Transport in animals-transport of oxygen and carbon dioxide

Question 1

what are erythrocytes?

Answer 1

red blood cells which carry oxygen around the blood

Question 2

what are the adaptations of erythrocytes?

Answer 2

• biconcave shape: greater surface area to volume ratio for diffusion.
• no nucleus: more space for oxygen

Question 3

how does a prosthetic haem group help erythrocytes?

Answer 3

combines with oxygen to absorb and release it.

Question 4

what is haemoglobin?

Answer 4

a red pigment that carries oxygen and also gives them their colour. It is a large gobbler conjugated protein made of four polypeptide chains

Question 5

oxygen binds with haemoglobin to form what compound?

Answer 5

oxyhemoglobin which helps maintain a steep concentration gradient so diffusion rate is high

Question 6

what is positive cooperativity?

Answer 6

when oxygen binds with the haemoglobin, the arrangement changes making it easier for the next oxygen molecules to bind

Question 7

what does the oxygen dissociation curve show?

Answer 7

how the affinity of oxygen (percentage oxygen saturation) changes with partial pressure

Question 8

what is the shape of an oxygen dissociation curve?

Answer 8

s shape (sigma) graph

Question 9

what occurs when the partial pressure increases?

Answer 9

higher partial pressure means a faster uptake of oxygen as it is more readily available, so there is a higher percentage oxygen saturation

Question 10

Is there a high or low partial pressure of oxygen in the lungs?

Answer 10

High. This allows a steep concentration gradient causing rapid loading of oxygen into haemoglobin

Question 11

Is the partial pressure of oxygen in the body high or low?

Answer 11

lower than the lungs in the tissue to allow rapid offloading of oxygen. This effect is enhanced due to low pH in tissues compared with lungs

Question 12

What is partial pressure of oxygen?

Answer 12

the concentration of oxygen in a mixture of gases e.g air

Question 13

what is the Bohr effect?

Answer 13

as partial pressure of the carbon dioxide rises, haemoglobin gives away more oxygen (because haemoglobin is designed to give oxygen to respiring tissues)

Question 14

why does a very small change in partial pressure of oxygen make a significant difference to the saturation of haemoglobin with oxygen?

Answer 14

because once the first molecule is attached, the change in shape of the haemoglobin means other oxygen molecules are added rapidly

Question 15

Why does the oxygen dissociation curve level out?

Answer 15

all heam groups are bound to oxygen and so haemoglobin is saturated and cannot take up anymore

Question 16

what happens to oxygen when the body is not very active?

Answer 16

The rest of the oxygen not needed in body cells acts as a reservoir for when oxygen demands suddenly increase.

Question 17

what are the two reasons to why the Bohr effect is important to the body?

Answer 17

• in active tissues with high pressure of carbon dioxide, haemoglobin gives up its oxygen more readily
• in the lungs where the proportion of carbon dioxide in the air is low, oxygen binds to haemoglobin molecules easily.

Question 18

what does it mean when an oxygen dissociation graph is displaced to the left?

Answer 18

It has a higher affinity for oxygen. This means it loads oxygen readily but offloads less readily

Question 19

what examples of haemoglobin show the oxygen displaced to the left(higher affinity)?

Answer 19

-foetal haemoglobin has a higher affinity for oxygen than its mothers haemoglobin as it needs to steal oxygen from the mothers blood.

Question 20

why is the biconcave shape helpful for an erythrocyte?

Answer 20

large surface area to volume ratio and allows to pass through narrow capillaries

Question 21

how is a steep concentration gradient maintained in cooperative binding?

Answer 21

since the oxygen is bound to haemoglobin, the free oxygen concentration remains low until all the haemoglobin become saturated.

Question 22

how is oxygen from erythrocytes transported to body cells?

Answer 22

Oxygen from erythrocytes (high conc) move out to body cells (low conc).

Question 23

why is the Bohr effect important in the body?

Answer 23

• in active respiring tissue when there is a high partial pressure of oxygen
• in the lungs where the proportion of carbon dioxide in the air is low, oxygen binds to haemoglobin molecules easily

Question 24

what three different ways are carbon dioxide transported from the tissues to the lungs?

Answer 24

• dissolved in blood plasma- least common
• combines with amino acids in the polypeptide chain of haemoglobin to form carbaminohaemoglobin
• converted into hydrogen carbonate ions (HCO3-) in cytoplasm of red blood cells.-most common

Question 25

how are hydrogen carbonate ions formed?

Answer 25

carbon dioxide reacts with water to form carbonic acid (H2CO3-)- a reversible reaction. The carbonic acid then dissociates to form H+ ions and hydrogen carbonate ions

Question 26

describe the reaction of the formation of hydrogen carbonate ions?

Answer 26

in blood plasma the reaction is very slow. In the cytoplasm of red blood cells carbonic anhydrase catalyst

Question 27

What is the chloride shift?

Answer 27

The hydrogen carbonate ions move out of erythrocytes into the plasma by diffusion down a concentration gradient and negatively charged chloride ions move into the erythrocytes which maintain the electrical balance of the cell.

Question 28

How is carbon dioxide released from erythrocytes to lung tissue?

Answer 28

Blood reaches lung tissue (low conc of carbon dioxide). Hydrogen carbonate ions diffuse back into erythrocytes and react with hydrogen ions to form carbonic acid. It is broken down by carbonic anhydrase to form free carbon dioxide. This diffuses out of blood into lungs. Chloride ions diffuse out of red blood cells into plasma down an electrochemical gradient.

Question 29

How does haemoglobin act as a buffer?

Answer 29

prevents changes in pH by accepting free H+ ions in reversible reaction to form haemoglobinic acid