Biology Test - 10

Calcium ions are responsible for muscle contraction. The action potential stimulates the release of calcium ions from the sarcoplasmic reticulum, which binds to the troponin present on the actin filaments and exposes the myosin-binding sites due to conformational changes.

Magnesium, in muscle contraction, stimulates calcium re-uptake by the calcium-activated ATPase of the sarcoplasmic reticulum. It also affects the translocation of calcium ions through the smooth muscle cell membrane.

Hypopnea iswhen you take in shallow breaths for 10 seconds or longer while asleep and your airflow is at least 30% lower than normal. But your breathing doesn't totally stop since your airway is only partly blocked.

A. Unitegmic ovules - They are the ovules with one integument. Example: Higher dicots.

B. Bitegmic ovules - They are the ovules with two integuments. Example: Monocots.

C. Tritegmic ovules - They are the ovules with three integuments (rarely ovule). Example: Asphodelus.

D. Ategmic ovules - They are the ovules without integument. Example: Santalum.

Glucagon hormone is secreted by \(\alpha\) cells of islets of langerhans.

The Islets of Langerhans are the ductless glands present in the pancreas. They form the endocrine portion of the pancreas. The islets of Langerhans has 2 types of cells \(\alpha\) cells & \(\beta\) cells, the \(\alpha\) cells surround the \(\beta\) cells. The \(\alpha\) cells secrete glucagon, while Insulin is secreted by the β cells.

Trichoderma sps are fungi belonging to class Ascomycetes. These fungi are regular components of the soil. They prevent/protect the roots of the plant from pathogenic infection.It is used as a biocontrol agent against plant pathogens. It is a free-living fungus and is commonly found on the root surface.

Trichoderma spp. grow very fast and can produce polysaccharide-degrading enzymes, so it can be grown on a large number of substrates.

When testosterone is absent, the tissues develop into female sexual tissues. Primitive gonads become testes or ovaries. Tissues that produce a penis in males produce a clitoris in females. The tissue that will become the scrotum in a male becomes the labia in a female, that is, they are homologous structures.

Main source of elements for nitrate reductase is ferredoxin.

Nitrite reductase is an enzyme used in nitrogen assimilation. It converts nitrite into ammonia by using reduced ferredoxin. It is a type of oxidoreductase enzyme which catalyzes reversible reduction of nitrite ions and simultaneous oxidation of reduced ferredoxin.

Ethanol fermentation, also called alcoholic fermentation, is a biological process which converts sugars such as glucose, into cellular energy, producing ethanol and carbon dioxide as a byproduct.

• First, the glucose is converted into pyruvate with the generation of ATP and NADH.
• Next, the obtained pyruvate is converted into ethanol and carbon dioxide, with the consumption of NADH generate during glycolysis.

During glycolysis, triose phosphate acts as an electron donor during the conversion of glucose to pyruvate.

During the next stage, 2-acetaldehyde, formed from decarboxylation of pyruvate, accepts electrons from NADH and is reduced to ethanol.

The steps of sexual reproduction in plants are:-

Pollination-  the pollen grains are carried by wind, water or insects and animals to reach the stigma of the flower. This process of transfer of pollen grains is called pollination.

Germination-  the pollen tubes begins to grow towards the egg cell. These tubes are a pathway for the sperms or male gamete to reach the egg within the ovule.

Discharge of male gamete: The pollen tubes reach the ovule where it penetrates the ovule to reach the female gamete or egg.

Fertilization- the male gamete travel down the pollen tubes and fertilize an egg. In angiosperms, double fertilization takes place where both egg and the polar nuclei in the embryo sac are fertilized by the male gametes.