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Biology IB HL > D6 Gas Transport > Flashcards

D6 Gas Transport Flashcards

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1
Q

What is the inner surface of the alveolus lined by?

A

The inner surface of the alveolus is lined by a special type of alveolar cell called a pneumocyte

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2
Q

What is the structure of type 1 pneumocytes?

A

Type I pneumocytes are very thin in order to mediate gas exchange with the bloodstream (via diffusion)

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3
Q

WHat is the structure of type 2 pneumocytes?

A

Type II pneumocytes secrete a pulmonary surfactant in order to reduce the surface tension within the alveoli

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4
Q

What are alveolar air spaces surrounded by?

A

Alveolar air spaces are surrounded by a dense network of capillaries, which transport respiratory gases to and from the lungs

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5
Q

Where are capillaries in the lungs located and what is their structure?

A

The capillaries are located close to the pneumocytes and are composed of a very thin, single-layer endothelium

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6
Q

What do capillaries transport?

A

The capillaries transport oxygen within red blood cells

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7
Q

How may white blood cells travel into the lung tissue?

A

white blood cells may extravasate into the lung tissue

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8
Q

how is oxygen transported around the body?

A

Oxygen is transported throughout the body in red blood cells, which contain an oxygen-binding protein called haemoglobin

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9
Q

What is the structure of haemoglobin?

A

Haemoglobin is composed of four polypeptide chains, each with an iron-containing heme group that reversibly binds oxygen

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10
Q

How many oxygens can bind to Hb?

A

As such, each haemoglobin can reversibly bind up to four oxygen molecules (Hb + 4O2 = HbO8)

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11
Q

What happens after each oxygen molecule binds to Hb?

A

As each O2 molecule binds, it alters the conformation of haemoglobin, making subsequent binding easier (cooperative binding)

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12
Q

Where will Hb have a higher affinity for oxygen?

A

This means haemoglobin will have a higher affinity for O2 in oxygen-rich areas (like the lung), promoting oxygen loading

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13
Q

Where will Hb have a lower affinity for oxygen?

A

Conversely, haemoglobin will have a lower affinity for O2 in oxygen-starved areas (like muscles), promoting oxygen unloading

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14
Q

What does an oxygen dissociation curve show?

A

Oxygen dissociation curves show the relationship between oxygen levels (as partial pressure) and haemoglobin saturation

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15
Q

Is the saturation of Hb linear? Why

A

Because binding potential changes with each additional O2 molecule, the saturation of haemoglobin is NOT linear

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16
Q

What is the shape of the oxygen dissociation curve for adult Hb?

A

The oxygen dissociation curve for adult haemoglobin is sigmoidal (i.e. S-shaped) due to cooperative binding

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17
Q

When is there a low saturation of Hb?

A

There is a low saturation of haemoglobin when oxygen levels are low (haemoglobin releases O2 in hypoxic tissues)

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18
Q

When is there a high saturation of Hb?

A

There is a high saturation of haemoglobin when oxygen levels are high (haemoglobin binds O2 in oxygen-rich tissues)

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19
Q

Does foetal haemoglobin have the same composition as adult haemoglobin?

A

The haemoglobin of the foetus has a slightly different molecular composition to adult haemoglobin

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20
Q

How does the affinity of foetal Hb compared to adult Hb?

A

Consequently, it has a higher affinity for oxygen (dissociation curve is shifted to the left)

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21
Q

Why is the different affinity in foetal Hb important?

A

This is important as it means fetal haemoglobin will load oxygen when adult haemoglobin is unloading it (i.e. in the placenta)

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22
Q

When is foetal Hb almost entirely replaced by adult Hb?

A

Following birth, fetal haemoglobin is almost completely replaced by adult haemoglobin (~ 6 months post-natally)

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23
Q

What are the applications of foetal Hb?

A

Fetal haemoglobin production can be pharmacologically induced in adults to treat diseases such as sickle cell anaemia

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24
Q

What is myoglobin?

A

Myoglobin is an oxygen-binding molecule that is found in skeletal muscle tissue

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25
Q

What is the structure of myoglobin and how does this make it differ from Hb?

A

It is made of a single polypeptide with only one heme group and hence is not capable of cooperative binding

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26
Q

What is the shape for the oxygen dissociation curve of myoglobin?

A

Consequently, the oxygen dissociation curve for myoglobin is not sigmoidal (it is logarithmic)

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27
Q

What is the shape for the oxygen dissociation curve of myoglobin?

A

Consequently, the oxygen dissociation curve for myoglobin is not sigmoidal (it is logarithmic)

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28
Q

How does the affinity of myoglobin Hb differ from adult Hb?

A

Myoglobin has a higher affinity for oxygen than adult haemoglobin and becomes saturated at lower oxygen levels

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29
Q

Why is myoglobins high affinity important?

A

Myoglobin will hold onto its oxygen supply until levels in the muscles are very low (e.g. during intense physical activity)

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30
Q

Why is the delayed release of oxygen by myoglobin important?

A

The delayed release of oxygen helps to slow the onset of anaerobic respiration and lactic acid formation during exercise

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31
Q

What are the 3 ways for CO2 to be transported?

A

Some is bound to haemoglobin to form HbCO2

A very small fraction gets dissolved in water and is carried in
solution (~5% – carbon dioxide dissolves poorly in water)

The majority (~75%) diffuses into the erythrocyte and gets converted into carbonic acid

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32
Q

How does CO2 combine with Hb but not compete with O2 binding?

A

carbon dioxide binds to the globin and so doesn’t compete with O2 binding

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33
Q

TRANSPORT AS CARBONIC ACID

1. What does CO2 combine with when it enters the erythrocyte? What catalyses the reaction?

A

When CO2 enters the erythrocyte, it combines with water to form carbonic acid (reaction catalysed by carbonic anhydrase)

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34
Q

TRANSPORT AS CARBONIC ACID

2. What happens to the carbonic acid?

A

The carbonic acid (H2CO3) then dissociates to form hydrogen ions (H+) and bicarbonate (HCO3–)

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35
Q

TRANSPORT AS CARBONIC ACID

3. What happens to the bicarbonate ions? What is the purpose?

A

Bicarbonate is pumped out of the cell in exchange with chloride ions (exchange ensures the erythrocyte remains uncharged)

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36
Q

TRANSPORT AS CARBONIC ACID

4. What does the bicarbonate in the blood plasma combine with?

A

The bicarbonate in the blood plasma combines with sodium to form sodium bicarbonate (NaHCO3), which travels to the lungs

37
Q

TRANSPORT AS CARBONIC ACID

5. what is the role of the H+ ions in the erythrocyte?

A

The hydrogen ions within the erythrocyte make the environment less alkaline, causing haemoglobin to release its oxygen

38
Q

TRANSPORT AS CARBONIC ACID

6. What acts as a buffer in the Hb?

A

The haemoglobin absorbs the H+ ions and acts as a buffer to maintain the intracellular pH

39
Q

TRANSPORT AS CARBONIC ACID

7. What happens when the RBC reaches the lungs?

A

When the red blood cell reaches the lungs, bicarbonate is pumped back into the cell and the entire process is reversed

40
Q

What can be formed (2) when carbonic acid loses protons?

A

Carbonic acid may then lose protons (H+) to form bicarbonate (HCO3–) or carbonate (CO32–)

41
Q

What do the released H+ ions do to the blood?

A

The released hydrogen ions will function to lower the pH of the solution, making the blood plasma less alkaline

42
Q

What is sensitive to changes in blood pH?

A

Chemoreceptors are sensitive to changes in blood pH and can trigger body responses in order to maintain a balance

43
Q

How do the lungs regulate blood pH?

A

The lungs can regulate the amount of carbon dioxide in the bloodstream by changing the rate of ventilation

44
Q

How do the kidneys control the blood pH?

A

The kidneys can control the reabsorption of bicarbonate ions from the filtrate and clear any excess in the urine

45
Q

What is the range for blood pH?

A

The pH of blood is required to stay within a very narrow tolerance range (7.35 – 7.45) in order to avoid the onset of disease

46
Q

What in the blood buffers the pH?

A

This pH range is, in part, maintained by plasma proteins which act as buffers

47
Q

How does a buffering solution resist changes to pH?

A

A buffering solution resists changes to pH by removing excess H+ ions (↑ acidity) or OH– ions (↑ alkalinity)

48
Q

What molecules can buffer pH?

A

Amino acids are zwitterions – they may have both a positive and negative charge and hence can buffer changes in pH

49
Q

How do amino acids act as buffers?

A

The amine group may take on H+ ions while the carboxyl group may release H+ ions (which form water with OH– ions)

50
Q

What does the oxyhaemoglobin dissociation curve demonstrate?

A

The oxyhaemoglobin dissociation curve demonstrates the saturation of haemoglobin by oxygen under normal conditions

51
Q

Does pH affect the Hb curve?

A

pH changes alter the affinity of haemoglobin for oxygen and hence alters the uptake and release of O2 by haemoglobin

52
Q

How does CO2 affect the pH of the blood? What does this trigger Hb to do?

A

Carbon dioxide lowers the pH of the blood (by forming carbonic acid), which causes haemoglobin to release its oxygen

53
Q

What is the Bohr Effect?

A

This is known as the Bohr effect – a decrease in pH shifts the oxygen dissociation curve to the right

54
Q

What do cells with increased metabolism release?

A

Cells with increased metabolism (i.e. respiring tissues) release greater amounts of carbon dioxide (product of cell respiration)

55
Q

Why is a high CO2 conc. in respiring cells beneficial?

A

Hence haemoglobin is promoted to release its oxygen at the regions of greatest need (oxygen is an input of cell respiration)

56
Q

What receives signals from chemoreceptors to control ventilation?

A

he respiratory control centre in the medulla oblongata responds to stimuli from chemoreceptors in order to control ventilation

57
Q

What is the role of central chemoreceptors?

A

Central chemoreceptors in the medulla oblongata detect changes in CO2 levels (as changes in pH of cerebrospinal fluid)

58
Q

What is the role of peripheral chemoreceptors?

A

Peripheral chemoreceptors in the carotid and aortic bodies also detect CO2 levels, as well as O2 levels and blood pH

59
Q

What increases during exercise?

A

During exercise metabolism is increased, which results in a build up of carbon dioxide and a reduction in the supply of oxygen

60
Q
  1. What does the build-up of CO2 during exercise trigger?2
A

These changes are detected by chemoreceptors and impulses are sent to the respiratory control centre in the brainstem

61
Q
  1. exercise - where are singles from brainstem sent?
A

Signals are sent to the diaphragm and intercostal muscles to increase the rate of ventilation (this process is involuntary)

62
Q
  1. what is the role of an increase in ventilation rate?
A

As the ventilation rate increases, CO2 levels in the blood will drop, restoring blood pH (also O2 levels will rise)

63
Q
  1. what are long term effects of continual exercise?
A

Long term effects of continual exercise may include an improved vital capacity

64
Q

what is partial pressure?

A

Partial pressure is the pressure exerted by a single type of gas when it is found within a mixture of gases

65
Q

What two factors determine the partial pressure of a gas?

A

The partial pressure of a given gas will be determined by:

The concentration of the gas within the mixture (e.g. oxygen forms roughly 21% of the atmosphere)

The total pressure of the mixture (e.g. atmospheric pressure)

66
Q

What is the partial pressure at high altitudes?

A

At high altitudes, air pressure is lower and hence there is a lower partial pressure of oxygen (less O2 because less air overall)

67
Q

How is O2 uptake affected at low partial pressures?

A

This makes it more difficult for haemoglobin to take up and transport oxygen (lower Hb % saturation)

68
Q

What does a lower O2 uptake lead to?

A

Consequently, respiring tissue will receive less oxygen – leading to symptoms such as fatigue, headaches and rapid pulse

69
Q

In what two ways will red blood cells acclimatise to lower oxygen levels at high altitudes?

A

Red blood cell production will increase in order to maximise oxygen uptake and transport

Red blood cells will have a higher haemoglobin count with a higher affinity for oxygen

70
Q

How will vital capacity acclimate to lower oxygen levels at high altitudes?

A

Vital capacity will increase to improve rate of gas exchange

71
Q

How will muscles acclimate to lower oxygen levels at high altitudes?

A

Muscles will produce more myoglobin and have increased vascularisation to improve overall oxygen supply

72
Q

How will kidneys acclimate to lower oxygen levels at high altitudes?

A

Kidneys will begin to secrete alkaline urine (removal of excess bicarbonates improves buffering of blood pH)

73
Q

How will lungs acclimate to lower oxygen levels at high altitudes?

A

People living permanently at high altitudes will have a greater lung surface area and larger chest sizes

74
Q

What are the benefits of high altitudes?

A

Professional athletes will often incorporate high altitude training in order to adopt these benefits prior to competition

75
Q

In what two ways do athletes make use of high altitudes?

A

Athletes may commonly either train at high altitudes (live low – train high) or recover at high altitudes (live high – train low)

76
Q

What is emphysema?

A

Emphysema is a lung condition whereby the walls of the alveoli lose their elasticity due to damage to the alveolar walls

77
Q

What does the loss of elasticity lead to?

A

The loss of elasticity results in the abnormal enlargement of the alveoli, leading to a lower total surface area for gas exchange

78
Q

What does the degradation of the alveolar walls lead to/

A

The degradation of the alveolar walls can cause holes to develop and alveoli to merge into huge air spaces (pulmonary bullae)

79
Q

What is the major cause of emphesyma?

A

The major cause of emphysema is smoking, as the chemical irritants in cigarette smoke damage the alveolar walls

80
Q

What does damage to lung tissue lead to?

A

The damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase

81
Q

What does elastase lead to?

A

This elastase, released as part of an inflammatory response, breaks down the elastic fibres in the alveolar wall

82
Q

What can be another cause of emphysema apart from smoking?

A

A small proportion of emphysema cases are due to a hereditary deficiency in this enzyme inhibitor due to a gene mutation

83
Q

Is there a cure for emphysema?

A

There is no current cure for emphysema, but treatments are available to relieve symptoms and delay disease progression

84
Q

How are bronchodilators used to treat emphysema?

A

Bronchodilators are commonly used to relax the bronchiolar muscles and improve airflow

85
Q

How can corticosteroids be used to treat emphysema?

A

Corticosteroids can reduce the inflammatory response that breaks down the elastic fibres in the alveolar wall

86
Q

How can enzyme inhibitors be used to treat emphysema?

A

Elastase activity can be blocked by an enzyme inhibitor (α-1-antitrypsin), provided elastase concentrations are not too high

87
Q

How can oxygen supplementation be used to treat emphysema?

A

Oxygen supplementation will be required in the later stages of the disease to ensure adequate oxygen intake

88
Q

How can surgery be used to treat emphysema?

A

In certain cases, surgery and alternative medicines have helped to decrease the severity of symptoms

Biology IB HL (56 decks)

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