Lesson 3 - Transporting oxygen and carbon dioxide

Question 1

meaning oxyhaemoglobin

Answer 1

the molecule formed when oxygen binds to haemoglobin

Question 2

meaning bohr effect

Answer 2

the name given to changes in the oxygen dissociation curve of haemoglobin that occur due to a rise in carbon dioxide levels and a reduction of the affinity for oxygen than adult haemoglobin

Question 3

meaning fetal haemoglobin

Answer 3

a form of haemoglobin found only in the developing fetus with a higher affinity for oxygen than adult haemoglobin

Question 4

meaning myoglobin

Answer 4

a respiratory pigment found in the muscle tissue of vertebrates with a higher affinity for oxygen than haemoglobin

Question 5

meaning carbaminohemoglobin

Answer 5

the compound formed when carbon dioxide combines with haemoglobin

Question 6

meaning carbonic anhydrase

Answer 6

the enzyme that controls the rate of the reaction between carbon dioxide and water to form carbonic acid

Question 7

meaning serotonin

Answer 7

a chemical that causes the smooth muscle of the blood vessels to contract, narrowing them and cutting off the blood flow to the damaged area

Question 8

meaning thromboplastin

Answer 8

an enzyme that sets in progress a cascade of events that leads to the formation of a bloot clot

Question 9

meaning prothrmobin

Answer 9

a large, soluble protein found in plasma that is the precursor to the enzyme thrombin

Question 10

thrombin

Answer 10

an enzyme that acts on firbinogen, converting it to fibrin during clot formation

Question 11

fibrin

Answer 11

an insoluble protein formed from fibrinogen by the action of thrombin that forms a mesh of fibres that trap erythrocytes and platelets to form a blood clot

Question 12

describe the structure of haemoglobin

Answer 12

a large globular protein made up of 4 peptide chains, each with an iron-containing prosthetic group, which can pick up 4 oxygen molecules in a reversible reaction to form oxyhaemoglobin

Question 13

describe the bonding of oxygen molecules to the haemoglobin

Answer 13

The first oxygen binding to the haemoglobin changes the arrangement of the molecule, making it easier for the following oxygen molecule to bind. The final oxygen molecule binds extremely faster than the first. However, when oxygen is removed from the haemoglobin, it gets progressively harder to remove the oxygen molecule/

Question 14

describe the conc. of oxygen in the lungs

Answer 14

concentration of oxygen in red blood cells entering lungs is relatively low

Question 15

how is a high concentration gradient maintained between the air and the blood cells in the lungs

Answer 15

because oxygen is îcked up and bound to the haemoglobin, the free oxygen concentration in the cytoplasm of the red blood cells stays low. Thus, there’s a high conc. gradient and more and more oxygen diffused in

Question 16

Describe how oxygen is released and taken in to the haemoglobin with help of the conditions of the body

Answer 16

The conditions inside the lungs are very moist and humid, causing the oxygen saturation to increase. Thus oxygen is bonded rapidly to the haemoglobin. However, in the tissues, the oxygen saturation is low, so oxygen is released

Question 17

why does haemoglobin release oxygen rapidly

Answer 17

as the partial pressure of carbon dioxide is high, the affinity of haemoglobin for oxygen is reduced.

Question 18

how is oxygen transfer between the mother and fetus maximised

Answer 18

• fetal haemoglobin in the fetal blood has a higher affinity for oxygen than the mother, removing oxygen from the maternal blood
• the maternal and fetal blood run in opposite directions, so there’s a counter-current exchange system

Question 19

how does myoglobin release its oxygen molecules in very active muscle

Answer 19

the oxygen levels in active muscle is low, and the levels of carbon dioxide is high. Thus, the myoglobin finally releases its store of oxygen

Question 20

why is myoglobin useful as a oxygen store

Answer 20

myoglobin has a much higher affinity for oxygen than haemoglobin, so it easily becomes saturated with oxygen. So, once myoglobin binds to oxygen, it does not give it up easily

Question 21

describe the reaction between carbon dioxide and water, when carbon dioxide is dissolved in the blood

Answer 21

the carbon dioxide reacts slowly with water to form carbonic acid. The carbonic acid separates to form the ions H + and HCO3 -

Question 22

formula for carbonic acid

Answer 22

H2CO3

Question 23

State 3 ways in which carbon dioxide can be transported

Answer 23

• 5% carried by plasma
• 10-20% combines with haemoglobin to form carbaminohemoglobin
• rest transported in cytoplasm of red blood cells as hydrogen carbonate ions

Question 24

what is the role of carbonic anhydrase in body tissues

Answer 24

as there’s a high concentration of carbon dioxide in body tissues, carbonic anhydrase catalyses the formation of carbonic acid

Question 25

what is the role of carbonic anhydrase in the lungs

Answer 25

as there's a low concentration of carbon dioxide in the lungs, carbonic anhydrase catalyses the reverse reaction, and free carbon dioxide diffuses out of the blood into the lungs

Question 26

why does the blood clot

Answer 26

it seals up damaged blood vessels to minimise blood loss and prevent pathogens getting in

Question 27

explain the blood clotting cascade

Answer 27

1. plasma, blood cells and platelets flow from a cut vessel. Contact between the platelets and tissue components causes the platelets to break open and release serotonin and thromboplastin 2. Thromboplastin catalyses the conversion of prothrombin into thrombin. This happens at large scale at the site of the wound. Calcium ions need to be present in the blood for this reaction. 3. Thrombin also catalyses the conversion of fibrinogen into fibrin. This forms a mesh of fibres to cover the wound 4. More platelets and blood cells poure from the wound and get trapped in the fibrin mesh, forming a clot 5. Special proteins in the structure of the platelets contract, making the clot tighter and tougher to form a scab.

Question 28

Prothrombin and fibrinogen are both precursors. Discuss the similarities and differences between these 2 proteins

Answer 28

Both precursors are involved in blood clotting and are produced in the liver. However, as prothrombin is converted into thrombin, fibrinogen is converted into fibrin. Also, fibrinogen is dependent on vitamin K, whilst fibrinogen isn't