Circulation 8

Question 1

carbonic anhydrase (2)

Answer 1

• essential enzyme for many different systems/processes
• found in almost all living things

Question 2

CA reaction

Answer 2

• catalyzes CO2 + H2O <–> H+ + HCO3-

Question 3

what is CA’s role in respiratory gas exchange in the RBC (2)

Answer 3

• CO2 excretion in RBCs
• converts CO2 into H+ and HCO3- at tissues and converts these back into CO2 at the gills

Question 4

what is unique about sharks and CO2 excretion (2)

Answer 4

• sharks don’t need their blood
  to maintain normal CO2 excretion
• hagfish and chondrichthyans have CA outside the RBC at the gills

Question 5

what is CA’s role in respiratory gas exchange (2)

Answer 5

• facilitates CO2 excretion in gills and RBC
• facilitates O2 delivery in the heart and red muscle (aerobically-demanding tissues)

Question 6

what environmental condition drives O2 offloading (2)

Answer 6

• hemoglobin pH sensitivity/Bohr effect
• O2 saturation (O2 binding affinity) decreases when pH decreases

Question 7

root effect (2)

Answer 7

• describes how telosts experience a decrease in binding affinity AND binding capacity when pH decreases
• membrane bound CA and root effect help with O2 offloading at tissues

Question 8

betaNHE (2)

Answer 8

• protects O2 binding at gills
• moves H+ out of Hb in low pH stress to maintain O2 binding at the gill

Question 9

how do the sequences in fish with gill CA differ from those without

Answer 9

• histidine substitution (his-64) with a different amino acid occurs

Question 10

how does his-64 contribute to activity (2)

Answer 10

• RBC CA activity is significantly lower in fish with gill CA
• CA activity is driven by His-64

Question 11

how has the pattern of CA evolved in fish with and without gill CA

Answer 11

• CA isoform types are mutually exclusive; only those without gill CA have high activity RBC CA

Question 12

why was the red drum used to study CA in teleosts (4)

Answer 12

• has root effect
• has betaNHE
• has membrane-bound CA
• has high-activty RBC CA

Question 13

does RBC CA activity impact O2 offloading rate

Answer 13

• yes, CA addition increases O2 offloading from baseline and vice versa

Question 14

how much does CA impact O2 offloading

Answer 14

• CA inhibition decreases O2 offloading 1:1
• CA addition increases O2 offloading 1:1

Question 15

red blood cell CA: activity (2)

Answer 15

• dictated by amino acid His-64
• may have evolved with O2 delivery capabilities

Question 16

red blood cell CA: activity in red drum

Answer 16

• dictates Hb-O2 offloading in red drum

Question 17

what is the role of membrane bound CA

Answer 17

• takes HCO3- from the chloride exchanger and H+ from betaNHE and converts it to CO2 at the tissues

Question 18

will hypoxia training help fish outcompete non-acclimatized counterparts (3)

Answer 18

• CA4a gene expression, protein levels and localization did not change
• CA4a activity does not change
• no, aerobic performance did not change

Question 19

standard metabolic rate

Answer 19

• resting swim speed with relatively low O2 consumption

Question 20

maximum metabolic rate

Answer 20

• highest swim speed until failure with relatively high oxygen consumption

Question 21

burst during performance

Answer 21

• level when ‘sprinting’ starts

Question 22

aerobic scope

Answer 22

• O2 consumption and swim speed between standard metabolic rate to maximum metabolic rate

Question 23

what was the predicted outcome of hypoxia acclimatized fish (2)

Answer 23

• increased aerobic scope
• increased maximum metabolic rate

Question 24

what were some changes that did occur in hypoxia acclimatized fish (3)

Answer 24

• increased Hb binding affinity
• increased O2 uptake
• decreased Hb pH sensitivity

Question 25

membrane-bound CA

Answer 25

- CA4a is maintained under hypoxia, but is not as important for performance in the red drum

Question 26

what is the function of CA4a in zebrafish

Answer 26

- respiratory gas exchange

Question 27

what is the function of CA4a in rainbow trout

Answer 27

- metabolic processes

Question 28

what is the function of CA4a in red drum

Answer 28

- acid-base and ion regulation