mass transport in animals

Question 1

what is the role of haemoglobin and where is it found?

Answer 1

-it is found in red blood cells
-role is to carry oxygen around the body

-there are chemically similar types of haemoglobin found in other organisms, which carry out the same function
-it is found in earthworms, starfish, some insects, some plants and some bacteria

Question 2

what is the structure of haemoglobin?

Answer 2

-large protein with a quaternary structure
-made up of four polypeptide chains
-each chain has a haem group which contains and iron ion and gives haemoglobin its red colour
-each molecule can carry four oxygen molecules

Question 3

when is oxyhaemoglobin made?

Answer 3

in the lungs, when oxygen joins to haemoglobin during gas exchange

Question 4

write the haemoglobin - oxyhaemoglobin reversible reaction.

Answer 4

associating/loading
Hb + 4O2 <–> HbO8 disassociating/ unloading

Question 5

what does ‘affinity for oxygen mean’ and what is haemoglobins?

Answer 5

the tendency a molecule has to bind with oxygen.

haemoglobins affinity varies depending on the conditions its in, including the partial pressure of oxygen (pO2)

Question 6

what does partial pressure of oxygen (pO2) mean?

Answer 6

a measure of oxygen concentration

the greater the concentration of dissolved oxygen in cells, the higher the partial pressure

Question 7

relate partial pressure of oxygen to haemoglobin.

Answer 7

as pO2 increases, haemoglobins affinity for oxygen also increases.
-oxygen loads onto haemoglobin to form oxyhaemoglobin where there’s a high pO2
-oxyhaemoglobin unloads its oxygen where there’s a lower pO2

Question 8

describe these 4 features at the alveoli and respiring tissues:
-oxygen concentration
-pO2
-affinity for oxygen
-loads or unloads

Answer 8

alveoli:
-HIGH oxygen concentration
-HIGH pO2
-HIGH affinity
-oxygen LOADS

respiring tissues:
-LOW oxygen concentration
-LOW pO2
-LOW affinity
-oxygen UNLOADS

Question 9

what does an oxygen dissociation curve show?

Answer 9

how saturated the haemoglobin is with oxygen at any given partial pressure.
the affinity for haemoglobin for oxygen affects how saturated the haemoglobin is

Question 10

what are the two axis on an oxygen dissociation curve?

Answer 10

Y= %saturation of haemoglobin with oxygen

X= partial pressure of O2 / kPa

Question 11

why is an oxygen dissociation curve an ‘s’ shape?

Answer 11

because the saturation of haemoglobin can also affect the affinity

Question 12

how does the saturation of haemoglobin affect its affinity?

Answer 12

-when haemoglobin binds with the first oxygen molecule, its shape alters in a way that makes it easier for the other O2 molecules to bind
-however as the haemoglobin gets too saturated, it gets harder for oxygen molecules to join
-this means the curve is a bit steeper in the middle where its easy for oxygen molecules to join and shallower bits at the start and end

Question 13

how does the partial pressure of carbon dioxide (pCO2) affect oxygen unloading and how does this affect the dissociation curve?

Answer 13

-haemoglobin gives up more oxygen readily at a higher pCO2
-when cells respire they produce CO2 which raises the pCO2 causing more oxygen to be unloaded
-the dissociation curve ‘shifts’ to the right
-this is called the Bohr effect

Question 14

what type of haemoglobin do organisms in low oxygen environments (e.g. lugworms) have and how does this effect the dissociation curve?

Answer 14

-haemoglobin with a higher affinity for oxygen
-this is because there is less oxygen available, so the haemoglobin needs to be good at loading any available
-the dissociation curve is to the left of ours

Question 15

what type of haemoglobin do organisms in high activity level (e.g. birds) environments have and how does this effect the dissociation curve?

Answer 15

-has a lower affinity for oxygen
-their haemoglobin needs to be able to unload oxygen easily so its available for them to use
-the dissociation curve sits to the right of humans

Question 16

what type of haemoglobin do small organisms have (e.g. rats) and how does this affect the dissociation curve?

Answer 16

-tend to have a higher surface area to volume ratio meaning they lose heat quickly so have a high metabolic rate to keep them warm, meaning they have a high oxygen demand
-haemoglobin will have a lower affinity for oxygen because it needs to be able to unload oxygen easily
-their dissociation curve sits to the right of a human one

Question 17

why do multicellular organisms need a circulatory system?

Answer 17

have a low surface area to volume ratio so need a specialised mass transport system to carry raw materials from specialised exchange organs to their body cells

Question 18

name the 6 vessels in the human circulatory system and where they carry blood from and to.

Answer 18

the PULMONARY ARTERY carries deoxygenated blood from the HEART to the LUNGS

the PULMONARY VEIN carries oxygenated blood from the LUNGS to the HEART

the AORTA carries oxygenated blood from the HEART to the BODY

the VENA CAVA carries deoxygenated blood from the BODY to the HEART

the RENAL ARTERY carries oxygenated blood from the BODY to the KIDNEYS

the RENAL VEIN carries deoxygenated blood from the KIDNEYS to the VENA CAVA

Question 19

what gives the heart its blood supply?

Answer 19

the left and right coronary arteries

Question 20

what kind of substances does blood transport around the body?

Answer 20

respiratory gases, products of digestion, metabolic wastes and hormones

Question 21

what is the structure of arteries and how do these features relate to their function?

Answer 21

-the muscle layer is thick so vasodilation and vasoconstriction can happen
-elastic layer is relatively thick to allow recoil to maintain pressure so blood can get to extremities
-thick wall to prevent bursting under high pressure
-no valves as blood pressure is high
-the inner lining (the endothelium) is folded so the artery can stretch
-they divide into smaller vessels called arterioles

Question 22

what is the structure of arterioles and how do these feature relate to their function?

Answer 22

-muscle layer is thicker then in arteries to allow more vasodilation and vasoconstriction for control of blood flow to capillaries
-elastic layer is thinner than in arteries and blood pressure is lower so less recoil is required

Question 23

what is the structure of veins and how do these features relate to their function?

Answer 23

-the overall thickness of the wall is thinner as blood pressure is lower
-muscle layer is relatively thin as there is not need to regulate flow to tissues
-elastic layer is relatively thin as there is no need for recoil
-they contain valves at intervals to prevent backflow of blood as it is under low pressure

Question 24

what is the structure of capillaries and how do these features relate to their function?

Answer 24

-walls consist mainly of the lining layer (endothelium) so there is a short diffusion distance
-there are numerous of them in capillary beds and they are highly branched for a large surface area
-there are spaces between endothelial cells so there is space for tissue fluid formation and white blood cells to move out
-they have a narrow lumen (7 micrometres) so red blood cells are squeezed close to cells
-narrow diameter so they can penetrate close to exchange surfaces

Question 25

what is tissue fluid and how do cells use it for transport of substances?

Answer 25

the fluid that surrounds cells in tissues. it is their immediate environment

cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it

in a capillary bed, substances move in and out of the capillaries into the tissue fluid by pressure filtration

Question 26

how does hydrostatic pressure relate to transport of substances between the capillaries and tissue fluid?

Answer 26

-at the start of the capillary bed, the hydrostatic pressure inside capillaries is higher than in the tissue fluid
-this difference means an overall outward pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid
-as fluid leaves, the hydrostatic pressure in the capillaries reduces so it is much lower at the venule end of the capillary (nearest the veins)

Question 27

how does water potential link to capillaries and the lymphatic system?

Answer 27

-due to fluid loss and an increasing concentration of plasma proteins in the capillaries, water potential at the venule end is lower then that in the tissue fluid
-this means some water re-enters the capillaries by osmosis
-any excess tissue fluid is drained into the lymphatic system which transports it and passes it back into the circulatory system

Question 28

what is tissue fluid made up of?

Answer 28

molecules that leave the blood plasma, e,g. oxygen, water and nutrients

Question 29

what are the adaptions to these structures in the heart that make them suitable for their function:
-left ventricle
-ventricles
-atrioventricular valve
-semi luna valve
-cords

Answer 29

left ventricle:
-has thicker, more muscular walls than the right to allow it to contract more powerfully and pump blood all the way around the body

ventricles:
-thicker walls then atria so they can push blood out of the heart whereas atria only need to pump blood to the ventricles

AV valves:
-link the atria to the ventricles and stop blood flowing back into the atria

SL valves:
-link ventricles to the pulmonary artery and aorta to stop blood flowing back into the heart after ventricular contractions

cords:
-attach the AV valves to the ventricles and stop them being forced up into the atria when the ventricles contract

Question 30

how do the heart valves function?

Answer 30

-whether they are open or closed depends on the relative pressure of the heart chambers
-if there’s higher pressure behind a valve, its force open, but if the pressure is higher in front of the valve, its forced shut
-this means the flow of blood is unidirectional- it only flows in one direction

Question 31

describe the three stages of the cardiac cycle.

Answer 31

1. atrial systole
   -ventricles relax, atria contract
   -this decrease the volume of the atria and increases the pressure pushing blood into the ventricles
   -slight increase in ventricular pressure and chamber volume as they receive ejected blood from the atria
2. ventricular systole
   -ventricles contract, atria relax
   -ventricular pressure increases as volume decreases
   -pressure becomes higher than the atria, forcing the AV valve to shut
   -pressure in the ventricles is higher than the aorta and pulmonary artery forcing the semi lunar valve to open
3. diastole
   -ventricles relax, atria relax
   -higher pressure in the pulmonary artery and aorta closes the semi lunar valve
   -blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and pulmonary vein
   -starts to increase pressure in the atria
   -ventricular pressure falls below atrial pressure so the atrioventricular valve opens
   -blood flows passively into the ventricles

Question 32

what is the equation for cardiac output?

Answer 32

cardiac output = stroke volume x heart rate

Question 33

what is stroke volume?

Answer 33

the volume of blood pumped during each heart beat measured in cm3

Question 34

what is cardiac output?

Answer 34

volume of blood pumped by the heart per minute measured in cm3min-1

Question 35

what is cardiovascular disease?

Answer 35

term used to describe disease associated with the heart and blood vessels

Question 36

describe the risk factors for cardiovascular disease.

Answer 36

high blood pressure:
-increases the risk of damage to artery walls
-damaged walls have an increased chance of forming atheroma’s which can cause blood clots
-a blood clot may result in a myocardial infraction (heart attack)

high blood cholesterol and poor diet:
-high cholesterol= above 240mg per 100cm3
-cholesterol is one of the main constituents of the fatty deposits that form atheroma’s
-a diet high in saturated fat is associated with high blood cholesterol levels
-a diet high in salt increases blood pressure which is a risk factor

smoking:
-both carbon monoxide and nicotine increase the risk of cardiovascular disease and heart attacks
-carbon monoxide with haemoglobin and reduces the amount of oxygen transported in the blood so reduces the amount of oxygen available for tissues, if the heart muscle doesn’t receive enough oxygen it can result in a heart attacks
-also decreases the amount of antioxidants in the blood which means cell damage in the coronary artery walls is more likely which can lead to atheroma formation