WEBVTT

00:00:03.000 --> 00:00:07.570
- WELCOME TO LIPIDS PART 4,
DOUBLE CHECK, CHOLESTEROL.

00:00:07.720 --> 00:00:08.870
ALL RIGHT.

00:00:09.120 --> 00:00:12.300
SO CHOLESTEROL HAS TWO
PRIMARY ROLES IN THE BODY.

00:00:12.450 --> 00:00:14.690
ONE,
TO REINFORCE THE STRUCTURE

00:00:14.840 --> 00:00:16.450
OF THE CELL MEMBRANE,
AND THE OTHER,

00:00:16.600 --> 00:00:21.030
IT'S AN IMPORTANT PRECURSOR
TO MANY COMPOUNDS.

00:00:21.180 --> 00:00:22.360
LET'S GO AHEAD AND GET

00:00:22.510 --> 00:00:25.060
STARTED AND LOOK AT CHOLESTEROL
A LITTLE MORE CLOSELY.

00:00:25.210 --> 00:00:27.570
ALL RIGHT. SO--

00:00:27.720 --> 00:00:31.480
WE'LL ALSO TALK ABOUT SOME OTHER
STEROID HORMONES, AS WELL.

00:00:31.630 --> 00:00:33.840
ALL RIGHT.
SO THIS FIRST ROLE,

00:00:34.090 --> 00:00:36.570
WE'VE ALREADY TALKED ABOUT WHEN
WE WERE LEARNING ABOUT CELL

00:00:36.720 --> 00:00:37.750
MEMBRANES, RIGHT?

00:00:38.000 --> 00:00:41.330
THAT THE CHOLESTEROL IS
DISTRIBUTED

00:00:41.480 --> 00:00:46.480
AMONG THOSE HYDROPHOBIC TAILS
OF THE PHOSPHOLIPIDS, RIGHT?

00:00:46.630 --> 00:00:50.540
TO HELP MAINTAIN THE STRUCTURE
OF THE MEMBRANE.

00:00:50.690 --> 00:00:52.090
SO THIS--

00:00:52.240 --> 00:00:54.450
THE CELL MEMBRANES ARE
VERY BUSY,

00:00:54.600 --> 00:00:57.210
SO IT'S HARD TO FIND
A GOOD SCHEMATIC.

00:00:57.360 --> 00:00:58.510
BUT IF WE LOOK HERE,

00:00:58.660 --> 00:01:03.750
THESE LITTLE CIRCLES ARE
REPRESENTING CHOLESTEROL.

00:01:04.000 --> 00:01:06.090
SO IF WE LOOK CLOSELY,

00:01:06.240 --> 00:01:10.780
WE CAN SEE THAT THEY'RE
DISTRIBUTED ALL OVER THE INSIDE

00:01:11.030 --> 00:01:12.360
OF THE CELL MEMBRANE,

00:01:12.510 --> 00:01:15.570
GIVING IT RIGIDITY
AND STRUCTURE.

00:01:15.720 --> 00:01:17.180
SO-- ALL RIGHT.

00:01:17.330 --> 00:01:19.810
AND HERE'S ONE
POINTED OUT RIGHT HERE.

00:01:20.060 --> 00:01:22.870
ALL RIGHT.
SO THEN JUST TO KIND OF GIVE

00:01:23.120 --> 00:01:26.780
A BRIEF RECAP OF
CELL MEMBRANE STRUCTURE, RIGHT?

00:01:27.030 --> 00:01:28.150
SO WE ALWAYS HAVE--

00:01:28.300 --> 00:01:30.360
RIGHT, THERE'S THE PHOSPHOLIPIDS

00:01:30.510 --> 00:01:33.240
WITH THEIR POLAR
HEADS POKING OUT

00:01:33.390 --> 00:01:35.750
AND THEIR HYDROPHOBIC TAILS
IN THE CENTER.

00:01:36.000 --> 00:01:39.600
WE SEE OUR MEMBRANE PROTEINS
ACTING AS CHANNELS

00:01:39.750 --> 00:01:41.060
AND RECEPTORS.

00:01:41.210 --> 00:01:43.540
AND THEN WE CAN NOTICE HERE--

00:01:43.690 --> 00:01:48.180
HERE'S A GLYCOLIPID AND WE SEE
THESE SUGARS THAT ALSO REACT--

00:01:48.330 --> 00:01:50.600
ACT AS RECEPTORS.

00:01:50.750 --> 00:01:53.750
SO THAT'S THE MAIN--

00:01:54.000 --> 00:01:56.870
THE MAIN PARTS WE NEED
TO KNOW ABOUT A CELL MEMBRANE.

00:01:57.120 --> 00:02:00.570
SO NOW WE'LL GO
ON TO CHOLESTEROL'S OTHER ROLE

00:02:00.720 --> 00:02:04.420
IN THE BODY IS THAT BASICALLY
IT'S A VERY IMPORTANT

00:02:04.570 --> 00:02:10.540
BIOLOGICAL PRECURSOR
TO A TON OF IMPORTANT COMPOUNDS.

00:02:10.690 --> 00:02:12.690
SO HERE'S OUR BODY CHOLESTEROL.

00:02:12.840 --> 00:02:14.600
WE'VE LOOKED AT IT
SEVERAL TIMES.

00:02:14.750 --> 00:02:18.060
WE RECOGNIZED RIGHT THERE
IS THE STEROID RING.

00:02:18.210 --> 00:02:21.450
AND THEN WE KNOW
IT'S CALLED CHOLESTEROL

00:02:21.600 --> 00:02:24.510
BECAUSE OF
THAT ALCOHOL FUNCTIONAL GROUP.

00:02:24.660 --> 00:02:31.390
SO WE'LL STUDY BILE ACIDS
MORE CLOSELY IN A FUTURE VIDEO

00:02:31.540 --> 00:02:34.360
BUT THEY ARE MADE
FROM CHOLESTEROL.

00:02:34.510 --> 00:02:36.480
VITAMIN D, WE
ALL KNOW ABOUT THAT.

00:02:36.630 --> 00:02:39.420
IT'S IMPORTANT
FOR STRONG TEETH AND BONES.

00:02:39.570 --> 00:02:42.510
AND IF WE DON'T HAVE ENOUGH
OF IT, WE GET RICKETS.

00:02:42.660 --> 00:02:45.600
AND THEN, OF COURSE,
THE HORMONES WHICH ARE--

00:02:45.750 --> 00:02:49.090
FOR THE MOST PART ARE
STEROID BASED.

00:02:49.240 --> 00:02:51.540
SO LET'S LOOK A LITTLE CLOSE--

00:02:51.690 --> 00:03:00.870
MORE CLOSELY NOW AT CHOLESTEROL
AND ITS ROLE AS A PRECURSOR.

00:03:01.120 --> 00:03:06.060
SO WE HAVE THE STRUCTURE ONE
MORE TIME.

00:03:06.210 --> 00:03:10.300
AND WE'LL SEE THAT
THE CHOLESTEROL IS THE PRECURSOR

00:03:10.450 --> 00:03:14.030
FOR FIVE DIFFERENT CLASSES
OF STEROID HORMONES.

00:03:14.180 --> 00:03:16.510
SO HERE'S CHOLESTEROL,
RIGHT?

00:03:16.660 --> 00:03:18.360
SO WE JUST WANT TO TRAIN OUR EYE

00:03:18.510 --> 00:03:24.570
TO LOOK FOR THE FEW
STEROID RINGS,

00:03:24.720 --> 00:03:26.660
THE FOUR FEW STRINGS.

00:03:26.810 --> 00:03:30.570
AND THEN WE'LL LOOK
A LITTLE MORE CLOSELY.

00:03:30.720 --> 00:03:36.390
SO WHAT ARE THESE OTHER FIVE
CLASSES OF HORMONES THAT WE--

00:03:36.540 --> 00:03:40.570
THAT CHOLESTEROL WILL
BE USED TO SYNTHESIZE?

00:03:40.720 --> 00:03:44.030
SO WE HAVE THE GLUCOCORTICOIDS.

00:03:44.180 --> 00:03:45.870
AND AS YOU WOULD IMAGINE,
RIGHT,

00:03:46.120 --> 00:03:48.030
IT'S RELATED TO CARBOHYDRATES

00:03:48.180 --> 00:03:51.150
BUT ALSO PROTEIN
AND LIPID METABOLISM.

00:03:51.300 --> 00:03:54.660
THERE ARE ALSO VERY
POWERFUL ANTI-INFLAMMATORY

00:03:54.810 --> 00:03:58.330
AND IMMUNOSUPPRESSANT AGENTS.

00:03:58.480 --> 00:04:03.480
AND THEN WE
HAVE THE MINERALOCORTICOIDS.

00:04:03.630 --> 00:04:06.360
AND SO AS THEIR NAME WOULD
IMPLY, RIGHT, MINERALS,

00:04:06.510 --> 00:04:11.690
METALS LIKE SODIUM
AND POTASSIUM AND OTHER--

00:04:11.840 --> 00:04:13.720
AND OTHER TRACE METALS,

00:04:13.870 --> 00:04:15.090
THEY'RE--

00:04:15.240 --> 00:04:18.780
HOPES TO REGULATE THEIR BALANCE
IN THE TISSUES.

00:04:19.030 --> 00:04:23.390
AND THEN THE LAST
GROUP WOULD BE THE--

00:04:23.540 --> 00:04:25.480
BASICALLY WHAT WE WOULD--

00:04:25.630 --> 00:04:27.540
THE SEX HORMONES.

00:04:27.690 --> 00:04:32.450
SO THE PROGESTINS
LIKE PROGESTERONE,

00:04:32.600 --> 00:04:36.780
THE ANDROGENS SUCH
AS TESTOSTERONE

00:04:37.030 --> 00:04:39.450
WHICH WE THINK OF MORE
IS THE MALE HORMONES,

00:04:39.600 --> 00:04:42.840
AND THEN THE ESTROGENS SUCH
AS ESTRADIOL

00:04:43.090 --> 00:04:44.870
WHICH WE THINK OF MORE-- RIGHT,

00:04:45.120 --> 00:04:47.390
SO WE TEND
TO THINK OF THE ESTROGENS

00:04:47.540 --> 00:04:51.120
AS FEMALE
AND TESTOSTERONE AS MALE.

00:04:51.270 --> 00:04:54.600
OF COURSE, WITHIN US, WE ALWAYS
HAVE A MIXTURE OF BOTH.

00:04:54.750 --> 00:04:56.450
IT'S JUST WHICH DOMINATES.

00:04:56.600 --> 00:05:01.570
AND THE FEMALE HORMONES ARE
SYNTHESIZED FROM TESTOSTERONE.

00:05:01.720 --> 00:05:06.660
SO THAT PRETTY MUCH
WRAPS UP CHOLESTEROL, RIGHT?

00:05:06.810 --> 00:05:10.480
THERE'S-- WE WANT TO KNOW
ABOUT ITS TWO MAJOR FUNCTIONS,

00:05:10.630 --> 00:05:12.420
ITS ROLE IN THE CELL MEMBRANES,

00:05:12.570 --> 00:05:14.510
AND THEN ITS ROLE
AS A PRECURSOR,

00:05:14.660 --> 00:05:16.660
AND THEN YOU WANT
TO KNOW THE ROLE

00:05:16.810 --> 00:05:21.510
OF THE FIVE DIFFERENT CLASSES
OF CHOLESTEROL BASED STEROIDS.

00:05:21.660 --> 00:05:24.210
SO PLEASE TAKE SOME TIME NOW
TO WORK HOMEWORK PROBLEMS

00:05:24.360 --> 00:05:27.420
TO REINFORCE YOUR UNDERSTANDING.