Name: 7.1 蛋白質。蛋白質的結構 (7.1 Protein: Structure of Proteins)
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- WELCOME TO CHAPTER 6 DISCUSSION ON PROTEIN.

WE'RE GOING TO START BY TALKING ABOUT PROTEIN STRUCTURE.

AMINO ACIDS ARE THE BUILDING BLOCKS OF PROTEIN.

BUT THE STRUCTURE OF PROTEIN IS MUCH MORE COMPLEX

WHEREAS THE PURPLE REPRESENTS THE NITROGEN

WHAT I WANT YOU TO KNOW ABOUT IS THAT THESE UNITS

AND THEY'RE LINKED TOGETHER BY A VERY STRONG PEPTIDE BOND.

AND THEN THE NITROGEN REALLY MAKES THIS UNIQUE.

IF WE TAKE A CLOSER LOOK AT THE AMINO ACIDS YOU CAN SEE HERE

THE NITROGEN THAT I WAS TALKING ABOUT AND THEN THE BONDS.

YOU'RE NOT REQUIRED TO KNOW THE STRUCTURE.

THE CATEGORIES OF AMINO ACIDS ARE DIVIDED INTO ESSENTIAL,

NONESSENTIAL, AND CONDITIONALLY ESSENTIAL.

AND THESE ARE FOR THE STANDARD AMINO ACIDS.

AND I DON'T EXPECT YOU TO KNOW THE 20 AMINO ACIDS,

BUT I DO WANT YOU TO KNOW THE DEFINITIONS AND WHAT THESE MEAN.

ESSENTIAL IS THE SAME DEFINITION WE'VE BEEN TALKING ABOUT.

AND THERE ARE NINE OF THEM, NEED TO BE SUPPLIED BY THE DIET.

AND THAT'S BECAUSE THE BODY CANNOT SYNTHESIZE THEM,

THE NONESSENTIAL AMINO ACIDS ARE THE AMINO

SO THE NONESSENTIAL MEANS THAT THEY TAKE THE ESSENTIAL

AMINO ACIDS AND THE BODY CAN THEN CONVERT THOSE

INTO THE NONESSENTIAL AMINO ACIDS WHEN NEEDED.

AND IT DOESN'T NECESSARILY MEAN THAT SOME ARE

IT JUST MEANS THAT THERE IMPORTANT IN THE SENSE

THAT WE HAVE TO OBTAIN THOSE FROM THE DIET.

THEN THERE ARE THE CONDITIONALLY ESSENTIAL AMINO ACIDS,

NORMALLY THE BODY CAN MAKE THEM, BUT AT TIMES--

REMEMBER THE DEFINITION OF ESSENTIAL IS THAT THE BODY

CANNOT MAKE OR CANNOT MAKE ENOUGH FOR ITS NEEDS AND THAT'S

WHY SOME OF THE NONESSENTIAL AMINO ACIDS WILL THEN BECOME

CONDITIONALLY ESSENTIAL UNDER CERTAIN CONDITIONS.

AND WE'RE GOING TO START UP WITH THIS STRING OF AMINO ACIDS.

SO JUST LIKE WE TALKED ABOUT, YOU CAN SEE THE AMINO ACID.

AND WHEN WE LOOK AT THIS WE CAN SEE THE CHAIN OF

AMINO ACIDS THAT ARE ALL LINKED TOGETHER.

AND EVEN THOUGH IT MIGHT HAVE ALL THE AMINO ACIDS NECESSARY,

IT DOESN'T FUNCTION AT ALL WHEN IT'S JUST

AND WE CAN SEE TWO DIFFERENT TYPES OF STRUCTURES,

IF YOU CAN THINK OF SOMETHING COILING AROUND.

THE AMINO ACIDS ARE THEN BONDED TOGETHER IN THIS

COIL OR THEY BECOME SHEETS SO THEY ARE PLEATED LIKE THIS.

NOW THE TERTIARY STRUCTURE IS WHEN THESE--

THIS IS GOING TO BE OUR TERTIARY STRUCTURE.

AT THIS POINT THE PROTEIN CAN BECOME FUNCTIONAL

BUT IT MORE OFTEN FUNCTIONS AS THE QUATERNARY STRUCTURE,

WHICH IS WHEN THESE UNITS HERE JOIN TOGETHER,

AND THEN THIS IS GENERALLY AT OUR FULLY FUNCTIONAL PROTEIN.

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7.1 蛋白質。蛋白質的結構 (7.1 Protein: Structure of Proteins)

essentially

essential

determine

structure