Biochem Exam 3- Blood Ph

Front 1

pH of the blood must be maintained at...

Back 1

7.4

Front 2

in the CO2 bicarbonate system, what is the most abudant (between CO2 or carbonic acid)?

Back 2

anhydrous CO2

Front 3

CO2 bicarbonate equation

Back 3

anhydrous CO2 + H2O <-->H2CO3 (carbonic acid) <-->HCO3- (bicarbonate) + H+

Front 4

pH =

Back 4

pKa + log[HCO3-]/[disCO2] where pKa=6.1

Front 5

for every mm Hg the partial pressure of CO2 (pCO2) increases...
(and give the equation)

Back 5

the amount of dissolved CO2 in plasma increases by 0.0301 mM

0.0301 = mM dissolved CO2/pCO2

Front 6

total CO2=

Back 6

[disCO2] + [HCO3-]

Front 7

what is the normal ratio of [HCO3-]/[disCO2]?

Back 7

~20/1

Front 8

a plasma pH of lower than 7.4 would result when...

Back 8

[HCO3-] is lowered (less base to take up H+ = more H+) or when [disCO2] is increased (make more acid) relative to HCO3-

Front 9

abnormal blood pH may be caused by...

Back 9

metabolic problems (abnormal HCO3-)
respiratory problems (abnormal disCO2)

Front 10

how does the body compensate for metabolic/respiratory problems (2)

Back 10

1) metabolic issue: compensated with respiratory response (e.g. expel more CO2)
2) respiratory problems: compensated by with a metabolic response (difficulty breathing-->increased CO2-->kidneys will retain HCO3- to buffer it)

Front 11

what contributes more to total CO2 changes?

Back 11

HCO3- due to 20:1 ratio with disCO2

Front 12

metabolic acidosis causes (4)

Back 12

1) ingestion of acidic compounds (ingested acids can combine with HCO3-)
2) endogenous production of acidic products (lactic acid, ketone bodies) due to starvation, diabetes
3) inability to excrete H+ due to kidney failure
4) loss of HCO3- due to diarrhea

Front 13

compensation for metabolic acidosis

Back 13

lungs increase respiration rate (to expel CO2?)

Front 14

what organ secretes HCO3-

Back 14

pancreas, which is then reabsorbed into GI. if you have a lot of diarrhea you don't absorb it.

Front 15

respiratory acidosis cause (2)

Back 15

diminished rate or depth of respiration (suffocation)
high CO2 content in inspired air

Front 16

respiratory acidosis compensation (2)

Back 16

kidney retains more HCO3
kidney excretes more H+ in exchange for Na+

Front 17

process by which H+ are excreted by kidneys

Back 17

some H+ are secreted as free protons, but most of them are excreted after combining with NH3 or HPO4-2

Front 18

metabolic alkalosis causes (2)

Back 18

loss of acid due to vomiting (so dissociate carbonic acid to compensate, which releases HCO3-)
ingestion of alkaline compounds

Front 19

compensation for metabolic alkalosis

Back 19

lungs decrease respiration rate

Front 20

respiratory alkalosis cause

Back 20

rapid respiration rate (blows off CO2)

Front 21

compensation for respiratory alkalosis (2)

Back 21

kidney excretes more HCO3- (and less Cl-)
kidney excretes less H+ and more Na+

Front 22

other important things to consider as acid-base condition cannot be used as a single diagnostic tool (3)

Back 22

patient history
normal levels of expected compensation
other blood work (anion gap)

Front 23

what type of compensation is rare?

Back 23

100% compensation for chronic respiratory acidosis
ergo, what appears to be completely compensated respiratory acidosis is often a metabolic alkalosis superimposed on the respiratory acidosis

Front 24

anion gap (and what is the gap itself)

Back 24

difference between sum of the cations Na+ and K+ and the sum of the anions Cl- and HCO3-
the gap indicates amount of random organic acid salts
so...
([Na+]+[K+])-([Cl-]+[HCO3-])

Front 25

reference range for anion gap

Back 25

12-16 mM

Front 26

larger than normal anion gap indicates...

Back 26

higher than normal levels of organic acid salts (can indicate metabolic acidosis)

Front 27

what causes HbS? (mutation, etc)

Back 27

mutation of b chain 6Glu (negative) to Val (hydrophobic)

Front 28

hydrophobic pocket

Back 28

a pocket on each beta subunit of Hb that is only exposed when O2 tension is low (deoxyhemoglobin)

Front 29

what causes the cell to be sickle shaped?

Back 29

the hydrophobic valine allows for a beta subunit on HbS to fit into hydrophobic pockets of deoxyhemoglobin, which causes Hb to polymerize within the RBC. this distorts the shape of RBC to sickle shaped.

Front 30

HbS polymerizes into...

Back 30

14 chain superstructures

Front 31

what happens when RBC are sickle shaped?

Back 31

they block capillaries-->hypoxia-->more deoxy Hb-->more sickling

hypoxia can cause organ damage
you get a vicious cycle

Front 32

why do patients with sickle cell anemia have low hematocrit? (2)

Back 32

hematocrit is ratio of cell volume to total volume
sickle cells take up less volume than discoid cells
lots of stress on sickle cell membrane due to weird shape causes them to be more fragile (lyse)

Front 33

why do patients with sickle cell often have elevated bilirubin?

Back 33

bilirubin is the breakdown product of heme. HbS tends to lyse easily so you'd get more breakdown products in the blood.

Front 34

why would hiking or physical activity cause an onset of sickle cell anemia? (2)

Back 34

if you were hiking in high elevations, you get a decrease in O2.
likewise, physical activity utilizes a lot of O2 by muscle, which decreases O2 in blood.
decrease in O2 leads to more deoxyhemoglobin -->more polymerization

Front 35

treatment of sickle cell disease (5)

Back 35

O2
analgesics- for pain; sickle cell can be very painful due to tissue death which recruits WBC-->swelling, painful
hydroxyurea- stimulates transcription of many genes, including gamma chain of heme.
Exchange transfusion- replace blood with healthy blood
Folate supplements

Front 36

what is the purpose of giving sickle cell patients hydroxyurea?

Back 36

since it stimulates transcription of gamma chains of heme, you get more gamma subunits, which can associate with a/b chains to form a hybrid a2bg hemoglobin unit. these units do not have pockets (gamma does not have pockets) on one end so they can "cap" the forming chains of deoxyhemoglobin.

Front 37

when is exchange transfusion recommended?

Back 37

only if hydroxyurea is contraindicated, e.g. in pregnant women and children, where there is development involved (because hydroxyurea can affect many genes, some of which are involved in development)

Front 38

why is folate supplementation sometimes recommended? (what does folate do)

Back 38

folate --> THF -->single C xfer rxns-->nucleotide synthesis
can help support higher rates of DNA synthesis for compensation of sickle cells that are lost to lysing

Front 39

sickle cell disease is inherited as...

Back 39

autosomal recessive (need 2 HbS allele to show disease)

Front 40

sickle cell carriers are special in that...

Back 40

they are symptomatic but have increased resistance to malaria plasmodium

Front 41

why is SCD more common in ______ race?

Back 41

blecks
because they get a lot of malaria over there

Front 42

plasmodia are ______ that infect...

Back 42

parasitic protozoa
red blood cells

Front 43

how do plasmodia affect their host cell? (2)

Back 43

located in rbc, while consuming "food", they produce CO2, increasing CO2 levels.
this increases likelihood that Hb is in tense state = decrease in O2 binding.
also decrease in pH (because of increase in CO2)

Front 44

why are SCD carriers immune to malaria plasmodium?

Back 44

production of CO2 and transformation of the infected Hb to tense state by the parasite causes some mutated deoxyHb to polymerize. the cell sickling leads to cell lysis, which then exposes the parasite to the immune system where it dies.

Front 45

ref range for pH

Back 45

7.4

Front 46

ref range for [HCO3-]

Back 46

24-27 mM

Front 47

ref range for pCO2

Back 47

40 mm Hg

Front 48

ref range for total CO2

Back 48

25-28 mM