WE END UP PRODUCING LACTIC ACID IN OUR CELLS.
AND THAT LEADS TO THE SORENESS WE CAN FEEL--
WE FEEL AFTER HEAVY PHYSICAL EXERTION. ALL RIGHT.
SO, LET'S LOOK A LITTLE MORE CLOSELY, RIGHT?
SO, THE LACK OF OXYGEN
WILL SLOW DOWN THE ELECTRON TRANSPORT CHAIN.
AND THAT'S PART OF STAGE THREE THAT WE'LL TALK ABOUT SOON.
AND THAT--SO, WITHOUT THE ELECTRON TRANSPORT CHAIN
WE GET A BUILD UP OF NADH. AND WE HAVE DECREASING NAD+.
AND WE NEED THAT FOR GLYCOLYSIS.
SO, WITHOUT ANY D+, GLYCOLYSIS CAN'T CONTINUE.
SO, WHAT DOES THE BODY DO?
IT STARTS REDUCING THE PYRUVATE TO PRODUCE ADDITIONAL NAD+,
RIGHT?
SO, HERE'S THE NORMAL GLYCOLYSIS PATHWAY.
SO, WE CAN SEE HOW THEY'RE RELATED.
AND SO, THEN WHAT HAPPENS HERE IS IF WE HAVE TO,
WE'LL REDUCE THE PYRUVATE WHICH HAPPENS HERE TO GET THE NAD+
WHICH THEN CAN BE USED TO FUEL ADDITIONAL GLYCOLYSIS.
ALL RIGHT.
IT'S INTERESTING TO NOTE THAT TISSUES WITH LOW OXYGEN CONTENT
SUCH AS SKELETAL MUSCLES,
THEY PRETTY MUCH RELY ON THE ANAEROBIC--I GOT A TYPO THERE.
THEY RELY ON ANAEROBIC PRODUCTION OF ATP,
BY GLYCOLYSIS.
AND THEN, AS YOU GO INTO YOUR MICRO CLASSES,
YOU'LL LEARN ABOUT HOW BACTERIA
CAN CONVERT PYRUVATE INTO LACTATE
UNDER THESE ANAEROBIC CONDITIONS,
AND THAT'S THE CHEMISTRY BEHIND KIMCHI, SAUERKRAUT,
AND YOGURT WITH THE BACTERIA THAT HAVE THE ENZYMES
FOR THOSE CONVERSIONS.
AND THEN, THOSE OF US THAT ENJOY ALCOHOLIC BEVERAGES, RIGHT,
THE YEAST CAN CONVERT THE PYRUVATE TO ETHANOL AND CO2
UNDER ANAEROBIC CONDITIONS.
SO, THAT CONCLUDES THIS TUTORIAL ON THE FIRST TWO STAGES
OF CARBOHYDRATE CATABOLISM.
AND STAY TUNED FOR OUR BIO ENERGETICS CHAPTER
FOR STAGE THREE.
NOW, WOULD BE A GOOD TIME TO WORK A FEW HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING WITH THESE IMPORTANT CONCEPTS.