- WELCOME TO CARBOHYDRATES, PART FOUR.
IN THIS TUTORIAL WE'LL FOCUS ON POLYSACCHARIDES.
LET'S GET STARTED. ALL RIGHTY.
SO POLYSACCHARIDES ARE BASICALLY POLYMERS.
AND I KNOW IN THE PREVIOUS NOTES I SAID 10 MONOSACCHARIDES,
AND THIS IS JUST A GOOD EXAMPLE I TOOK FROM TWO DIFFERENT BOOKS.
SO BASICALLY POLY MANY, MANY SUGARS LINKED TOGETHER.
AND BECAUSE THERE ARE SO MANY SUGARS LINKED TOGETHER
THEY ARE NO LONGER SOLUBLE IN WATER.
BUT, THE HYDROXYL GROUPS CAN BE HYDRATED
AND SO THEY OFTEN FORM THICK SUSPENSIONS.
SO, WHERE DO WE SEE POLYSACCHARIDES?
WELL, STARCH.
RIGHT [INAUDIBLE] CORN STARCH
AND WATER YOU COULD SEE THAT THICK SUSPENSION,
AND GLYCOGEN.
SO THESE ARE TWO EXAMPLES OF IMPORTANT POLYSACCHARIDES.
AND THE ROLE FOR THESE TWO THEY SHARE IS ENERGY STORAGE.
THE EVER COMMON ROLE FOR POLYSACCHARIDES
WE WILL SEE WITH CELLULOSE.
AND THAT'S MORE FOR STRUCTURAL SUPPORT.
SO WHERE DO WE ENCOUNTER THESE POLYSACCHARIDES?
WELL, STARCH IS THE ENERGY STORAGE MOLECULE FOR PLANTS.
WITHIN ANIMALS, IT'S--
IT HAS A VERY SIMILAR STRUCTURE BUT WE CALL IT GLYCOGEN,
SO THERE ARE DIFFERENT--
THERE ARE SOME STRUCTURAL DIFFERENCES
BETWEEN PLANTS AND ANIMALS AND HOW WE STORE ENERGY.
BASICALLY, TAKE THOSE EXTRA GLUCOSE MOLECULES
AND PUT THEM INTO POLYMERS TO STORE THEM FOR A RAINY DAY.
AND THEN WITH CELLULOSE IT WILL BE--
IT'S LIKE, IF YOU THINK ABOUT LIKE THE CELLULOSE CELL WALLS.
SO ALSO FOR PLANTS.
NOW, WHAT'S INTERESTING THEN IS THAT BOTH STARCH AND GLYCOGEN
THEY ARE GOING TO USE THE ALPHA GLYCOSIDIC LINKAGES.
AND THE INTERESTING THING
TO ME HERE IS THAT WE HAVE THE ABILITY,
RIGHT, WE CAN DIGEST STARCH, RIGHT?
SO WHEN WE EAT PLANTS WE CAN DIGEST THE STARCH.
RIGHT? SO HUMANS ARE ABLE
TO DIGEST STARCH AND OTHER ANIMALS.
THE CELLULOSE ON THE OTHER HAND IS NOT DIGESTED BY HUMANS.
AND EVEN LIKE WITH COWS, RIGHT,
SO ANIMALS THAT CAN EAT PLANTS,
RIGHT, THE HERBIVORES
THEY ACTUALLY DON'T EVEN HAVE BIOCHEMISTRY
TO DIGEST TO THE CELLULOSE,
THEY HAVE BACTERIA IN THEIR STOMACHS
THAT HAVE THE RIGHT ENZYMES TO BREAK DOWN THE CELLULOSE.
SO WHAT IS IT THAT MAKES THIS DISTINCTION
BETWEEN BEING DIGESTIBLE
OR BEING AN ENERGY SOURCE FOR ANIMALS
AND NOT BEING DIGESTED?
IT COMES DOWN TO THE GLYCOSIDIC LINKAGES.
CELLULOSE HAS THE BETA GLYCOSIDIC LINKAGES.
SO THE DIFFERENCE
BETWEEN THE GLYCOSIDIC LINKAGES LEADS TO A LOT
OF DIFFERENT THINGS IN BIOCHEMISTRY.
SO HERE, WE HAVE A COUPLE EXAMPLES. RIGHT?
SO HERE ARE STARCH AND GLYCOGEN,
AND THEY HAVE VERY SIMILAR STRUCTURES,
AND THEY'LL HAVE THE IMPORTANT ROLE OF THE ALPHA LINKAGES.
AND WE TALKED ABOUT THOSE IN--
A LOT IN OUR DISACCHARIDE TUTORIAL.
SO, IF YOU NEED TO KNOW MORE
ABOUT GLYCOSIDIC LINKAGES PLEASE GO BACK
TO THE PART THREE VIDEO TUTORIALS.
THE MAIN THING I WANT YOU TO NOTE HERE IS NOTE
THAT THE ALPHA LINKS,
RIGHT, THEY CREATE BRANCHING.
AND THEN IF WE COMPARE THAT TO CELLULOSE
WITH THE BETA LINKS NOTICE HOW TIGHTLY
THAT THE POLYMERS CAN ALIGN THEMSELVES.
SO NOTICE THE TIGHT PACKING
WITH THE BETA LINKAGES. OKAY.
AND THEN IF YOU WANT TO DIG IN DEEPER AND LOOK HERE--
ARE THE VARIOUS-- SO,
THAT-- NOW, THERE ARE SOME BETA LINKAGES IN THE STARCH
AND GLYCOGEN BUT THE DOMINANT LINKAGE IS THE ALPHA
AND THAT'S THE ONE WE'RE ABLE TO BREAK DOWN.
SO REALLY AS FAR AS POLYSACCHARIDES GO,
FOR MY CLASS THAT'S ALL I
REALLY WANT YOU TO FOCUS ON IS RECOGNIZING THE DIFFERENT
BIOLOGICAL RULES OF THE THREE PRIMARY POLYSACCHARIDES
AND THE DIFFERENCE IN THE GLYCOSIDIC LINKAGES.
SO PLEASE TAKE SOME TIME NOW TO WORK A LITTLE HOMEWORK
TO REINFORCE YOUR UNDERSTANDING.