o2 + co2 transport in blood

Question 1

what % of total oxygen in blood is carried by haemoglobin

Answer 1

98%

Question 2

what is haemoglobin saturation defined as

Answer 2

Haemoglobin saturation: percentage of total Hb binding sites available for oxygen binding that are occupied by oxygen

Question 3

_____ is the dissolved o2 in blood NOT the o2 bound to haemoglobin

Answer 3

artial pressure is the dissolved o2 in blood NOT the o2 bound to haemoglobin

Question 4

what are the 3 forms co2 exists in the blood as

Answer 4

• CO2 in blood exists in three forms:1) Dissolved CO2 ~ 10%2) CO2 reacted with water to form bicarbonate – HCO3- ~ 60%3) CO2 bound to Haemoglobin – (at different site from oxygen) ~ 30%
  (percentages for venous blood; relative amounts same arterial blood )

Amount dissolved CO2 arterial blood plasma determined by amount CO2 in lung alveoli - equilibrium.

NB: The majority of CO2 in blood is not transported by a carrier. This means that the more CO2 produced by tissues the more can be delivered to lungs to be exhaled.

• Arterial blood: 85% of co2 in blood is transported as carbonic acid, 10% is carried by hemoglobin as carbamate, and 5% is transported as either dissolved gas or carbonic acid

Question 5

what is Polycythaemia

Answer 5

Polycythaemia is where we have too much Hb because too many RBCs (i.e. increased hematocrit)

n.b.Athletes who abuse ERYTHROPOITIN (hormone that increases rbc production) can lead to polycythaemia

Question 6

what is anaemia
vs iron deficiency anaemia

Answer 6

is a problem of not having enough healthy red blood cells or hemoglobin to carry oxygen to the body’s tissues.
(i.e. decreased hematocrit)
Iron deficiency anaemia is where your body does not produce enough red blood cells because the level of iron in your blood is too low.

Question 7

what is mean corpuscular haemoglobin vs mean corpuscular haemoglobin conc

Answer 7

amount of haemoglobin in a cell
vs amount of haemoglobin relative to size of rbc

Question 8

what is a hematocrit
+ what happens if hematocrit too high/low

Answer 8

the hematocrit is of a volume of blood, how much of that volume of blood is taken up by red blood cells

if hematocrit too high we get obstruction in small blood vessels we can get strokes/ blood clots.
if hematocrit too low the body may not be able to function properly due to a lack of oxygen

Question 9

what do we mean when we say a cell is hypochromic

Answer 9

Hypochromia/ hypochromic cells means that the red blood cells have less color than normal when examined under a microscope. This usually occurs when there is not enough of the pigment that carries oxygen (hemoglobin) in the red blood cells

Question 10

what is a reticulocyte

Answer 10

‘teenage/immature red blood cell’ its gotten rid of nucleus, slightly bigger than mature rbc

Reticulocytes change into mature RBCs ~ 1 day after entering circulation. Able to carry oxygen but not as efficiently as mature RBCs.
* Called reticulocytes because of reticular (mesh-like) network of ribosomal RNA visible with methylene blue stain. Ribosomes enable reticulocytes to complete production of haemoglobin

Question 11

where are red blood cells made

Answer 11

bone marrow

Question 12

Mature RBCs have ____ nuclei or mitochondria!

Answer 12

Mature RBCs have no nuclei or mitochondria!

Question 13

how do rbc’s get ATP for energy since they have no mitochondria

Answer 13

GLYCOLYSIS= derive energy from glucose in absence of oxygen

glucose-> PEP->pyruvate->lactate

glucose taken through facilitated diffusion so RBC do this without insulin

Question 14

RBCs produce ATP by glycolysis: (conversion of glucose to pyruvate followed by conversion of pyruvate to lactic acid - less efficient than aerobic metabolism). RBC glucose uptake is mediated by Glut 1 transporters: Glut1 works by facilitated diffusion and not regulated by insulin.

In a further step, some NAD+ is converted into NADP+ by NAD+ kinase, which phosphorylates NAD+.

• Due to high pO2 in RBCs, NAD+ spontaneously formed from NADH (O2 took electron – oxidation)
• RBCs then use enzymes convert NAD+ to NADPH.
• Formation of NADPH counteracts oxidative stress in RBCs.

    ○ NADPH required for enzyme \_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_ which is required to maintain adequate cellular levels \_\_\_\_\_\_\_\_ – key anti-oxidant

RBCs also have ______ – another anti-oxidant

Answer 14

RBCs produce ATP by glycolysis: (conversion of glucose to pyruvate followed by conversion of pyruvate to lactic acid - less efficient than aerobic metabolism). RBC glucose uptake is mediated by Glut 1 transporters: Glut1 works by facilitated diffusion and not regulated by insulin.

In a further step, some NAD+ is converted into NADP+ by NAD+ kinase, which phosphorylates NAD+.

• Due to high pO2 in RBCs, NAD+ spontaneously formed from NADH (O2 took electron – oxidation)
• RBCs then use enzymes convert NAD+ to NADPH.
• Formation of NADPH counteracts oxidative stress in RBCs.

    ○ NADPH required for enzyme GLUTATHIONE REDUCTASE which is required to maintain adequate cellular levels GLUTATHIONE – key anti-oxidant

RBCs also have VITAMIN C – another anti-oxidant

Question 15

G6PD deficiency most common enzyme deficiency in world – what might be associated pathology?

Answer 15

it can manifest as hemolytic anemia, favism (especially in G6PD Mediterranea), chronic non-spherocytic hemolysis, spontaneous abortions

if ppl don’t go through a lot of oxidative stress they won’t know they have it (certain food/ meds that increases oxidative stress causing them to break down rbc’s) U WILL SEE IN CLINICAL PRACTISE

Question 16

• Porphyrin ring: large ring molecule consisting of 4 pyrroles, - smaller rings made from 4 carbons and 1 nitrogen
• When porphyrin ring has iron atom bound in centre called _____
• Several enzymes contain haem group - known as haem proteins. Examples:

myoglobin, cytochromes, catalases, heme peroxidase, and endothelial nitric oxide synthase

Answer 16

• Porphyrin ring: large ring molecule consisting of 4 pyrroles, - smaller rings made from 4 carbons and 1 nitrogen
• When porphyrin ring has iron atom bound in centre called HAEM.
• Several enzymes contain haem group - known as haem proteins. Examples:

myoglobin, cytochromes, catalases, heme peroxidase, and endothelial nitric oxide synthase

Question 17

what is steric hindrance in Hb

Answer 17

Hb function has been explained in terms of equilibrium between two classical states: the tense (T) state (unliganded Hb) which exhibits low affinity for O2, and the relaxed (R) state (liganded Hb) which exhibits high affinity for O2.

The T-state has lower affinity for dioxygen due to the tilting of the proximal histidine and steric hindrance of the O2 coordination site. 6,12. Steric hindrance makes it difficult for oxygen molecule to enter the site and bind to Fe

Question 18

what is methaemoglobin

Answer 18

Methemoglobin is a form of hemoglobin that has been oxidized, changing its heme iron configuration from the ferrous (Fe2+) to the ferric (Fe3+) state. Unlike normal hemoglobin, methemoglobin does not bind oxygen and as a result cannot deliver oxygen to the tissues

Methemoglobin cannot bind oxygen, which means it cannot carry oxygen to tissues. a condition in congenital disorders

mature haemoglobin as cells age enzyme levels decrease - methaemoglobin increases.
~1-2 % of healthy people’s haemoglobin is methaemoglobin - higher percentage genetic deficiency methaemoglobin reductase (rare) or caused by exposure to various chemicals - Methaemoglobinemia.

Question 19

as Rbc get old what happens

Answer 19

RBC’s progressively damaged by o2

RBC senscence characterised by rise in RBC methaemoglobin– cause markers to change on RBC membrane. Change detected by cells liver + spleen which remove RBCs

As aging RBCs undergo changes in plasma membrane - susceptible to recognition by phagocytes and subsequent phagocytosis in spleen, liver and bone marrow

Question 20

SaO2 is percentage of haemoglobin that is carrying oxygen - written as % Hb saturation.

Arterial SaO2 can be measured with a _____ _____

Answer 20

SaO2 is percentage of haemoglobin that is carrying oxygen - written as % Hb saturation.

Arterial SaO2 can be measured with PULSE OXIMETER (put ur finger in it and it measures o2 by looking at absorption of light in haemoglobin) much less acurate in ppl w darker skin

Question 21

Can you think of condition where Hb saturation is fine but patient hypoxic?

Answer 21

It doesn’t tell u the tissue oxygen levels, even tho Hb themselves fully oxygenated= the condition is anaemia; all Hb fully saturated but not enough RBC’s so not enough o2 delivered to the tissues

Question 22

what does The oxygen/haemoglobin (Hb) dissociation curve show

Answer 22

Graph showing how changes in partial pressure of oxygen change Hb saturation

Saturation is expressed as the percentage of Hb that has bound oxygen against 100% saturation - independent of Hb concentration
For example, if there were only one Hb molecule in your body but it was carrying 4 oxygen molecules it would be 100% saturated
Haemoglobin saturation itself therefore does not tell us how much haemglobin is in blood

Question 23

what is erythropoetin

Answer 23

hormone that controls red blood cell synthesis. Formed in kidney renal cortex

Question 24

We are producing co2 in tissues, that co2 diffuses down its partial pressure gradient into the venous blood bathing the tissues. So partial pressure of co2 in tissues is higher than the partial pressure of co2 in blood. It diffuses out then into the RBC where co2 react with water to form carbonic acid– this reaction is accelerated by ________ found in RBC. The reaction leads to bicarbonate which leaves rbc in exchange for chloride. Bicarbonate- chloride exchange transporter = we are left with a proton. This is a fully reversible reaction. In the lungs the partial pressure of co2in alveoli is lower, so the co2 levels in blood after co2 has diffused into alveoli is lower than co2 levels in rbc, so co2 leaving rbc into alveoli to be exhaled. As long as we can maintain a lower partial pressure of co2 in the alveoli relative to the blood relative to red blood cell; then co2 will leave rbc into blood into alveoli to be exhaled.

Answer 24

We are producing co2 in tissues, that co2 diffuses down its partial pressure gradient into the venous blood bathing the tissues. So partial pressure of co2 in tissues is higher than the partial pressure of co2 in blood. It diffuses out then into the RBC where co2 react with water to form carbonic acid– this reaction is accelerated by CARBONIC ANHYDRASE found in RBC. The reaction leads to bicarbonate which leaves rbc in exchange for chloride. Bicarbonate- chloride exchange transporter = we are left with a proton. This is a fully reversible reaction. In the lungs the partial pressure of co2in alveoli is lower, so the co2 levels in blood after co2 has diffused into alveoli is lower than co2 levels in rbc, so co2 leaving rbc into alveoli to be exhaled. As long as we can maintain a lower partial pressure of co2 in the alveoli relative to the blood relative to red blood cell; then co2 will leave rbc into blood into alveoli to be exhaled.

Question 25

when the o2 dissociation curve shifts to the RIGHT, what does it mean + when does it happen?

Answer 25

it means its EASIER FOR haemoglobin to release its o2 (reduced affinity)

curve shifts to the right when:
*increased temperature
*increased H+
*increased 2,3-DPG

*n.b. think about it as when the tissues are more active; they are hotter, produce more acid (need more o2, so ofc affinity of haemoglobin to o2 is reduced!)

Question 26

when the o2 dissociation curve shifts to the LEFT, what does it mean + when does it happen?

Answer 26

it means its HARDER FOR haemoglobin to release its o2 (increased affinity)

curve shifts to the right when:
*decreased temperature
*decreased H+
*decreased 2,3-DPG

Question 27

what is 2,3DPG

Answer 27

2,3-DPG acts as a regulator of the allosteric properties of hemoglobin in the RBC. When 2,3-DPG is bound to hemoglobin, it stabilizes the T-state conformation and decreases hemoglobin affinity for oxygen.

.

Question 28

why do people who live at high altitude have more rbc’s (+ they have more 2,3DPG)

Answer 28

Oxygen pressure in the air at high altitude is lower than the Oxygen pressure at low altitude. This means there is slower Oxygen exchange in lungs in high altitude. This causes low Oxygen in Red blood cells. So This low Oxygen status triggers Erythropoetin (EPO) hormon synthesis and EPO triggers bone marrow to produce more red blood cells. With more Red blood cells lung can take oxygen more easily in high altitude. This is an adaptation.

Question 29

what is myoglobin

Answer 29

Myoglobin is an o2 store for musclrs

Mb form of haemoglobin found in muscle.
Single subunit protein (1 polypeptide chain) with higher affinity for oxygen than haemoglobin (Hb);

has only 1 haem grp, so only needs 1, it slowly oxidises to methaemoglobin

Therefore O2 is transferred to MbO2 from Hb as blood passes through muscle capillaries.

Mb thus forms a ‘buffer store’ of oxygen in muscle- especially important start of exercise. Myoglobin is not normally found in smooth muscle

Question 30

what drives rbc synthesis

Answer 30

horomone erythropoetin

Question 31

what is hypoxia

Answer 31

Hypoxia is a state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis;

aka in short
hypoxia = low tissue oxygen relative to need