The scientist who first observed chloroplasts was:
A. Robert Hooke
B. Julius von Sachs
C. Antonie van Leeuwenhoek
D. Andreas Schimper
Answer: Option D
Solution (By JKExamLibrary)
Andreas Schimper first described chloroplasts and coined the term in 1883. Hooke discovered cells, Leeuwenhoek observed live cells, Sachs showed starch is produced by photosynthesis.
Explanation:
Transcription is the first step of gene expression, where a specific segment of DNA is copied into RNA (specifically mRNA) by the enzyme RNA polymerase. This occurs in the nucleus of eukaryotes. The mRNA then carries the genetic code from the DNA to the ribosomes in the cytoplasm for translation (protein synthesis).
Explanation:
Angiotensin II is a powerful octapeptide hormone formed in the blood by the action of angiotensin-converting enzyme (ACE). It has multiple effects to increase blood pressure and volume. It is a potent vasoconstrictor, increasing systemic vascular resistance. Crucially, it also acts on the zona glomerulosa of the adrenal cortex to stimulate the secretion of the mineralocorticoid hormone aldosterone. Aldosterone then acts on the kidneys to increase sodium and water reabsorption, further increasing blood volume and pressure.
Explanation:
The endosperm is a triploid tissue in angiosperm seeds that stores starch, proteins, and lipids to nourish the embryo during germination. It is formed by double fertilization. In some seeds (e.g., legumes) the endosperm is absorbed and the cotyledons become storage organs. The seed coat protects.
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