8.4 Transport of oxygen and carbon dioxide in blood

Question 1

Why is the biconcave shape of an erythrocyte (red blood cell) an adaptation to its main function of transporting oxygen?

Answer 1

It provides a larger surface area than a simple disc or spherical structure, so it increases the area available for the diffusion of gases

It also helps them to pass through narrow capillaries

Question 2

In adults, where are erythrocytes (red blood cells) continuously formed?

Answer 2

In the red bone marrow

Question 3

Fill in the blanks: By the time mature ____________ enter the ___________ they have lost their nuclei, which maximises the amount of ___________ that fits into the cells.

Answer 3

a) Erythrocytes
b) Circulation
c) Haemoglobin

Question 4

The life of erythrocytes (red blood cells) is limited to how many days?

Answer 4

Around 120

Question 5

What substance do erythrocytes (red blood cells) contain that carries oxygen and also gives them their colour?

Answer 5

Haemoglobin - a red pigment

Question 6

Fill in the blanks: Haemoglobin is a very large ________ conjugated protein made up of four _______ chains, each with an iron-containing haem

Answer 6

a) Globular
b) Peptide
c) Prosthetic

Question 7

How many haemoglobin molecules are there in each erythrocyte (red blood cell) approximately?

Answer 7

300 million

Question 8

How many oxygen molecules can each haemoglobin molecule bind to?

Answer 8

Four

Question 9

What product is formed in the loose binding of oxygen to haemoglobin? (This reaction is reversible)

Answer 9

Oxyhaemoglobin

Question 10

Are oxygen levels relatively low when erythrocytes (red blood cells) enter the capillaries in the lungs?
(Yes/No)

Answer 10

Yes

Question 11

In terms of a steep concentration gradient being formed, where would that be between in terms of oxygen?

Answer 11

The inside of the erythrocytes (red blood cells) and the air in the alveoli

Question 12

Oxygen moves into the erythrocytes (red blood cells) and binds with.. what?

Answer 12

Haemoglobin

Question 13

Fill in the blanks: The arrangement of the ___________ molecule means that as soon as one oxygen molecule binds to a ____ group, the molecule changes _____, making it easier for the next ______ molecules to bind. This is known as positive cooperativity.

Answer 13

a) Haemoglobin
b) Haem
c) Shape
d) Oxygen

Question 14

Does the free oxygen concentration in the erythrocyte stay high or low due to oxygen being bound to the haemoglobin?

Answer 14

Low

Question 15

Is a steep concentration gradient maintained until all of the haemoglobin is saturated with oxygen? (Yes/No)

Answer 15

Yes

Question 16

When blood reaches the body tissues, the positive cooperativity situation reverses so that the concentration of oxygen in the erythrocytes (red blood cells) is higher than the oxygen in what component of the body cells?

Answer 16

The cytoplasm

Question 17

Once the first oxygen molecule is released by the haemoglobin in the reverse reaction, what happens to the molecule?

Answer 17

It changes shape, so it becomes easier to remove the remaining oxygen molecules.

Question 18

What is an oxygen dissociation curve an important tool for?

Answer 18

Understanding how the blood carries and releases oxygen

Question 19

What is plotted on an oxygen dissociation curve?

Answer 19

The percentage saturation haemoglobin in the blood against the partial pressure of oxygen (pO2).

Question 20

What do oxygen dissociation curves show?

Answer 20

The affinity of haemoglobin for oxygen.

Question 21

Fill in the blanks: A very small change in the _______ pressure of oxygen in the surroundings makes a ___________ difference to the saturation of the ___________ with oxygen, because once the first molecule becomes attached, the change in _____ of the haemoglobin means other oxygen molecules are added rapidly.

Answer 21

a) Partial
b) Significant
c) Haemoglobin
d) Shape

Question 22

Why does the curve on an oxygen dissociation curve graph level out at the highest partial pressures of oxygen?

Answer 22

All the haem groups are now bound to oxygen so the haemoglobin is saturated and cannot take up any more.

Question 23

Fill in the blanks: At the ____ partial pressure of oxygen in the lungs, the ___________ in the erythrocytes (red blood cells) is rapidly loaded with oxygen.

Answer 23

a) High

b) Haemoglobin