NUCLEOLUS
is a spherical structure surrounded by nucleoplasm, each nucleolus is produced by a nucleolar organizer region (NOR) located in a specific chromosome nucleolus organizer. This organelle remains attached to the NOR. A genome may include one or more chromosomes and nucleolus organizers may be one or more nucleoli in the same nucleus, the nucleoli are fused, so that a nucleolar count is not an indication of the number of nucleolar organizing chromosomes in a complement of chromosomes . The NOR is located near the end of a chromosome and a satellite chromosome is projected beyond the NOR.
5S RNA produced in the nucleoplasm and ribosomal subunit proteins imported from cytoplasm to form ribosomal subunits precursors in the nucleolus. Mature subunits in the nuclear limits or immediately adjacent cytoplasm once they have been transported outside the nucleus.
can distinguish four components:
1. Granular zone: containing particles diffuse about 25 nm wide, which represent close to complete ribosomal subunits.
2. Fibrilar area, with ill-defined fibrils RNA transcripts in the form of nucleoprotein, are 5 nm in diameter.
3. Nucleolar Chromatin Area: consists of 10 bags cromosomitas nm in width that extends beyond the point of accession with the NOR chromosome.
4. Nucleolar matrix: no structure in which these materials are distributed.
The nucleolus can be enlarged in active cells and inactive cells reduced due to the expansion or reduction of the granular zone.
QUESTIONNAIRE
1.-Explain what may be the reason for the free passage of water through the cell membrane.
The contents of all living cells are surrounded by a thin membrane called the plasma membrane, or cell, which marks the boundary between the cell contents and the environment external. The plasma membrane is a continuous film formed by a double layer of lipid molecules and proteins, between 4and 5 nm thick and acts as a selective barrier regulating the chemical composition of the cell. Most of the ions and water-soluble molecules are unable to cross this barrier spontaneously, or require the concurrence of specific transport proteins or channel proteins. This keeps the cell concentration of ions and small molecules different from those prevailing in the external environment. Another mechanism is the formation of small membrane vesicles that are incorporated into the plasma membrane or separated it, allows animal cells to transfer even larger macromolecules and particles through the membrane.
2.-Say is the purpose of placing the blood in an isotonic solution.
water concentration remains constant within and outside the cell, so its volume and shape is not altered. With erythrocytes can be stored for long periods in a solution of sodium chloride 0.9% have shown no change or hemolysis.
3 .- What are the differences observed between the animal and plant cells in the presence of hypotonic solution? And explain the cause.
In animal cells erythrocytes swell and become broken, in the case of plant cells rigid cell wall helps them avoid an excessive increase, therefore no breakdown of the cell wall.
4.-Of the substances used (starch, ammonium hydroxide and phenolphthalein). Tell which one (s) cross the membrane of cellophane and as demonstrated this.
The substance that crossed the membrane was phenolphthalein and ammonium hydroxide was demonstrated when the glass of 500ml. Phenolphthalein was added water and stirred, and then change the color from clear to very faint pink.
5.-If the results of his practice were not expected, please explain which could be due.
were not obtained and we could not do the cellophane. QUESTIONNAIRE
1.-Tell that to be the biggest release of oxygen in some tissues.
For the peroxisomes that are more abundant in the tissues.
2.-Explain that represents the value of the slope in the equations obtained
The concentration of each sample.
3.-Explain the usefulness of the method of least squares in biological studies. Help
to graph or draw an average of data obtained from a biological study.
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