GK (Science)

Hirudin is the specific anticoagulant produced by medicinal leeches (Hirudo medicinalis) to prevent blood clotting while they feed. Heparin is produced by mast cells and basophils in mammals, not leeches. Sodium citrate is an artificial anticoagulant used in laboratory settings, not a natural leech product.

CO has about 200-250 times higher affinity for hemoglobin than oxygen, forming carboxyhemoglobin. This displaces oxygen and reduces oxygen delivery to tissues, causing hypoxia even when sufficient oxygen is present in the air.

In open circulatory systems (found in arthropods and mollusks), the circulating fluid is haemolymph. It directly bathes the organs and tissues, unlike blood in closed circulatory systems which is confined to vessels.

Adrenaline (epinephrine) directly stimulates the sinoatrial (SA) node, increasing heart rate and cardiac output. It binds to beta-1 adrenergic receptors on SA node cells, enhancing the rate of depolarization and firing frequency.

William Harvey published 'De Motu Cordis' in 1628, demonstrating that blood circulates through the body in a continuous loop pumped by the heart. This overturned the previous Galenic belief that blood was consumed by tissues.

Pulse pressure is the difference between systolic and diastolic blood pressure. It reflects the force that the heart generates each time it contracts. Normal pulse pressure is around 30-50 mmHg.

Monocytes are the largest white blood cells (12-20 micrometers). They are agranular leukocytes that differentiate into macrophages when they migrate into tissues. Basophils and acidophils are much smaller granulocytes.

At high altitudes, the number of RBCs increases.

Oxyhaemoglobin dissociates to release oxygen in tissues where oxygen partial pressure is low. This pressure gradient drives oxygen from hemoglobin into tissues. In lungs, high O2 pressure promotes oxygen binding.

Pulmonary veins are unique - they are the only veins that carry oxygenated blood, returning it from the lungs to the left atrium of the heart. All other veins carry deoxygenated blood back to the heart.

Carborundum is the trade name for silicon carbide (SiC), an extremely hard synthetic compound used as an abrasive and in cutting tools. It's not silicon dioxide (quartz), nitride, or phosphide.

Diamond is pure carbon (an element). Ruby (Al2O3 with Cr), Sapphire (Al2O3 with Ti/Fe), and Emerald (Be3Al2Si6O18 with Cr) are all compounds or minerals with multiple elements.

Allotropes are different structural forms of the same element with different physical properties (like diamond and graphite for carbon), but they form identical chemical compounds because they are the same element. Isotopes differ in mass, isomers have same formula but different structure, and isotones have same neutron count.

Graphite is an excellent lubricant because of its layered structure. The weak van der Waals forces between graphene layers allow them to slide easily over each other, reducing friction. Diamond is extremely hard, silica is abrasive, and iron oxide is rust - none serve as lubricants.

Galvanised iron is coated with zinc through a process called galvanisation. The zinc layer protects the underlying iron from rusting by acting as a sacrificial anode. Tin is used for tin plates, lead is toxic and not used for galvanising, and chromium is used for chrome plating.

Antigens on the surface of red blood cells determine blood groups and are inherited genetically. The ABO and Rh blood group systems are based on specific antigens present on RBCs. Hemoglobin is the oxygen-carrying protein, antibodies are in plasma, and 'blood groups' is the result, not the factor.

Erythroblastosis fetalis (hemolytic disease of the newborn) occurs when an Rh-negative mother carries an Rh-positive fetus. During delivery or placental disruption, fetal Rh-positive RBCs enter maternal circulation, triggering antibody production. In subsequent pregnancies, these antibodies attack fetal RBCs.

Purkinje fibers are specialized cardiac muscle fibers located in the ventricles. They form the conduction pathway that rapidly transmits electrical impulses from the AV bundle to the ventricular myocardium, ensuring coordinated ventricular contraction. They are not in auricles or striated muscle generally.

Permanent hardness of water caused by sulfates can be removed by zeolites through ion exchange. Zeolites exchange sodium ions for calcium and magnesium ions, effectively softening the water. Nitrates don't remove hardness, sulphonates are not water softeners, and 'none of these' is incorrect since zeolites work.

Allotropes are different structural modifications of the same element. Carbon, diamond, and graphite are all pure carbon with different bonding arrangements and physical properties but identical chemical behavior. Isomers are for molecules, isotopes involve different masses, and isobars have different chemistry.

Wood charcoal (also called activated carbon) is used in sugar refineries to decolorize raw sugar through adsorption. Its porous structure efficiently removes colored impurities. Animal charcoal (bone char) can also be used, but wood charcoal is the standard. Sugar and coconut charcoals have specialized uses.

“Silver” is the metal that is present in the photo film and the reason for it is that it creates darkness on the film or photo. The developer dissolves the unreacted silver and makes the film or photo stable to light.

When a cart is pulled by a horse, the force that causes the horse to move forward is the force that the ground exerts on it.