Biology Test 269

The dark reactions of photosynthesis are purely enzymatic and slower than the primary photochemical reaction. They take place in stroma portion of the chloroplast and are independent of light, i.e., they can occur either in presence or in absence of light provided that assimilatory power is available.

Glycolysis is the first step of glucose breakdown in both animals and plants. During glycolysis 6-carbon glucose molecule is converted into 2 molecules of 2 carbon pyruvic acid. In this process net gain of 2 ATP and 2 NADH2 occurs. It is a common pathway for both aerobic and anaerobic modes of respiration.

Glycolysis or EMP pathway is the breakdown of glucose to two molecules of pyruvic acid through a series of enzyme mediated reaction releasing energy. Pyruvic acid is a 3-carbon compound. In glycolysis net gain of 2ATP and 2 NADH2 molecules occurs.

It can be represented in equation form as –

Spraying sugarcane crop with gibberellins increases the length of the stem and increasing the yield by as much as 20 tonnes per acre.

Gibberellic acid involved in growth promoting activities, such as cell division, cell enlargement, pattern formation, tropic growth, flowering, fruiting and seed formation and is called plant growth promoters. It breaks seed dormancy which is antagonistic to abscisic acid.

Boy aged two years will have milk teeth. Milk teeth of man include 8 incisors, 4 canines, 8 molars. Premolars are absent.

Paneth cells, present in the bottom of crypts of Lieberkuhn, are rich in zinc and contain acidophilic granules. There is evidence that these cells secrete antibacterial lysozyme. Zymogen cells or peptic cells are present in stomach and secrete pepsinogen. Kupffer cells are present in liver. They are phagocytic in nature and engulf disease causing microorganisms, dead cells, etc. Argentaffin cells, found in crypts of Lieberkuhn, synthesise hormone secretin and 5- hydroxytryptamine.

Inspiration is initiated by the contraction of diaphragm that increases the volume of thoracic chamber in the antero-posterior axis. The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorso-ventral axis. The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intrapulmonary pressure to less than the atmospheric pressure which forces the air from outside to move into the lungs.

Expiratory capacity is the total volume of air a person can expire after normal inspiration. It includes tidal volume (TV) and expiratory reserve volume (ERV).

EC = TV + ERV = 500 mL + 1000 mL = 1500 mL

Thrombocytes are called blood platelets. They are minute disc-shaped cell fragments in mammalian blood. They are formed as fragments of larger cells found in red bone marrow; they have no nucleus. They play an important role in blood clotting and release thromboxane A2, serotonin and other chemicals, which cause a chain of events leading to the formation of a plug at the site of the damage, thus preventing further blood loss. A reduction in their number can lead to clotting factors which will lead to excessive loss of blood from the body.