Cell membrane structure
The cell membrane is a thin sheet of fats or lipids, alternating with large protein molecules. The lipid molecule has two halves: a water-soluble end and water-repellent. The membrane is a double layer of phospholipid molecules.
The water repellent ends form the outer surfaces, and the water soluble ends are mixed between them.
The cell membrane controls the flow of materials into and out of cells and maintains cell integrity.
Lipid bilayer
This fat double layer contains:
Phospholipids - fatty molecules containing phosphorus;
• cholesterol molecules that stabilize the lipid layer;
• glycoproteins consisting of protein molecules and carbohydrates (sugar) on the extracellular (outer) surface of the protein.
Cell membrane
Microvilli
These are tiny, finger-like projections or folds of the cell membrane itself.
The function of microvilli is to increase the surface area of the cell. This allows the cell to more efficiently absorb more substances from their environment, as well as to secret molecules.
Types of cell transition
Tight or tight connection
It is formed by protein molecules of neighboring cell membranes, merging together. Close connections are found between epithelial cells that line the digestive tract.
Desmosome or mount, connection
On these transitions, on the inner sides of neighboring cells, there are riveted bulges, called plaques. They are attached to the opposite side of the cell membrane by a keratin thread (flexible protein threads, also used in the hair).
Linker proteins extend from plaques and cross the space between cells.
Break or bond connection
Proteins pass through both membranes of two neighboring cells.
Proteins are located in groups (connexons), which form a hollow channel through the cell membrane.
These compounds are found in the heart muscles and in the intestinal muscles.
Selective barrier
The cell membrane is a protective barrier that controls which substances move inside and outside the cell. Although oxygen and carbon dioxide pass freely, it is difficult for other substances to pass through the membrane.
Cytoplasm
Cytoplasm (semi-liquid mixture) is a cellular material outside the nucleus (control center) and inside the cell membrane. In humans, as well as all plants and other animals, components of the cytoplasm of the cytosol (gel liquid), cytoplasmic organelles (mini organ) and inclusions (chemicals). Prokaryotic cells (bacteria and primitive algae) have cytoplasm and inclusions, but not organelles.
In general, the cytoplasm promotes the movement of organelles and the transfer of substances inside the cell; provides an environment in which biochemical reactions can occur; and helps maintain and shape the cell.
cytosol
It is a gel-like translucent liquid, consisting mainly of water. It contains dissolved sugars, salts and other solutes.
Large molecules, such as proteins, form colloids. Cytosol keeps other elements of the cytoplasm in suspension.
Thus, many important substances, such as starch, are stored in the cytosol until they are needed by the organelles in the cell.
Cytosol can vary from semi-fluid to a more solid state (in combination with the cytoskeleton). This is important for many cell functions.
Inclusions are substances stored in the cytosol. Inclusion depends on the type of cell. In adipocytes (fat cells), a lipid (fatty) drop is an inclusion. Pigments (stains), such as melanin in skin cells, are also considered inclusions.
Cytoskeleton structure
The cytoskeleton is a kind of intracellular forest.
It consists of a complex network of tiny protein fibers and tubes suspended in the cytosol (gel fluid) inside the cell. The cytoskeleton is a dynamic structure that constantly changes as the cell grows and especially when it divides. It combines three types of protein structures: microtubules (tiny tubes); microfilaments (tiny fibers); and intermediate threads. None of them has a covering membrane.
microfilaments
• Microfilaments are thin threads of protein actin.
• They are 5–9 nm wide (nm).
• Organic subunits are located in two chains.
• Actin has the ability to enter into a contract (reduce).
• Microfilaments form bundles, flat meshes or three-dimensional nets.
• They are most common on the periphery of the cell.
• They often break and reassemble.
Microtubules
• Microtubules are hollow cylinders of tubulin proteins.
• They have a width of about 20-25 nm.
• Subjects tubulin spherical.
• Microtubules radiate from the centromere (structure in the center of the cell).
• Like microfilaments, they often break and reassemble.
Organelles are located along microtubules.
Intermediate threads
• These are fibers made from a range of proteins.
• Intermediate threads have a width of about 10 nm.
• These filaments spread throughout the cytoplasm.
They are attached to the cell membrane and can span the cell from one side to the other.
• Intermediate threads form a mesh inside the core.
• Intermediate filaments are the most permanent and stable part of the cytoskeleton.
