Name: how hemoglobin loads and releases oxygen
Uploaded: 2024-09-12T13:22:46.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Human Anatomy and Physiology

Absorption And Excretion

Respiratory System

Oxygen Transport in the Blood

血液は主に赤血球のヘモグロビンに結合した酸素を輸送しますが、血液への溶解度が低いため、血漿に溶解する割合はわずかです。
ヘモグロビンは、鉄分に富むヘム基を含む4本のポリペプチド鎖で構成されており、4つの酸素分子に結合することができます。
解離曲線に見られるように、ヘモグロビンへの酸素の結合は、酸素またはPO2の分圧に大きく影響されます。
P O2が増加すると、より多くの酸素がヘモグロビンに結合します。
このため、酸素が豊富な動脈血中のヘモグロビンは98%が酸素で飽和しています。
全身の毛細血管に到達すると、PO2が低いため、酸素飽和度が低下します。
いくつかの生理学的要因が、酸素に対するヘモグロビンの親和性に影響を与えます。
このグラフに見られるように、細胞の温度が上昇すると、この親和性が低下します。
さらに、ボーア効果は、PCO2が高く、Hイオンが高いと血液のpHが低下し、ヘモグロビンからの酸素の排出が促進されるときに発生します。
さらに、RBCはグルコース代謝中に1,3-ビスホスホグリセリン酸を産生し、ヘモグロビンからの酸素のアンロードも増加させます。

血液中の酸素輸送

ヘモグロビン (Hb) は人体に不可欠な分子で、4 つのポリペプチド鎖から成り、各鎖は鉄を含むヘム基に結合しています。この独特な構造により、ヘモグロビンは酸素と結合することができます。各分子は 4 つの酸素分子と結合できるため、酸素を迅速かつ可逆的に取り込むことができます。酸素が完全に取り込まれた状態はオキシヘモグロビンと呼ばれ、酸素を放出したヘモグロビンは還元ヘモグロビンまたはデオキシヘモグロビンと呼ばれます。ヘモグロビンは酸素と結合すると形状が変化し、追加の酸素分子をより効率的に取り込むことができます。この構造的適応により、酸素の取り込みと放出の両方のプロセスが非常に効率的になります。

ヘモグロビンが酸素を結合または放出する速度は、酸素分圧 (pO_2)、温度、血液 pH、二酸化炭素分圧 (pCO_2)、血液中の 2,3-ビスホスホグリセリン酸 (2,3-BPG) の濃度など、いくつかの要因によって細かく制御されます。これらの要因が連携して、組織細胞への十分な酸素供給を保証します。

通常の安静状態では、動脈血ヘモグロビンは通常 98% の酸素飽和度で、全身動脈血 100 ml あたり約 20 ml の酸素が含まれており、これは酸素含有量 20 vol% (体積パーセント) として表されます。血液が全身毛細血管を流れると、血液 100 ml あたり約 5 ml の酸素が放出され、その結果、静脈血の Hb 飽和度は 75%、酸素含有量は 15 vol% になります。これは、静脈血にはまだ必要なときに利用できる酸素が大量に残っていることを意味します。

pO_2 以外にも、温度、血液 pH、pCO_2、BPG 濃度などの要因が、特定の PO_2 でのヘモグロビン飽和度に影響します。赤血球 (RBC) はグルコース代謝中に 2,3-BPG を生成し、酸素濃度が慢性的に低いと、その濃度が上昇します。これらの要因はヘモグロビンの 3 次元構造を変化させ、最終的に酸素に対する親和性を変化させます。血液中の温度、pCO_2、H^ + イオン、または 2,3-BPG 濃度の上昇は、ヘモグロビンの酸素に対する親和性を低減し、酸素放出を促進します。逆に、これらの要因を低下させると、ヘモグロビンの酸素に対する親和性は高まります。

注目すべきは、これらの因子が通常、酸素の放出が不可欠な全身毛細血管で最も高いことです。細胞がグルコースを代謝して酸素を消費すると、二酸化炭素が生成され、毛細血管の血液中の pCO_2 と H^ + 濃度が上昇します。これにより、ボーア効果として知られる現象である Hb-O_2 結合が弱まります。さらに、活動組織の温度が上昇すると、ヘモグロビンの酸素に対する親和性が低下し、酸素の放出がさらに促進されます。

血液は主に赤血球のヘモグロビンに結合した酸素を輸送しますが、血液への溶解度が低いため、血漿に溶解する割合はわずかです。
...

Education

JoVE Core

Anatomy and Physiology

解剖生理学

Unit 1

ユニット1

The Respiratory System

呼吸器系

KEY TERMS AND CONCEPTS

主要用語と概念

how hemoglobin loads and releases oxygen

Hemoglobin is the main molecule that carries oxygen in blood. It is found in red blood cells and has four polypeptide chains, each attached to an iron-containing heme group. This structure lets one hemoglobin molecule bind up to four oxygen molecules quickly and reversibly.

When hemoglobin is fully loaded with oxygen, it is called oxyhemoglobin. When it has released oxygen, it is called reduced hemoglobin, or deoxyhemoglobin. As hemoglobin binds oxygen, its shape changes, which helps it pick up more oxygen molecules efficiently.

Several factors control how easily hemoglobin binds or releases oxygen. These include the partial pressure of oxygen (pO2), temperature, blood pH, partial pressure of carbon dioxide (pCO2), and the amount of 2,3-bisphosphoglycerate, or 2,3-BPG, in the blood. Together, these factors help make sure tissue cells get enough oxygen.

At rest, arterial blood is usually about 98% saturated with oxygen. In 100 mL of systemic arterial blood, there are about 20 mL of oxygen, which is described as 20 vol% oxygen content. As blood moves through systemic capillaries, it gives up about 5 mL of oxygen per 100 mL of blood. Venous blood then has about 75% hemoglobin saturation and about 15 vol% oxygen content, so it still carries an oxygen reserve.

Even at the same pO2, temperature, pH, pCO2, and BPG levels can change hemoglobin saturation. Red blood cells make 2,3-BPG during glucose metabolism, and its level rises when oxygen has been low for a long time. These changes alter hemoglobin’s three-dimensional shape and shift its affinity for oxygen.

Higher temperature, more pCO2, more H+ ions, or more 2,3-BPG lower hemoglobin’s affinity for oxygen and make release easier. Lower levels of these factors increase oxygen affinity. These conditions are usually strongest in systemic capillaries, where oxygen unloading is needed most.

As body cells use glucose and consume oxygen, they produce carbon dioxide. This raises pCO2 and H+ in capillary blood and weakens the hemoglobin-oxygen bond. This effect is called the Bohr effect. Increased temperature in active tissues also helps hemoglobin release oxygen more readily.

How Hemoglobin Loads and Releases Oxygen

overview of respiratory system

How Breathing Moves Air and Gases

The respiratory system moves air in and out of the body and exchanges oxygen and carbon dioxide with the environment. This gas exchange is part of respiration, which is essential for life. The system supplies the blood with oxygen so it can carry that oxygen to the rest of the body. Breathing starts when air enters through the nose or mouth. The nose and nasal cavity form the main external opening and the first part of the airway. Air then passes through the pharynx, or throat, which is shared...

nose and nasal cavity

How the Nose Filters and Senses Air

The nose filters, warms, moistens, and senses the air that enters the body. It also helps shape speech as sound vibrations pass through its large air spaces. The nose has an external part that is visible on the face and an internal part called the nasal cavity. The external nose is built from bone and hyaline cartilage, which gives it flexibility. It is covered by skin and muscle and lined with a mucous membrane. The frontal bone, nasal bones, and maxillary bone support this structure. The...

pharynx

Pharynx Pathways for Air and Food

The pharynx is a muscular tube lined with mucous membrane that connects the nasal cavities to the throat. It is divided into three parts: the nasopharynx, oropharynx, and laryngopharynx. Each part has a different role in moving air and food through the upper throat. The nasopharynx sits behind the nasal cavity and serves only as an air passage. Its upper region contains the pharyngeal tonsils, also called adenoids. These are clusters of lymphoid reticular tissue, similar to a lymph node, and...

larynx

Voice Box Anatomy and Function

The larynx is the voice box in the neck. It carries air into the lungs and helps produce voice. Its structure is complex because it must support both breathing and sound production. The larynx contains cartilage, muscles, and the vocal cords, also called vocal folds. It includes three large unpaired cartilages: the thyroid, cricoid, and epiglottis. It also includes three paired cartilages: the arytenoids, corniculates, and cuneiforms. Ligaments and membranes hold these parts together. The...

trachea

Trachea: Layers, Rings, and Airflow

The trachea is the windpipe, and it is a key airway in the human respiratory system. It carries air between the larynx and the bronchi so oxygen can reach the lungs. About half of the trachea lies in the neck, and it sits in front of the esophagus. In an average adult, the trachea is about 10 to 12 cm long. It extends from the larynx at the level of the sixth cervical vertebra to the level of the fifth thoracic vertebra. Its wall is supported by C-shaped cartilaginous rings. The back side is...

the bronchial tree

Bronchial Branching and Airflow Control

The bronchial tree carries air from the trachea into the lungs and helps control breathing. The trachea, or windpipe, connects the larynx to the bronchi. At the carina, the trachea splits into two primary bronchi. The right primary bronchus is wider, shorter, and more vertical than the left. Because of that shape, foreign objects and infections are more likely to enter the right lung. The carina is a cartilaginous ridge at the split in the airway. It helps keep the airway open. It also has...

alveoli and alveolar ducts

How Alveoli Enable Gas Exchange

The respiratory zone of the human body is where gas exchange happens. It begins when the terminal bronchioles branch into respiratory bronchioles, the smallest bronchiole type. These then lead into alveolar ducts and finally into clusters of alveoli. Alveoli are tiny air sacs that look like bunches of grapes. They connect to alveolar ducts, and a group of alveoli forms an alveolar sac. A single alveolus is about 200 μm wide, and its elastic shape lets it expand during inhalation. Nearby...

gross anatomy of the lungs

Lung Lobes, Airways, and Blood Flow

The lungs are paired organs that connect to the trachea through the left and right bronchi. Their base rests against the diaphragm, the dome-shaped muscle below the lungs. The lungs are covered by the pleurae and sit next to the mediastinum, the central space in the chest. The right lung is shorter and wider than the left lung, and it has a larger volume. The left lung has a cardiac notch, which is an indentation for the heart. The top of each lung is the apex, and the lower part is the base.

pleura of the lungs

Pleura Layers and Lung Protection

The pleura are membranes that protect the lungs inside the chest cavity. They are a type of serous membrane and wrap around each lung. The pleura have two layers: the visceral pleura and the parietal pleura. The visceral pleura covers the surface of the lung. The parietal pleura is the outer layer. It lines the thoracic wall, the mediastinum, and the diaphragm. The hilum is the point where the visceral and parietal layers connect. The space between these layers is called the pleural cavity. <br...

pressure relationships in thoracic cavity

pressure-relationships-in-thoracic-cavity

How Pressure Drives Breathing in the Lungs

Breathing depends on pressure changes in the lungs, chest, and airways. Pulmonary ventilation is the movement of air into and out of the lungs. It is driven by atmospheric pressure, intra-alveolar pressure inside the alveoli, and intrapleural pressure in the pleural cavity. Inhalation and exhalation rely on pressure differences between the atmosphere and the lungs. Gas pressure comes from the movement of confined molecules. Boyle’s law explains that pressure and volume are inversely...

pulmonary ventilation: inhalation

Pulmonary Ventilation and Breathing Pressures

Pulmonary ventilation depends on breathing movements and the pressure changes that move air into and out of the lungs. It supports the exchange of oxygen and carbon dioxide by letting the body take in oxygen and remove waste carbon dioxide. Boyle's law is important here because changes in volume and pressure affect how air moves in the respiratory system. Several respiratory volumes help describe how much air the lungs move. Tidal volume is the air inspired or expired during normal, quiet...

pulmonary cycle: exhalation

Exhalation and Lung Pressure Changes

Exhalation is the process of expelling air from the lungs. It depends on pressure differences between the lungs and the atmosphere. During normal quiet breathing, exhalation is passive and does not require muscle contraction. The elastic recoil of the lungs and chest wall helps both structures return to their resting positions after inhalation. When the muscles used for inhalation stop working, the diaphragm and external intercostal muscles relax. The diaphragm moves upward, and the ribs move...

factors affecting pulmonary ventilation

What Changes Breathing Ease in the Lungs

Breathing ease in the lungs depends on alveolar surface tension, lung compliance, and airway resistance. These factors affect how hard it is to move air during pulmonary ventilation, along with the pressure difference between the outside environment and the lungs. Alveolar surface tension comes from the fluid lining the inside of the alveoli. Water molecules in this fluid attract each other more strongly than they attract the air, so the liquid tends to pull the alveoli inward. That force must...

respiratory volumes and capacities

Lung Volume Measurements in Breathing

Lung volume measurements show how air moves in and out of the respiratory system during breathing. They help explain how the body takes in oxygen and removes carbon dioxide. Respiratory volumes and capacities also give useful information about lung function. Tidal volume is the air breathed in and out during normal, quiet breathing. Inspiratory reserve volume is the extra air that can be forcefully inhaled beyond tidal volume. Expiratory reserve volume is the extra air that can be forcefully...

physical principles governing gas exchange

physical-principles-governing-gas-exchange

Gas Laws in Lung Gas Exchange

Gas laws explain how oxygen and carbon dioxide move during respiration. External respiration is the exchange of gases in the lungs. Oxygen diffuses into the blood, and carbon dioxide diffuses out. Internal respiration happens in body tissues, where the gases move in the opposite directions. Two gas laws guide this process: Dalton's law of partial pressures and Henry's law. Dalton's law says the total pressure of a gas mixture equals the sum of the pressures of each gas acting alone. The...

external and internal respiration

Gas Exchange in Lungs and Tissues

Gas exchange in the lungs and body tissues moves oxygen into the blood and removes carbon dioxide. External respiration happens in the lungs, where inhaled oxygen enters the alveoli, the tiny air sacs that provide a large surface area for diffusion. Oxygen moves across the thin alveolar membrane into the pulmonary capillaries because its partial pressure is higher in the alveoli than in the blood. At the same time, carbon dioxide moves in the opposite direction and is later breathed out during...

oxygen transport in the blood

Hemoglobin is the main molecule that carries oxygen in blood. It is found in red blood cells and has four polypeptide chains, each attached to an iron-containing heme group. This structure lets one hemoglobin molecule bind up to four oxygen molecules quickly and reversibly. When hemoglobin is fully loaded with oxygen, it is called oxyhemoglobin. When it has released oxygen, it is called reduced hemoglobin, or deoxyhemoglobin. As hemoglobin binds oxygen, its shape changes, which helps it pick...

carbon dioxide transport in the blood

How Blood Carries Carbon Dioxide

Carbon dioxide is carried in the blood from body tissues to the lungs. Cells make about 200 mL of CO2 each minute, and the lungs remove about the same amount. The blood moves this waste gas in three main forms. A small amount, about 7-10%, stays dissolved in the plasma. Just over 20% binds to hemoglobin and forms carbaminohemoglobin. In this case, CO2 attaches to the amino acids of globin, not to the heme part of hemoglobin. The rest, about 70%, is carried as bicarbonate ions, or HCO3-. CO2...

hypoxia

Hypoxia: Types and Carbon Monoxide Poisoning

Hypoxia is a medical condition in which body tissues do not get enough oxygen. It can cause a bluish color in the skin and mucosae, especially in fair-skinned people. This sign is often seen when hemoglobin (Hb) saturation drops below 75%. Hypoxia can happen for several different reasons. Anemic hypoxia occurs when there are too few red blood cells (RBCs) or when RBCs have abnormal or too little Hb. Ischemic hypoxia comes from poor blood circulation or blocked blood flow, so blood becomes...

neural control of respiration

Brainstem Centers That Control Breathing

Breathing is controlled by nerve centers in the brainstem. These respiratory centers send nerve signals to the muscles that move the lungs. The main centers are in the medulla oblongata and the pons.

chemical factors affecting respiration centers

chemical-factors-affecting-respiration-centers

How Blood Gases Control Breathing Rate

Blood gases and blood pH help control breathing rate and depth. Changes in carbon dioxide, oxygen, and hydrogen ion levels in arterial blood are detected by chemoreceptors, which are special sensors in the body. Central chemoreceptors are found throughout the brain stem, including the ventrolateral medulla. Peripheral chemoreceptors are located in the aortic arch and carotid arteries. Together, these sensors help the respiratory system respond to chemical changes in the blood. Carbon dioxide...

other factors affecting respiration centers

other-factors-affecting-respiration-centers

Respiratory Reflexes That Change Breathing

Breathing is controlled by the brainstem, but it can also be changed by the nervous system and by body signals. The cerebral motor cortex can override the medullary respiratory centers and send signals directly to the breathing muscles. This makes voluntary actions like holding your breath or taking deeper breaths possible. That control is limited. When carbon dioxide, or CO2, builds up in the blood to a critical level, the brainstem respiratory centers start breathing again. This is why a...

hyperpnea and hyperventilation

Breathing Changes in Exercise and Anxiety

Breathing changes in exercise and anxiety can look similar, but they do not have the same cause. Hyperventilation is a higher-than-normal rate and depth of breathing. It often happens during anxiety attacks and can push out more carbon dioxide than the body needs to remove. When too much carbon dioxide is lost, the blood develops hypocapnia, which means an unusually low level of carbon dioxide. Hypocapnia can narrow cerebral blood vessels and reduce blood flow to the brain. This may cause...

chronic obstructive pulmonary disease

COPD Signs, Causes, and Lung Damage

COPD is a lung condition that causes ongoing breathing problems. It leads to shortness of breath, cough, and sputum production because the airways become blocked and airflow is reduced. Smoking is the main risk factor for COPD, and more than 80% of patients have a history of it. People with COPD often develop worsening dyspnea, or labored breathing. They may also cough often and get repeated lung infections. Many patients with COPD can develop respiratory failure. This happens when...

other pulmonary disorders

Asthma, TB, Lung Cancer, and Sleep Apnea

Asthma, lung cancer, tuberculosis, and sleep apnea are major pulmonary disorders. They affect breathing in different ways. Some are chronic, some are infectious, and some can become life-threatening if not found and treated early. Asthma is marked by chronic airway inflammation and hypersensitivity. It can cause airway obstruction from bronchial spasms, mucosal edema, increased mucus secretion, or epithelial damage. Triggers vary and can include allergens or emotional upset. Treatment often...

key terms and concepts

Learn how hemoglobin in red blood cells binds oxygen, changes shape, and releases it in tissues. Explore the Bohr effect, BPG, pH, and CO2.

How Hemoglobin Loads and Releases Oxygen | JoVE K12

anatomy and physiology

JoVE Core 解剖学と生理学では、人体の解剖学的および生理学的な詳細を、包括的で明確で魅力的なビデオ アニメーションで紹介します。このレッスン集は、人体の構造、コンポーネント、機能、要件に焦点を当てています。この知識を実際の医療および研究現場で応用することを実証する科学者による実際のビデオによって補完されています。

Alabama Course of Study Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.HA.1.9.a

9-12.HA.1.9.c

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.44

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Digestive System

How Hemoglobin Loads and Releases Oxygen

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