CELL STRUCTURE

THE CELL

The cell is a structure consisting of three essential elements: plasma membrane, cytoplasm and genetic material (DNA). It has the ability to perform three vital functions: nutrition, relationship and reproduction MEMBRANE. It is also called plasmic, plasma, protoplasmic or only membrane. Many cells have a much thicker layer called the secretion membrane or cell wall that is common in plant cells. In-plant cells

The membrane and the protoplasm are surrounded by the cell wall and have a large number of pores that are of respectable dimensions, so it does not constitute a barrier for the passage of substances into the cell. The function of the cell wall is to “shape and stiffen the cell.” 

CYTOPLASM 

The cytoplasm is the cellular space between the plasma membrane and the nuclear envelope. It consists of cytosol, cytoskeleton and cellular organelles. 

Cytosol (also called hyaloplasm) is the internal medium of the cytoplasm. In it float the cytoskeleton and ribosomes.

It is formed by 85% of water with a high content of substances dispersed in it colloidally (proteins, lipids, carbohydrates, nucleic acids and nucleotides as well as dissolved salts. Among its functions are the realization, thanks to ribosomes and synthesis of proteins, with the amino acids dissolved in the cytosol. These proteins remain in the cytosol (enzymes, energy reserve proteins or proteins that will form the cytoskeleton).In it, there is a considerable amount of critical metabolic reactions: glycolysis, gluconeogenesis, lactic fermentation, etc. 

The cytoskeleton appears in all eukaryotic cells. The chemical composition is a network of protein fibres (microfilaments, intermediate filaments and microtubules).

Its functions are to maintain the shape of the cell, form pseudopods, contract muscle fibres, transport and organize cellular organelles. ENDOPLASMIC RETICULUM.

It was formed from the fundamental membrane so its ultrastructure will be PLP or gel. It is all over the cellular interior, like a network, but it does not touch the nucleus. Within the reticulum, there are interstitial fluids (than there is outside) so that it has much more selection surface the membrane communicates the outside with the nucleus (it is contiguous). The membrane rolled and inside. It holds the entire interior, protecting.

It can be of 2 types:

  • Smooth (the one just described).
  • Regular G (when the reticulum is very close to corpusculosà ribosomes).

MITOCHONDRIA.

Rounded particles present in most cells and that is always very close to the endoplasmic reticulum. The structure and ultrastructure coincide because they look almost the same in the two microscopes. They have a PLP or gel membrane (they originate from the diaphragm). Its function depends on the content: sugars, ATP and RNA. It is assumed that its purpose is for RNA, and this is protein synthesis.

Protein synthesis: in ribosomes, which have many RNA chains and are detained in the reticulum. There are many amino acids.

The protoplasm needs some protein, so one of its enzymes communicates to the nucleus the lack of protein X. The core opens the DNA message to form the sequence of amino acids that will form the protein (more than 50 amino acids). The negative message deciphered by the RNA goes to the protoplasm, and this is deciphered by an RNA (positive).

RIBOSOMAS 

They are also known as “Palade corpuscles.” They are small spherical organelles that are attached to the endoplasmic reticulum and free in the cytoplasm. They are chemically constituted by approximately two-thirds of ribonucleic acid (RNA). Its function is to synthesize LISOSOMAS proteins. Rounded organelles (1/3 the size of ribosomes) in almost all cells. They are native to the membrane, and their structure and ultrastructure coincide. Having no specific arrangement, they depend on their content: enzymes capable of breaking chemical structures (smooth). They defend the cell by destroying foreign particles and helping it to carry out digestive processes. GOLGI COMPLEX

It is a formation discovered by Golgi in the 60s. It was determined as a structure always present, but not of the same size or with the same position. Some cells have tiny and others a lot. It is native to the membrane. By photon microscope, it looks like a spot near the nucleus. This spot by electronic microscope looks like a blister and a cistern (they are the same, but the swelling is up, and the tank is down). It contains individual sections of the epithelial tissues. When a gland is not secreted, the presence of the Golgi apparatus is almost null (and vice versa). It is related to defence.

CORE.

The nucleus is an essential structure of the cell. They are usually 1/3 the size of the cell. They direct cellular functions. Many times the division of the battery is due to the loss of relationship and capacity between the nucleus and the rest of the cell.

There are several ways (all imaginable) — starred, spherical, ovoid, etc. No cell survives without a nucleus, except for the cornea cells of some mammals and the phloem (conductive vessels of the tracheophytes).

It is usually central (in the center of the cell), but there are also at other points.

Its functions are vital because it is the cellular controller, so there is a direct relationship between its services and its structure.

A photonic microscope shows a non-homogeneous content limited by a PLP or gel membrane (chariot) and where there are dense and bright parts.

The parts analyzed in electronic (ultrastructure) have given that:

  • Carioca: it can be PLP or gel
  • Nuclear juice: a substance, a mixture of compounds where there are sugars, enzymatic proteins, lipids and ATP.
  • Chromatin: is formed by chromosomes (individualized structures), which are the ones that direct the cellular functioning.
  • Nucleoli: constituted by fibres. They form the achromatic spindle. They have RNA and ATP.

The most important discovered are chromosomes.

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