Componenet 2.3 Adaptations for transport in animals Flashcards
closed circulation system
blood travels through blood vessels with the impetus (momentum) being generated by a muscular pump or heart
open circulation system
the ‘blood’ bathes all the cells and organs of the body.
The blood is called haemolymph and is in the body cavity or haemocoel.
Open circulation is a feature of all arthropods.
There are no red blood cells to transport oxygen; oxygen is delivered directly to the tissues by the tracheae.
Many animals with an open circulation do have a heart that pumps the haemolymph from one area of the haemocoel to another, the blood returns to the heart without the aid of blood vessels.
which is quicker open or closed circulation
Closed circulation systems deliver blood quickly to tissues under pressure. Red blood cells contain haemoglobin which transports oxygen within the circulatory system. The rapidity of transport has enabled the evolution of larger size in animals.
single circulation
blood passes through the heart once in each circulation.
Eg fish
Direction of blood flow in a fish
The heart has two chambers; the atrium, which receives deoxygenated blood from the veins of the body, and the ventricle, which pumps the blood to the gill capillaries via afferent arteries. The blood gains oxygen and flows through efferent arteries to the organs.
do fish have haemoglobin
Their blood contains haemoglobin which has a high affinity for oxygen and transports it from the gills to the tissues.
disadvantages of single circulation
the blood loses pressure around the circuit, resulting in slower circulation.
SINGLE
CLOSED
double circulation
The blood passes through the heart twice in one circulation of the system.
pulmonary circulation + systemic circulation
pulmonary circulation
The right side of the heart pumps blood to the lungs for gas exchange
systemic circulation
The blood returns to the heart and is pumped out to the tissues from the left side
describe including the terms systemic circulation
you can see the deoxygenated blood returning from the systemic circulation of the head and body to the right-hand side of the heart, passing to the lungs on each side, then returning to the left side of the heart to be pumped to the tissues of the head and body.
advantage of double circulation
blood is repressurized when it leaves the gas exchange surface, giving a faster and more efficient circulation to the tissues.
flow of both systemic and pulmonary circulation
Blood moves from the heart to:
Artery → arteriole → capillary → venule → vein →
back to the heart
Arteries take blood Away from the heart.
VeINs take blood INto the heart.
diagram of arterial wall
tunica externa
The outermost tissue layer is the tunica externa which consists of collagen rich connective tissue, this resists stretching of the blood vessel due to the hydrostatic pressure of the blood
tunica media
The middle layer is the tunica media, this contains elastic fibres and muscle tissue. Elastic fibres allow the blood vessel to expand to accommodate the blood flow.
endothelium cells
The innermost layer is a single layer of endothelium cells which provide a smooth surface with little friction and resistance to blood flow. The endothelium is surrounded by the tunica intima.
artery
The heart is a pump that generates pressure, so arteries are adapted to carry blood at high pressure.
They have a thick tunica externa containing collagen fibres, to resist overstretching under pressure.
The layer of muscle and elastic tissue is thick to provide elastic recoil aiding propulsion of blood and maintaining blood pressure.
The lumen of arteries is relatively small to maintain the pressure of the blood.
arterioles vs artery
arterioles have more muscles - they constrict and dilate to control the flow of blood to the capillaries
diagram artery, vein and capillary
artery, vein and capillary function
artery, vein and capillary structure of wall
artery, vein and capillary lumen
artery, vein and capillary lumen
artery, vein and capillary valves
artery, vein and capillary how structure fits function
capillaries
Capillaries consist of a single layer of endothelial cells and are a tissue rather than an organ.
They are the site of gas exchange and the single layer of flattened cells gives a short diffusion path.
Capillary beds are extensive and have a massive surface area for diffusion.
why is pressure of capillary low
As blood passes through capillaries the pressure is lowered. This is because a capillary bed has a much greater cross-sectional area than the arteriole feeding into it.
narrow lumen effect capillary
Capillaries are narrow so resistance to blood flow is greater and blood flow slows. This is great for gas exchange as the slower flow gives more time for diffusion.
affect of small diameter capillary
The capillaries have a slightly smaller diameter than a red blood cell, so the red blood cells have to bend to squeeze through.
describe the structure of a vein
Veins have a large lumen providing little resistance to the blood which is flowing through at low pressure. The tunica media and externa are far thinner than in arteries as the blood is under much lower pressure and less resistance to pressure is needed.
what do the valves in veins do
Backflow of the blood is prevented by valves at intervals along the veins.
flow of the blood around the body including pressure
The pressure in the main arteries leaving the heart is at its highest. Blood entering the main artery on the left side (the aorta) has the highest pressure as the left ventricle muscle is thicker and generates most pressure. As blood enters the aorta (and other smaller arteries), the vessel expands until it reaches a maximum and recoils, pushing the blood forwards. Where arteries pass close under the skin, this expansion and recoil is felt as a pulse. The flow in the aorta, arteries and arterioles is described as pulsatile; the pressure goes up when the ventricles contract and drops when the ventricles relax. Pressure drops from the aorta to the arteries to the arterioles, this is because the total cross-sectional area of smaller vessels is larger than that of larger vessels. Narrower vessels have more resistance to the flow of blood.
which side of the heart is thinner
The same pattern is seen in the pulmonary circulation, but the pressures are much lower as the right ventricle has a much thinner muscle than the left.
describe pressure graph systemic circulation
describe pressure graph pulmonary circulation
graph to show diameter cross sectional area and volume circulation loop
myogenic
the heart is stimulated to beat from within its muscle wall. If the heart is isolated from its nerve supplies, it will continue to beat, but irregularly. Heart rate is regulated by nerve impulses from the medulla oblongata in the brain.
heart nerve impulses
A group of cells in the right atrium called the sinoatrial node (SAN), or pacemaker, sends out a wave of excitation across the muscle of the atria. The muscle responds by contracting (atrial systole). The wave of excitation is a wave of depolarisation of muscle cells. When the cells depolarize, they contract; when they relax, they are repolarized.
The wave of excitation is prevented from passing to the ventricles by fibrous tissue between the atria and ventricles. The wave of excitation passes to the atrioventricular node (AVN), located in the septum at the atrioventricular junction. The AVN delays the wave of excitation allowing the atria to complete contraction and the ventricles to fill, ensuring that the ventricles contract after the atria.
The AVN passes the wave of excitation to the bundle of His in the septum. The wave of excitation is passed through the bundle of His to the apex of the heart. This is important as the ventricles will contract from the apex upwards so that the blood will be pushed up to the arteries.
From the bundle of His, the wave of excitation passes through Purkinje fibres in the muscle of the ventricles. The spread is upwards through the ventricle walls, so the contraction begins at the apex.A group of cells in the right atrium called the sinoatrial node (SAN), or pacemaker, sends out a wave of excitation across the muscle of the atria. The muscle responds by contracting (atrial systole). The wave of excitation is a wave of depolarisation of muscle cells. When the cells depolarize, they contract; when they relax, they are repolarized.
The wave of excitation is prevented from passing to the ventricles by fibrous tissue between the atria and ventricles. The wave of excitation passes to the atrioventricular node (AVN), located in the septum at the atrioventricular junction. The AVN delays the wave of excitation allowing the atria to complete contraction and the ventricles to fill, ensuring that the ventricles contract after the atria.
The AVN passes the wave of excitation to the bundle of His in the septum. The wave of excitation is passed through the bundle of His to the apex of the heart. This is important as the ventricles will contract from the apex upwards so that the blood will be pushed up to the arteries.
From the bundle of His, the wave of excitation passes through Purkinje fibres in the muscle of the ventricles. The spread is upwards through the ventricle walls, so the contraction begins at the apex.
diagram heart impulses
SAN
AVN
P
The P wave represents the wave of depolarisation of the atrial walls from the SAN that causes atrial systole.
QRS
The QRS complex represents the depolarisation of the ventricular walls causing ventricular systole; this complex masks the repolarisation of the atria.
T
The T wave represents the repolarisation of the ventricular walls during ventricular diastole.
The trace above shows no pattern at all, waves of excitation are passing over the ventricles randomly. This is termed ventricular fibrillation and indicates that the person is having a heart attack.
The trace above shows QRS complexes, but the P waves before are showing that electrical activity is happening randomly across the atria; this is atrial fibrillation. The QRS complexes are not evenly spaced, the heart is ‘missing a beat’.
The trace above shows ‘heart block’; where there are three waves between the QRS complexes. It indicates that some P waves are not followed by QRS. The atria are contracting but the wave is not passing to the ventricles. There are different degrees of heart block. The treatment is to install a pacemaker in the AVN which takes over the transmission to the bundle fibres. Heart block may also manifest as longer than usual P-Q intervals or almost flat lines between the QRS complexes, which are often wider than usual.
As the time scale is known on an ECG, heart rate can be calculated. Slow heart rate is called bradycardia (<50bpm) and rapid heart rates show tachycardia (>100bpm).
Adaptations of Red Blood Cells for Oxygen Transport:
Biconcave Disc Shape:
Increases surface area for maximum diffusion of oxygen and reduces diffusion distance, especially at the thin central region.
Flexibility:
The thinner middle section allows red blood cells to bend and squeeze through narrow capillaries, ensuring efficient circulation even in tiny blood vessels.
No Nucleus or Organelles:
This creates more internal space for haemoglobin, the protein that binds and carries oxygen.
Lack of Mitochondria:
Prevents the cells from using the oxygen they carry for aerobic respiration, ensuring all oxygen is delivered to body tissues.
Structure and Function of Haemoglobin:
- Haemoglobin is a quaternary protein made of four polypeptide chains:
2 alpha (α) chains
2 beta (β) chains
- Each chain is associated with a prosthetic haem group containing an iron ion (Fe²⁺).
- Each Fe²⁺ ion can bind 1 oxygen molecule (O₂):
So 1 haemoglobin (Hb) molecule can carry 4 oxygen molecules (O₂) = 8 oxygen atoms.
- When haemoglobin binds oxygen, it forms oxyhaemoglobin:
Haemoglobin (Hb) + O₂ → Oxyhaemoglobin (HbO₈)
- Writing convention:
Always write out “haemoglobin (Hb)” and “oxyhaemoglobin (HbO₈)” in full the first time.
You can use the abbreviations (Hb, HbO₈) afterward.
How many oxygen molecules can be carried by one haemoglobin molecule?
4
Oxygen Transport and the Role of Haemoglobin
In the lungs:
Blood arriving via pulmonary arteries has low oxygen and high carbon dioxide.
Oxygen diffuses into red blood cells (erythrocytes) from the alveoli.
Haemoglobin (Hb) binds to oxygen — this is called loading or association.
Oxygen-rich blood leaves the lungs via the pulmonary veins and returns to the heart.
Oxygen Transport and the Role of Haemoglobin
In the body tissues:
Blood is pumped into systemic circulation from the heart.
No gas exchange occurs until blood reaches capillaries in tissues.
Oxygen is unloaded from haemoglobin — this is called unloading or dissociation.
Unloaded oxygen is used in aerobic respiration by body cells.
Role of Partial Pressure of Oxygen (pO₂):
- The partial pressure of oxygen (pO₂) affects how much oxygen is loaded or unloaded:
- High pO₂ (e.g., in lungs) → more oxygen binds to haemoglobin (loading).
- Low pO₂ (e.g., in respiring tissues) → oxygen is released from haemoglobin (unloading).
- Tissues with a high rate of respiration:
- Use more oxygen → have a lower pO₂.
- Haemoglobin responds by unloading more oxygen.
- This relationship is shown by the oxygen dissociation curve:
-A graph that plots % saturation of haemoglobin with O₂ against pO₂. - The curve is sigmoidal (S-shaped) due to cooperative binding of oxygen.
Oxygen Dissociation Curve – Key Points
Oxygen Dissociation Curve – Key Points
Shape of the Curve:
Oxygen Dissociation Curve
Diagram
Interpreting the Oxygen Dissociation Curve:
Haemoglobin curve vs theoretical line:
Haemoglobin transports more oxygen at each partial pressure than the straight (theoretical) line suggests.
This is due to co-operative binding, allowing haemoglobin to load and unload oxygen more efficiently.
At High pO₂ (e.g., in the lungs ~10 kPa+):
The curve levels off (plateaus) — haemoglobin is almost fully saturated.
This means haemoglobin remains highly saturated even if pO₂ changes slightly — helpful for oxygen loading in the lungs.
Ensures maximum oxygen carriage from lungs to tissues.
At Moderate pO₂ (4–7 kPa):
The curve is steep — small drops in pO₂ lead to large amounts of oxygen being released.
This steep region reflects efficient oxygen unloading in actively respiring tissues, where oxygen demand is high.
The steeper slope compared to the theoretical line shows faster loading/unloading of oxygen.
Why This Matters:
The S-shaped curve allows:
High oxygen loading in the lungs (even if conditions vary)
Rapid oxygen unloading in tissues where it’s most needed
- Organisms in Low Oxygen Environments
- Foetal Haemoglobin
- Myoglobin (in Muscle Cells)
graph
Myoglobin
Foetal Haemoglobin
normal haemoglobin
Transport of Carbon Dioxide in the Blood
1. CO₂ Transport Pathways:
✅ All these reactions are reversible, allowing efficient CO₂ uptake in tissues and release in the lungs.
Transport of Carbon Dioxide in the Blood
2. Role of Haemoglobin:
✅ All these reactions are reversible, allowing efficient CO₂ uptake in tissues and release in the lungs.
Transport of Carbon Dioxide in the Blood
3. CO₂ in Plasma:
✅ All these reactions are reversible, allowing efficient CO₂ uptake in tissues and release in the lungs.
Transport of Carbon Dioxide in the Blood
4. In the Lungs (Gas Exchange Reversed):
✅ All these reactions are reversible, allowing efficient CO₂ uptake in tissues and release in the lungs.
diagram transport of CO2 in the blood
What is the enzyme called that catalyses the reaction between carbon dioxide and water?
🔄 The Bohr Shift – Explained
📈Bohr Shift:
Effect on the Oxygen Dissociation Curve:
🧪 Other Triggers of the Bohr Shift:
Increased temperature
Lower pH (acidity)
Both indicate high metabolic activity → more oxygen needed.
✅ Why the Bohr Shift Matters:
Ensures oxygen is delivered to actively respiring tissues.
Improves efficiency of aerobic respiration during exercise, stress, or illness.
Diagram Bohr Effect
🩸 Transport Roles of Blood – Eduqas A-Level Biology Summary
Oxygen
Oxygen (O₂)
Transported by haemoglobin (Hb) in red blood cells.
Each Hb molecule binds up to 4 O₂ molecules forming oxyhaemoglobin (HbO₈).
Loading (association) occurs in the lungs where partial pressure of oxygen (ppO₂) is high.
Unloading (dissociation) happens at tissues where ppO₂ is low and oxygen is needed for respiration.
Oxygen dissociation curve:
Sigmoid shape due to cooperative binding.
Shifts right in presence of high CO₂ → Bohr shift.
🩸 Transport Roles of Blood – Eduqas A-Level Biology Summary
Carbon Dioxide
Carbon Dioxide (CO₂)
Produced by respiring cells and transported in 3 ways:
85% as hydrogen carbonate ions (HCO₃⁻) in plasma.
CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻ (via carbonic anhydrase)
Chloride shift maintains electrochemical balance.
10% as carbaminohaemoglobin (binds directly to Hb).
5% dissolved in plasma as carbonic acid.
Increased CO₂ lowers pH → promotes oxygen release (Bohr effect).
🩸 Transport Roles of Blood – Eduqas A-Level Biology Summary
🌡️ Heat
Blood distributes heat produced by cellular respiration.
Helps maintain core body temperature (homeostasis).
🩸 Transport Roles of Blood – Eduqas A-Level Biology Summary
🧪 Hormones
Produced by endocrine glands (e.g., adrenal, pituitary).
Secreted directly into the bloodstream.
Carried to target organs/cells, which have specific receptors on their membranes.
Enables long-distance chemical communication across the body.
🩸 Transport Roles of Blood – Eduqas A-Level Biology Summary
🍬 Nutrients
🩸 Transport Roles of Blood – Eduqas A-Level Biology Summary
🚽 Excretory Products
🧠 Key Exam Terms to Use:
Partial pressure (ppO₂ and ppCO₂)
Cooperative binding
Oxyhaemoglobin, carbaminohaemoglobin
Bohr effect / Bohr shift
Chloride shift
Carbonic anhydrase
Deamination
Endocrine signalling
Plasma vs red blood cells
Haemoglobin (Hb):
A red blood cell protein that binds and transports oxygen.
Oxyhaemoglobin (HbO₈):
Formed when haemoglobin binds to oxygen in the lungs.
Partial Pressure (ppO₂ / ppCO₂):
A measure of oxygen or carbon dioxide concentration in a gas mixture or liquid.
Loading / Association:
Oxygen binding to haemoglobin (usually in lungs where ppO₂ is high).
Unloading / Dissociation:
Oxygen being released from haemoglobin (in tissues where ppO₂ is low).
Cooperative Binding:
As each O₂ molecule binds to Hb, the next binds more easily due to shape change.
Oxygen Dissociation Curve:
A graph showing the % saturation of Hb with O₂ at different ppO₂ levels.
Bohr Effect / Bohr Shift:
Increased CO₂ or acidity causes Hb to release O₂ more easily (curve shifts right).
Carbonic Anhydrase:
An enzyme in red blood cells that speeds up the conversion of CO₂ and water to carbonic acid.
Chloride Shift:
Movement of Cl⁻ into red blood cells to balance charge when HCO₃⁻ diffuses out.
Hydrogen Carbonate Ion (HCO₃⁻):
The main way CO₂ is transported in blood plasma.
Carbaminohaemoglobin:
CO₂ bound directly to haemoglobin.
Plasma:
The liquid part of blood that carries nutrients, hormones, and waste products.
Endocrine Gland:
A gland that releases hormones directly into the blood (e.g. pituitary, adrenal).
Hormone:
A chemical messenger that travels in blood and affects specific target cells.
Deamination:
Removal of the amine group from amino acids in the liver to form urea.
Urea:
A nitrogenous waste product transported in the blood to the kidneys for excretion.
💧 Tissue Fluid
Definition:
A watery fluid that surrounds all body cells and allows exchange of substances between blood and cells.
💧 Tissue Fluid
Contents:
Similar to plasma, but without plasma proteins (too large to leave capillaries).
💧 Tissue Fluid
Formed from:
Blood plasma forced out of capillaries at the arterial end due to high hydrostatic pressure.
💧 Tissue Fluid
Contains:
Oxygen
Glucose
Amino acids
Fatty acids
Hormones
Ions
💧 Tissue Fluid
Function:
Supplies cells with substances needed for metabolism.
Receives waste like carbon dioxide and urea from cells.
bathe all cells
help maintain a constant environment around cells
supply oxygen, glucose, hormones and ions to cells
remove waste from cells.
💧 Tissue Fluid
Return to circulation:
Most fluid returns to blood at the venous end of capillaries via osmosis.
Excess tissue fluid is drained into the lymphatic system.
Blood enters a capillary bed from an arteriole.
💧 Tissue Fluid Formation & Return – Key Points
🔸 At the Arterial End of Capillaries:
High hydrostatic pressure in arterioles forces fluid out of capillaries.
Fluid passes through fenestrations (small gaps between endothelial cells).
Plasma proteins stay in blood → they’re too large to leave.
This creates a low water potential in the capillaries.
Net movement: Out of capillaries into surrounding tissue = tissue fluid forms.
💧 Tissue Fluid Formation & Return – Key Points
🔸 At the Venule End of Capillaries:
Loss of fluid lowers hydrostatic pressure in capillaries.
Plasma proteins now exert greater osmotic pull.
Water moves back into the capillaries by osmosis.
Net movement: Into the capillaries = reabsorption of some tissue fluid.
💧Tissue Fluid Formation & Return – Key Points
🔸 Lymphatic System:
Not all fluid is reabsorbed – excess tissue fluid drains into lymph vessels.
Lymph moves through lymphatic system and drains into the blood via the thoracic duct.
discuss image
Factors affecting tissue fluid formation
Oedema
is swelling caused by more tissue fluid being formed than can be reabsorbed or drained by the lymph vessels.
High blood pressure can cause oedema by increasing the hydrostatic pressure, forcing more fluid out of the capillaries.
Factors affecting tissue fluid formation
Kwashiorkor
is caused by severe protein deficiency. A lack of protein in the blood raises the water potential, meaning that at the venule end of the capillary, the osmotic gradient is lower than normal. Less tissue fluid is reabsorbed, and the accumulation causes oedema.
Factors affecting tissue fluid formation
Blockage of lymph vessels
by parasites or external pressure from tumours, means that less tissue fluid is drained into the lymph vessels, causing oedema.
A. Autotrophs (make their own food)
1. Autotrophic – general term for making complex organics from inorganic substances. 2. Photoautotrophic – use light as energy. 3. Chemoautotrophic – use chemicals (like hydrogen sulphide) as energy.
Mnemonic: “Auto = Alone”, and remember Photo = Light, Chemo = Chemicals
B. Heterotrophs (eat others)
4. Heterotrophic – can’t make own food, must consume it.
C. Ways heterotrophs feed
5. Saprotrophic/Saprobiontic – external digestion (enzymes secreted out). 6. Holozoic – internal digestion (take food in first).
Mnemonic:
• Sapro = Spill enzymes • Holo = Hold it in (eat first, then digest inside)
D. Special cases
7. Parasitic – live in/on a host, harm it. • Ecto = outside • Endo = inside 8. Symbiosis/Mutualism – both organisms benefit.
