Respiratory gas transport
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RESPIRATORY GAS TRANSPORT. Biochemistry Departement Medical Faculty Of Andalas University Padang. Oxygen Transport. Total Body Oxygen Stores . Oxygen in the Lung (~500 ml O 2 ). Oxygen in the Blood (~850 ml O 2 ). Oxygen in the Cells (very little except Mb-bound). At the Lung Level.

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Respiratory gas transport


Biochemistry Departement

Medical Faculty Of Andalas University


Oxygen transport

Oxygen Transport

Total body oxygen stores

Total Body Oxygen Stores

  • Oxygen in the Lung (~500 ml O2).

  • Oxygen in the Blood (~850 ml O2).

  • Oxygen in the Cells (very little except Mb-bound).

Respiratory gas transport

At the Lung Level

Respiratory gas transport

At the Tissue Level

Oxygen is carried in blood in 2 forms

Oxygen Is Carried in Blood in 2 Forms

  • Bound to hemoglobin in red blood cells.

  • Dissolved in plasma. Normally insignificant.



  • Each “heme” molecule is capable of binding with 1 O2 molecule and each “globin” molecule is capable of binding with 1 CO2 molecule.

  • So, each molecule of Hb can bind to either 4 molecules of O2 and 1 molecule of CO2

  • 100 ml of blood has about 15 gm of Hb, at Hct = 0.45

Respiratory gas transport

  • Binding of O2 to 4 heme sites given by:

  • Equilibrium constants for different reactions different

    • Binding of first O2 relatively low affinity

    • 2nd, 3rd and 4th - much higher affinity

Oxygen as oxyhemoglobin

Oxygen as Oxyhemoglobin

  • Each gram of Hb can store about 1.34 ml of O2:

  • 1 L of blood (150 gm of Hb) can store about 208 ml of O2  Oxygen Capacity of Hb.

  • With normal cardiac output, about 1040 ml of O2 can be carried in blood per minute. (4 times of the metabolic demands).

O 2 saturation

O2 Saturation.

  • Units: percent.

  • Fraction or percentage of all the hemoglobin binding sites that are currently occupied by oxygen.

Oxygen saturation of hb

Oxygen Saturation of Hb

Four 5 6 things change oxyhemoglobin affinity

Four (5-6?) Things Change Oxyhemoglobin Affinity

  • Hydrogen Ion Concentration, [H+]

  • Carbon Dioxide Partial Pressure, PCO2

  • Temperature

  • [2,3-DPG]

  • Special Case: Carbon Monoxide

  • Hemoglobin variants

Factors affecting hb o 2 affinity summary

Factors Affecting Hb-O2 Affinity: Summary

  • Hydrogen Ion:

    • Increased H+ (decreased pH) increases H+ binding to Hb and reduces O2 affinity (HbO2+H+HbH++O2).

  • Carbon Dioxide (Bohr effect):

    • Increased PCO2 increases CO2 binding to Hb and reduces O2 affinity (increased O2 delivery to tissue).

    • Increased PCO2 increases H+ and reduces O2 affinity (fixed acid Bohr effect).

  • Temperature and 2,3-DPG (diphosphoglycerate):

    • Increased temperature and 2,3-DPG reduces O2 affinity.

Effect of co anemia on hb o 2 affinity

Effect of CO & Anemia on Hb-O2 Affinity

Normal blood with Hb=15 gm/dl, anemia with Hb=7.5 gm/dl, and normal blood with 50% HbCO (carboxyhemoglobin).



  • Increase temperature

  • Increased PCO2 and

  • Decreased pH (acidosis)

2 3 dpg


  • 2,3-DPG is a glycolytic intermediate

    • accumulates to uniquely high levels in RBCs

      -Increased 2,3-DPGright shift

      -Decreased 2,3-DPG left shift

  • Increased 2,3-DPG associated with hypoxia.

Conditions with increased 2 3 dpg

Conditions with Increased 2,3-DPG

  • acclimatization to high altitudes.

  • chronic lung disease; emphysema.

  • anemia.

  • hyperthyroidism.

  • right to left shunt.

  • congenital heart disease.

  • pulmonary vascular disease.

Carbon dioxide transport

Carbon Dioxide Transport

Respiratory gas transport

At the Tissue Level

Respiratory gas transport

At the Lung Level

Carbon dioxide transport1

Carbon Dioxide Transport

  • CO2 is transported in blood in dissolved form, as bicarbonate ions, and as protein-bound carbamino compound.

  • Protein-bound CO2 (carbamino compounds):

  • Amount of CO2 stored as carbamino compounds is about 21 ml/L (4% of the total art CO2).

Carbon dioxide transport2

Carbon Dioxide Transport

  • A majority amount of CO2 is transported in the form of bicarbonate ions (HCO3-):

  • Amount of CO2 in HCO3- form at PCO2=40 mmHg is about 420 ml/L (90% of the total arterial CO2).

Carbon dioxide transport3

Carbon Dioxide Transport

  • Haldane Effect: Increasing O2-saturation reduces CO2 content and shifts the CO2 dissociation curve to right. This is because, increasing PO2 leads to :

    • Decrease in the formation of carbamino compound.

    • Release of H+ ions from the hemoglobin and resulting in dehydration of HCO3-.

Carbon dioxide dissociation curve

Carbon Dioxide Dissociation Curve

Over the normal physiological range (PCO2 = 30 to 55 mmHg and PO2 = 40 to 100 mmHg), the CO2 equilibrium curve is nearly linear. But, O2 equilibrium curve is highly nonlinear.

Bicarbonate in rbcs

Bicarbonate in RBCs.

  • Carbonic anhydrase is present in RBCs

  • CO2 forms carbonic acid which dissociates to H+ and HCO3-

  • Released H+ is buffered by histidine residues (imidazole group)

• Percent of the total PaCO2: 70%

Carbamino compounds in rbcs

Carbamino Compounds in RBCs.

  • Approximately 30% of RBC contents is Hb

  • CO2 forms carbamino hemoglobin

  • Released H+ is buffered by histidine residues (imidazole group)

• Percent of the total PaCO2: 23 %

Co 2 formation in plasma

CO2Formation in Plasma

  • Carbamino compounds

    • CO2 binds the amine groups of plasma proteins to form carbamino compounds.

Respiratory gas transport

O2 pickup CO2 release

Respiratory gas transport

O2 release CO2 pickup

Chloride shift hamburger shift

Chloride Shift (Hamburger Shift)

  • Newly formed HCO3- passes out of RBC

  • Cl- diffuses into RBC to maintain electroneutrality

    • Chloride shift is rapid

    • Complete before the RBCs exit capillary

Tissue gas exchange summary

Tissue-Gas Exchange: Summary

  • Gas exchange processes in the peripheral organs are essentially opposite those in the lungs.

  • O2 is released from the capillary blood to the tissues and diffuses to the mitochondria where O2 is converted to CO2 and energy (ATP) through cellular metabolism.

  • CO2 diffuses from the tissues to the blood stream and is transported to the lungs for elimination.

  • The exchange of O2 and CO2 in the blood-tissue exchange unit depends on PO2, PCO2, and also on O2 and CO2 saturation curves.

Gas transport in cell

Gas Transport in Cell

Pelepasan co 2

Pelepasan CO2

  • Dilakukan oleh:

    1. isositrat dehidrogenase

    2. α-ketoglutarat dehidrogenase

  • Pelepasan CO2 tidak mengkonsumsi oksaloasetat.

Siklus atp adp

Siklus ATP/ADP

  • Berperan untuk menghubungkan proses-proses yg menghasilkan P-berenergi-tinggi dgn proses yg menggunakan P-berenergi-tinggi.

  • ATP dikonsumsi & dibentuk kembali secara kontinu.

  • Depot ATP/ADP sangat kecil, sehingga hanya cukup untuk mempertahankan jaringan aktif dlm waktu beberapa detik saja.

Siklus atp adp1

Siklus ATP/ADP



Pernapasan: Penggunaan energi:

pembentukan energi - biosintesis makro-

dari; - karbohidrat molekul

- lemak - kontraksi otot

- protein - transpor ion aktif

- termogenesis


ADP + Pi

Fosforilasi oksidatif

Fosforilasi Oksidatif

  • Adalah sistem dalam mitokondria yang memasangkan respirasi dengan proses pembentukan intermediat berenergi tinggi, ATP.

  • Sistem ini memungkinkan organisme aerob menangkap energi bebas dari substrat respiratorik dalam jumlah lebih besar dibanding organisme anaerob.

Peran rantai respirasi

Peran Rantai Respirasi

asam lemak

+ b-oksidasi

gliserol ATP


glukosa Asetil KoA SAS 2H H2O

rantai respirasi

Asam amino ADP


Produk atp pada fosforilasi oksidatif

Produk ATP pada Fosforilasi Oksidatif

Berdasarkan hipotesis kimiosmotik dari Mitchell


rantai bekerja --> proton dipompa keluar dari membran dlm mitokondria --> pH antar membran turun --> proton balik ke dalam matrik lewat tonjolan ATP-sintase--> fosforilasi ADP menjadi ATP.

Produk atp pada fosforilasi oksidatif1

Produk ATP pada Fosforilasi Oksidatif

  • Diperkirakan satu ATP disintesis setiap dua proton melewati tonjolan tsb.

  • Hasilnya ialah;

    - 3 mol. ATP utk oksidasi 1 mol. NADH

    - 2 mol. ATP utk oksidasi 1 mol. FADH2

  • Laju fosforilasi oksidatif dikendalikan oleh;

    NADH, oksigen, ADP



  • BIOEN 589: Integrative Physiology. Download 24 jan 05.

  • Kennelly, PJ., Rodwell, V W. Proteins: Myoglobin & Hemoglobin. In: Harper’s Illustrated Biochemistry. 27th Ed. 41- 8.

  • Miliefsky, M. Respiratory System Ch.23. Download 24 Nov 10.

  • Sheardown, H. Blood Biochemistry. McMaster University. Download 20 Mei 07.

  • Irvin, CG. Respiratory Physiology. Lecture 4A CO2 Transport. In: MEDICAL PHYSIOLOGY 30. Download 22 Jun 09.

  • Marks, DB., Marks, AD., Smith CM. Basic medical biochemistry: a clinical approach. 1996. Dalam: B.U. Pendit, penerjemah. Biokimia Kedokteran Dasar: Sebuah Pendekatan Klinis. Eds. J. Suyono., V. Sadikin., L.I. Mandera. Jakarta: EGC, 2000

  • R.K. Murray, D.K. Granner, P.A. Mayes, V.W. Rodwell Harper’s Biochemistry. 27th ed. McGraw-Hill Companies, New York. 2006.

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