3.4.1 mass transport in animals (not complete)

Describe the role of red blood cells and haemoglobin in oxygen transport

• red blood cells contain lots of haemoglobin

• HB associated with/ binds/ loads oxygen at gas exchange surfaces (lungs) where partial pressure of oxygen is high

• This forms oxyhaemoglobin which transports oxygen

• HB dissociates from/ unloads oxygen near cells/ tissues where partial pressure of oxygen is low

Describe the structure of haemoglobin

• protein with a quaternary structure

• Made of 4 polypeptide chains

• Each chain contains a haem group containing an iron ion

What are some structural advantages of the red blood cells

• no nucleus and biconcave so…

• more space for haemoglobin

• High SA:V

• Short diffusion distance

What are haemoglobins

A group of chemically similar molecules found in many different organisms

Describe the transport of oxygen in respiring tissues

• areas with low partial pressure of oxygen

• So HB has low affinity for oxygen

• So oxygen readily unloads/ dissociates with HB

• So % saturation is low

Describe the transport of oxygen in gas exchange surfaces

• areas with high partial pressure of oxygen

• HB has a high affinity for oxygen

• So oxygen readily loads/ associated with HB

• So % saturation is high

Explain how the co-operative nature of oxygen binding results in a sigmoid (s-shaped) dissociation curve

• binding of first oxygen changes tertiary/ quaternary structure of haemoglobin

• This uncovers haem group binding sites, making further bindings of oxygen easier

Describe evidence for the cooperative nature of oxygen binding

• at low partial pressure of oxygen, as oxygen increases there is little/ slow increase in % saturation of HB with oxygen

• This is when the first oxygen is binding

• At a higher partial pressure of oxygen, as oxygen increases there is a rapid increase in % saturation of HB with oxygen

• Showing it has got easier for oxygens to bind

What is the Bohr effect

• the effect of CO2 concentration on dissociation of oxyhaemoglobin

• Curve shifts to the right

Explain the effect of CO2 concentration on the dissociation of oxyhaemoglobin

• increases blood CO2 (due to increased respiration)

• Lowers blood pH (more acidic)

• Reducing Hb’s affinity for oxygen as shape/ tertiary/ quaternary structure changes slightly

• So more/ faster unloading of oxygen to respiring cells at a given partial pressure of oxygen

Describe evidence for the Bohr effect

At a given partial pressure of oxygen, the saturation of haemoglobin with oxygen is lower

Explain an advantage of the Bohr effect (e.g during exercise)

• more dissociation of oxygen

• So faster aerobic respiration/ less anaerobic respiration

• So more ATP produced

Explain why different types of haemoglobin can have different oxygen transport properties

• different types are made of polypeptide chains with slightly different amino acid sequences

• Resulting in different tertiary/ quaternary structure/ shape

• So they have different affinities for oxygen

How are organisms adapted to their environment by having different types of haemoglobin: HB has higher affinity for oxygen (curve shift left)

• more oxygen associated with HB more readily

• At gas exchange surfaces where the partial pressure of oxygen is lower

• E.g Organisms in low oxygen environments (high altitudes, underground, foetuses)

How are organisms adapted to their environment by having different types of haemoglobin: HB has lower affinity for oxygen

• more oxygen dissociated from HB more readily

• At respiring tissues where oxygen is needed

• E.g organisms with high rates of respiration/ metabolic rate (may be small or active)

Describe the general pattern of blood circulation in a mammal

• closed double circulatory system - blood passes through heart twice for every circuit around body

• Deoxygenated blood in the right side of the heart is pumped to the lungs, oxygenated blood returns to the left side

• Oxygenated blood in the left side of the heart to the rest of the body, deoxygenated blood returns to the right

Suggest the importance of a double circulatory system

• prevents mixing of oxygenated/ deoxygenated blood

• So blood pumped to body is fully saturated with oxygen for aerobic respiration

• Blood can be pumped to body at a higher pressure (after being lower from lungs)

• Substances taken to/ removed from body cells quicker/ more efficiently

Draw a diagram to show the general pattern of blood circulation in a mammal

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Name the blood vessels that carry deoxygenated blood

• vena cava transports deoxygenated blood from respiring blood tissues to the heart

• Pulmonary artery transports deoxygenated blood from the heart to the lungs

Name the blood vessels that carry oxygenated blood

• pulmonary vein transports oxygenated blood blood from lungs to the heart

• Aorta transports oxygenated blood from heart to respiring body tissues

Name the blood vessels entering and leaving the kidneys

• renal arteries - oxygenated blood to the kidneys

• Renal veins - deoxygenated blood to vena cava from kidneys

Name the blood vessels that carry oxygenated blood to the heart muscle

• coronary arteries - located on surface of the heart, branching from aorta

Label a diagram to show the gross structure of the human heart (inside)

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Suggest why the wall of the left ventricle is thicker than that of the right

• thicker muscles to contract with greater force

• To generate higher pressure to pump blood around the entire body