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By the end of this section, you will be able to:
  • Describe the principles of oxygen transport
  • Describe the structure of hemoglobin
  • Compare and contrast fetal and adult hemoglobin
  • Describe the principles of carbon dioxide transport

The other major activity in the lungs is the process of respiration, the process of gas exchange. The function of respiration is to provide oxygen for use by body cells during cellular respiration and to eliminate carbon dioxide, a waste product of cellular respiration, from the body. In order for the exchange of oxygen and carbon dioxide to occur, both gases must be transported between the external and internal respiration sites. Although carbon dioxide is more soluble than oxygen in blood, both gases require a specialized transport system for the majority of the gas molecules to be moved between the lungs and other tissues.

Oxygen transport in the blood

Even though oxygen is transported via the blood, you may recall that oxygen is not very soluble in liquids. A small amount of oxygen does dissolve in the blood and is transported in the bloodstream, but it is only about 1.5% of the total amount. The majority of oxygen molecules are carried from the lungs to the body’s tissues by a specialized transport system, which relies on the erythrocyte—the red blood cell. Erythrocytes contain a metalloprotein, hemoglobin, which serves to bind oxygen molecules to the erythrocyte ( [link] ). Heme is the portion of hemoglobin that contains iron, and it is heme that binds oxygen. One hemoglobin molecule contains iron-containing Heme molecules, and because of this, each hemoglobin molecule is capable of carrying up to four molecules of oxygen. As oxygen diffuses across the respiratory membrane from the alveolus to the capillary, it also diffuses into the red blood cell and is bound by hemoglobin. The following reversible chemical reaction describes the production of the final product, oxyhemoglobin    (Hb–O 2 ), which is formed when oxygen binds to hemoglobin. Oxyhemoglobin is a bright red-colored molecule that contributes to the bright red color of oxygenated blood.

Hb + O 2 Hb   O 2 MathType@MTEF@5@5@+=feaagyart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeisaiaabkgacaqGGaGaae4kaiaabccacaqGpbWaaSbaaSqaaiaabkdaaeqaaOGaeyiLHSQaaeisaiaabkgacaqGGaGaeyOeI0Iaaeiiaiaab+eadaWgaaWcbaGaaeOmaaqabaaaaa@42D6@

In this formula, Hb represents reduced hemoglobin, that is, hemoglobin that does not have oxygen bound to it. There are multiple factors involved in how readily heme binds to and dissociates from oxygen, which will be discussed in the subsequent sections.

Erythrocyte and hemoglobin

This diagram shows a red blood cell and the structure of a hemoglobin molecule.
Hemoglobin consists of four subunits, each of which contains one molecule of iron.

Function of hemoglobin

Hemoglobin is composed of subunits, a protein structure that is referred to as a quaternary structure. Each of the four subunits that make up hemoglobin is arranged in a ring-like fashion, with an iron atom covalently bound to the heme in the center of each subunit. Binding of the first oxygen molecule causes a conformational change in hemoglobin that allows the second molecule of oxygen to bind more readily. As each molecule of oxygen is bound, it further facilitates the binding of the next molecule, until all four heme sites are occupied by oxygen. The opposite occurs as well: After the first oxygen molecule dissociates and is “dropped off” at the tissues, the next oxygen molecule dissociates more readily. When all four heme sites are occupied, the hemoglobin is said to be saturated. When one to three heme sites are occupied, the hemoglobin is said to be partially saturated. Therefore, when considering the blood as a whole, the percent of the available heme units that are bound to oxygen at a given time is called hemoglobin saturation. Hemoglobin saturation of 100 percent means that every heme unit in all of the erythrocytes of the body is bound to oxygen. In a healthy individual with normal hemoglobin levels, hemoglobin saturation generally ranges from 95 percent to 99 percent.

Questions & Answers

Capillary permeability
what do you want to know about it?
Ramsin
Hello, I want to search about the topic, information and pictures
syncitium is the property of which of the following muscle
Shahab Reply
can I get the questions of human physiology that is present in HSC 2nd semester
Sai Reply
i now madam
irpa
ha can u please send me the PDF of questions
Sai
it's important to me to have that information please send as fast as u can
Sai
me too if possible?
Ramsin
If a molecule can only pass through a membrane with the assistance of a membrane protein, but the direction of its travel is controlled only by its concentration, the process is called?
osmosis
chozen
A 52 year old woman turned her head quickly, during a tennis game and suddenly felt a sharp pain in her neck along her upper limb. Physical examination and medical imaging revealed a herniated degenerated IV disc in the cervical region of her vertebral column.
Isaac
a. What probably caused the IV disc herniation? b. What cause IV disc degeneration? c. What are the result of disc degeneration?
Isaac
b
Mirasol
Describe the neural control of erection and ejaculation.
Nana Reply
A 52 year old woman turned her head quickly, during a tennis game and suddenly felt a sharp pain in her neck along her upper limb. Physical examination and medical imaging revealed a herniated degenerated IV disc in the cervical region of her vertebral column. a)What probably caused the IV di
Isaac
a) What probably caused the IV disc herniation? b) What cause IV disc degeneration? c) What are the result of disc degeneration?
Isaac
iv disc herniation compress the nerve cause numbness tingling sensation even paralysis in severe cases...
Khawaja
explain more
DANIELLA Reply
yes
Ramzan
function of skeleton
Josiah Reply
- for movement - blood production by the bone marrow
Daniel
production of calsium and phosphorus
Juma
Shortly after childbirth, a woman consulted her physician about a tender swelling in her perineal region. 8. What fossa related the perineal swelling? 9. Describe what vessel may cause the collection of blood in the fossa after childbirth?
Isaac
what is heart
Subhajit Reply
it is the tissue..which pump blood to the all parts of body
GRAY
the heart is a conical , hollow, muscular organ which works continuously through out the life of a person ,it is about the size of a clenched fist and weighs about 300 grams and also the heart is in the chest just behind the breast bone and between the two lungs
Mary
a hollow muscular organ that pumps blood through the circulatory system by regular contractions
Johnny
is a muscular organ that pumps blood lungs and other body tissues through vessels
Nolosha
Shortly after childbirth, a woman consulted her physician about a tender swelling in her perineal region. 8. What fossa related the perineal swelling? 9. Describe what vessel may cause the collection of blood in the fossa after childbirth?
Isaac
Shortly after childbirth, a woman consulted her physician about a tender swelling in her perineal region. 8. What fossa related the perineal swelling? 9. Describe what vessel may cause the collection of blood in the fossa after childbirth?
Isaac Reply
inguinal fossa femoral vein?
Jeen
if you dont the answer by now you should seek another line of work. as a professor it is my duty to let you know about your lacking.
Arif
branches of brachial plexus
Arooj Reply
musculocutaneous, median, ulnar, axillary, and radial nerves.
Shakerah
Shortly after childbirth, a woman consulted her physician about a tender swelling in her perineal region. a.What fossa related the perineal swelling? b.Describe what vessel may cause the collection of blood in the fossa after childbirth?
Isaac
What is great Auricular nerve?
ZUBAIR Reply
it originates from the cervical plexus that provides sensory innervation to the skin.
Daniel
why it is called Auricular nerve
Amber
is any payment is needed to use this app
Suprith Reply
is it a question?
Samenjo
doubt about this app
Suprith
which lines divide the body into nine quadrant
Julius Reply
nine regions of abdomen can b marked using two horizontal & two vertical lines...the vertical lines are the mid clavicular lines taken from the mid point of each clavicle. the upper horizontal lines is the subcostal line taken from the inferior parts of the lowest costal cartilage...
Khawaja
to get a better understanding for the function
Rashana Reply
anatomy and physiology work closely together
Rashana
anatomy to you about the structure of the while physiology is the the study of the body function
Rashana
what is the difference between negative and positive feedback
Rashana
The key difference bewteen positive and negative feedback is their response to change. Positive feedback amplifies change while negative reduces change.
ladychen
negative feed back produces a response that brings back to normal while positive feed back produces a response that stimulates
Julius
examples of the body structure
Naki Reply
body's structure
Naki

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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