I think the statement above is true. <span>Metamorphic rocks can be made up of newly-crystallized minerals formed during metamorphism but they can also include pre-existing minerals unchanged since their crystallization in an igneous rock.</span>
BE CAREFUL. Here we ask about the nucleolus precisely and not about the nucleus in general, the precise role of the nucleolus is to assemble the ribosomal RNA and the ribosomal proteins to form the ribosomes. So the answer is B.
In cell biology, the nucleolus is the largest nucleus subcompartment of eukaryotic cells. This particular space of the nucleus is not delimited by a membrane, nevertheless some authors consider it as an organelle and others do not. The number of nucleoli can vary during the cell cycle (usually only 1 in G0 phase).
The nucleolus is composed of proteins, DNA and RNA and is formed around particular chromosomal regions called NOR (Nucleolar Organizing Regions).
It is in particular the place where the transcription of the ribosomal RNAs (5.8S, 18S and 28S rRNA), the processing of these ribosomal RNAs from precursors and the first part of the assembly of the two ribosome subunits takes place. with the association of certain ribosomal proteins. The end of the ribosome assembly occurs in the cytoplasm on mRNA after export of pre-ribosomes through the nuclear pore.
The cell membrane is a lipid bilayer that prevents that passage of water and ions. This allows cells to maintain a higher concentration of sodium ions out the outside of the cell. Cells also maintain a higher concentration of potassium ions and organic acids on their inside.
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Answer:
Explanation:
In a cross-section of an adult tree trunk, the outer layer that interacts with the environment is called periderm (Layer D). The second layer that follows the periderm is the phloem (Layer C). The next layer is the cambium, which produces phloem cells and xylem cells (Layer B). The secondary xylem follows the vascular cambium (Layer A) and finally, the medulla is located in the middle of the trunk.
The secondary xylem proceeds from the vascular cambium activity. Its cells are orientated in different ways composing the vertical/axial system and the horizontal/transversal system. The secondary xylem is essential to the tree growth in high because of its resistance and the capacity to transport water long distances. Secondary xylem functions are to transport water and minerals through its vessels and tracheids, to provide support and resistance to the plant, and to store reserve substances.
