- WELCOME TO PART SIX OF LIPIDS.
THIS WILL BE ANOTHER BRIEF TUTORIAL
TO LOOK AT BILE SALTS AND LIPOPROTEINS.
LET'S GET STARTED.
SO WE REALLY WANT TO TALK ABOUT FAT CATABOLISM,
BUT THE TRICK IS THE,
RIGHT, THE HYDROPHOBIC NATURE
OF FATS AND OILS REQUIRE SOME SPECIAL EMULSIFIERS
AND TRANSPORT MOLECULES,
RIGHT, BECAUSE THEY'RE NOT SOLUBLE
IN OUR AQUEOUS BODILY FLUIDS.
SO UNLIKE THE AMINO ACIDS OR THE PROTEINS
AND AMINO ACIDS AND CARBOHYDRATES,
LIPIDS ARE NOT WATER SOLUBLE,
SO BEFORE WE CAN TALK ABOUT THE CATABOLISM OF FATS AND OILS,
WE NEED TO BE AWARE OF THESE SPECIAL EMULSIFIERS,
WHICH ARE THE BILE SALTS,
AND THE LIPOPROTEINS, WHICH ARE THE TRANSPORT MOLECULES.
SO WE'LL LOOK BRIEFLY AT THOSE.
AND THEN IN THE NEXT TUTORIAL, WE CAN--
THEN WE'RE READY TO TALK ABOUT HOW WE BREAK DOWN
AND DIGEST FATS.
ALL RIGHT.
SO THE BILE SALTS, THEY'RE THE EMULSIFIERS, RIGHT?
THEY HELP THE--
THEY EMULSIFY THE FATTY ACIDS
SO THAT THE ENZYMES FOUND IN THE AQUEOUS FLUIDS
CAN GET IN THERE AND BREAK THOSE LIPIDS
DOWN SO THAT WE CAN USE THEM AS THE ENERGY SOURCE.
SO WHEN YOU THINK ABOUT A BILE SALT,
RIGHT, YOU'RE THINKING ABOUT AN EMULSIFIER.
AND SO NOW, LET'S LOOK AT THE BILE SALT
AND EXPLAIN WHY, RIGHT?
SO AN EMULSIFIER IS SOMETHING THAT HAS A HYDROPHOBIC
AND A HYDROPHILIC PART.
SO BASICALLY, IT CAN ACT AS LIKE A DIPLOMAT BETWEEN THE NONPOLAR
AND THE POLAR REGIONS OF OUR BODY TO HELP MAKE A BRIDGE.
SO WE CAN SEE HERE, RIGHT?
THERE'S OUR STEROID, STEROIDAL RINGS.
SO THIS PART IS NONPOLAR.
SO IT CAN INTERACT WITH THE FATS OR OILS, RIGHT?
SO IT INTERACTS WITH OTHER NONPOLAR HYDROPHOBIC SUBSTANCES.
AND THEN WE CAN SEE THAT THE BILE SALT HAS HYDROXYL GROUPS
AND A FULL CHARGE, RIGHT?
SO ALL OF THESE REGIONS ARE HYDROPHILIC.
SO THEY HELP TO CREATE THE SOLUBILITY
IN THE AQUEOUS BODILY FLUIDS.
SO THAT'S THE MAIN THING ABOUT BILE SALTS.
SO WE KNOW BILE COMES RIGHT FROM OUR GALLBLADDER NEAR--
IN THE LIVER TO HELP US PRIMARILY DIGESTING FATS.
NOW, THE LIPOPROTEINS,
THOSE ARE THE TRANSPORT MOLECULES.
SO THESE ARE--
THEY'RE INTERESTING BECAUSE UNLIKE OUR CELL MEMBRANE,
WHICH WAS A BILAYER, THESE ARE A PHOSPHOLIPID MONOLAYER.
AND WE NEED THAT, RIGHT? IT'S RIGHT THERE.
THE PHOSPHOLIPID BIO OR MONOLAYER,
SO JUST LIKE BEFORE, RIGHT?
THE POLAR HEADS ARE ON THE OUTSIDE.
AND THAT'S WHAT CREATES--
POLAR HEADS, RIGHT, THAT CREATES THE WATER SOLUBILITY, RIGHT?
AND THEY'RE CALLED LIPOPROTEINS
BECAUSE THERE ARE ALSO PROTEINS PRESENT IN THE--
IN THE BARRIER OR THE MONOLAYER,
BUT THEN, RIGHT, BUT THEN THERE'S--
HERE'S ALL THE NONPOLAR TAILS,
AND SO THE NONPOLAR TAILS, RIGHT,
THEY CAN INTERACT WITH ALL OF THE LIPIDS, RIGHT?
SO HERE ARE THE FATS AND OILS,
AND THEIR BREAKDOWN PRODUCTS AS THEY GET SMALLER
AND SMALLER OR AT THE CENTER,
RIGHT, AT CENTER OF LIPOPROTEIN.
SO THE POLAR HEADS CREATE THE WATER SOLUBILITY
SO THERE ARE THESE LITTLE SPHERES AND--
THAT HAVE THE NONPOLAR SUBSTANCES INSIDE,
AND SO THOSE WE CONSIDER THE TRIGLYCERIDES
AND WE'LL ALSO HAVE CHOLESTEROL.
ALL RIGHTY.
SO THEN LET'S LOOK AT--
THERE'S A VARIETY OF LIPOPROTEINS OUT THERE.
SO THE LARGEST, WE CAN SEE THAT THEY'RE RANKED BY SIZE.
SO HERE'S THE SCALE OF SIZE
WITH CHYLOMICRONS OR A FULL MICROMETER,
AND WE CAN LOOK AT THEIR DENSITY,
THEN WE TALK ABOUT THEIR RATIO OF LIPIDS TO PROTEINS,
AND SO THE CHYLOMICRONS,
THEY TRANSPORT THE LARGER LIPIDS,
THE LARGER TRIGLYCERIDES. OKAY.
AND THEN WE--
IT GOES BY DENSITY.
SO THE CHYLOMICRONS JUST GO BY SIZE.
WHEN WE LOOK AT THESE OTHER ONES, VLDL,
VERY-LOW-DENSITY LIPOPROTEIN,
INTERMEDIATE, LOW, AND HIGH DENSITY.
SO WHERE DOES--
WHERE DO THESE DENSITY NAMES COME FROM?
WELL, IF WE LOOK OVER HERE,
WE CAN LOOK AT WHAT HAPPENS TO THE DENSITY
AS WE CHANGE THE LIPID TO PROTEIN RATIO.
SO-- RIGHT?
SO AS THIS NUMBER GOES DOWN,
THAT'S TELLING US THAT WE HAVE LESS LIPIDS.
SO AS WE LOOK HERE,
WE NOTICE THAT THE AMOUNT OF LIPID IS DECREASING.
AND SO THAT WOULD MEAN SIMULTANEOUSLY
THAT THE RATIO OF PROTEIN IS INCREASING.
AND SO AS WE LOOK AT THE--
AS THE LIPID RATIO DROPS,
WHAT HAPPENS TO THE DENSITY,
WE CAN LOOK HERE AND SEE THAT THE DENSITY IS INCREASING.
AND THAT MAKES SENSE, RIGHT?
BECAUSE PROTEINS ARE HIGHLY POLAR AND IONIC,
AND SO THEY'RE GOING TO PACK TIGHTLY TOGETHER.
SO WHAT THIS INFERS IS THAT PROTEINS HAVE HIGHER DENSITY
AND LIPIDS HAVE LOWER DENSITY.
SO IF THERE'S MORE LIPID PRESENT,
IT'S A LOWER DENSITY LIPOPROTEIN.
IF WE HAVE MORE PROTEIN PRESENT, IT BECOMES HIGHER DENSITY.
SO THERE'S AN EXPLANATION OF WHERE THE NAMES COME FROM.
NOW, THESE GROUPS--
SO WE'LL LOOK AT THE LOW DENSITY ONES FIRST.
SO THESE HAVE TO DO WITH TRANSPORTING LIPIDS
FROM THE LIVER. OKAY.
AND SO THERE'S A WHOLE BUNCH MORE,
WHEN WE GET OUR BLOOD WORK DONE,
WE FOCUS ON THE LDL AND THE HDL,
AND SO BECAUSE THE LDL IS A PRIMARY TRANSPORT
FOR THE CHOLESTEROL LIPIDS, RIGHT?
SO REMEMBER TO KEEP IN MIND, RIGHT?
WHEN WE SAY LIPID, IT COULD BE FOR THE TRIGLYCERIDES.
SO, THESE TEND TO BE FOR THE TRIGLYCERIDES,
AND THEN THE VERY LOW DENSITY IS TRANSPORTING CHOLESTEROL
FROM THE LIVER.
THIS ONE IS CHARACTERIZED BY THE NAME--
WE TEND TO CALL IT THE BAD CHOLESTEROL,
JUST TO--
I'M NOT GOING TO--
YOU KNOW, I'M NOT GOING TO PROMOTE A VALUE JUDGMENT
AGAINST THE LIPOPROTEINS,
BUT IF YOU'RE IN CONVERSATION,
THIS IS THE ONE THEY'RE REFERRING TO AS THE BAD ONE.
AND THEN THE HDL IS ALSO RESPONSIBLE
FOR CHOLESTEROL TRANSPORT.
HOWEVER, IT IS THE SCAVENGER.
SO THE HDL, IT'S THE ONE THAT'S TRANSPORTING CHOLESTEROL
FROM DEAD CELLS.
SO IT'S CONSIDERED THE GOOD CHOLESTEROL
BECAUSE IT'S OUT THERE,
YOU KNOW, TAKING CARE OF OUR BLOOD
AND KEEPING EVERYTHING CLEAN,
AND PICKING UP ANY OLD CHOLESTEROL THAT'S NOT NEEDED
FROM DEAD CELLS.
ALL RIGHTY.
SO THAT WRAPS UP OUR TUTORIAL ON BILE SALTS AND LIPOPROTEINS.
AND IT'S JUST REALLY IMPORTANT TO UNDERSTAND
THAT IT'S WITH OUR TRIGLYCERIDES,
OUR FATS AND OILS, THAT WE NEED THESE SPECIAL COMPOUNDS
BECAUSE WE HAVE THE ISSUE OF WATER SOLUBILITY.
PLEASE TAKE THE TIME NOW TO REINFORCE YOUR UNDERSTANDING
WITH SOME HOMEWORK PROBLEMS.