Cellular Components: Structure and Function

Posted on Mar 12, 2025 in Geology

Membrane Components

The cell membrane (CM) surrounds the cell, separating the internal environment from the external. These organelles have a similar composition:

  1. Lipids: Phospholipids (glycerin + fatty acids + phosphoric acid or amino alcohol) and sphingolipids (amino alcohol + saturated or unsaturated fatty acids + another component (galactose, oligosaccharides or complex). They have an amphipathic character in bilayers, performing rotational movements, lateral diffusion, flip-flop, and flexion.
  2. Proteins: Performing movements of flexion and rotation, can be intrinsic and extrinsic, cross the membrane, localized to one side or another.
  3. Carbohydrates: Located on the outside, bind to lipids or proteins, forming the glycocalyx, which only covers the plasma membrane.

Fluid Mosaic Membrane Theory: The CM is a biological fluid, asymmetrical, a bilayer composed of proteins, lipids, and carbohydrates, and later integrated components in a mosaic. In the CM, there is a series of differences:

  1. Microvilli, invaginations, and intercellular junctions (waterproof or narrow slit and desmosomes in band).

Matrix Components

  1. Polysaccharides: (glycosaminoglycan and proteoglycans)
  2. Proteins: (structural and collagen, elastin, and adhesive such as fibronectin and laminin) Supports the cell.

Hyaloplasm

Formed by water, proteins, nucleic acids, salts, metabolites, and lipid inclusions, glycogen, and pigments.

Cytoskeleton

A protein scaffolding formed by proteins:

  1. Microfilaments: Actin and myosin, contractile function, cell movement, support anchorage, cell division, pseudopods, contractile.
  2. Microtubules: The protein tubulin forms working demos. During mitosis, they are the spindle fibers; centrioles are the ones that form cilia and flagella, shaping the cell and serving as transport guides for proteins.
  3. Intermediate Filaments: Intermediate size of effect of the other two, tubular proteins, provide mechanical stability and assist in the formation of the cytoskeleton.

Centrosome

Only in animal cells, it is the center organizer of microtubules and consists of:

  • The centriole (2 cylindrical structures arranged at right angles, formed and forming triplets).
  • The aster microtubules that are the emerging center of the centrosome and centrosome matrix that surrounds the small fibers of the centrioles.

Function: Involved in cell division and the formation of spindle microtubules; centrioles participate in the formation of cilia and flagella.

Cilia and Flagella

Are external appendages on the cell membrane. Cilia perform numerous swings, while flagella undulate. They are constituted by the ciliary apparatus, ciliary centriole, and a like structure.

Ribosomes

Are free in the cytosol, attached to the rough endoplasmic reticulum (RER), and bound to the outer nuclear membrane and internal membranes of chloroplasts and mitochondria. They are formed by 2 subunits: the small one with 2 active sites: P site and peptidyl, where the first aminoacyl-tRNA is placed for the first methionine codon that transports the A or aminoacyl place where the second codon is. Ribosomes synthesize proteins.

Peroxisome

Located near the RER, if small, they are called microperoxisomes. Provides oxidative enzymes and mitochondria with the use of O. Ribosomes. They have no DNA or action. They are very important in liver and kidney cells. Plants have photorespiration peroxisomes, which are called glyoxysomes in seeds, being able to transform fatty acids into sugars.

Vacuole

In typical plant cells, there may be only one or multiple vacuoles that act as storage organelles for substances, such as regulatory cell turgor. They may contain lysosomes. Other vacuoles: pulsating: that extract water from the cytoplasm and digestive vacuole: are the phagosomes responsible for carrying out nutrient digestion.