- WELCOME TO LIPIDS PART 4, DOUBLE CHECK, CHOLESTEROL.
ALL RIGHT.
SO CHOLESTEROL HAS TWO PRIMARY ROLES IN THE BODY.
ONE, TO REINFORCE THE STRUCTURE
OF THE CELL MEMBRANE, AND THE OTHER,
IT'S AN IMPORTANT PRECURSOR TO MANY COMPOUNDS.
LET'S GO AHEAD AND GET
STARTED AND LOOK AT CHOLESTEROL A LITTLE MORE CLOSELY.
ALL RIGHT. SO--
WE'LL ALSO TALK ABOUT SOME OTHER STEROID HORMONES, AS WELL.
ALL RIGHT. SO THIS FIRST ROLE,
WE'VE ALREADY TALKED ABOUT WHEN WE WERE LEARNING ABOUT CELL
MEMBRANES, RIGHT?
THAT THE CHOLESTEROL IS DISTRIBUTED
AMONG THOSE HYDROPHOBIC TAILS OF THE PHOSPHOLIPIDS, RIGHT?
TO HELP MAINTAIN THE STRUCTURE OF THE MEMBRANE.
SO THIS--
THE CELL MEMBRANES ARE VERY BUSY,
SO IT'S HARD TO FIND A GOOD SCHEMATIC.
BUT IF WE LOOK HERE,
THESE LITTLE CIRCLES ARE REPRESENTING CHOLESTEROL.
SO IF WE LOOK CLOSELY,
WE CAN SEE THAT THEY'RE DISTRIBUTED ALL OVER THE INSIDE
OF THE CELL MEMBRANE,
GIVING IT RIGIDITY AND STRUCTURE.
SO-- ALL RIGHT.
AND HERE'S ONE POINTED OUT RIGHT HERE.
ALL RIGHT. SO THEN JUST TO KIND OF GIVE
A BRIEF RECAP OF CELL MEMBRANE STRUCTURE, RIGHT?
SO WE ALWAYS HAVE--
RIGHT, THERE'S THE PHOSPHOLIPIDS
WITH THEIR POLAR HEADS POKING OUT
AND THEIR HYDROPHOBIC TAILS IN THE CENTER.
WE SEE OUR MEMBRANE PROTEINS ACTING AS CHANNELS
AND RECEPTORS.
AND THEN WE CAN NOTICE HERE--
HERE'S A GLYCOLIPID AND WE SEE THESE SUGARS THAT ALSO REACT--
ACT AS RECEPTORS.
SO THAT'S THE MAIN--
THE MAIN PARTS WE NEED TO KNOW ABOUT A CELL MEMBRANE.
SO NOW WE'LL GO ON TO CHOLESTEROL'S OTHER ROLE
IN THE BODY IS THAT BASICALLY IT'S A VERY IMPORTANT
BIOLOGICAL PRECURSOR TO A TON OF IMPORTANT COMPOUNDS.
SO HERE'S OUR BODY CHOLESTEROL.
WE'VE LOOKED AT IT SEVERAL TIMES.
WE RECOGNIZED RIGHT THERE IS THE STEROID RING.
AND THEN WE KNOW IT'S CALLED CHOLESTEROL
BECAUSE OF THAT ALCOHOL FUNCTIONAL GROUP.
SO WE'LL STUDY BILE ACIDS MORE CLOSELY IN A FUTURE VIDEO
BUT THEY ARE MADE FROM CHOLESTEROL.
VITAMIN D, WE ALL KNOW ABOUT THAT.
IT'S IMPORTANT FOR STRONG TEETH AND BONES.
AND IF WE DON'T HAVE ENOUGH OF IT, WE GET RICKETS.
AND THEN, OF COURSE, THE HORMONES WHICH ARE--
FOR THE MOST PART ARE STEROID BASED.
SO LET'S LOOK A LITTLE CLOSE--
MORE CLOSELY NOW AT CHOLESTEROL AND ITS ROLE AS A PRECURSOR.
SO WE HAVE THE STRUCTURE ONE MORE TIME.
AND WE'LL SEE THAT THE CHOLESTEROL IS THE PRECURSOR
FOR FIVE DIFFERENT CLASSES OF STEROID HORMONES.
SO HERE'S CHOLESTEROL, RIGHT?
SO WE JUST WANT TO TRAIN OUR EYE
TO LOOK FOR THE FEW STEROID RINGS,
THE FOUR FEW STRINGS.
AND THEN WE'LL LOOK A LITTLE MORE CLOSELY.
SO WHAT ARE THESE OTHER FIVE CLASSES OF HORMONES THAT WE--
THAT CHOLESTEROL WILL BE USED TO SYNTHESIZE?
SO WE HAVE THE GLUCOCORTICOIDS.
AND AS YOU WOULD IMAGINE, RIGHT,
IT'S RELATED TO CARBOHYDRATES
BUT ALSO PROTEIN AND LIPID METABOLISM.
THERE ARE ALSO VERY POWERFUL ANTI-INFLAMMATORY
AND IMMUNOSUPPRESSANT AGENTS.
AND THEN WE HAVE THE MINERALOCORTICOIDS.
AND SO AS THEIR NAME WOULD IMPLY, RIGHT, MINERALS,
METALS LIKE SODIUM AND POTASSIUM AND OTHER--
AND OTHER TRACE METALS,
THEY'RE--
HOPES TO REGULATE THEIR BALANCE IN THE TISSUES.
AND THEN THE LAST GROUP WOULD BE THE--
BASICALLY WHAT WE WOULD--
THE SEX HORMONES.
SO THE PROGESTINS LIKE PROGESTERONE,
THE ANDROGENS SUCH AS TESTOSTERONE
WHICH WE THINK OF MORE IS THE MALE HORMONES,
AND THEN THE ESTROGENS SUCH AS ESTRADIOL
WHICH WE THINK OF MORE-- RIGHT,
SO WE TEND TO THINK OF THE ESTROGENS
AS FEMALE AND TESTOSTERONE AS MALE.
OF COURSE, WITHIN US, WE ALWAYS HAVE A MIXTURE OF BOTH.
IT'S JUST WHICH DOMINATES.
AND THE FEMALE HORMONES ARE SYNTHESIZED FROM TESTOSTERONE.
SO THAT PRETTY MUCH WRAPS UP CHOLESTEROL, RIGHT?
THERE'S-- WE WANT TO KNOW ABOUT ITS TWO MAJOR FUNCTIONS,
ITS ROLE IN THE CELL MEMBRANES,
AND THEN ITS ROLE AS A PRECURSOR,
AND THEN YOU WANT TO KNOW THE ROLE
OF THE FIVE DIFFERENT CLASSES OF CHOLESTEROL BASED STEROIDS.
SO PLEASE TAKE SOME TIME NOW TO WORK HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING.