Biology (Medical Entrance) - 7

Corpus luteum secretes two pregnancy hormones: progesterone and relaxin.

One primary spermatocyte produces four sperms and one primary oocyte produces one ovum.

Trichogyne is a long hair-like receptive structure for male sperms.

 Adrenal cortex secretes aldosterone which increases water absorption in kidneys.

Somatostatin secreted by pancreas inhibits the release of certain hormones like growth hormone.

 Epinephrine secreted by the adrenal gland regulates stress responses.

When levels of cortisol secreted by adrenal cortex increase in blood, a rare condition called Cushing's syndrome occurs indicated by weight gain, fragile skin and rounded face.

 G2 phase is responsible for replication of the chromatin material resulting in the formation of similar sister homologous chromosomes, which maintain the ploidy status in the daughter nucleus, as in mitosis and if it occurs so in meiosis then the number of chromosomes will be doubled in the zygote and consequently in the progeny as that of parents and ploidy will be doubled in the progeny with each generation resulting in genetic abnormality.

 In prokaryotic cell during glycolysis, 2 ATP is consumed and 4 ATP and 2 NADH is produced from each glucose, and each NADH produces 3 ATP, thus a total of 4 + 6 ATP = 10 ATP and net production of 10 - 2 ATP = 8 ATP  is produced, and 30 ATP in kerb cycle and pyruvic acid oxidation, thus net production of 30+8 =38 ATP occurs. 

 Transpiration creates negative pressure in adjacent subsidiary cells of the stomata, which get transferred down the xylem, which results in uptake of the water and nutrients from the soil which is ultimately utilised in the process of photosynthesis. Thus, its absence can affect overall functioning of plants.

 During prophase 1 of meiosis, homologous chromosome pair comes closer together and they are held in pairs with the help of protein structures called synaptonemal complex.

 The gametes of an individual are haploid, i.e. they carry half the number of genome, similarly the other half comes from the gametes of the contributing parents, so that the number of genome is restored in the progeny to the parental level. Examples- Haploid of 2n is n, haploid of 4n is 2n. Similarly haploid of 6n is 3n. Monoploid means presence of just one set of chromosomes in the genome of an individual. Examples- Some species of potatoes are monoploid n. Humans are diploid, i.e. 23 (n) + 23 (n) = 46 (2n).

 Heterospory results in the variation in the size of spores, which results in the formation of different sized spores, larger in female reproductive structure, which in the course of evolution gets modified into egg in the ovule and the smaller sized spores get modified into pollen grains, the male gametes. This modification results in fertilisation of egg in the ovary by male gametes derived from pollen grains and ultimately formation of seed.

The only means of gaseous movement within the plant body is diffusion. Diffusion is the movement of particles of different substances including the gaseous particles from the region of higher concentration to the region of lower concentration.

The inhibitory effect of oxygen on the rate of photosynthesis is called as Warburg effect.

In plants, water is transported by xylem.

In CAM plants, the initial carbon dioxide acceptor is phosphoenol pyruvic acid.

The dark reaction of photosynthesis occurs in stroma of chloroplast.

Agranal chloroplast is found in C4 plants.

The glycine diffuses into a mitochondrion, where two glycine molecules are converted to glycerate (a three-carbon molecule) and CO_2.

Antifertilizin is secreted by animal sperm before fertilisation.

The rate of photosynthesis in plants is independent of duration of light.

Transportation of water in rooted plants is always unidirectional.

Isotonic solutions have equal solute concentrations.

In plants, transport of substances over longer distances proceeds mainly by translocation.