Applicable for A-Level, IB, DSE, AP-Level Exams

Biological Molecules    Cell Structure    Cell Transport    Immunology    Exchange    Mass Transport    DNA, Genes & Protein Synthesis    Genetic Diversity    Biodiversity    Photosynthesis    Respiration    Energy & Ecosystems    Stimuli and Response    Nervous Coordination & Muscles    Homeostasis    Inheritance    Populations & Evolution    Ecosystems    Gene Expression    Recombinant DNA Technology   


Haemologin-oxhaemoglobin dissociation curves allow us to see the oxhaemoglobin saturation against different partial pressures of oxygen. As the curve shifts right, affinity for oxygen decreases. As the curve shifts left, affinity for oxygen increases. This is because there is a higher oxhaemoglobin saturation as lower partial pressures of oxygen. Different organisms have different heamoglobin affinity and dissociation curves to adapt to their environment.

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Circulatory System

Our myogenic heart pumps blood around the body for the movement of nutrients and gases such as oxygen and carbon dioxide. The cardiac cycle includes atrial systole, ventricular systole and ventricular disatole. The contraction and relaxtaion of atria and ventricules allow blood to be pumped around the double circulatory system. Semi-lunar valves and atrioventricular valves prevent backflow of blood in the heart.

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Cardiovascular Disease

There are many different types of cardiovascular diseases including pulmonary embolism when a blood vessel in your lungs is blocked or thrombosis where there is a blood clot inside a blood vessel.

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Tissue Fluid

Tissue fluid is produced by the hydrostatic pressure at the arteriole end of the capillary, forcing fluids out of the capillary. This is combated by the outward osmotic force. At the venous end of the capillary, the outward osmotic force is greater than the hydrostatic pressure, hence tissue fluid is forced out. Excess tissue fluid is drained by lympatic capillaries which return to the circulatory system to the atria near the heart.

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The xylem transports water from the roots to the leaf for evaporation. The cohesion-tension theory explains how water is being pulled up the xylem against gravity: The evaporation of water causes water moving up and is pulled up as a unit upwards the xylem down a pressure gradient due to the cohension nature of water by hydrogen bonding. Transpiration pull puts the xylem under tension - there is a negative pressure within the xylem.

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Translocation is the process by which organic molecules and some mineral ions are transported from one part of a plant to another. The mass-flow theory explains how sucrose is being transported around the phloem. At the source, there is a high concentration of sucrose due to active transport of sucrose from companion cells to the phloem with the aid of H+ ions. Water moves in from the xylem down a water potential gradient, generating a high hydrostatic pressure. At the sink cells, sucrose is active transported into companion cells near sink cells. Water moves out to the xylem and there is a low hydrostatic pressure. Hence sucrose and organic ions are being transported due to hydrostatic pressure gradient.

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