- WELCOME TO LIPIDS, PART TWO.
IN THIS TUTORIAL, WE'LL LOOK AT MEMBRANE LIPIDS,
WHICH WAS KIND OF WHERE WE LEFT OFF ON THE LAST ONE
LOOKING AT LIKE THE CIS VERSUS THE TRANS FATS.
LET'S SEE WHY WE CARE ABOUT THAT.
LET'S GET STARTED.
ALL RIGHTY.
SO, MEMBRANE LIPIDS,
THEY'RE A LITTLE MORE COMPLICATED.
THINGS ARE RAMPING UP.
THERE'S THE PHOSPHOLIPIDS AND THE SPHINGOLIPIDS.
AND THEN, WE'LL LOOK BRIEFLY AT CHOLESTEROL.
WE'LL LOOK AT CHOLESTEROL
AND IN MORE DETAIL IN A FUTURE TUTORIAL.
BUT HERE, WE'RE JUST GOING TO LOOK AT CHOLESTEROL
AND HOW IT'S PART OF FORMING THE CELL MEMBRANES.
ALL RIGHTY.
NOW, THE PHOSPHOLIPIDS
AND THE SPHINGOLIPIDS SHARE THREE MAIN QUALITIES.
THEY EACH HAVE A POLAR HEAD, ALL RIGHT?
SO, THE POLAR HEAD TAKES ONE OF TWO STRUCTURAL ARRANGEMENTS
WHETHER IT'S AN AMINO ALCOHOL WITH A PHOSPHATE GROUP OR SUGAR.
THE MAIN THING IS THAT IT'S POLAR.
EITHER IT'S FULLY IONIC, RIGHT,
OR HIGHLY POLAR, RIGHT?
AND WHEN WE THINK ABOUT SUGARS, WE RECOGNIZE, RIGHT,
THAT THERE'S H BONDING, ALL RIGHT?
SO, WE HAVE VERY STRONG
ELECTROSTATIC INTERACTIONS, POLAR.
NEXT COMES THE CARBON BACKBONE,
IT'S DESCRIBED HERE AS THE ALCOHOL.
BUT WE'RE GOING TO THINK OF IT AS THE CARBON BACKBONE.
NOW, IN THE FIRST TYPE OF MEMBRANE LIPID,
WE WILL HAVE THE GLYCEROL BACKBONE, RIGHT?
SO, WE'RE GOING TO SEE THIS IS A VARIATION OF FATS AND OILS,
THE TRIGLYCERIDES.
HOWEVER, WITH THE OTHER TWO TYPE OF MEMBRANE LIPIDS,
THEY HAVE THE SPHINGOSINE,
CARBON BACKBONES.
SO, THE GLYCERIN,
GLYCEROL IS REPLACED WITH SPHINGOSINE.
AND WE CAN NOTICE HERE
THAT THE SPHINGOSINE REPLACES ONE OF THE FATTY ACID CHAINS.
OKAY. SO, LET'S LOOK AT THOSE THEN, RIGHT?
SO, THESE FATTY ACID CHAINS ARE RIGHT HERE, RIGHT?
AND SO, WE CAN SEE WITH THE GLYCEROPHOSPHOLIPIDS
THAT BOTH OF THE HYDROPHOBIC TAILS
COME FROM FATTY ACID CHAINS.
HOWEVER, FOR THE SPHINGOMYELIN, AND THE GLYCOLIPID ONLY
ONE OF THE NON-POLAR TAILS COMES FROM THE FATTY ACID CHAINS,
SINCE ONE OF THEM HAS BEEN REPLACED BY THE SPHINGOSINE.
SO, MAYBE WE SHOULD PUT THAT THERE, RIGHT? OKAY.
SO, THERE WE HAVE IT AS A BLOCK DIAGRAM,
BUT WE WANT TO BE ABLE TO LOOK AT ACTUAL BIOLOGICAL MOLECULES
AND RECOGNIZE THESE THREE COMPONENTS OF MEMBRANE LIPIDS.
SO, NOW, LET'S LOOK AT SOME ACTUAL MOLECULES,
SO WE CAN PRACTICE IDENTIFYING, RIGHT?
SO, HERE WE SEE THE PHOSPHATE GROUP
AND THE AMINO ALCOHOL, RIGHT?
SO, HERE IS OUR POLAR--
THE POLAR HEADS, RIGHT?
AND WE CAN SEE THESE ARE JUST BASICALLY IDENTICAL.
AND THEN, WE LOOK HERE
AND WE RECOGNIZE OUR SUGAR MOLECULE, ALL RIGHT?
SO, YEAH, I WANT TO DO IT LIKE THAT, OKAY, RIGHT?
SO, THERE'S OUR POLAR HEADS.
NEXT, WE WANT TO BE ABLE TO IDENTIFY THE CARBON BACKBONE,
SO FOR THE GLYCEROL PHOSPHOLIPIDS,
RIGHT, IT'S THE GLYCERIN.
HOWEVER, FOR THE SPHINGOMYELIN,
AND THE GLYCOLIPIDS, RIGHT,
IT'S THE SPHINGOSINE.
SO, THERE'S OUR CARBON BACKBONE.
AND THEN, LAST BUT NOT THE LEAST,
WE WANT TO BE ABLE TO SEE THE HYDROCARBON,
OR THE FATTY ACID TAILS--
THE FATTY ACID CHAINS.
OKAY.SO, WE LOOKED AT MEMBRANE PROTEINS LIKE, SCHEMATICALLY.
AND NOW, WE HAVE TAKEN AND APPLIED THAT KNOWLEDGE
OF THE SCHEMATIC STRUCTURE TO ACTUAL MEMBRANE PROTEINS.
NOW, THIS PART MAYBE CAUSING YOU A LITTLE BIT OF CONFUSION.
SO, LET'S LOOK HERE, RIGHT?
SO, FOR PHOSPHOLIPIDS, WE NOTICE THAT THE GLYCEROPHOSPHOLIPID
AND THE SPHINGOMYELIN ARE LUMPED TOGETHER AS PHOSPHOLIPIDS.
AND THIS MAKES SENSE BECAUSE NOTICE
UNDER THIS CLASSIFICATION,
WE'RE FOCUSING ON THE POLAR HEAD.
THESE TWO SHARE THE SIMILAR STRUCTURE OF POLAR HEAD
WHEN COMPARED WITH A GLYCOLIPID.
SO, IF WE'RE LOOKING--
IF WE'RE COMPARING AND CONTRASTING PHOSPHOLIPIDS
TO GLYCOLIPIDS,
RIGHT, WE'RE--
RIGHT, WE'RE LOOKING AT THE POLAR HEADS. OKAY.
IF HOWEVER, WE WANT TO LOOK AT THE OTHER CLASSIFICATION, RIGHT?
SO, NOW, WE SAY THESE ARE BOTH, RIGHT,
SPHINGOMYELIN AND GLYCOLIPIDS ARE BOTH SPHINGOLIPIDS.
BUT THIS IS GLYCEROPHOSPHOLIPID, RIGHT?
SO, WHEN WE DO THIS COMPARISON,
NOW, WHAT ARE WE DOING, RIGHT?
SO, NOW, WE'RE COMPARING THE CARBON BACKBONE.
SO, THE SECOND DISTINCTION, RIGHT,
IT COMES FROM LOOKING AT THE CARBON BACKBONE.
SO, IT JUST DEPENDS ON ONE ASPECT
OF THE CHEMISTRY IS RELEVANT FOR HOW WE GROUP THEM, RIGHT?
SO, GLYCERIN VERSUS SPHINGOSINE
AND IT'S LABELED THERE, GLYCERIN.
OKAY. ALL RIGHTY.
SO, NOW THAT WE HAVE THE BASIC STRUCTURE,
ONE OF THE MOST FREQUENTLY ASKED QUESTIONS
ON QUIZZES AND EXAMS IS,
"CAN YOU DISTINGUISH BETWEEN THESE THREE TYPES
OF MEMBRANE LIPIDS?"
SO, HERE ARE A FEW EXAMPLES FOR YOU, RIGHT?
SO, IF WE LOOK AT THESE THREE,
OH, JUST GET TO THERE, RIGHT?
SO, CLASSIFY THE FOLLOWING MEMBRANE LIPIDS
AS EITHER GLYCEROPHOSPHOLIPIDS, SPHINGOMYELIN,
OR GLYCOLIPID, OKAY?
THERE'S ONE OF EACH, SO FOR THIS FIRST ONE, RIGHT?
IT'S A-- TO ME, IT JUST JUMPS RIGHT OUT,
WOW, THAT'S A SUGAR, RIGHT?
AND WE KNOW BIOCHEMICALLY,
SUGAR IS REPRESENTED WITH THE PREFIX GLYCO.
SO, THE SUGAR MOLECULE IS VERY DISTINCT
FROM ALL OF THE OTHER ASPECTS OF THESE MEMBRANE LIPIDS.
AND SO, THIS ONE IS CLEARLY A GLYCOLIPID.
ALL RIGHT.
LET'S GO TO THE NEXT LIPID.
ALL RIGHT.
SO, NOW, WE SEE, HMM, WE'VE GOT TWO FATTY ACID TAILS,
THEY ARE BOTH ESTERS AND WE CAN SEE HERE,
THERE'S THE GLYCERIN BACKBONE,
RIGHT, GLYCERIN CARBON BACKBONE.
SO, THAT'S THE CLUE WE NEEDED FOR THIS ONE.
WE KNOW THIS NOW AS A GLYCEROL, RIGHT, PHOSPHOLIPID.
SO, MEMBRANE LIPID B IS AN EXAMPLE
OF A GLYCEROPHOSPHOLIPID AND NOW,
IF WE LOOK AT THIS FINAL ONE, ALL RIGHTY, RIGHT?
SO, WE SEE A POLAR HEAD WITH THE PHOSPHATE GROUP.
THERE'S NO GLYCERIN ANYWHERE,
SO WE WANT TO TRAIN OUR EYE TO SEE RIGHT HERE,
HERE IS THE SPHINGOSINE, OKAY?
AND THEN, HERE IS OUR, RIGHT,
THERE'S OUR FATTY ACID CHAIN.
NOTICE THAT ALSO, IT'S AN AMIDE,
RIGHT, AS THE LINKAGE, OKAY.
SO, THIS MEMBRANE LIPID IS DEFINITELY GOING TO BE
A SPHINGOMYELIN, OKAY.
SO, THERE WE GO,
SO WE'VE PRACTICED APPLYING OUR KNOWLEDGE
OF MEMBRANE LIPID FUNCTION.
NOW, TO--
NOW, THAT WE UNDERSTAND ABOUT THE STRUCTURE,
WE CAN START TO LOOK AT THE BIOLOGICAL RULE.
SO, MEMBRANE LIPIDS ARE AMPHIPATHIC,
WHICH MEANS THAT THEY LIKE WATER,
AND OIL, ALL RIGHT?
SO, LET'S SEE HOW THIS WOULD OCCUR.
SO, THE CIRCLES WILL REPRESENT THE POLAR HEADS.
AND SO, RIGHT, SO, THESE POLAR HEADS,
RIGHT, THEY LOVE WATER.
SO, THEY ARE GOING TO ORIENT THEMSELVES TOWARDS OUR AQUEOUS
BODILY FLUIDS, ALL RIGHT?
AND THAT WILL HAPPEN,
SO THEY'RE GOING TO LIKE, RIGHT,
LIKE DISSOLVES LIKE, LIKE WANTS TO BE WITH LIKE.
SO, WE CAN SEE THAT THIS AMPHIPATHIC CHARACTER
LEADS TO THE FORMATION OF THE LIPID BILAYER.
THE POLAR HEADS WANT TO BE INTERACTING WITH THE AQUEOUS
BODILY FLUIDS.
AND THEN, THE NON-POLAR TAILS,
THEY WANT TO BE ASSOCIATED WITH EACH OTHER, RIGHT?
SO, NON-POLAR TAILS INTERACT, ALL RIGHT?
SO, THE CELL MEMBRANE OVERALL IS CONSIDERED NON-POLAR, ALL RIGHT?
SO, MEMBRANES, BECAUSE OF THIS NON-POLAR REGION,
MEMBRANES ARE DESCRIBED AS NON-POLAR.
SO, THAT'S WHY LIKE PEOPLE LIKE PATCHES,
LIKE BIRTH CONTROL PATCHES, RIGHT?
SO, BIRTH CONTROL PATCHES ARE HORMONES
WHICH WE WILL LEARN IN A LATER TUTORIAL ARE NON-POLAR.
SO, WE CAN PUT A PATCH ON THE SKIN
AND THE NON-POLAR CHEMICALS CAN GO RIGHT THROUGH THE MEMBRANE.
AND WE'LL LOOK MORE AT THAT IN FUTURE TUTORIALS.
BUT THE MAIN THING TO KEEP IN MIND
IS THAT WE THINK ABOUT CELL MEMBRANES
AS NON-POLAR BECAUSE OF THIS TAIL REGION.
SO, THE LAST BIT
ON MEMBRANE STRUCTURE IS THE ROLE OF CHOLESTEROL.
SO, CHOLESTEROL HAS MANY ROLES IN THE BODY.
BUT WE COULD THINK ABOUT, RIGHT,
HAVING THESE POLAR HEADS,
RIGHT, AND NON-POLAR TAILS.
THIS IS A VERY FLUID STRUCTURE, RIGHT?
THERE'S NOT A LOT OF RIGIDITY THERE.
AND SO, WHAT HAPPENS THEN IS THE CHOLESTEROL MOLECULE
COMES IN AND KIND OF FIRMS UP,
CREATES SOME STRUCTURAL INTEGRITY
INSIDE THE CELL MEMBRANE.
SO, THAT WILL BE THE CHOLESTEROL.
ALL RIGHTY.
SO, LET'S LOOK AT A LITTLE CLOSER AT CHOLESTEROL, RIGHT?
SO, LET'S CIRCLE THE FEATURE
THAT LETS US KNOW CHOLESTEROL IS A STEROID, RIGHT?
THAT'S DEFINITELY GOING TO BE, RIGHT, THE FOUR FUSES RINGS.
THERE'S THE STEROID FEATURE.
AND THEN, THINKING ABOUT WHAT WE KNOW ABOUT NOMENCLATURE, RIGHT?
LET'S BOX THE STRUCTURAL FEATURE
THAT GIVES CHOLESTEROL ITS SUFFIX, RIGHT?
AND THAT WOULD BE THE ONE ALCOHOL GROUP RIGHT THERE.
ALL RIGHT. SO, NOW, LET'S BRING EVERYTHING
WE KNOW ABOUT THE STRUCTURE OF CELL MEMBRANES TOGETHER.
ALL RIGHTY, RIGHT?
SO, HERE'S OUR PHOSPHOLIPID BILAYER, RIGHT?
HERE ARE ALL THE POLAR HEADS, RIGHT?
SO, THE POLAR HEADS, RIGHT,
THOSE ARE HYDROPHILIC.
SO, THEY WANT TO BE ON THE OUTSIDE,
SO THAT THEY CAN INTERACT WITH OUR AQUEOUS BODILY FLUIDS.
AND THEN, WE HAVE THE HYDROPHOBIC REGION,
RIGHT, IN THE MIDDLE.
AND THEN, CHOLESTEROL, RIGHT,
SO, CHOLESTEROL COMES IN.
AND SO, THESE BIG, LARGE CIRCLES ARE REPRESENTING THE CHOLESTEROL
THAT HELPS TO ADD STRUCTURAL INTEGRITY
AND RIGIDITY TO OUR MEMBRANE.
AND THEN, LET'S THINK ABOUT THE OTHER BIOLOGICAL MOLECULES
THAT WE'VE LEARNED ABOUT ALREADY THIS SEMESTER, RIGHT?
SO, WE KNOW CARBOHYDRATES, RIGHT, THEY'LL FORM SIDE CHAINS.
AND THIS IS TYPICALLY ABOUT COMMUNICATION
AND CHEMICAL RECEPTORS.
AND THEN, WE'VE LEARNED ABOUT PROTEINS, RIGHT?
THE INTEGRAL PROTEINS
THAT WE SEE SEVERAL OF THOSE AND WE RECOGNIZE THOSE ARE GOING--
THOSE ARE ABOUT TRANSPORT OF,
RIGHT, OF SUBSTANCES ACROSS THE MEMBRANE.
SO, BASICALLY, MEMBRANE PROTEINS AND THEN,
THERE'S JUST THE PERIPHERAL PROTEINS.
WE'LL LOOK MORE AT THOSE LATER.
AND THEN, JUST KEEPING THIS ALL IN TOUCH WITH RIGHT
HERE IS THE CELL, RIGHT?
SO, THERE'S THE NUCLEUS OF THE CELL, THE CYTOPLASM,
HERE IS THE CELL MEMBRANE.
SO, IT IS THE BARRIER FOR ALLOWING SUBSTANCES
IN AND OUT OF THE CELL.
AND SO, UNDERSTANDING THE STRUCTURE
OF THE CELL MEMBRANE WILL THEN HELP US UNDERSTAND
HOW SUBSTANCES CAN CROSS THE MEMBRANE,
IN AND OUT OF OUR CELL IN OUR FUTURE VIDEO TUTORIAL.
ALL RIGHTY.
SO, I THINK, THAT WRAP-- THAT WRAPS IT UP.
SO, PLEASE TAKE SOME TIME NOW
TO REINFORCE YOUR UNDERSTANDING WITH SOME HOMEWORK PROBLEMS.