CELL HOMEOSTASIS

Question 1

UNDER NORMAL CONDITIONS WHAT IS THE EC[NA]

Answer 1

145MM

Question 2

WHAT IS THE IC[NA]

Answer 2

15MM

Question 3

WHY IS IT IMPORTANT TO KEEP THE NA GRADIENT IN AN EXCITABLE CELL

Answer 3

IF IC[NA] INCREASED, THE INWARD CHEMICAL GRADIENT WOULD NOT BE AS LARGE. THEREFORE THE NERNST FOR SODIUM WOULD DECREASE. AN AP WOULD TAKE LONGER TO DEVELOP AND NOT BE AS LARGE. MAY BE PROBLEMS WITH AP PROPAGATION AND SLOW CONDUCTION.

Question 4

HOW DOES NA/K ATPASE WORK

Answer 4

1. PUMP OPEN TO INSIDE OF CELL
2. NA BINDS X3
3. PUMP PHOSPHORYLATED BY ATP
4. CONFORMATIONAL CHANGE
5. NA X3 NOW EXPOSED TO OUTSIDE OF CELL
6. K X2 ENTERS CLEFT
7. DEPHOSPHORYLATION
8. CONFORMATIONAL CHANGE
9. K X2 ENTERS CELL

Question 5

HOW IS THE RATE OF TRANSPORT OF NA/K ATPASE SATURABLE

Answer 5

1. CONC NA
2. CONC K
3. CONC ATP

Question 6

WHAT INHIBITS THE NA/K ATPASE

Answer 6

CARDIAC GLYCOSIDES SUCH AS OUABAIN AND DIGOXIN

Question 7

WHAT IS THE DIFFERENCE IN CONCENTRATION BETWEEN EC AND IC CONC OF CA

Answer 7

10,000 FOLD

Question 8

WHAT ARE THE MECHANISMS OF CALCIUM HOMEOSTASIS

Answer 8

1. NA/CA EXCHANGER

2. CA ATPASE

Question 9

WHAT IS THE NA/CA EXCHANGER

Answer 9

EXCHANGES EXRACELLULAR NA FOR INTRACELLULAR CA
3 NA ENTER THE CELL
1 CALCIUM LEAVES THE CELL

THIS IS TO EQUAL THE IC/EC GRADIENTS
NA - 10 FOLD GRADIENT
CA - 10,000 FOLD GRADIENT

BY 3 NA ENTERING THE CELL AT A TIME = CUBES GRADIENT

Question 10

EXAMPLE OF NA/CA EXCHANGER

Answer 10

NA/CA EXCHANGER PART OF THE SLC8 FAMILY IN THE CACA SUPERFAMILY
IN MAMMALS, EXIST 3 FORMS: NCX1, NCX2, NCX3

Question 11

WHAT FAMILY DO THE CA ATPASES COME FROM

Answer 11

P TYPE ATPASE FAMILY

Question 12

WHAT CA PUMPS CAN A CELL CONTAIN

Answer 12

1. PMCA - PLASMA MEMBRANE - PUMP CA OUT OF CELL
2. SERCA - SR OR ER MEMBRANE - ACT TO PUMP CA INTO ORGANELLES THAT ACT AS CA STORES
3. SPCA - ON THE GOLGI APPARATUS - ALSO TRANSPORT MN2+

Question 13

WHAT TYPES OF CA CHANNELS ARE THERE IN THE PLASMA MEMBRANE

Answer 13

1. VOLTAGE OPERATED (VOCC)
2. RECEPTOR OPERATED (ROCC)
3. MECHANICALLY ACTIVATED (MACC)
4. STORE OPERATED (SOCC)

Question 14

WHAT ARE THE STORE OPERATED CALCIUM CHANNEL PATHWAYS

Answer 14

1. IP3 RECEPTORS
   CHANNELS ACTIVATED BY IP3 BINDING
2. RYANODINE RECEPTORS
   LOW CONC OF RYANODINE ACTIVATE THE CHANNEL

Question 15

WHAT OTHER SUBSTANCES ACTIVATE RYANODINE RECEPTORS

Answer 15

1. CAFFEINE

2. CADP RIBOSE

Question 16

WHAT OCCURS UPON LOSS OF CA FROM INTRACELLULAR STORES

Answer 16

SOCC OPENS IN THE PLASMA MEMBRANE TO LET CA INTO THE CELL TO RESTORE THE ORGANELLE STORES
BELIEVED TO BE A PHYSICAL LINK BETWEEN STIM1 CALCIUM BINDING PROTEIN THAT BIND WITH THE CELL MEMBRANE UNDER CONDITIONS OF LOW CA TO PHYSICALLY OPEN SOCC