-- WELCOME TO ACIDS AND BASES PART 7: BUFFERS.
THIS IS A KEY CONCEPT IN THE HEALTH OF OUR BODY.
WE NEED TO HAVE BUFFER SYSTEMS TO KEEP US ALIVE AND WELL.
LET'S FIGURE OUT AND LEARN ABOUT EXACTLY WHAT BUFFER SYSTEMS ARE.
SO BUFFERS ARE A COMBINATION OF SUBSTANCES THAT ACT TOGETHER
TO PREVENT DRASTIC CHANGES IN PH.
THE TYPICAL BUFFER SYSTEMS ARE A WEAK ACID
AND ITS CONJUGATE BASE.
AND SO THIS IS A CONCEPT FROM THE BRONSTED-LOWRY DEFINITION
OF ACIDS AND BASES, SO IF YOU'RE NOT SURE
WHAT I'M TALKING ABOUT HERE, PLEASE GO BACK TO THAT TUTORIAL.
AND SO THE OTHER IMPORTANT PART ABOUT BUFFERS
IS TYPICALLY THEY ARE GOING TO BE AT SIMILAR CONCENTRATIONS.
SO, HERE, IT IS IN ENGLISH, SYMBOLICALLY,
SO WE WOULD HAVE LIKE A WEAK ACID,
AND WE WOULD COME ADD IN SOME OF ITS CONJUGATE BASE,
AND THESE CONCENTRATIONS WOULD BE SIMILAR.
SO, THE CONCENTRATION OF HA WOULD BE APPROXIMATELY EQUAL
TO THE CONCENTRATION OF A-.
THIS WOULD BE OUR IDEAL BUFFER SYSTEM. ALL RIGHT.
SO, WE'LL JUST KEEP THINKING IN TERMS OF HA, RIGHT,
OUR ACID AND A-, OUR CONJUGATE BASE.
AND SO LET'S LOOK AT A GENERIC BUFFER SYSTEM.
SO, HERE WE HAVE THE IDEAL BUFFER SYSTEM.
SO, IN THE IDEAL BUFFER SYSTEM, WE HAVE OUR CONJUGATE ACID,
OUR ACID AND OUR CONJUGATE BASE PAIR AT EQUAL CONCENTRATIONS.
SO, WE HAVE A WEAK ACID AND A WEAK BASE.
THERE'S AN INTRODUCTION OF H+,
SO IF WE ADD H+, WHAT'S THE H+ GOING TO DO?
THE H+ REACTS WITH THE A- AND IT PRODUCES HA.
ALL RIGHT. SO, WE CAN SEE HERE THAT WE LOSE SOME OF OUR A-
BECAUSE IT REACTS WITH H+ AND WE PRODUCE MORE HA.
SO, THE CONCENTRATION OF HA INCREASES
AND A- DECREASES.
BUT NOTICE THAT THERE'S STILL BUFFER CAPACITY, RIGHT?
SO, HERE'S OUR IDEAL BUFFER AND THERE'S STILL WEAK ACID
AND CONJUGATE BASE PRESENT,
SO IF MORE ACID OR BASE IS ADDED,
THERE ARE COMPONENTS OF THE BUFFER SYSTEM TO REACT.
NOW, WHAT HAPPENS IF WE ADD HYDROXIDE TO OUR BUFFER SYSTEM.
THE HYDROXIDE IS GOING TO REACT WITH THE WEAK ACID,
AND THAT'S GOING TO PRODUCE, WATER + A-.
SO, WE'LL SEE THAT WE LOSE, OUR HA CONCENTRATION DECREASES.
WE'RE GOING TO LOSE SOME OF OUR WEAK ACID,
AND WE'RE GOING TO PRODUCE SOME ADDITIONAL CONJUGATE BASE.
HOWEVER, THE BUFFER SYSTEM IS STILL ABLE TO REACT
WITH ADDITIONAL ACID OR BASE.
SO, WE STILL HAVE A BUFFER SYSTEM.
OKAY. WELL, WE CAN SEE WHERE THIS IS GOING.
THERE IS THE CONCEPT OF BUFFER CAPACITY.
EVENTUALLY, IF WE ADDED A HUGE AMOUNT OF HYDROGEN IONS
OR A HUGE AMOUNT OF HYDROXIDE, WE MAY RUN OUT
OF OUR BUFFER SUBSTANCES.
SO, WE DESCRIBE THAT AS THE BUFFER CAPACITY,
THE GREATEST AMOUNT OF ACID OR BASE THAT A BUFFER SYSTEM
CAN ACCOMMODATE WHILE MAINTAINING THE PH.
SO, WHENEVER WE HEAR THE WORDS PH,
WE RECOGNIZE THAT'S THE -LOG OF THE HYDROGEN ION CONCENTRATION.
AND SO THE WHOLE IDEA OF BUFFERS, IS TO MAINTAIN THE PH.
THERE CAN BE LIMITS TO A BUFFER SYSTEM.
SO, NOW THAT WE HAVE A SENSE OF THE OVERALL THEORY
BEHIND BUFFER SYSTEMS, LET'S LOOK AT THE TWO IMPORTANT
BUFFERING SYSTEMS IN OUR BODY,
AMINO ACIDS ARE ANOTHER ONE, BUT WE'RE NOT READY TO TALK
ABOUT THOSE YET.
SO, WE'LL TALK ABOUT THE BUFFERING SYSTEMS IN THE BODY
THAT WE ARE ABLE TO TALK ABOUT SO FAR.
SO, WHEN WE'RE TALKING ABOUT BUFFERING SYSTEMS,
IT'S REALLY ABOUT EQUILIBRIUM AND ACID BASE CHEMISTRY.
SO, IF YOU HAVEN'T HAD A CHANCE, YOU WILL PROBABLY WANT
TO REVIEW THE EQUILIBRIUM VIDEO TUTORIAL BEFORE TRYING THIS.
OKAY. SO, LET'S GO BACK TO OUR EXAMPLE OF HYPERVENTILATION,
WHERE BREATHING IS TOO FAST.
THE CO2 IS CONTROLLED THROUGH OUR BREATH AND THE HYDROGEN IONS
AND THE BICARBONATE, THESE ARE FOUND IN OUR BLOOD.
SO, THE BICARBONATE SYSTEM IS PRIMARILY RESPONSIBLE
FOR HELPING TO MAINTAIN THE PH OF OUR BLOOD.
ALL RIGHTY. SO, IF WE ARE BREATHING VERY FAST,
WHAT DOES THAT DO TO OUR CO2 CONCENTRATION IN OUR BLOOD?
IT'S GOING TO DECREASE IT BECAUSE WE'RE EXHALING
VERY QUICKLY.
SO, THAT'S GOING TO SHIFT THE EQUILIBRIUM TO THE LEFT.
ALL RIGHTY.
SO, WE ALREADY ANSWERED THIS QUESTION.
WE WOULD EXPECT THE PATIENT'S BLOOD, CO2 CONCENTRATION
TO DECREASE BECAUSE OF OUR RAPID BREATH RATE.
WHAT HAPPENS TO THE HYDROGEN ION CONCENTRATION?
WELL, IF WE'VE SHIFTED THE EQUILIBRIUM TO THE LEFT
WHERE THE BODY'S PULLING OUT THE HYDROGEN IONS,
SO WE WOULD HAVE A DECREASE IN THE HYDROGEN ION CONCENTRATION.
SO, NOW, WE BRING IN THE LAST PIECE ABOUT PH, RIGHT?
SO, SINCE THE PH IS THE -LOG OF THE HYDROGEN ION CONCENTRATION,
AND IF THIS VALUE IS DECREASING, WHAT HAPPENS TO THE PH?
THEN THE PH INCREASES BECAUSE OF THE -LOG RELATIONSHIP.
ALL RIGHT. SO, WE WOULD HAVE AN INCREASED PH
BECAUSE THERE IS LESS HYDROGEN IONS PRESENT.
SO, WE WOULD EXPECT THE PH TO INCREASE.
NOW, LET'S LOOK AT THE PHOSPHATE BUFFER SYSTEM
THAT WE WERE INTRODUCED TO IN THE EARLIER
EQUILIBRIUM TUTORIAL.
IN THIS PHOSPHATE BUFFER SYSTEM, AS WE KNOW,
THIS HELPS TO REGULATE THE PH INSIDE OUR CELLS.
SO, IF SOMEBODY HAS RENAL FAILURE, THEY ARE NOT ABLE
TO EXCRETE THE DIHYDROGEN PHOSPHATE.
SO, NORMALLY, THE DIHYDROGEN PHOSPHATE IS EXCRETED
IN OUR URINE.
BUT IF WE'RE NOT ABLE TO URINATE,
WHAT'S GOING TO HAPPEN? RIGHT?
WE'RE GOING TO GET A BUILD UP OF DIHYDROGEN PHOSPHATE.
SO, RENAL FAILURE IS GOING TO CREATE AN INCREASE
IN THE CONCENTRATION OF THE DIHYDROGEN PHOSPHATE.
SO, LET'S PUT THAT ONTO OUR EQUILIBRIUM TEETER-TOTTER.
THE DIHYDROGEN PHOSPHATE IS ON THE REACTANT SIDE,
SO WE ARE GOING TO HAVE AN INCREASE THAT'S GOING TO
PUSH OUR TEETER-TOTTER TO THE RIGHT.
SO, IT SHIFTS THE EQUILIBRIUM TO THE RIGHT WHICH IS THE PRODUCTS,
AND WHAT'S A PRODUCT?
HYDROGEN'S A PRODUCT.
SO WE WOULD EXPECT THE HYDROGEN ION CONCENTRATION TO INCREASE.
AND SO NOW THE LAST POINT TO BRING IN THEN IS,
WHAT DOES THAT DO TO THE PH?
SO, THE PH IS ONCE AGAIN, THE -LOG OF THE HYDROGEN
ION CONCENTRATION.
SO, IF WE'RE INCREASING THE HYDROGEN ION CONCENTRATION,
WE ARE LOWERING THE PH, ALL RIGHT,
BECAUSE THERE'S MORE H+.
SO, THAT'S A VERY IMPORTANT RELATIONSHIP
THAT AS WE LOWER THE HYDROGEN ION CONCENTRATION,
THE PH INCREASES
AND AS WE INCREASE THE HYDROGEN ION CONCENTRATION,
WE LOWER THE PH.
SO, WE COULD SAY THAT AS WE LOWER THE PH,
IT'S BECOMING--THE SOLUTION IS BECOMING MORE ACIDIC,
AND AS WE RAISE THE PH, WE'RE SAYING THAT THE SOLUTION
IS GOING TO BECOME MORE BASIC.
SO, THAT CONCLUDES THE BUFFER TUTORIAL
AND I HOPE YOU'LL TAKE A FEW MINUTES NOW
TO WORK A FEW HOMEWORK PROBLEMS TO REINFORCE YOUR UNDERSTANDING.