A-Level Biology OCR Notes
3.1.2 Transport in animals
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Mass Transport in Animals
- Red blood cells transport oxygen using the protein haemoglobin
- Haemoglobin is made up of four polypeptide chains, each containing a prosthetic haem group. Each haem group binds one oxygen molecule
- Haemoglobin saturation depends on the partial pressure of oxygen (pO2). Binding of the first O2 molecule causes a conformational change in the haemoglobin, making the haem groups more accessible to oxygen.
- Fetal haemoglobin has a higher oxygen affinity than adult haemoglobin because fetal haemoglobin must be able to bind oxygen from adult haemoglobin in the placenta.
- Carbon dioxide is transported in the blood for release from the lungs.
- 5% of the carbon dioxide transported is dissolved in the blood plasma
- 10% of the carbon dioxide transported is combined with haemoglobin to form carbaminohaemoglobin
- 85% is transported as hydrogencarbonate ions (HCCO3-) dissolved in blood plasma
- Bohr affect- haemoglobin’s oxygen binding affinity is inversely related to the concentration of carbon dioxide, causing the oxygen dissociation curve to shift
- A good transport system has
- A fluid medium to transport substances
- A pump to create pressure for the circulation of the transport fluid
- Exchange surfaces
- An open circulatory system is one in which the blood is not held in vessels e.g. in insects.
- A close circulatory system the blood is contained within vessels.
- A single circulatory system the blood flows through the heart once for each circuit of the body.
- A double circulatory system blood within double circulatory systems flows through the heart twice for each circuit of the body
- Circulatory system:
The Heart
- The cardiac cycle is the sequence of events that occur within one full beat of the heart.
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- Systole is the contraction stage and diastole is the relaxation stage
- Cardiac muscle is myogenic, meaning it can contract and relax without receiving signals from the nervous system
- The sinoatrial node (SAN) sends out regular waves of electrical activity to the left & right atrial wall causing contraction. The electrical waves are then passed onto the atrioventricular node (AVN), then to the bundle of His, with a slight delay. The bundle of His splits into the Purkynge tissue, causing contraction of the left & right ventricles from the bottom up.
- The rate at which the SAN fires is controlled unconsciously by the medulla oblongata in the autonomic nervous system
- ECGs can detect the electrical signals through the skin
- P wave shows atrial systole
- QRS complex shows ventricular contraction
- T wave shows diastole
- Bradycardia- slow heart rate:
- Tachycardia- fast heart rate:
- Atrial fibrillation- atria beats more rapidly than the ventricles:
- Ectopia- irregular heartbeat:
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