- WELCOME TO LIPIDS PART SEVEN.
NOW, THAT WE KNOW ABOUT BILE SALTS AND LIPOPROTEINS,
WE'RE READY TO LOOK AT THE CATABOLISM
OF FATS AND OILS ALSO KNOWN AS TRIGLYCERIDES.
LET'S GET STARTED. ALL RIGHT.
SO, BY NOW, WE'VE DONE THE CATABOLISM
OF PROTEINS AND CARBOHYDRATES.
SO, YOU'RE STARTING TO RECOGNIZE THE STEPS,
RIGHT, SO, THE FIRST STEP,
HYDROLYSIS, RIGHT, SO,
HYDROLYSIS OF TRIGLYCERIDES, RIGHT,
OR TRIACYLGLYCERIDES, SO MANY NAMES.
NOW, THE PART THAT WILL BE UNIQUE
TO TRIGLYCERIDES IS THE BETA-OXIDATION.
AND SO, THIS HAS TO HAPPEN AFTER THE HYDROLYSIS.
SO, IT'S ACTUALLY THE FATTY ACIDS
THAT UNDERGO THE BETA-OXIDATION.
AND THEN, THE LAST BUT NOT THE LEAST,
WHAT THEY ALL SHARE IS THE ENERGY PRODUCTION.
AND SO, WE WILL LOOK AT THAT IN OUR BIOENERGETICS,
RIGHT, THAT WILL BE THE CITRIC ACID CYCLE
AND THE ELECTRON TRANSPORT CHAIN WITH OXIDATIVE PHOSPHORYLATION.
NOW, YOU MIGHT BE WONDERING, WAIT A MINUTE,
WITH THOSE OTHER BIOMOLECULES,
WE SAID STAGE TWO WAS ACETYL-COA PRODUCTION.
WELL, WHAT WE'LL FIND IN THIS VIDEO IS THE BETA-OXIDATION
OF FATTY ACIDS IS THE ACETYL COA PRODUCTION.
SO, WE'LL EXPLORE THAT LATER IN THE TUTORIAL.
ALL RIGHT.
SO, WE JUST TESTED OUR MEMORY ON OUR UNDERSTANDING.
AND NOW, WE'LL LOOK AT OUR SCHEMATIC, RIGHT?
SO, HERE IS STAGE ONE,
WHERE WE HAVE HYDROLYSIS, RIGHT?
AND SO, RECOGNIZING, RIGHT,
THAT THE TRIGLYCERIDES WILL HYDROLYZE INTO GLYCEROL
AND THE FATTY ACIDS.
SO, THE GLYCEROL WILL FOLLOW ITS OWN PATH TO FORM ACETYL-COA,
AND THEN, THE FATTY ACIDS IS THE PART WE'RE INTERESTED IN HERE,
RIGHT, THAT WILL BE THE BETA-OXIDATION.
SO, THIS IS THE NEW PART THAT WE'LL LEARN IN THIS CHAPTER.
WE'RE NOT GOING TO FOCUS ON HOW GLYCEROL GETS TO ACETYL-COA.
YOU CAN LEARN THAT SOME OTHER TIME, RIGHT?
AND THEN, OF COURSE, THE LAST PART IS STAGE THREE,
WHERE WE HAVE ENERGY PRODUCTION.
ALL RIGHTY.
SO, THINKING ABOUT IT IN WORDS AND THEN, A PICTURE.
SO, LET'S LOOK AT WHAT HAPPENS. ALL RIGHT.
SO, HOW DO WE EAT FATS?
WELL, WE GOT TO CHEW THEM.
SO, WHEN EATEN, FATS PASS THROUGH THE MOUTH UNCHANGED
AND ENTER THE STOMACH. ALL RIGHT.
SO, LET'S COMPARE THIS TO WHAT WE'VE LEARNED ABOUT PROTEINS
AND CARBOHYDRATES, RIGHT?
HOW DOES THIS PROCESS DIFFER THAN CARBOHYDRATES, RIGHT?
SO, REMEMBER THAT CARBOHYDRATES, THEY BEGIN,
UM, DIGESTING IN OUR MOUTH.
ALL RIGHT. SO, YOU WOULD WANT--
AND SO, IN YOUR MIND, YOU SHOULD HAVE THE ENZYME IN MIND,
RIGHT, RIGHT, THIS AMYLASE, RIGHT, SO,
THE AMYLASE IN OUR SALIVA
BEGINS THE BREAKDOWN
OF CARBOHYDRATES WHILE WE'RE CHEWING.
SO, THAT'S WHY WHEN WE'RE LITTLE,
WE GET CONSTANTLY REMINDED TO CHEW OUR FOOD WELL.
HOWEVER, FATS THERE ARE NO SPECIAL ENZYMES IN OUR--
IN OUR SALIVA FOR FATS.
SO, THEY JUST GO STRAIGHT TO THE STOMACH
AND START INTERACTING WITH THE STOMACH ACID.
AND SO, NOW, WE'LL LOOK A LITTLE MORE CLOSELY
AT THE HYDROLYSIS AND TRANSPORT ON THE NEXT PAGE.
ALL RIGHTY.
SO, WE'VE ALREADY LEARNED ABOUT THE HYDROLYSIS
BUT I JUST WANTED TO REMIND YOU,
RIGHT, FOCUS ON THOSE CARBONYL CARBONS.
AND WE RECOGNIZE THE WATER WILL COME IN HERE.
AND THERE WILL BE OUR HYDROLYSIS.
AND, OF COURSE, WE'LL NEED THREE WATER MOLECULES AND AN ENZYME.
AND SO, THEN, WE HAVE OUR GLYCEROL,
RIGHT, AND OUR FATTY ACIDS. OKAY.
SO, NOW, LET'S SEE HOW EVERYTHING FITS TOGETHER, RIGHT?
SO, THE BILE ACIDS OR SALTS AND THE PHOSPHOLIPIDS
THEY HELP TO EMULSIFY THE FATTY ACIDS.
SO, THE LIPASE CAN GET IN THERE AND BREAKDOWN THOSE LIPIDS
INTO THE GLYCEROL AND THE FATTY ACIDS.
SO-- AND EVEN ONCE WE BREAK IT DOWN THIS FAR,
WE STILL, RIGHT,
WE STILL KNOW THAT FATTY ACIDS ARE NOT WATER SOLUBLE,
SO THAT'S WHY WE NEED THOSE ADDITIONAL LIPOPROTEINS.
ALL RIGHT.
SO, THE HYDROPHOBIC LIPIDS GET TRANSPORTED THAT WAY.
SO, THEN, THE HYDROLYSIS CONTINUES UNTIL WE GET SMALLER
FATTY ACIDS AND GLYCEROL WHICH ARE FINALLY WATER SOLUBLE.
AND THEN, THEY CAN BE ABSORBED DIRECTLY
THROUGH THE SURFACE OF THE VILLI THAT LINE OUR SMALL INTESTINES.
AND WE JUST HAVE TO KEEP BREAKING IT DOWN SMALLER
AND SMALLER UNTIL WE GET TO WATER SOLUBLE.
THE CHYLOMICRONS REMEMBER ARE THE LARGEST OF THE LIPOPROTEINS.
AND THEY SURROUND THE STILL INSOLUBLE LARGER FATTY ACIDS
WITHIN THE INTESTINE
TO HELP FACILITATE FURTHER HYDROLYSIS BY THE LIPASES.
ALL RIGHT.
SO, I'VE TALKED ABOUT IT IN A VERBAL DESCRIPTION.
AND THEN, WE CAN SEE EVERYTHING HERE, RIGHT?
SO, THERE'S THE FATS FROM OUR DIET.
THERE'S OUR STOMACH, THE BILE DUCT OF THE--
OFF OF OUR LIVER.
AND THEN, BASICALLY,
EVERYTHING THAT I JUST DESCRIBED VERBALLY IS HERE
FOR YOU IN A DIAGRAM THAT YOU CAN READ AT YOUR LEISURE.
SO, I HIT--
I HIT THE BIG POINTS.
MAYBE I'LL CONNECT THE BIG POINTS TO THE DIAGRAM, RIGHT,
SO, THIS STATEMENT HERE ABOUT THE BILE ACIDS,
RIGHT, THAT FOCUSES RIGHT THERE.
AND THEN, THE TRANSPORT MOLECULES,
RIGHT, FOR TWO AND FOUR.
THE-- A LOT OF THE TRANSPORT MOLECULES
AREN'T SHOWN IN THE DIAGRAM AND THEN,
THE HYDROLYSIS OCCURRING, ALL RIGHT?
SO, THAT WILL HELP CONNECT THE WRITTEN DESCRIPTION
TO THE DIAGRAM. OKAY.
SO, NOW, LET'S GET ON TO THE NEW PART,
FATTY ACID OXIDATION.
SO, THIS IS A VERY INTERESTING PATHWAY
THAT WE'LL LOOK AT RIGHT NOW,
GET IT IN POSITION.
THERE WE GO.
OKAY. ALL RIGHTY.
SO, WHAT HAPPENS HERE IS WE HAVE OUR FATTY ACID.
AND IT'S IN THE CYTOSOL OF THE CELL
AND THE FIRST THING WE NEED TO DO IS ACTIVATE IT.
SO, THE WAY THAT WE ACTIVATE
A FATTY ACID IS WE ARE GOING TO DO A THIOESTER FORMATION.
SO, REMEMBERING, RIGHT, SO,
WE'LL TAKE THE HYDROXYL GROUP HERE.
AND THEN, THE HYDROGEN THERE, RIGHT?
AND WE'RE GOING TO DO THIOESTER FORMATION, RIGHT?
SO, THE PART THAT'S NOT SHOWN
IS THAT WE WOULD ALSO BE PRODUCING WATER.
SO, WE SEE THAT WE CAN LINK THE FATTY ACID TO COENZYME.
HOPEFULLY EVERYBODY LOOKS AT THIS SUBSTANCE
AND SEES COENZYME-A.
AND SO, THEN BASICALLY,
I THINK THIS IS A CUTE NAME, RIGHT?
WE HAVE A FATTY ACYL-COA.
SO, ONCE IT'S BEEN ACTIVATED,
THEN, IT WILL TRANSPORT INTO THE MITOCHONDRIA.
SO, IF WE LOOK HERE, RIGHT, SO,
THE ACTIVATION HAPPENS IN THE CYTOSOL.
AND THEN, IT HAS TO GET TRANSPORTED TO THE MITOCHONDRIA.
AND THEN, WE CAN BEGIN, RIGHT?
SO, THEN BETA-OXIDATION THEN TAKES PLACE
HERE IN THE MITOCHONDRIA.
ALL RIGHT.
SO, LET'S LOOK CLOSELY AT THESE STEPS.
MAYBE WE SHOULD WRITE THAT RIGHT HERE, RIGHT?
SO, THIS IS CYTOSOL
AND THEN, BETA-OXIDATION, MITOCHONDRIA.
ALL RIGHT. OKAY.
SO, NOW, LET'S LOOK AT THE STEPS, SLOWLY.
OH, GOOD, WE CAN JUST FIT IT.
HOORAY. OKAY.
SO, WHAT HAPPENS IN THIS FIRST STEP, RIGHT, WE JUST SAW THAT,
RIGHT, THAT WE'RE HAVING TO USE ENERGY.
WE'RE TAKING TWO SMALL--
SMALLER MOLECULES AND MAKING A LARGER MOLECULE, RIGHT?
SO, THE TYPE OF ENZYME THAT WE WOULD NEED HERE,
RIGHT, WOULD BE A LIGASE, RIGHT,
FROM THE FRENCH LIGARE, LINKING.
AND NOTICE ENERGY REQUIRED, RIGHT, SO, PRACTICING OUR SKILLS
FOR RECOGNIZING ENZYMES.
NOW, LET'S LOOK AT WHAT HAPPENS IN THE NEXT CHANGE.
ALL RIGHT. SO, NOW, WE HAVE OUR ACTIVE FATTY ACID.
AND WHAT IS CHANGING?
WELL, WE LOOK AT THE CARBONYL.
AND THEN, WE NOTICE THE TWO CARBONS NEXT TO THE CARBONYL,
WE NOTICE A LOSS OF HYDROGEN, RIGHT?
WE GO FROM A SATURATED TO AN UNSATURATED GROUP.
ALL RIGHT.
SO, THAT'S THE LOSS OF HYDROGEN.
AND WE RECOGNIZE THAT AS AN OXIDATION.
AND WE NOTICE WE HAVE A COENZYME, RIGHT?
SO, THE FAD IS BEING REDUCED.
SO, WE SEE THAT IN THIS STEP HERE,
WE WOULD NEED AN OXIDOREDUCTASE ENZYME. OKAY.
I THINK THAT'S ENOUGH THERE. ALL RIGHT.
NOW, LET'S LOOK AT THE NEXT STEP.
WHAT HAPPENS IN THE NEXT STEP?
SO, WE FORM THE DOUBLE BOND BY OXIDIZING THESE TWO CARBONS.
AND NOW, WE BRING IN WATER.
AND WHAT DOES THE WATER DO, RIGHT?
THE WATER NOW ADDS ACROSS THE DOUBLE BOND.
SO, WE WOULD DESCRIBE THAT AS A HYDRATION REACTION.
AND SO, THE TYPE OF ENZYME WE WOULD NEED HERE
WOULD BE THE LYASE. OKAY.
WHAT HAPPENS IN THE NEXT STEP?
HERE, WE SEE ON THE CARBON DESCRIBED AS A BETA CARBON
THAT WE HAVE AN ALCOHOL.
WHEN WE LOOK TO THE PRODUCT,
WE SEE THAT WE NOW HAVE A KETONE.
SO, THE SUBSTRATE HAS UNDERGONE OXIDATION.
AND ANYTIME WE HAVE OXIDATION,
WE LOOK AROUND BECAUSE WE KNOW WHAT NEEDS TO BE COMPLEX--
COMPLIMENTED WITH REDUCTION AND TRUE ENOUGH,
WE SEE THAT WE HAVE A REDUCED COENZYME FORMING.
SO, ONCE AGAIN,
WE'RE GOING TO NEED A DIFFERENT OXIDOREDUCTASE ENZYME.
AND THEN, THIS LAST STEP CAN BE A LITTLE
TRICKY BECAUSE IT'S PRETTY BUSY.
SO, LET'S GO THROUGH THIS CAREFULLY.
WE SEE THAT WE HAVE ANOTHER COENZYME-A.
AND WE LOOK AT OUR PRODUCT.
HMM, AND WE SEE THAT IF WE LOOK HERE--
OOPS, OKAY.
WE SEE THERE'S THE 14 CARBONS.
AND THERE IS THE 14 CARBONS.
AND SO, WHAT WE CAN--
AS WE DISCERN HERE WE LOOK AND WE SEE THAT THIS PIECE
OF THE MOLECULE IS GETTING--
PUT TOGETHER TO FORM A THIOESTER WITH HERE.
SO, WE'RE BASICALLY-- WHAT IS THIS?
THIS IS A GIANT ACYL GROUP.
SO, AS WE LOOK AT THIS MOLECULE
WE SEE THAT THIS ACYL GROUP IS BEING TRANSFERRED
FROM THE SUBSTRATE TO THE COENZYME-A.
SO, WE HAVE A ACYL GROUP TRANSFER.
AND THEN, THIS PART OF THE MOLECULE
HERE IS REPRESENTED HERE BACK TO THE ACETYL-COA.
SO, THE ACETYL-COA FORMS HERE.
AND SO, THAT'S HOW WE TALKED ABOUT THAT THE BETA-OXIDATION
WAS ACETYL-COA PRODUCTION.
SO, HERE IS THE ACETYL-COA PRODUCTION
THAT WE THINK OF AS STAGE TWO.
SO, WHAT TYPE OF REACTION HAS OCCURRED?
WE HAD AN ACYL TRANSFER.
AND SO, THE TYPE OF ENZYME
WE WOULD NEED THERE THEN WOULD BE A TRANSFERASE.
AND THEN, THAT STARTS TO EXPLAIN THE SPIRAL,
RIGHT, BECAUSE IF WE LOOK,
WE HAVE OUR ACETYL COA PRODUCTION.
AND THEN, THE ACETYL-COA, RIGHT, IT WILL GO ON, RIGHT,
FOR ENERGY PRODUCTION WITH THE CITRIC ACID CYCLE
AND THE ELECTRON TRANSPORT CHAIN.
AND THEN, WHAT WE HAVE HERE NOW IS WE HAVE A FATTY,
RIGHT, ACYL-COA BUT NOTICE WITH TWO LESS CARBONS.
ALL RIGHT.
SO, WE CAN'T CALL THIS A CYCLE--
OOPS, LET ME SLIDE THIS UP A LITTLE, RIGHT?
SO, IT'S NOT A CYCLIC PATHWAY.
SO, WE SHOW IT AS A SPIRAL BECAUSE WITH EACH TURN,
OUR FATTY ACYL-COA WILL LOSE TWO CARBONS
FOR ACETYL-COA PRODUCTION.
SO, THEN, IT'LL BE TWO CARBONS SMALLER.
SO, THEN, IT'S A DIFFERENT SUBSTRATE
THAT GOES THROUGH THE CYCLE AGAIN,
SPITS OUT ONE MOLECULE OF ACETYL-COA.
NOW, THE FATTY ACYL-COA IS TWO CARBONS SMALLER.
SO, IT'S A-- TECHNICALLY, A DIFFERENT SUBSTRATE.
SO, EACH TIME A FATTY ACYL-COA GOES THROUGH THE ACYL--
EXCUSE ME, THE BETA-OXIDATION CYCLE,
IT'S GOING TO PRODUCE ONE MOLECULE OF ACETYL-COA AND THEN,
A FATTY ACYL-COA WHICH HAS TWO LESS CARBONS.
ALL RIGHT. SO, NOW,
THAT WAS A LOT TO DESCRIBE VERBALLY.
SO, LET'S LOOK AT THE NEXT PAGE,
SO WHERE IT'S DRAWN OUT FOR YOU.
I THINK, IT'LL BE EASIER TO UNDERSTAND.
SO, WHAT I WAS DOING MY BEST
TO EXPLAIN TO YOU WAS CAPTURED HERE, RIGHT?
THAT THE FATTY ACIDS UNDERGO, YOU KNOW,
REPEATING CYCLES OF BETA-OXIDATION
UNTIL WE GET TO THE FINAL FOUR CARBON FATTY ACYL-COA.
WHICH IS THEN CONVERTED INTO TWO ACETYL-COAS, RIGHT?
SO, THE FINAL FOUR MAKES TWO ACETYL-COAS, RIGHT?
SO, FOR EXAMPLE, IF WE STARTED WITH A 16 CARBON FATTY ACID,
AFTER THE FIRST CYCLE, THEN, WE WOULD HAVE
ONE MOLECULE OF ACETYL-COA.
AND THEN, WE'D HAVE 14
AFTER THE NEXT TURN 12, 10, 8, 6, 4. AND THEN,
WHEN WE GET TO THAT LAST, RIGHT,
THIS IS THE LAST STEP HERE, RIGHT, THE LAST CYCLE.
WE HAD FOUR CARBONS.
AND SO, WE'RE GOING TO END UP
WITH TWO MOLECULES OF ACETYL-COA.
SO, A COMMON QUESTION THAT SHOWS UP
ON QUIZZES AND EXAMS IS LIKE HOW MANY TURNS DO WE NEED, RIGHT?
SO, HOW MANY TURNS, RIGHT,
OF THE BETA-OXIDATION CYCLE OR--
A BETA IS NOT-- BECAUSE IT'S NOT--
A CYCLE WOULD BE A-- WOULD BE A RING.
SO, THAT'S WHY THIS IS A SPIRAL, RIGHT?
SO, THERE-- SO, YOU CAN JUST REASON IT THROUGH
OR A SIMPLE ALGORITHM IS YOU WOULD
TAKE THE NUMBER OF CARBONS DIVIDE BY TWO.
AND THEN, SUBTRACT ONE.
AND THIS WOULD GIVE THE NUMBER OF TURNS, RIGHT?
SO, THE NUMBER OF CARBONS IS THE NUMBER OF CARBONS
IN THE FATTY ACID.
SO, FOR THIS EXAMPLE, RIGHT, WE HAD 16 CARBONS.
WE DIVIDE BY TWO.
SO, THAT WOULD BE EIGHT.
AND THEN, WE SUBTRACT ONE.
SO, FOR A 16 CARBON FATTY ACIDS SUCH AS PALMITIC ACID,
WE WOULD NEED SEVEN TURNS OF THE BETA-OXIDATION PATHWAY.
OKAY. AND SO, THEN,
JUST TO KIND OF BRIEFLY WRAP UP BECAUSE THAT'S
WHERE WE'RE HEADED IN THE NEXT SERIES OF TUTORIALS, RIGHT?
STAGE ONE, HYDROLYSIS WHICH WE'RE VERY GOOD AT NOW.
AND THEN, STAGE TWO, WE REALLY FOCUSED HERE
ON THE BETA OXIDATION FOR ACETYL-COA PRODUCTION.
AND THEN, WHERE WE'RE HEADED NEXT
WITH BIOENERGETICS IS THE CITRIC ACID CYCLE
AND THE ELECTRON TRANSPORT CHAIN
WHICH WILL BE STAGE THREE. OKAY.
SO, THAT WRAPS UP OUR TUTORIAL ON FATTY ACID CATABOLISM.
PLEASE TAKE A LITTLE BIT OF TIME NOW
TO REINFORCE YOUR UNDERSTANDING WITH SOME HOMEWORK PROBLEMS.