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PHSL 232 > L17 > Flashcards

L17 Flashcards

1
Q

O2 is carried in the blood in two forms. what are these

A
  1. Dissolved O2

2. Combined with haemoglobin

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2
Q

per 100mL of blood how much O2 can be dissolved

A

0.3mL

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3
Q

arterial blood has a PO2 of about 100 mmHg. how many mL of O2 could be dissolved in the blood

A

only 3 ml dissolved O2 / litre

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4
Q

describe the structure of hemoglobin

A

it is a protein complex with 4 subunits (tetramer)

it subunits known as globin (2 alpha and 2 beta)

there is 1 heme group
attached to each subunit (therefore 4 heme groups in total)

each heme group has a iron atom which is what allows O2 to bind

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5
Q

describe the structure of the Heme in relation to haemoglobin ability to carry O2

A

Each heme can ’bind’ one O2 molecule

there are 4 Heme’s in each Hb molecule therefore each Hb molecule can carry 4 O2

O2 forms an easily reversible combination with Hb to give
oxyhaemoglobin:
O2 + Hb ↔ HbO2

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6
Q

what does a lack of iron result in

A

anemia

which affects O2 binding/carrying
capacity

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7
Q

what makes up hemoglobin

A

4 Heme + Globin (4 peptides) = hemoglobin (Hb)

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8
Q

what does binding of O2 to Hb depend on

A

Binding depends on 𝑃𝑂2 - dissociation curve - saturation

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9
Q

what is the real colours of oxygenated and deoxygenated blood

A

Oxygenated/arterial blood = bright red

Deoxygenated/venous = dark red

no O2 = black

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10
Q

what contributes to the colour of blood

A

Heme group and its
iron atom account
for color ± O2

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11
Q

in clinical setting if you were to take arterial blood and it had a dark red colour, what would this mean

A

there is something wrong with the patients partial pressure

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12
Q

what does the Oxygen-haemoglobin dissociation curve tell us

A

Tells us how much hemoglobin is bonding to the O2 and how that depends on the PP of oxygen

As the pressure increases so does the hemoglobin O2 saturation

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13
Q

describe the Oxygen-haemoglobin dissociation curve shape

A

sigmoidal

the curve has 2 parts

The flat part

And the steep low part

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14
Q

describe the upper flat part of the Oxygen-haemoglobin dissociation curve

A

moderate changes in
𝑃𝑂2 around the normal value (~100 mmHg) have only
small effects on the % saturation and therefore the
amount of O2 carried by arterial blood

therefore the upper part provides some reserve capacity.

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15
Q

describe the steep part of the oxygen-haemoglobin dissociation curve at lower 𝑃𝑂2

A

helps with
loading of Hb in lungs AND unloading of O2 to the tissues.

Small changes in PO2 result in large changes in amount of O2 bound to Hb.

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16
Q

why can the Oxygen-haemoglobin dissociation curve

shift left or right

A

because of the Bohr effect

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17
Q

what could cause the Oxygen-haemoglobin dissociation curve to shift to the right

A

natural right shift occurs as blood flows through the capillaries of the tissues (because of high metabolic demand and therefore high CO2 and H+) to facilitate O2 release.

increased 2,3 BPG (DPG), H+, temperature and CO2

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18
Q

what does a right shift cause in terms of Hb’s affinity for O2

A

more likely to release O2

favors the release of O2 from Hb to the
tissues (offloading).

Right = Release

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19
Q

what does a left shift cause in terms of Hb’s affinity for O2

A

more likely to bind O2

favors the binding of O2 to Hb
(onloading)

Left = Loading

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20
Q

what could cause the Oxygen-haemoglobin dissociation curve to shift to the left

A

natural left shift occurs as blood flows through the lung capillaries (Less CO2
and H+)

facilitates the uptake of O2 from the alveoli into the blood

decreased 2,3 BPG (DPG), H+, temperature and CO2

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21
Q

what is the main factor that cases the Oxygen-haemoglobin dissociation curve to shift left or righ

A

the partial pressure of CO2

22
Q

what is 2,3 BPG (DPG)

A

Di or bi phosphoglycerate

it is a byproduct of glycolysis

23
Q

what is the result of the Bohr effect

A

it improves both the pick up and delivery of O2 by Hb

24
Q

describe CO-hemoglobin disassociation

A

the curve is vertical as Hb has a much higher affinity for CO than it does for O2

affinity is 200x more

25
Q

what does binding of CO to Hb cause

A

less O2 can be bound therefore less O2 is carried around the body

it also shifts the O2-Hb dissociation curve to the left causing the release O2 in the tissue only at very low PO2

26
Q

what is the O2 carrying capacity

A

The maximal amount of O2 that can be combined with Hb is called O2 carrying capacity

i.e Amount of O2 carried when Hb 100% saturated

27
Q

one gram can combine with how many moles of O2

A

1.34

28
Q

what is O2 content

A

How much O2 is the blood carrying

29
Q

how do you calculate O2 content

A

O2 content = O2 capacity x saturation

+( O2 dissolved)

30
Q

calc O2 content of the arterial blood

(Assume 150g of Hb/litre; PaO2 100 mmHg; SaO2 98%).

A

O2 content = O2 capacity x saturation
+( O2 dissolved)

1.34 x 150 x 98/100 +(0.03 x 100) = 200mL O2/litre blood

31
Q

what are the units for O2 content

A

mL O2/litre blood

32
Q

what is the a-v difference

A

amount of O2 extracted by tissues

33
Q

compare the normal a-v difference to the a-v difference when excersizing

why does this happen

A

More oxygen is extracted and used by tissues when exercising. therefore the a-v O2 difference will increase

Normal a - v difference = 50 ml O2/L blood

Exercise a - v difference might be 150 ml O2/L

the steeper part of the O2-Hb disassociation curve allows for this

34
Q

what does anemia do to the O2-Hb dissociation curve

A

Saturation curve stays same as there are no problems with the saturation part it has to do with the content

O2 content reduced (because of low hemoglobin level)

Exercise problems from a-v difference
e.g Can’t remove 150 ml/L when only have 100

35
Q

what does anemia become a problem

A

at rest the individual will usually be fine

however when they start exercising is when the problem presents itslef

this is because of issues with the a-v difference eg you can’t remove 150 ml/L when only have 100

therefore in anemia you loose the steep part of the O2-Hb dissociation curve

36
Q

CO2 is transported in 3 forms. what are these

A
  1. Dissolved in plasma
  2. As bicarbonate
  3. Combined with proteins as carbamino compounds
37
Q

how many x more soluble is CO2 in the plasma compared to O2

A

20x

38
Q

what % of CO2 is transported dissolved in plasma

A

10%

39
Q

what % of CO2 is transported as bicarbonate

A

(70%)

40
Q

what % of CO2 is transported in hemoglobin

A

20%

41
Q

what is it called when Co2 is bound to Hb

A

carbaminohemoglobin

42
Q

what causes the increase in H+ when CO2 is transported

A

when CO2 is transported in Hb it interacts with N, when it does this it knocks off a H+ making the blood more acidic (decreasing the pH)

when bicarbonate is made H+ is a byproduct

43
Q

how is CO2 converted into bicarbonate (HCO3-)

A

CO2 + H2O –> H+ + HCO3-

carbonic anhydrase catalyzes this reaction

44
Q

what catalyses the bicarbonate reaction

A

carbonic anhydrase

45
Q

what is the difference between the CO2 and the O2-Hb disassociation curve

A

CO2 is more linear and it gets shifted up and down instead of left and right

46
Q

what causes the upward shift of the CO2-Hb dissociation curve

A

a decrease in O2 partial pressure (PO2)

47
Q

what causes the downward shift of the CO2-Hb dissociation curve

A

a increase in O2 partial pressure (PO2)

48
Q

what is the result of the upward shift of the CO2-Hb dissociation curve

A

CO2 and H+ bind more readily to globin
chain when the heme contains less O2

i.e., as arterial blood flows through the tissue capillaries losing O2, the change in molecular configuration of Hb favours the onloading of CO2 onto the globin chain

49
Q

what is the result of the downward shift of the CO2-Hb dissociation curve

A

CO2 and H+ bind less readily to globin
chain when the heme contains more O2

i.e., as venous blood flows through the lung
capillaries gaining O2, the change in molecular configuration of Hb to promote the release of CO2 in the alveoli

50
Q

The majority of CO2 transport in the blood occurs as:

A. dissolved.

B. Carbamino-hemoglobin.

C. Combined with heme.

D. HCO3-

E. A and B.

A

D

PHSL 232 (30 decks)

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