Answer:
The correct order is dehydration, embed in wax, cut into sections, staining
Explanation:
There are certain proceedings needed to obtain stained sections of vegetable or animal tissues for their microscope observations.
These steps are:
- Obtention of the material: The tissue is cut to an adequate size.
- Fixation: When tissues are extracted from the organism, they suffer autolysis and putrefaction, so they need to be fixated in order to keep their cells in the best state possible. Fixation involves preserving the original morphological and molecular characteristics of the tissue. Fixation avoids autolysis, putrefaction, distortion, and retraction of cells and the tissue that could affect its volume or morphology.
- Dehydration. Once fixated, the fixator must be eliminated and the tissue is dehydrated by using a gradual series of solutions with alcohol in ascendant concentrations. Dehydration must be gradual to avoid tissue deformation.
- Inclusion. To obtain thin cuts that can be observed under the optic microscope, the tissues must be included in a consistent, firm substance, that might be either hydrophilic or hydrophobic. A hydrophobic medium is paraffin wax, that provides hardness and plasticity.
- Cut. The tissue included in wax must be cut in slides or sections thin enough to allow the diffusion and penetration of light. A microtome is used to perform these cuts. When using paraffine for tissue inclusion, the cuts are about 5 to 20 micrometers of thickness.
- Stain. Once the cuts are performed, paraffin wax must be eliminated. This can be done by using an organic solvent. Then the tissue must be stained. Hematoxylin and Eosin are the most common dyes. Animal tissues in general do not have any natural color, so they need to be stained to be observed.
Answer:
A covalent bond.
Explanation:
A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms.
Answer:
The link reaction converts pyruvic acid to Acetyl-CoA.
I hope it's helpful!
Answer:
Explanation:
The genes in DNA encode protein molecules, which are the "workhorses" of the cell, carrying out all the functions necessary for life. For example, enzymes, including those that metabolize nutrients and synthesize new cellular constituents, as well as DNA polymerases and other enzymes that make copies of DNA during cell division, are all proteins.
In the simplest sense, expressing a gene means manufacturing its corresponding protein, and this multilayered process has two major steps. In the first step, the information in DNA is transferred to a messenger RNA (mRNA) molecule by way of a process called transcription. During transcription, the DNA of a gene serves as a template for complementary base-pairing, and an enzyme called RNA polymerase II catalyzes the formation of a pre-mRNA molecule, which is then processed to form mature mRNA (Figure 1). The resulting mRNA is a single-stranded copy of the gene, which next must be translated into a protein molecule.
