A Level Biology Revision "Transport of Carbon Dioxide (OCR)"

00:04:40
https://www.youtube.com/watch?v=1PlJhRaTTLA

Resumo

TLDRThis video covers how carbon dioxide (CO2) is transported in the blood. It discusses three primary methods: about 5% dissolves directly in plasma; around 20% forms carbaminohemoglobin by reacting with hemoglobin; and the majority, approximately 75%, is transported as hydrogen carbonate ions after CO2 reacts with water. The enzyme carbonic anhydrase accelerates this process. In the lungs, CO2 is released back into the plasma for exhalation, reversing the processes that occur in respiring tissues. The video also explains the chloride shift and how hemoglobin helps buffer pH by binding hydrogen ions.

Conclusões

  • 🧪 Carbon dioxide is transported in three ways: dissolution, carbaminohemoglobin, and as hydrogen carbonate.
  • 🧬 About 5% of CO2 dissolves in blood plasma directly.
  • 🩸 Approximately 20% of CO2 forms a compound with hemoglobin, known as carbaminohemoglobin.
  • 🔄 The reaction of CO2 and water to form carbonic acid is reversible and accelerated by carbonic anhydrase.
  • ⚖️ Hydrogen carbonate ions diffuse out of red blood cells, requiring chloride ions to enter (chloride shift).
  • 🧼 Hemoglobin acts as a buffer by binding to hydrogen ions, forming hemoglobinic acid.
  • ⬆️ In high CO2 areas, carbon dioxide forms carbonic acid, which dissociates into hydrogen carbonate.
  • 🌬️ In the lungs, low CO2 levels reverse these processes, releasing CO2 for exhalation.
  • 🔍 Carbonic acid breakdown in the lungs releases CO2 into the blood plasma for exhalation.
  • 📊 Understanding these processes is crucial for understanding respiratory physiology.

Linha do tempo

  • 00:00:00 - 00:04:40

    In this section, the video introduces the topic of carbon dioxide transport in blood, emphasizing its production during aerobic respiration and the need for transport from respiring tissues to the lungs for exhalation. It outlines three transport methods, detailing that about 5% dissolves in plasma, 20% reacts with hemoglobin to form carbaminohemoglobin, and 75% is transported as hydrogen carbonate ions.

Mapa mental

Vídeo de perguntas e respostas

  • How is carbon dioxide transported in the blood?

    Carbon dioxide is transported in the blood via three methods: dissolved in plasma, as carbaminohemoglobin with hemoglobin, and as hydrogen carbonate ions.

  • What role does carbonic anhydrase play?

    Carbonic anhydrase is an enzyme in red blood cells that speeds up the conversion of carbon dioxide and water into carbonic acid.

  • What is the chloride shift?

    The chloride shift is the movement of chloride ions into red blood cells to maintain charge balance when hydrogen carbonate ions diffuse out.

  • How does hemoglobin help in regulating blood pH?

    Hemoglobin can bind to hydrogen ions to form hemoglobinic acid, helping to buffer changes in blood pH.

  • What happens to carbon dioxide in the lungs?

    In the lungs, hydrogen carbonate ions re-enter red blood cells, combine with hydrogen ions to reform carbonic acid, which is then broken down to release carbon dioxide for exhalation.

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  • 00:00:00
    [Music]
  • 00:00:02
    hi and welcome back to free science
  • 00:00:03
    lessons by the end of this video you
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    should be able to describe how carbon
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    dioxide is transported in the blood and
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    this is for the ocr spec only
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    now all cells produce carbon dioxide
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    when they carry out aerobic respiration
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    and i'm showing you the equation for
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    aerobic respiration here
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    this carbon dioxide has to be
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    transported in the blood from actively
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    respiring tissues to the lungs where
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    it's breathed out
  • 00:00:28
    there are three ways that carbon dioxide
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    can be transported in the blood
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    firstly around five percent of the
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    carbon dioxide dissolves directly into
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    the blood plasma
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    around twenty percent of the carbon
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    dioxide forms a compound with hemoglobin
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    molecules in the red blood cells
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    remember that hemoglobin contains four
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    polypeptide chains and in each of these
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    polypeptides the first amino acid has a
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    free amino group
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    each of these amino groups can react
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    with the molecule of carbon dioxide so
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    one molecule of hemoglobin can react
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    with four molecules of carbon dioxide
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    when carbon dioxide reacts with
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    hemoglobin it forms a compound
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    carbominohemoglobin
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    this is a reversible reaction
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    when the blood passes through respiring
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    tissue the level of carbon dioxide is
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    high and carbaminohemoglobin forms
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    however in the lungs the level of carbon
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    dioxide is low and the
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    cobaminohemoglobin breaks down releasing
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    carbon dioxide
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    so we've now seen how around 25 of the
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    carbon dioxide has carried in the blood
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    the remaining 75 is transported as
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    hydrogen carbonate ions in the blood
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    plasma and we're going to look at that
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    now
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    i should point out that this may seem a
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    bit tricky but it's not as difficult as
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    it looks
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    carbon dioxide can react with water to
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    form the compound carbonic acid and i'm
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    showing that reaction here
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    as you can see this is a reversible
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    reaction
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    now this reaction usually takes place
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    slowly
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    however red blood cells contain an
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    enzyme which speeds up this reaction
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    this enzyme is called carbonic anhydrase
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    and you need to learn that name
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    so when carbon dioxide diffuses into red
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    blood cells it rapidly forms carbonic
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    acid
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    by converting the carbon dioxide to
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    carbonic acid this ensures that the
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    level of carbon dioxide in the red blood
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    cell is low
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    so this means that there's a steep
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    concentration gradient for carbon
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    dioxide and because of this steep
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    concentration gradient there's a high
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    rate of diffusion of carbon dioxide into
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    the red blood cells
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    now once the carbonic acid is formed it
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    then dissociates or splits forming the
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    hydrogen carbonate ion and the hydrogen
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    ion h plus
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    the hydrogen carbonate ion now diffuses
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    out of the red blood cell to the blood
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    plasma
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    now there is a problem here the hydrogen
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    carbonate ion has a negative charge
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    when the hydrogen carbonate ion diffuses
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    out of the red blood cell this creates a
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    charge imbalance
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    so to prevent this as the hydrogen
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    carbonate ion diffuses out of the red
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    blood cell a negative chloride ion
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    diffuses into the red blood cell
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    scientists call this the chloride shift
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    and this prevents a charge imbalance in
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    the red blood cell
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    now as we said before when carbonic acid
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    dissociates it also releases the
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    hydrogen ion h plus
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    these hydrogen ions could cause the ph
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    of the blood to fall
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    however to prevent this the hemoglobin
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    and red blood cells can bind hydrogen
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    ions and in this way the hemoglobin is
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    acting as a buffer
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    when hemoglobin binds to hydrogen ions
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    it forms hemoglobinic acid
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    okay so as we've seen when the level of
  • 00:03:46
    carbon dioxide is high for example in
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    the spire and tissue the carbon dioxide
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    forms carbonic acid and then hydrogen
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    carbonate ions
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    however when the level of carbon dioxide
  • 00:03:56
    is low for example in the lungs the
  • 00:03:58
    opposite happens
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    in this case the hydrogen carbonate ions
  • 00:04:03
    diffuse back into the red blood cells in
  • 00:04:05
    exchange for chloride ions
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    the hydrogen carbonate ions then combine
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    with hydrogen ions to reform carbonic
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    acid
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    at this point the carbonic acid is
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    broken down by carbonic anhydrase
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    forming carbon dioxide and the carbon
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    dioxide now diffuses out of the red
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    blood cells and into the blood plasma
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    once in the blood plasma the carbon
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    dioxide can be exhaled from the lungs
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    when the blood passes through the
  • 00:04:30
    alveoli
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    okay so hopefully now you can describe
  • 00:04:34
    how carbon dioxide is transported in the
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    blood
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    [Music]
Etiquetas
  • carbon dioxide
  • blood transport
  • hemoglobin
  • carbonic anhydrase
  • respiration
  • hydrogen carbonate
  • chloride shift
  • pH regulation
  • gas exchange
  • exhalation