8.2.2

Oxygen Dissociation

Test yourself on Oxygen Dissociation

Test your knowledge with free interactive questions on Seneca — used by over 10 million students.

Dissociation Curves

The relationship between the percentage saturation of haemoglobin and oxygen partial pressure of the surrounding tissues can be shown in a dissociation curve.

Low pO<sub>2</sub>

Low pO2

  • When partial pressure is low, haemoglobin has a low affinity for oxygen.
  • The percentage saturation of haemoglobin is low because oxygen dissociates from the haemoglobin.
Increasing pO<sub>2</sub>

Increasing pO2

  • As pO2 increases, affinity of haemoglobin for oxygen increases slightly.
  • When the first molecule of O2 binds to haemoglobin, the protein undergoes a conformational change.
  • The change in shape allows the other O2 molecules to bind to haemoglobin more easily.
  • The percentage saturation of haemoglobin increases quickly.
Plateau in percentage saturation

Plateau in percentage saturation

  • As more molecules of O2 bind to haemoglobin, it becomes more difficult for more O2 molecules to bind.
  • The percentage saturation of haemoglobin begins to plateau.
S-shaped curve

S-shaped curve

  • The increasing affinity of haemoglobin with increasing pO2 in this way creates an S-shaped curve.
  • The S-shaped curve is called the dissociation curve.
Higher altitudes

Higher altitudes

  • The partial pressure of oxygen is lower at higher altitudes. This makes it difficult to saturate haemaglobin with oxygen. It can be difficult to deliver enough oxygen to tissues.
  • To compensate for this, people who live at higher altitudes have a higher red blood cell count. This increases the amount of haemoglobin in blood.
    • The hormone erythropoietin stimulates red blood cell production at low partial pressures of oxygen. (You do not need to remember the name of this hormone).
  • This process is called acclimation.

The Bohr Effect

The partial pressure of carbon dioxide (pCO2) also influences the affinity of haemoglobin for oxygen. This is called the Bohr effect.

High pCO<sub>2</sub>

High pCO2

  • Respiring cells use oxygen in respiration and produce carbon dioxide.
  • The respiring cells have low pO2 and high pCO2.
  • When pCO2 is high, the rate of oxygen dissociation increases.
Bohr effect

Bohr effect

  • The increased dissociation of oxygen causes a shift in the oxyhaemoglobin dissociation curve to the right.
  • The shift in the dissociation curve means that oxygen will dissociate from haemoglobin at a lower pO2 than normal.
  • This is called the Bohr effect.
Jump to other topics
1

Cell Structure

1.1

Cell Structure

1.1.1Studying Cells - Microscopes1.1.2Introduction to Eukaryotic & Prokaryotic Cells1.1.3Ultrastructure of Eukaryotic Cells1.1.4Ultrastructure of Eukaryotic Cells 21.1.5Ultrastructure of Eukaryotic Cells 31.1.6Prokaryotic Cells1.1.7Viruses1.1.8End of Topic Test - Cell Structure1.1.9Exam-Style Question - Microscopes1.1.10A-A* (AO2/3) - Cell Structure
2

Biological Molecules

2.1

Testing for Biological Modules

2.1.1Tests for Sugars & Starch2.1.2Tests for Lipids & Proteins
2.2

Carbohydrates & Lipids

2.2.1Monomers & Polymers2.2.2Carbohydrates2.2.3Examples of Carbohydrates2.2.4Triglycerides & Phospholipids2.2.5Types of Fatty Acids2.2.6Exam-Style Question - Carbohydrates2.2.7End of Topic Test - Carbohydrates & Lipids
2.3

Proteins

2.3.1Amino Acids & Overview of Protein Structure2.3.2Primary & Secondary Structure2.3.3Tertiary & Quaternary Structure2.3.4Globular & Fibrous Proteins2.3.5Haemoglobin2.3.6Collagen2.3.7End of Topic Test - Proteins
2.4

Water

2.4.1Water Structure & Function2.4.2End of Topic Test - Water
3

Enzymes

3.1

Enzymes

3.1.1Enzyme Action3.1.2Factors Affecting Enzyme Activity3.1.3Factors Affecting Enzyme Activity 23.1.4A-A* (AO2/3) - Enzymes
4

Cell Membranes & Transport

4.1

Biological Membranes

4.1.1Fluid Mosaic Model4.1.2Cell Signalling4.1.3End of Topic Test - Biological Membranes4.1.4Exam-Style Question - Membranes
4.2

Movement Into & Out of Cells

4.2.1Passive Movement Across the Membrane4.2.2Active Movement Across the Membrane4.2.3Osmosis4.2.4Osmosis & Plant Cells4.2.5Surface Area to Volume Ratio4.2.6Adaptions to Surface Area to Volume Ratio4.2.7Calculations - Volume4.2.8Calculations - Surface Area
5

The Mitotic Cell Cycle

5.1

Replication & Division of Nuclei

5.1.1Chromosomes5.1.2The Cell Cycle5.1.3Mitosis5.1.4Role of Mitosis5.1.5Stem Cells5.1.6Mitosis & Cancer5.1.7End of Topic Test - Replication & Division5.1.8A-A* (AO2/3) - Cell Cycle & Transport
6

Nucleic Acids & Protein Synthesis

6.1

Nucleic Acids

6.1.1Introduction to DNA & RNA6.1.2Nucleotides6.1.3Polynucleotides6.1.4ADP & ATP6.1.5DNA6.1.6DNA Replication6.1.7RNA6.1.8End of Topic Test - Nucleic Acids & ATP
6.2

Protein Synthesis

6.2.1The Genetic Code6.2.2Polypeptide Synthesis6.2.3RNA Processing in Eukaryotes6.2.4Mutations6.2.5Exam-Style Question - Protein Synthesis6.2.6A-A* (AO2/3) - Coronavirus Translation
7

Transport in Plants

7.1

Transport in Plants

7.1.1Plant Vessels7.1.2Xylem7.1.3Investigating Transpiration7.1.4Adaptations to Water Availability7.1.5Phloem7.1.6End of Topic Test - Transport in Animals & Plants7.1.7A-A* (AO2/3) - Transport in Animals & Plants
8

Transport in Mammals

8.1

Circulatory System

8.1.1Double Circulation8.1.2Blood Vessels8.1.3Important Blood Vessels8.1.4Blood Cells8.1.5Tissue Fluid
8.2

Transport of Oxygen & Carbon Dioxide

8.2.1Haemoglobin8.2.2Oxygen Dissociation
8.3

The Heart

8.3.1Structure of the Heart8.3.2The Cardiac Cycle8.3.3Coordination of Heart Action
9

Gas Exchange

9.1

Gas Exchange System

9.1.1Mammalian Gas Exchange9.1.2Smoking
10

Infectious Diseases

10.1

Infectious Diseases

10.1.1Transmission of Disease10.1.2Tuberculosis10.1.3HIV10.1.4Malaria10.1.5Cholera10.1.6Measles
10.2

Antibiotics

10.2.1Antibiotics
11

Immunity

11.1

The Immune System

11.1.1Phagocytes11.1.2Antigens11.1.3Lymphocytes11.1.4Primary & Secondary Response
11.2

Antibodies & Vaccination

11.2.1Antibodies11.2.2Monoclonal Antibodies11.2.3Immunity11.2.4Vaccines11.2.5Exam-Style Question - Immune System11.2.6A-A* (AO2/3) - Disease & Immune System
12

Energy & Respiration (A2 Only)

12.1

Energy

12.1.1Energy & ATP12.1.2Respiratory Substrates & Quotient12.1.3Respirometers
12.2

Respiration

12.2.1Introduction to Respiration12.2.2Anaerobic Respiration12.2.3Aerobic Respiration12.2.4Chemiosmosis & Coenzymes12.2.5Mitochondria12.2.6Respiration Experiments12.2.7End of Topic Test - Respiration12.2.8A-A* (AO3/4) - Respiration
13

Photosynthesis (A2 Only)

13.1

Photosynthesis

13.1.1Introduction to Photosynthesis13.1.2Light-Dependent Reactions13.1.3Light-Independent Reactions13.1.4Limiting Factors13.1.5Investigating Photosynthesis13.1.6End of Topic Test - Photosynthesis13.1.7A-A* (AO3/4) - Photosynthesis
14

Homeostasis (A2 Only)

14.1

Homeostasis

14.1.1Homeostasis14.1.2Negative Feedback
14.2

The Kidney

14.2.1Kidneys & Osmoregulation
14.3

Cell Signalling

14.3.1Messengers & cAMP
14.4

Blood Glucose Concentration

14.4.1Blood Glucose Concentration14.4.2Controlling Blood Glucose14.4.3Urinalysis
14.5

Homeostasis in Plants

14.5.1Stomata & Guard Cells
15

Control & Coordination (A2 Only)

15.1

Control & Coordination in Mammals

15.1.1Neurones15.1.2Receptors15.1.3Taste15.1.4Reflexes15.1.5Action Potentials15.1.6Saltatory Conduction15.1.7Synapses15.1.8Cholinergic Synnapses15.1.9Neuromuscular Junction15.1.10Skeletal Muscle15.1.11Sliding Filament Theory Contraction15.1.12Sliding Filament Theory Contraction 215.1.13Menstruation15.1.14Contraceptive Pill
15.2

Control & Co-Ordination in Plants

15.2.1Venus Flytrap15.2.2Auixns15.2.3Gibberellins
16

Inherited Change (A2 Only)

16.1

Passage of Information to Offspring

16.1.1Meiosis16.1.2Gametogenesis16.1.3Meiosis & Genetic Diversity
16.2

Genes & Phenotype

16.2.1Key Terms in Genetics16.2.2Inheritance16.2.3Linkage16.2.4Multiple Alleles16.2.5Chi-Squared Test16.2.6Mutations16.2.7Specific Mutations16.2.8End of Topic Test - Genetics16.2.9A-A* (AO2/3) - Genetics
16.3

Gene Control

16.3.1lac Operon16.3.2Transcription Factors16.3.3Gibberellins & DELLA Proteins
17

Selection & Evolution (A2 Only)

17.1

Variation

17.1.1Phenotypic Variation17.1.2Continuous & Discontinuous Variation17.1.3t-Tests
17.2

Natural & Artificial Selection

17.2.1Natural Selection & Evolution17.2.2Types of Selection17.2.3Types of Selection Summary17.2.4Genetic Drift & Founder Effect17.2.5Populations17.2.6Hardy-Weinberg Principle17.2.7Artificial Selection
17.3

Evolution

17.3.1Evolution by Natural Selection17.3.2Evidence for Evolution17.3.3Speciation17.3.4Extinction
18

Classification & Conservation (A2 Only)

18.1

Biodiversity

18.1.1Key Terms18.1.2Biodiversity18.1.3Sampling Methods18.1.4Correlation18.1.5Spearman’s Rank18.1.6Measuring Biodiversity
18.2

Classification

18.2.13-Domain Classification System18.2.2Linnaean Classification System
18.3

Conservation

18.3.1Importance of Biodiversity18.3.2Conservation18.3.3Zoos, Seedbanks, & Other Conservation Methods18.3.4Assisted Reproduction & Contraception18.3.5Non-Governmental Organisations
19

Genetic Technology (A2 Only)

19.1

Manipulating Genomes

19.1.1Recombinant DNA & Genetic Engineering19.1.2Restriction Endonucleases19.1.3Gel Electrophoresis19.1.4DNA Probes & Microarrays19.1.5End of Topic Test - Manipulating Genomes19.1.6A-A* (AO2/3) - Manipulating Genomes
19.2

Genetic Technology Applied to Medicine

19.2.1Bioinformatics19.2.2Applications of Recombinant DNA19.2.3Genetic Screening19.2.4Gene Therapy19.2.5Ethics19.2.6DNA Profiling & Forensics
19.3

Genetically Modified Organisms in Agriculture

19.3.1GM Crops & Livestock19.3.2Ethics

Practice questions on Oxygen Dissociation

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Which of the following statements about the dissociation curve are true?True / false
  2. 2
    What is the impact on haemoglobin when the first molecule of oxygen binds?Multiple choice
  3. 3
    What is the shape of the dissociation curve?Multiple choice
  4. 4
    Which of the following statements about the Bohr effect are true?True / false
  5. 5
    How does a high pCO<sub>2</sub> impact haemoglobin affinity for oxygen?Multiple choice
Answer all questions on Oxygen Dissociation

Unlock your full potential with Seneca Premium

  • Unlimited access to 10,000+ open-ended exam questions

  • Mini-mock exams based on your study history

  • Unlock 800+ premium courses & e-books

Get started with Seneca Premium

Haemoglobin

Structure of the Heart