Module 2 exchange and transport
1 / 159

Module 2 Exchange and Transport - PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

Module 2 Exchange and Transport. Unit One Cells, Exchange and Transport AS Biology OCR Specification. Learning Outcomes. Explain, in terms of surface area:volume ratio, why multicellular organisms need specialised exchange surfaces and single-celled organisms do not.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Presentation

Module 2 Exchange and Transport

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Module 2Exchange and Transport

Unit One

Cells, Exchange and Transport

AS Biology

OCR Specification

Learning Outcomes

  • Explain, in terms of surface area:volume ratio, why multicellular organisms need specialised exchange surfaces and single-celled organisms do not.

Exchanges between organisms and their environment

  • Exchange can take place in two ways

    • Passively (no energy is required)

      • E.g. diffusion and osmosis

    • Actively (energy is required)

      • Active transport

      • Pinocytosis and phagocytosis

Surface area to volume ratio

  • Exchange takes place at the surface of an organism, but the materials absorbed are used by cells that mostly make up its volume.

  • For exchange to be effective, the surface area of the organism must therefore be large compared with its volume.

Learning outcomes

  • Explain, in terms of surface area:volume ratio, why multicellular organisms need specialised exchange surfaces and single-celled organisms do not.

Evolution of organisms

  • A flattened shape

  • A central region that is hollow

  • Specialised exchange surfaces

    • Large areas to increase the surface area to volume ratio

Why organisms need special exchange surfaces

  • Oxygen for…

  • Glucose as a source of …

  • Proteins for … and …

  • Fats

  • Water

  • Minerals

  • To remove waste materials

Features of a specialised exchange surface

  • Good exchange surfaces have:

    • A large surface area

    • Thin barrier to reduce diffusion distance

    • Large concentration gradient

      • Fresh supply of molecules on one side

      • Removal of required molecules on other side

Specialised Exchange Surfaces

  • Alveoli in the lungs

  • Small intestine

  • Liver

  • Root hairs in plants

  • Hyphae of fungi

Progress Question

  • Very small organisms such as the amoeba do not have specialised gas exchange systems.

  • Mammals are large, multicellular organisms and have a complex gas exchange system.

  • Explain why the mammal needs such a system when an amoeba does not.

Progress Question - suggestions

  • Why do we need gas exchange?

    • Oxygen is needed for respiration

    • Body needs to get rid of waste carbon dioxide.

  • How do simple animals take in the oxygen they need?

    • Diffusion through the surface membranes e.g. amoeba or flatworm

Progress Question - suggestions

  • Why can’t multi-cellular organisms do this?

    • Cells are too far away from the oxygen in the external environment.

    • Need a specialised exchange surface.

  • In humans the specialised gas exchange surface is the alveoli.

Learning Outcomes

  • Describe the features of an efficient gas exchange surface, with reference to diffusion of oxygen and carbon dioxide across and alveolus.

Gas Exchange

  • Gaseous exchange is the movement of gases between an organism and its environment.

  • Gas exchange takes place by diffusion.

    • The rate of diffusion depends on three factors.

      • The surface area of the gas exchange surface

      • Difference in concentration

      • The length of the diffusion pathway


  • Adaptations of alveoli to gas exchange

    • Large surface area

    • Thin walls of alveoli and blood capillaries

    • Steep concentration gradient

    • Good blood supply

    • Ventilation

  • Blood is constantly moving through the lungs to maintain the concentration gradients.

  • The air in the alveoli is continually refreshed by ventilation.

Alveoli and gas exchange

  • Large surface area – 70m2

  • Extremely thin – lined with squamous epithelium – allows for rapid diffusion

    • 0.1μm to 0.5μm thick

  • Kept moist / surfactant

  • Extensive capillary network

    • Capillaries 7-10μm in diameter

    • Blood flow through capillaries is slowed

  • Ventilation

Applying your knowledge

  • Alf smoked for 40 years. He had a bad “smoker’s cough” and easily got out of breath. His health got worse so he went to see his doctor. The doctor said that he had emphysema. She explained that the coughing had damaged a lot of the alveoli in his lungs and reduced their surface area.

    • Explain as fully as you can why Alf got out of breath easily.

    • Alf’s illness got worse. He couldn’t walk very far and he had to breathe oxygen from a cylinder. Explain why.

Structure of the Mammalian Lung

Learning Outcomes

  • describe the features of the mammalian lung that adapt it to efficient gaseous exchange;

  • outline the mechanism of breathing (inspiration and expiration) in mammals, with reference to the function of the rib cage, intercostal muscles and diaphragm;


  • Why is the volume of oxygen that has to be absorbed and the volume of carbon dioxide that has to be removed in mammals so large?

    • Large organisms with large volume of living cells

    • Maintain a high body temperature

      • High metabolic rate

      • High respiratory rate

Mammalian Lungs

  • Structure of the lungs

    • Trachea

    • Rib cage

    • Intercostal muscles

    • Bronchi

    • Bronchioles

    • Alveoli (site of gaseous exchange)

      • 100μm – 300μm in diameter

      • 300 million in each lung

Revision Activity

  • Design a poster

  • Your poster should show the distribution of tissues and highlight the functions of each of the tissues

    • cartilage

    • Cilia

    • goblet cells

    • smooth muscle

    • elastic fibres

Learning Outcomes

  • describe, with the aid of diagrams and photographs, the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchi, bronchioles and alveoli of the mammalian gaseous exchange system

  • describe the functions of cartilage, cilia, goblet cells, smooth muscle and elastic fibres in the mammalian gaseous exchange system;

Ciliated Epithelium


Smooth Muscle

Squamous Epithelium


Functions of cells, tissues and fibres


  • Flexible supporting material

  • Incomplete rings support the smooth muscle keeping the tubes open.

  • Prevents trachea and bronchi from collapsing when air pressure lowers during inhalation


  • Synchronised movement to transport mucus towards the pharynx

Goblet cells

  • Produce the mucus that forms a thin layer over surface of the trachea and bronchi

  • The mucus is sticky and traps bacteria. Pollen and dust particles, the air is “filtered”.

Smooth muscle

  • Contraction of the smooth muscle allows the bronchioles to constrict.

  • This controls the flow of air to the alveoli.

Elastic fibres

  • Elastic fibres become stretched when the smooth muscle contracts, when the smooth muscles relaxes the elastic fibres recoil back into their original positions.

  • This dilates the bronchioles.

Difference in structure of Trachea, bronchi and bronchioles

  • Cartilage in trachea and bronchi keep airways open and air resistance low.

    • Trachea has c-shaped rings

    • Bronchi has irregular blocks

  • Bronchioles have smooth muscle which contracts and elastic fibres to control their diameter

Learning Outcomes

  • outline the mechanism of breathing (inspiration and expiration) in mammals, with reference to the function of the rib cage, intercostal muscles and diaphragm;



Fill in the gaps Mammalian Lungs (1)

  • Two reasons why mammals require a large and constant supply of oxygen are (1) and (2). The main organs for gaseous exchange are the lungs, which are connected to the outside by a tube called the (3). This branches into two (4), one of which enters each lung.

Fill in the gaps Mammalian Lungs (2)

  • The actual site of gaseous exchange is in the alveoli, which have a diameter of (5) and have walls made of (6) which is very thin, being only (7) in thickness. The total number of alveoli for both lungs is around (8) giving them a very large surface area of about (9).

Fill in the gaps Gaseous Exchange in the alveoli (1)

  • Gaseous exchange occurs in the alveoli, with the gas called (1) moving into the blood and the gas called (2) moving in the opposite direction. The diameter of an alveolus is (3) and it is surrounded by squamous epithelial cells that are only (4) thick and so allow rapid (5) of gases across them.

Fill in the gaps Gaseous exchange in the alveoli (2)

  • Each alveolus is surrounded by a network of (6) that are around (7) in diameter, causing (8) within them to be flattened against their surface, thus improving the rate of exchange of gases between themselves and the alveoli.

Learning Outcomes

  • explain the meanings of the terms tidal volume and vital capacity;

  • describe how a spirometer can be used to measure vital capacity, tidal volume, breathing rate and oxygen uptake;

  • analyse and interpret data from a spirometer

Breathing Rate

  • Breathing refreshes the air in the alveoli so that concentration of O2 and CO2 remains constant

Lung Capacities

  • Tidal volume

    • The volume of air breathed in or out in a single breath

  • Residual volume

    • The amount of air that remains in the alveoli and airways after forced exhalation.

  • Vital Capacity

    • The volume of air that can be exchanged between maximum inspiration and maximum expiration

  • The effect of exercise on breathing is measured by calculating ventilation rate, which is the total air moved into the lungs in one minute.

    Ventilation rate = tidal volume X breathing rate

  • Ventilation brings about changes in lung volume, these changes can be ,measured by a spirometer.

Measuring Oxygen Uptake

  • If someone breathes in and out of a spirometer for a period of time, the carbon dioxide level increases to dangerous levels.

  • To avoid this, soda lime is used to absorb the carbon dioxide exhaled.

  • This means the total volume of gas in the spirometer will go down.

Measuring Oxygen Uptake

  • The volume of CO2 breathed out is the same as the volume of O2 breathed in.

  • This allows us to make calculations of oxygen used under different conditions.

Spirometer trace (4 marks)

  • A spirometer measures the volume of gas breathed in and out of the lungs.

  • The spirometer trace shows the results obtained from a 17 year old male who was sitting down while breathing in and out of a spirometer.

  • Describe this person’s breathing between points J and K on the spirometer trace

Spirometer trace answers


Unit One

Cells, Exchange and Transport

AS Biology

OCR Specification

Learning Outcomes

  • Explain the need for transport systems in multi-cellular animals in terms of size, activity and surface area to volume ratio

  • Explain the meaning of the terms single and double circulatory systems with reference to the circulatory systems of fish and mammals

  • explain the meaning of the terms open circulatory system and closed circulatory system, with reference to the circulatory systems of insects and fish

The Mammalian Transport System

Why do multi-cellular animals require a transport System?

The Internal Transport System

  • Cell Metabolism – What do cells need?

    • Amino acids, glucose, oxygen

    • Removal of waste products

  • What is important in determining whether an organism has a transport system?

    • Size

    • Surface area to volume ratio

    • Level of activity

Pupil Activity

  • Using the table on the next slide, determine the importance of the three factors and give information to support your answers?

    • Size

    • Surface area to volume ratio

    • Level of activity

Different Transport Systems

Determining the need for a transport system!

Determining the need for a transport system!

Determining the need for a transport system!

Why transport systems?

  • Diffusion only works effectively in large surface area to volume ratios

    • Small organisms. Oxygen diffuses into cells, to mitochondria for use in respiration

  • Large organisms can not rely on this

    • Body surface is not large enough

    • Distances from surface are too great

  • Less active organisms have a smaller requirement for glucose and oxygen.

  • Surface Area:Volume ratios

    Surface Area:Volume ratios

    Surface area: volume ratio

    • With a cube shape

      • As it gets bigger the volume increases faster than the surface area

      • Larger multi-cellular animals need a transport system and special gas exchange surfaces

    Open Circulation

    • Insects have an open circulation

      • Blood is not enclosed in vessels, and it circulates in body spaces.

    Closed circulation

    • Blood flows inside vessels

    • Single circulation e.g. Fish

      • Blood flows through heart once in every circulation of the body.

    Closed Circulation

    • Double Circulation e.g. mammals

      • Blood passes through the heart twice in every circulation of the body.

      • Two circuits

        • Pulmonary circuit

        • Systemic circuit

    Advantages of a double circulation

    • Simultaneous high pressure delivery of oxygenated blood to all regions of the body

    • Oxygenated blood reaches respiring cells undiluted by deoxygenated blood.

    The Mammalian Heart

    Structure of the Heart


    Learning Outcomes

    • describe, with the aid of diagrams and photographs, the external and internal structure of the mammalian heart;

    • explain, with the aid of diagrams, the differences in the thickness of the walls of the different chambers of the heart in terms of their functions;

    External Structure of the heart

    • Observe and draw the external structure of the heart, identifying the following parts.

      • Cardiac muscle

      • coronary arteries

      • Aorta

      • pulmonary artery

      • Vena cava

      • pulmonary vein

    Internal structure of the heart

    • Observe and draw the internal structure of the heart

    • Identify and describe

      • Septum

      • atriumand ventricle

      • Atrio-ventricular valves

        • mitral/bicuspid

        • tricuspid

    Revision of structure of heart

    • Label the diagram of the heart

      • Right atria / left atria

      • Right ventricle / left ventricle

      • Aorta / pulmonary artery

      • Vena cava / pulmonary vein

    • Colour in deoxygenated blood blue / oxygenated blood red

    • Fill in the missing gaps in the summary.

    • You have got 10 minutes for this activity

    The Mammalian Heart

    The Cardiac Cycle

    Learning outcomes

    • describe the cardiac cycle, with reference to the action of the valves in the heart;

    Cardiac Cycle

    • The sequence of events of a heart beat

    • Alternate contractions (systole) and relaxations (diastole)

    • Between 70 and 75 bpm

    Cardiac Cycle

    • Blood flows through the heart

      • Muscles contract

      • Volume chamber decreases

      • Pressure increases

      • Blood forced to a region of lower pressure

      • Valves prevent backflow

    Cardiac Cycle

    • There are 3 main stages to the cardiac cycle

      • Atrial systole

      • Ventricular systole

      • Diastole

    Atrial Systole

    • Heart is full of blood and ventricles relaxed

    • Both atria contract

    • Blood passes into ventricles

    • A-V valves open due to pressure

    • 70% blood flows passively atria - ventricle

    Atrial Systole

    Ventricular Systole

    • Atria relax

    • Ventricles contract

    • Forces blood into pulmonary artery and aorta

    • A-V valves close (lub)

    • S-L valves open

    • Pulse is generated

    Ventricular systole


    • Ventricles relax

    • Pressure in ventricle < pressure in arteries

    • High pressure blood in arteries cause S-L valves to shut (dub)

    • All muscles relax

    • Blood from vena cava and pulmonary vein enter atria


    Structure and function of heart muscle

    • Ventricle walls are thicker

      • Need greater force when contract

    • R. Ventricle –force relatively small, pumps to lungs

    • L. Ventricle – sufficient to push blood around body

    • Thickness left > right

    Exam Question

    • Answer the exam question

      • You have got 15 minutes for this

    Pressure and volume changes of the heart

    Pupil Activity

    • June 2003 2803/1 question 2

    Learning outcomes

    • Describe how heart action is coordinated with reference to the sinoatrial node (SAN), the atrioventricular node (AVN) and the Purkyne tissue.

    • Interpret and explain electrocardiogram (ECG) traces, with reference to normal and abnormal heart activity.

    Control of Heart Beat

    • Myogenic – heart muscle contracts and relaxes without having to receive impulses from the nervous system

      • Sino-atrial node

      • Atrio-ventricular node

    Sino-atrial Node

    • Special cardiac muscle tissue in right atrium

    • a.k.a. SAN or Pacemaker

    • Sets the rhythm at which all other cardiac muscle cells beat

    • Sends excitation wave (depolarisation) over atrial walls

    What happens next?

    • Collagen fibres prevent the wave of excitation from passing from the atria to the ventricle walls

    • Allows the ventricle to fill before they contract

    Atrio-ventricular Node

    • Patch of conducting fibres in the septum

    • a.k.a AVN

    • AVN picks up impulses that have passed through atrial tissue

    • Wave of excitation runs down purkyne tissue to the base of the septum

    Atrio-ventricular Node

    • Wave spreads upwards and outwards through the ventricular walls

    • Blood is squeezed up and out through arteries.

    Control of cardiac cycle - Summary

    • Cardiac muscles is myogenic

      • Wave excitation spreads out from SAN across atria, atria contract

      • septum prevents wave crossing to ventricles

      • Wave excitation passes through AVN, which lies between atria

      • AVN conveys wave excitation between ventricles along specialised muscle fibres known as bundle of His

      • This conducts wave through septum to base of ventricles, bundles branch into smaller fibres known as Purkyne tissue

      • Wave is released, ventricles contract from apex of heart upwards


    • Record of wave of electrical activity caused by atrial systole (P), ventricular systole (QRS), and the start of ventricular diastole (T)

    Translating ECGs

    • Elevation of the ST section indicated a heart attack

    • A small or unclear P wave indicated atrial fibrillation

    • A deep S wave indicates abnormal ventricular hypertrophy (increase in muscle thickness)

    ECG of an unhealthy heart

    • An abnormal ECG could indicate

      • Arrhythmia

        • Where the heart is beating irregularly

      • Fibrillation

        • Where the heart beat is not co-ordinated

      • Myocardial infarction

        • Heart attack


    • Excitation wave is chaotic

    • Small sections of the cardiac muscle contract whilst other sections relax

    • Heart wall flutter

    • Possible causes

      • Electrical shock

      • Damage to large areas of muscle in walls of heart

    Exam Question

    • Answer the practice exam question

    The Mammalian Transport System

    Structure and function of Arteries, Veins and Capillaries

    Learning Outcomes

    • describe, with the aid of diagrams and photographs, the structures and functions of arteries, veins and capillaries;

    Structure of Arteries, Veins and Capillaries

    GCSE Revision

    • Arteries carry blood away from the heart

    • Veins carry blood towards the heart

    • Capillaries are a network of thin tubes which link A to V, and take blood close to cell.

    Basic Structure


    (hollow centre of tube)

    • Tunica externa

    • outer layer containing collagen fibres.

    • Tunica media

    • Middle layer containing smooth muscle and elastic fibres

    • Tunica intima

    • Endothelium (single layer of cells)

    Microscope Artery

    Microscope Vein

    Microscope Capillary

    Blood Vessels

    Look at the image on the following page.

    What are structures X and Y

    What do parts 1 – 4 show or represent?








    • X is an artery

    • Y is a Vein

    • shows the smooth endothelial lining cells which reduce resistance to blood flow.

    • shows red blood cells within the lumen of the artery

    • shows the thick muscular wall of the artery

    • shows blood capillaries note their size compared to arteries and veins.

    Structure and Function of Arteries

    Look at this cartoon.

    What can you deduct about arteries?

    (answers on a postcard please)

    Structure of Arteries, Veins and Capillaries


    • Function

      • To transport blood, swiftly and at high pressure to the tissues.

      • The structure of the artery wall gives it strength and resilience

      • The large amounts of elastic tissue in the tunica media allow the walls to stretch as blood pulses through.

      • As arteries move away from the heart there is a decrease in elastic tissue and an increase in muscle tissue.

    Arteries (cont)

    • Elasticity of walls – 2 functions

      • “give”

      • Blood at low pressure in an artery gets a “push” as artery recoils  evens out blood flow

    • Arterioles

      • More smooth muscle

      • Contracts to help control the volume of blood flowing into tissues (dilation and constriction)


    • Function

      • To take blood as close as possible to all cells, allowing rapid transfer of substances between cells and blood

    • Network of capillaries  capillary bed


    • Venules/veins

      • Return blood to the heart

    • Low venous pressure

    • Semi-lunar valves

      • Form from endothelium

      • Allow blood to travel to the heart

      • Prevents the back flow of blood

    Systemic Circulation


     artery

     arteriole

     capillary

     venule

     vein

     vena cava

    Summary of function of A, V and C

    Revision Questions (1)

    • Suggest why arteries close to the heart have more elastic fibres in walls than arteries further away from the heart.

    • Suggest why there are no blood capillaries in the cornea of the eye. How might the cornea be supplied with its requirements?

    Revision Questions (2)

    • Suggest reasons for the following:

      • Normal venous pressure in the feet is about 25mm Hg. When a soldier stands at attention the blood pressure in their feet rises very quickly to about 90mm Hg.

      • When you breathe in (volume thorax increases), blood moves through the veins towards the heart.

    Pupil Activity

    • Bioviewer activity – slide set 68

      • Read the information on the front of the card.

        • how does the human circulatory system help to maintain cell life?

        • what are the three major parts of the human circulatory system?

      • Observe the following slides

        • Slide 1 – human blood

        • Slide 2 – Phagocyte

        • Slide 3 – artery and vein

        • Slide 4 – capillaries in the lung

    Blood, Tissue fluid and Lymph

    Blood – the transport medium

    • Plasma

      • Straw coloured, alkaline liquid

      • Consists mainly of water

    • Functions of blood

      • Defends body against disease

      • Maintains diffusion gradients

      • Acts as a buffer

      • Provides pressure

      • Distributes heat around body

    Blood plasma

    • Water with dissolved substances

      • Nutrients e.g. glucose

      • Waste products e.g. urea

      • Plasma proteins

        • Buffers

        • Solute potential

    Red Blood CellsErythrocytes

    • Origin

      • Bone marrow

    • Mature RBC transport respiratory gases

    • Life span 120 days

      • No nucleus/ cell organelles

      • Cytoplasm full of haemoglobin

  • Biconcave disc

    • Large SA: volume ratio

  • White Blood CellsLeucocytes

    • Protect body as part of the immune system

    • Originate in bone marrow thymus and lymph for growth and development

    • Lymphocytes

      • Production of antibodies

    • neutrophils, monocytes

      • phagocytosis

    Platelets(cell fragments)

    • Tiny packages cytoplasm containing vesicles with thromboplastins

      • Clotting factors

    • Made in bone marrow

    • Last 6 – 7 days

    Pupil Activity

    • Which of these functions could, or could not, be carried out by a RBC.

      • Protein synthesis

      • Cell division

      • Lipid synthesis

      • Active transport

    Protein Synthesis

    NO: no DNA so no mRNA can be transcribed.

    Cell Division

    NO; no chromosomes, so no mitosis; no centrioles for spindle formation

    Lipid Synthesis

    NO; occurs in smooth ER

    Active Transport

    YES; occurs across plasma membrane, can be fuelled by ATP from anaerobic respiration.

    Answers SAQ

    Tissue Fluid

    • Immediate environment of each individual body cell.

    • Homeostasis maintains composition of tissue fluid at a constant level to provide the optimum environment in which cells can work.

    • Contains less proteins than Blood plasma

    Forces for exchange on capillaries

    Blood proteins (e.g. albumins) can not escape and maintain the water potential of the plasma, preventing excess water loss, and help to return fluid to the capillary

    Arteriole end

    Venule end

    Blood in capillary

    Diffusion gradient

    Diffusion gradient

    Osmotic movement of water

    Ultrafiltration of water and small molecules (O2, glucose and amino acids) due to hydrostatic pressure

    Hydrostatic pressure reduced

    Tissue fluid


    • Similar composition to plasma with less proteins

    • Lipids absorbed in lacteals, give lymph milky appearance

    • Tiny blind ending vessels

    • Tiny valves in walls allow large molecules to pass in.

    • Drains back into blood plasma in subclavian vein.


    • If lymph does not take away proteins in tissue fluid between cells, YOU could die in 24 hours.

    • Get a build up in tissue fluid, called oedema.

    Movement in lymph capillaries

    • Contraction of muscles around vessels

    • Valves

    • Slow movement

      • Diagram: the relationship between blood, tissue fluid and lymph at a capillary network

        • Diagram: the lymph system

    Table summary

    Table summary

    Table summary

    The Mammalian Transport System

    Transport of Oxygen and Carbon Dioxide

    Partial Pressure

    • In a mixture of gases, each component gas exerts a pressure that is proportional to how much of it is present.

    • Concentration of gas is quoted as its partial pressure, in kilopascals kPa.

    • pO2 partial pressure of oxygen

    • pCO2 partial pressure of carbon dioxide

      pO2 = atmospheric pressure x % O2


    Pupil Activitycalculation of partial pressure

    • Assume the composition of air is 20% oxygen and 80% nitrogen, and is approx. the same at sea level (atmospheric pressure = 101.3kPa) and at 5000m above sea level (atmos. Pressure = 54.0 kPa) and at 10000m above sea level (atmos. Pressure = 26.4 kPa)

    • What is the partial pressure of oxygen at these altitudes?

    Transport of Oxygen

    • Haemoglobin in red blood cells (RBC)

      Hb + 4O2 HbO8

    Haemoglobin dissociation curve

    • A graph showing the amount of oxygen combining with haemoglobin at different partial pressures.

    • High pO2 – haemoglobin saturated with oxygen

    • Low pO2 – oxyhaemoglobin gives up its oxygen to respiring cells (dissociates)

    Haemoglobin dissociation curve

    S-shaped curve

    • Each Hb molecule has 4 haem groups

    • 1st O2 combines with first haem group

    • Shape of Hb distorted

    • Easier for other 3 O2 to bind with haem group

    high pCO2 increases dissociation of oxyhaemoglobin

    Oxyhaemoglobin releases oxygen where it is needed most – actively respiring tissues.

    Bohr Shift

    Fetal Hb has a higher affinity for O2 than adult Hb.

    This allows the fetal Hb to “steal” O2 from mothers Hb

    Fetal Haemoglobin

    Oxymyoglobin is more stable than oxyhaemoglobin

    Only gives up O2 at very low pO2.

    Myoglobin acts as an oxygen store


    Carbon Dioxide Transport

    • CO2 carried in three ways

      • 5% in solution in plasma as CO2

      • 10% combines with amino groups in Hb molecule (carbamino haemoglobin)

      • 85% hydrogen carbonate ions

    Carbon dioxide transport

    • Transported in blood as hydrogen carbonate ions

    • Carbonic anhydrase catalyses the reaction

      CO2 + H2O H2CO3

    Carbon Dioxide Transport

    • Carbonic acid dissociates

      H2CO3 H+ + HCO3-

    • H+ ions associate with haemoglobin (buffer)

      • Haemoglobinic acid (HHb)

  • Contributes to Bohr effect

  • Chloride Shift

    • Build up HCO3- causes them to diffuse out of RBC

    • Inside membrane positively charged

    • Cl- diffuse into RBC from plasma to balance the electrical charge

    Problems with Oxygen Transport

    Carbon Monoxide

    • Haemoglobin combines readily with carbon monoxide to form carboxyhaemoglobin (stable compound)

    • Carbon monoxide has a higher affinity with haemoglobin than oxygen does

    • 0.1% CO in air can cause death by asphyxiation.

    High Altitude

    • Pupil activity

      • question sheet on high altitude

      • Question

        • Atheletes often prepare themselves for important competitions by spending several months training at high altitude. Explain how this could improve their performance.

    Training at high altitude

    • Spending a length of time at high altitude stimulates the body to produce more red blood cells

    • When an athlete returns to sea level, these “extra” RBC remain in the body for sometime, and can supply extra oxygen to muscles enabling them to work harder and for longer than they would otherwise.

  • Login