NEET Biology Solved Question Paper 2003

Spirulina is a blue-green algae. Spirulina platensis is one of the richest source of protein, containing 40-50 percent crude protein on dry weight basis which under favourable condition may reach upto 70 percent. Its protein has balanced composition containing all essential amino-acids and lysine and tryptophan being present in sufficient quantities.

It is also rich in vitamins, particularly Vit. B₁₂ which is not common in plant products and contains considerable amounts of fats, carbohydrates and minerals. It's lipids are made up of unsaturated fatty acids that do not form cholesterol.

The gradually increasing contraction of ventricular muscles during systole first causes the closure of bicupsid and tricupsid valves (AV valves), producing a low- pitched "lubb" sound. Later, it causes the opening of the semilunar valves of systemic and pulmonary aorta. At the end of ventricular systole, semilunar valves shut, producing the second, louder heart sound, the "dup". Thus, each heart beat is accompained by a "lubb- dup" sound.

The source of somatostatin is same as that of vasopressin and oxytocin. Somatostatin is produced from hypothalamus (somatostatin neuron) and oxytocin and vasopressin are also produced in the nuclei of hypothalamus, though later they are stored and released from posterior pituitary.

In competitive inhibition, an inhibitor that resembles the normal substrate binds to the enzyme, usually at the active site and prevents the substrate from binding. 

An example of competitive inhibition of an enzyme is the inhibition of succinic dehydrogenase by malonic acid. It is the simple type of competitive inhibition. A competitive inhibitor resembles the substrate and binds to the active site of the enzyme. The substrate is then prevented from binding to the same active site.

Vasopressin or ADH secreted from posterior pituitary stimulates reabsorption of water by the distal convoluted tubule and the collecting renal tubules and thus regulates urine volume. It has no such important effect on glucose metabolism. Therefore, a person whose blood glucose level is normal, but passes much urine and drinks much water has a reduction in vasopressin secretion which ultimately leads to diabetes insipidus.

Patella is a sesamoid bone. Sesamoid bones are formed by ossification of a tendon where the tendon moves over a bony surface.

Normal blood sugar level in adult human varies from 80 - 100 mg/100 ml (fasting) to 100-120 mg/100 ml (after meal).

Normal blood urea is 20 - 40 mg/dl

Total blood volume is 4 - 5 litres

ESR or Erythrocyte Sedimentation Rate in wintrobe method is 0 - 9 mm in male and 0 - 20 mm in female.

In the process of photorespiration oxygen combines with RuBP (Ribulose- biphosphate) in chloroplast as following

O₂ + RuBP $\stackrel{\mathrm{Rubisco}}{\to }$3- Phosphoglycerate + $↴$

                              2- Phosphoglycerate $\to$CO₂

Phosphoglycolate enters in peroxisomes and is finally converted to CO₂.

Vagus nerve is known as pneumogastric nerve. It helps control several muscles of the throat and of the voicebox. It helps in regulating the heart rate and keeping the gastrointestinal tract in working order. It also carry sensory information from the internal organs back to the brain.

Excessive stimulation of vagus nerve in humans may lead to peptic ulcer. Vagal stimulation increases peristalsis which in excess, secretes more HCl and pepsin from stomach. These causes erosion through protective barrier of mucus and muscularis mucosa into the submucosa which leads to peptic ulcer.

As the person uses spectacles having concave lens, he must be suffering from myopia or short-sightedness. Here the eyeballs become elongated, so that parallel rays are focussed in front of retina.

Myopia is an eye disorder where light focuses in front of retina. This causes distant objects appear normal. It is also known as short- sightedness.