Module 3: Transport in animals

Question 1

Describe the structure of haemoglobin

5 points

Is haemoglobin water soluble?

Answer 1

-consists of 4 polypeptide chains bonded together
-there are 2 alpha sub-units and 2 beta sub-units
-each sub-unit contains a prosthetic group(haem)
-it is a globular protein found in RBCs
-it contains Fe2+ ions

yes

Question 2

How many oxygen molecules can bind to 1 haemoglobin?
How does oxygen bind to haemoglobin

Answer 2

4
by binding to the haem groups

Question 3

Oxygen binds loosly to haemoglobin , write the word equation for this reaction.
Is this reaction reversible / irreversible

Answer 3

Hb + 4O2 —— Hb(O2)4

haemoglobin + oxygen —– oxyhaemoglobin

this reaction is reversible

Question 4

Describe how each oxygen molecule binds to haemoglobin…

Answer 4

1st Oxygen- the haem groups are embedded in the molecule so its less accessible to the oxygen molecule meaning the molecule takes longer to bind
2nd and 3rd-the binding of the 1st oxygen causes haemoglobin to change shape which makes the haem groups more accessible so next 2 oxygen molecules can bind easily
4th-only 1 site is left so it is harder for oxygen to bind

Question 5

There are different types of haemoglobin , what is one factor that makes them different?

What does partial pressure of oxygen mean?
How does partial pressure affect the oxygen affinity of haemoglobin?
When oxygen affinity is high , does haemoglobin hold oxygen tightly/loosly?

Answer 5

they have different oxygen affinities

the concentration of oxygen

as partial pressure increases the affinity of haemoglobin for oxygen increases
holds on tightly

Question 6

Explain how the relationship between partial pressure and oxygen affinity is useful for respiration.
4 points

Answer 6

-during respiration oxygen is used up rapidly
-this decreases the partial pressure of oxygen in the area
-this therefore decreases haemoglobin’s affinity for oxygen
-this results in haemoglobin readily releasing oxygen to respiring tissues so respiration can occur

Question 7

How does the saturation of haemoglobin affect its oxygen affinity?
3 points

Answer 7

-the binding of the 1st oxygen causes a shape change
-the shape change increases the affinity for oxygen
-this makes it easier for oxygen molecules to bind

Question 8

What happens to haemoglobin when the partial pressure of carbon dioxide increases?

What is the name of this effect?

Answer 8

haemoglobin releases oxygen more easily

The Bohr Effect

Question 9

Why is the Bohr Effect important in the body?

Answer 9

it results in;
-haemoglobin giving up oxygen more readily to active tissues as they have a high partial pressure of CO2
-oxygen binding to haemoglobin more easily in the lungs where the partial pressure of CO2 in the air is low

Question 10

Name the 3 ways CO2 is transported from the tissues to the lungs
Give percentages

Answer 10

5% is carried dissolved in plasma
10% combines with the amino groups of haemoglobin’s chains to form carbaminohaemoglobin
85% is transported in the form of hydrogen carbonate ions (HCO3)-

Question 11

Describe the process of carbon dioxide transport , starting with its production from cell metabolism and finishing with the start of the reverse of this process

Answer 11

-CO2 travels from tissue cells to a red blood cell
-CO2 reacts with H2O to form carbonic acid(H2CO3)
-this reaction is catalysed by carbonic anhydrase
-carbonic acid then dissociates to form hydrogen ions and hydrogen carbonate ions
-hydrogen carbonate ions diffuse out of RBCs and into plasma down their concentration gradient
-negatively charged chloride ions move into the RBC to maintain the electrical balance of the cell
-hydrogen ions bind with haemoglobin in the RBCs to make haemoglobonic acid

Question 12

What is the name given to the exchange of hydrogen carbonate ions and chloride ions?

What does haemoglobin act as when it binds with hydrogen ions , what does this ensure?

Answer 12

the chloride shift

acts as a buffer to prevent hydrogen ions decreasing the pH

Question 13

Describe the process of carbon dioxide transport starting with the reverse of the previous steps and finishing with us breathing it out

Answer 13

-hydrogen carbonate ions diffuse back into RBCs and chloride ions diffuse out back into the plasma
-hydrogen carbonate ions react again with hydrogen ions to form carbonic acid
-carbonic acid is then converted back into CO2 and H2O , this reaction is catalysed by carbonic anhydrase
-the CO2 then leaves the RBC and diffuses into alveoli
-we breathe out the carbon dioxide

Question 14

The heart is myogenic , what does this mean?

Answer 14

the cardiac muscles are able to initiate their own contractions without the need for nervous stimulation

Question 15

Name the 4 chambers of the heart in order

Answer 15

right atrium
right ventricle
left atrium
left ventricle

Question 16

Name the location of the tricuspid atrioventricular valves , the bicuspid AV valves and semi lunar valves

Answer 16

tricuspid-between the right atrium and right ventricle
bicuspid-between the left atrium and left ventricle
semi lunar-pulmonary artery and aorta

Question 17

What is the function of valves?

Answer 17

to prevent the back flow of blood

Question 18

What is the location and function of the septum?

Answer 18

it runs through the centre of the heart and prevents the mixing of de-oxygenated and oxygenated blood

Question 19

What is the role of the coronary arteries?

Answer 19

to supply oxygenated blood to cardiac muscle to allow it to keep contracting and relaxing

Question 20

What is the name of the membranes that surround the heart and what is their function?

Answer 20

inelastic pericardial membranes
-help to prevent the heart from over-distending with blood

Question 21

Name the 3 stages of the cardiac cycle in order of occurence

Answer 21

atrial systole
ventricular systole
diastole

Question 22

State and describe the features of atrial systole

3 points

Answer 22

1)the atria both contract to pump blood into the ventricles
2)this contraction forces the AV valves to open
3)the semi lunar valves are shut

Question 23

State and describe the features of ventricular systole

3 points

Answer 23

1)both the ventricles contract to pump blood into the pulmonary artery and aorta
2)blood forces the AV valves shut
3)the semi lunar valves are forced open due to a pressure gradient between the ventricles and the vessels

Question 24

State and describe the features of diastole

4 points

Answer 24

1)all chambers relax
2)the hearts elastic recoils which decreases the pressure inside the chambers
3) semi lunar valves close to prevent blood flowing back into the heart from vessels
4)AV valves open to allow blood from vena cava and pulmonary veins to trickle down from atria to ventricles

Question 25

How do you calculate cardiac output?

Answer 25

heart rate x stroke volume

Question 26

How is the basic rhythm of the heart maintained?

Answer 26

by a wave of electrical excitation

Question 27

Name the 2 nodes involved in controlling heart rate

Answer 27

sino-atrial node
atrio-ventricular node

Question 28

Describe the first stage of the heart rhythm

Answer 28

a wave of electrical excitation begins in the SAN causing the atria to contract
-a layer of non conductive tissue prevents the excitation passing directly to ventricles

Question 29

Describe the second stage of the heart rhythm

Answer 29

electrical activity of the SAN is picked up by the AVN and the AVN creates a slight delay before stimulating the bundle of His which penetrates through the septum

Question 30

What is the bundle of His

Answer 30

a bundle of conductive tissue made up of Purkyne fibres

Question 31

Describe the two final stages of the hearts rhythm

Answer 31

-the bundle of His separates into 2 branches and conducts the wave of excitation to the apex of the heart

-at the apex the Purkyne fibres spread out through the ventricular walls , the spread of excitation triggers the contraction of the ventricles

Question 32

How does the bundle of His prevent atrial systole and ventricular systole happening at the same time?

Answer 32

it causes a time delay in the electrical wave of excitation reaching the ventricles

Question 33

What is Tachycardia?

What is Bradycardia?

Answer 33

when heartbeat is too rapid , it exceeds 100bpm

when heartrate slows down to below 60bpm

Question 34

What does ectopic heartbeat mean?

Answer 34

when there are extra heart beats that are out of the normal rhythm

Question 35

What is atrial fibrillation?

Answer 35

its an example of an arrhythmia

where rapid electrical impulses are generated in the atria
they contract very quickly but not properly and only some of the impulses travel to the ventricles
this results in the heart not pumping blood effectively