Why do large, multicellular animals need specialized transport systems?
High metabolic demand: Need large quantities of O₂ and nutrients; produce large amounts of waste.
Small SA:V ratio: Diffusion distances are large, and the surface area for exchange is relatively small.
Molecules made in one site, used in another: e.g., Hormones, enzymes, digested food.
Waste removal: Waste products (e.g., CO₂, urea) need to be transported to excretory organs.
Compare open and closed circulatory systems.
Open: Transport medium (haemolymph) is pumped into a body cavity (haemocoel). It bathes tissues directly. Found in insects/molluscs. Low pressure, cannot vary flow to tissues.
Closed: Blood is confined to vessels. Substances diffuse through vessel walls. Higher pressure, faster flow. Flow to tissues can be adjusted. Found in vertebrates, annelids, cephalopods.
Compare single and double circulatory systems.
Single: Blood passes through the heart once per complete body circuit. It flows through two capillary beds (e.g., gills + body), dropping pressure. Found in fish.
Double: Blood passes through the heart twice per complete body circuit (pulmonary & systemic). Blood only passes through one capillary network per circuit, maintaining high pressure and fast flow. Found in birds and mammals.
How is the structure of an artery related to its function?
Thick wall with elastic fibres: To withstand and smooth out high pressure from heart contractions (recoil maintains pressure).
Thick layer of smooth muscle: Can constrict/dilate to control blood flow.
Collagen: Provides structural strength to prevent bursting.
Small lumen: Maintains high pressure.
How is the structure of a capillary related to its function?
Walls one cell thick (endothelium): Short diffusion distance for efficient exchange.
Numerous and highly branched: Large surface area for exchange.
Narrow lumen: Red blood cells flow slowly and in single file, maximizing time for diffusion.
Spaces between endothelial cells: Allows plasma and dissolved substances to leak out and form tissue fluid.
How is the structure of a vein related to its function?
Thin walls with less muscle/elastin: Blood is under low pressure.
Large lumen: Maximizes capacity to act as a blood reservoir (~60% of blood volume).
Valves: Prevent the backflow of blood.
Surrounded by muscles: Muscle contractions help squeeze blood back towards the heart.
How is tissue fluid formed from plasma at the arterial end of a capillary?
High hydrostatic pressure (~4.6 kPa) inside the capillary (from heart contraction) forces fluid out.
This outward pressure is greater than the oncotic pressure (~ -3.3 kPa) (created by plasma proteins) pulling fluid in.
Net result: Ultrafiltration of fluid, forming tissue fluid (plasma without red blood cells and large proteins).
What is lymph and what is its role?
What it is: The 10% of tissue fluid that does not return to capillaries. It drains into blind-ended lymph capillaries.
Composition: Similar to tissue fluid but contains more lipids (absorbed from gut) and lymphocytes.
Role: Returns fluid to the blood (via subclavian veins), transports lipids, and is a major part of the immune system (lymph nodes filter pathogens and contain lymphocytes).
How is haemoglobin adapted to transport oxygen?
Quaternary structure: 4 polypeptide chains, each with a haem group containing Fe²⁺. Each Hb can carry 4 O₂ molecules.
Positive cooperativity: Binding of the first O₂ molecule changes the shape of Hb, making it easier for subsequent molecules to bind.
Biconcave RBCs: Large surface area for diffusion and no nucleus, maximizing space for Hb.
Why is the oxygen dissociation curve sigmoidal (S-shaped)?
Due to positive cooperativity.
At low pO₂, the first O₂ binds slowly (shallow curve).
This binding changes the shape of Hb, making it easier for the next O₂ molecules to bind (steep curve).
At high pO₂, the curve levels off as Hb becomes saturated and all binding sites are occupied.
How does fetal haemoglobin (HbF) differ from adult haemoglobin (HbA)?
HbF has a higher affinity for oxygen than HbA.
Its dissociation curve is to the left of the adult curve.
This allows the fetus to extract oxygen from the mother’s blood across the placenta, even at the low oxygen partial pressures found there.
How is carbon dioxide transported in the blood?
5%: Dissolved directly in plasma.
10-20%: Bound to haemoglobin as carbaminohaemoglobin.
75-85%: Converted into hydrogencarbonate ions (HCO₃⁻) in red blood cells.
CO₂ + H₂O ⇌ H₂CO₃ (catalyzed by carbonic anhydrase)
H₂CO₃ ⇌ H⁺ + HCO₃⁻
HCO₃⁻ diffuses out into plasma; Cl⁻ ions move in to balance charge (chloride shift).
H⁺ ions are buffered by haemoglobin.
What are the main stages of the cardiac cycle?
Diastole: Heart relaxes. Atria and ventricles fill with blood. AV valves are open.
Atrial Systole: Atria contract, topping up ventricular volume.
Ventricular Systole: Ventricles contract. AV valves close. High pressure forces open semilunar valves, ejecting blood into arteries.
Ventricles relax: Semilunar valves close (‘dub’ sound) to prevent backflow.
How is the basic rhythm of the heart initiated and coordinated?
The heart is myogenic; its rhythm is initiated by the heart muscle itself, not by nerves.
Sinoatrial Node (SAN): The pacemaker. Located in the right atrium wall. It generates a wave of electrical excitation, causing both atria to contract.
Atrioventricular Node (AVN): Located between the atria. It picks up the impulse from the SAN. There is a brief delay here to ensure the atria have fully emptied before the ventricles contract.
Bundle of His: A group of conducting fibers that carry the impulse down the interventricular septum.
Purkyne (Purkinje) Fibers: These spread the wave of excitation upwards from the apex (bottom) of the ventricles, causing them to contract from the bottom up, efficiently ejecting blood.
This coordinated sequence ensures the atria contract before the ventricles.
What do the following ECG patterns indicate?
Normal: Regular P, QRS, T waves. Rate 60-100 bpm.
Tachycardia: Regular rhythm but rate >100 bpm.
Bradycardia: Regular rhythm but rate <60 bpm.
Ectopic heartbeat: Extra beat out of normal rhythm.
Atrial fibrillation: Irregular rhythm with no clear P waves (atria quiver, not contract properly).
What do the two figures in a blood pressure reading (e.g., 120/80 mmHg) represent?
Systolic pressure (120): The maximum pressure in the arteries when the ventricles contract (systole).
Diastolic pressure (80): The minimum pressure in the arteries when the ventricles are relaxed (diastole).
What is the function of valves in veins?
To prevent the backflow of blood. Blood in veins is under low pressure and must often flow against gravity. Valves ensure it moves only towards the heart.
Why are coronary arteries vital?
They supply the cardiac muscle of the heart wall with oxygenated blood. If they become blocked (e.g., by a blood clot), the heart muscle is deprived of oxygen, leading to a heart attack (myocardial infarction).
Why is the wall of the left ventricle thicker than the right?
The left ventricle must pump blood all around the body (systemic circulation), which requires generating enough pressure to overcome the high resistance of the entire arterial system. The right ventricle only pumps blood to the lungs (pulmonary circulation), which is a shorter distance with lower resistance.
What is the function of the protein Albumin in Osmotic Balance
Albumin keeps the fluid part of your blood from leaking out of your blood vessels (the tubes your blood flows through) and into other tissues. The protein we use in this study, albumin, has a special role in regulating the osmotic pressure balance at the level of blood vessels, because it is the largest protein constituent of plasma and is present at a concentration of ≈40 mg/ml (≈0.6 mM).
What is blood plasma and what are its main functions?
What it is: The straw-colored liquid component of blood, mostly water.
What it transports:
Dissolved substances: Glucose, amino acids, mineral ions, hormones.
Plasma proteins: Albumin (maintains osmotic potential), fibrinogen (clotting), globulins (immunity/transport).
Blood cells, platelets, carbon dioxide.
Other functions: Helps maintain steady body temperature and acts as a pH buffer.
What is the structure and function of erythrocytes?
Function: To transport oxygen from the lungs to tissues and assist in transporting carbon dioxide back to the lungs.
Adaptations:
Biconcave shape: Increases surface area for gas diffusion.
No nucleus: Maximizes space for haemoglobin.
Contains haemoglobin: The red pigment that binds reversibly with oxygen.
Small and flexible: Allows them to squeeze through narrow capillaries.
What is the general function of leucocytes?
Main Function: Involved in the body’s immune response and defense against pathogens.
Types: There are many different types (e.g., lymphocytes, phagocytes) with specialized functions like producing antibodies or engulfing foreign material.
What are platelets and what is their function?
What they are: Small fragments of cells (from megakaryocytes in bone marrow), not whole cells.
Function: Essential for blood clotting (haemostasis) at sites of vessel damage to prevent blood loss and entry of pathogens.
-
2) Basic Components of Living Systems51
-
3) Biological Molecules55
-
4) Enzymes25
-
5) Plasma Membranes25
-
6) Cell Division59
-
7) Exchange Surfaces and Breathing33
-
8) Transport in Animals29
-
9) Transports in Plants25
-
10) Classification and Evolution40
-
11) Biodiversity48
-
12) Communicable Diseases57
-
13- Neuronal communication56
-
14-Hormonal Communication23
-
15- Homeostasis29
-
16-Plant Responses30
-
17- Energy for Biological Processes30
-
18-Respiration38
-
19-Genetics of Living Systems26
-
20-Patterns of inheritance and variation18
-
21- Manipulating Genomes23
-
22- Cloning and Biotechnology28
-
23- Ecosystems25
-
24- Populations and Sustainability34
