3 Substance exchange- Mass transport (animals)

Question 1

What is haemoglobin and its function?

Answer 1

Globular protein with a quaternary structure (4 polypeptide chains) found in red blood cells
Carries oxygen from lungs around the body

Question 2

What is dissociation?

Answer 2

When red blood cells reach tissues in the body (e.g. muscle cells), O2 is released from oxyhaemoglobin

Question 3

What are haem groups?

Answer 3

Each polypeptide chain in a haemoglobin molecule has a haem group- a prosthetic group attached to the protein. These contain iron (what makes haemoglobin red)

Question 4

How do oxygen and haemoglobin bind?

Answer 4

-Haemoglobin has a high affinity (attraction) for oxygen
-When red blood cells reach lungs, O2 diffuses into them- binding to haemoglobin. 4 oxygen molecules bind to one haemoglobin due to the haem groups
-Oxygen + haemoglobin = oxyhaemoglobin

Question 5

What is (pO2) partial pressure?

Answer 5

-Concentration of oxygen in the cells
-Important in determining whether oxygen binds to haemoglobin
-Determines affinity of haemoglobin for oxygen

Question 6

What happens when partial pressures of oxygen are high/low?

Answer 6

High- haemoglobin has a high affinity for oxygen, binds to haemoglobin
Low- haemoglobin has a low affinity for oxygen, dissociates from haemoglobin
Percentage saturation is low as oxygen dissociates

Question 7

What does the effect of pO2 on the affinity of haemoglobin allow?

Answer 7

Allows oxygen to be transported from lungs (where there’s lots of oxygen) to respiring tissues (where oxygen is limited). So, it travels to the cells which need it the most

Question 8

What effect does high altitude have on haemoglobin?

Answer 8

-Haemoglobin has a high affinity for oxygen, birds also possess this
-Advantage as air at higher altitudes has a much lower partial pressure than sea level

Question 9

What effect does high metabolic rate have on haemglobin?

Answer 9

-Haemoglobin that dissociates with oxygen very easily
-Oxygen can then be quickly and easily supplied to the cells for use in respiration

Question 10

What happens as partial pressure increases?

Answer 10

-Affinity of haemoglobin for oxygen increases slightly
-When first O2 molecule binds, the protein undergo a conformational change
-This allows the other O2 molecules to bind more easily and percentage saturation of haemoglobin increased quickly

Question 11

What causes a plateau in percentage saturation?

Answer 11

As more O2 molecules bind to haemoglobin, it becomes more difficult for them to bind and percentage saturation of haemoglobin plateaus

Question 12

What creates an S-shaped curve?

Answer 12

-Increasing affinity of haemoglobin with increasing partial pressure of oxygen
-This is called the dissociation curve

Question 13

What is the Bohr effect?

Answer 13

The partial pressure of carbon dioxide influencing the affinity of haemoglobin for oxygen
High pCO2- Rate of oxygen dissociation decreases, as respiring cells use oxygen in respiration, making CO2. So, they have a low pO2 and high pCO2.
Increased dissociation =shift in oxyhaemoglobin curve to right - oxygen will dissociate from haemoglobin at a lower pO2 than normal

Question 14

What is the circulatory system?

Answer 14

Specialised system for transporting nutrients throughout their bodies + removing waste products, that multicellular organisms require

Question 15

What is the role of the heart in the circulatory system?

Answer 15

-Centre of the circulatory system
-Double system- blood flows through the heart twice in one circuit
-Deoxygenated blood pumped to lungs
-Oxygenated blood pumped around body

Question 16

What is the role of the coronary arteries in the circulatory system?

Answer 16

Heart= muscle that’s constantly contracting and relaxing, so needs a constant supply of oxygen for respiration
Coronary arteries supply blood to the heart

Question 17

What are the roles of the pulmonary artery and vein?

Answer 17

Artery- deoxygenated blood pumped out of heart to lungs via here
Oxygen diffuses into deoxygenated blood in lungs, becomes oxygenated
Vein- oxygenated blood flows into heart from lungs via here

Question 18

What are the roles of the aorta & vena cava?

Answer 18

Aorta- oxygenated blood pumped out of heart around body via here. Blood is very high pressure to ensure blood can be pumped to all tissues in body
Oxygen dissociates with blood at respiring cells in body and blood becomes deoxygenated
Vena Cava- deoxygenated blood flows into heart from body via here

Question 19

What are the roles of the renal vein & artery?

Answer 19

Oxygenated blood flows out of aorta, to the kidneys
Artery- oxygenated blood enters the kidney via here
Oxygen diffuses out of blood to be used in kidney cells, blood becomes deoxygenated
Vein- deoxygenated blood flows out of kidneys via here

Question 20

What is the role of the right atrium?

Answer 20

-Deoxygenated blood flows into right atrium from body
-Vena cava= pumps deoxygenated blood into right atrium (first chamber it flows through)

Question 21

What is the role of the right ventricle?

Answer 21

-Deoxygenated blood flows into here when walls of right atrium contract
-Atrioventricular valves prevent blood from flowing back into atria ventricles
-Blood pumped out of pulmonary artery to the lungs when the walls of right ventricle contract
-Semi-lunar valves prevent blood from flowing back into right ventricle from pulmonary artery

Question 22

What are the roles of the left atrium and ventricle?

Answer 22

-Oxygenated blood flows into left atrium from lungs
-Pulmonary vein pumps oxygenated blood into left atrium
-Oxygenated blood flows flows into left ventricle when walls of left atrium contract
-Atrioventricular valves prevent blood from flowing back into atria from ventricles
-Walls of left ventricle are thicker than right, as they transport blood all around the body

Question 23

What is the role of the aorta?

Answer 23

-When left ventricle contracts, blood is pumped out of heart to rest of body
-Oxygenated blood leaves heart through aorta
-Semi lunar valves prevent blood from flowing back into left ventricle from aorta

Question 24

What is the cardiac cycle?

Answer 24

The flow of blood from the lungs to the heart and around the body
Continuous relaxing and contracting of the heart

Question 25

What happens during the first step of the cardiac cycle?

Answer 25

Atrial contraction

-Blood from lungs flows into left atrium and from body into right atrium simultaneously
-Atria contract and pressure increases (volume decreases)
-Blood in atria is forced into ventricles
-Ventricles are relaxed, fill with blood (volume increases)

Question 26

What happens during the second step of the cardiac cycle?

Answer 26

Ventricular contraction

-Atria relax, (volume increases) ventricles contract (volume decreases)
-Pressure in ventricles now increases
-Pressure shuts atrioventricular valves so blood doesn’t flow back into atria
-Blood in ventricles is forced out, out from the heart through pulmonary artery/aorta

Question 27

What happens during the third stage of the cardiac cycle?

Answer 27

Relaxation

-Blood in pulmonary artery & aorta at high pressure; this shuts atrioventricular valves so blood doesn’t flow back into ventricles
-Both ventricles (volume increase ) & atria relax (volume slight decrease), atrioventricular valves reopen
-Blood flows into ventricles and atria from pulmonary vein & vena cava
-Cycle continues

Question 28

What is the structure and function of the arteries?

Answer 28

-Transport blood away from heart, to organs
-Walls have thick layers of muscle; maintain high pressure so blood can be pumped around body
-Can stretch due to elastic fibres in artery wall
-Endothelium folded; allows arteries to stretch

Question 29

What is the structure and function of the arterioles?

Answer 29

-Arteries reach organ and split into smaller vessels, arterioles
-Smaller, Thinner walls, less elastic tissue
-Control direction of blood flow; contracting restricts blood flow and relaxing allows blood to flow

Question 30

What is the structure and function of veins?

Answer 30

-Transport blood back to heart
-Lumen wider than arteries, allows blood to flow at low pressure
-Thin muscle walls & elastic tissue in walls
-Have valves throughout to prevent backward flow of blood, so it reaches heart

Question 31

What is the structure and function of capillaries?

Answer 31

-Small vessels (allow only 1 RBC at a time), branch from arterioles into millions of capillaries; form networks (capillary beds) around body cells, creates large surface area for exchange of substances between bloodstream and tissues
-Blood pressure very low
-Fenestration; gaps to allow faster diffusion
-Thin walls (one cell thick, endothelium), pass close to body cells to allow exchange between blood + organs. Diffusion distance of substances (e.g. oxygen) from bloodstream to tissues very short; allows efficient exchange)

Question 32

What is tissue fluid?

Answer 32

Combination of water, oxygen and nutrients- surrounds cells in body
Substances carried in capillaries are transported to cells via tissue fluid

Question 33

How is tissue fluid formed and transported?

Answer 33

-There’s high pressure in capillaries at capillary bed entrance, creating a pressure gradient between the outside and the inside
-Fluid in capillaries flows down pressure gradient into surrounding space (pressure filtration), this creates tissue fluid- can now diffuse/be transported into cells
-Pressure inside capillaries decreases due to movement of fluid out of capillaries; pressure at exit is lower than entrance of capillary bed
-Fluid moves out of capillaries, plasma proteins remain inside; concentration increases and water potential decreases, gradient established. Water diffuses via osmosis back into capillaries from tissue fluid
-Excess tissue fluid flows into lymphatic system (recycles it into bloodstream)