cytoplasmic organelles

Cytoplasmic organelles
Plasma membrane
Structure. The plasma membrane is made of phospholipids, cholesterol, proteins, and oligosaccharide chains covalently linked to phospholipid and protein molecules. It is approximately 7.5 nm thick and consists of two layers, known as the lipid bilayer that contain associated integral and peripheral proteins. The inner layer of the plasma membrane faces the cytoplasm, and the outer layer faces the extracellular environment. Phospholipid molecules spontaneously orient to form a bilayer in which the hydrophobic tails are pointed inwards. The hydrophilic, ionic head groups are in the exterior and are thus in contact with the surrounding aqueous environment.

Function
1. Physical barrier: Establishes a flexible boundary, protects cellular contents, and supports cell structure. Phospholipid bilayer separates substances inside and outside the cell
2. Selective permeability: Regulates entry and exit of ions, nutrients, and waste molecules through the membrane
3. Electrochemical gradients: Establishes and maintains an electrical charge difference across the plasma membrane
4. Communication: Contains receptors that recognize and respond to molecular signals and controlling interaction between cells


Cytoplasm
Structure: Cytoplasm represents everything enclosed by the plasma membrane, with the exclusion of the nucleus. It consists mainly of a viscous fluid medium that includes salts, sugars, lipids, vitamins, nucleotides, amino acids, RNA, and proteins which contain the protein filaments, actin microfilaments, microtubules, and intermediate filaments. These filaments function in animal and plant cells to provide structural stability and contribute to cell movement.
Function:
1- Energy production through metabolic reactions,
2- Biosynthetic processes, and photosynthesis in plants.
3- The cytoplasm is also the storage place of energy within the cell.
Cytosol: is the fluid of the cytoplasm, refers only to the protein-rich fluid environment, excluding the organelles.
Cytoskeleton:
Structure: The cytoplasmic cytoskeleton is a complex array of protein fibers found in three forms:
(1) Microtubules: hollow structure, with an outer diameter of 25 nm and a wall 5 nm thick, give the rigidity to help maintain cell shape.
(2) Microfilaments: composed of actin, allow cellular motility and most contractile activity in cells
(3) Intermediate filaments: intermediate in size between the other two and with a diameter averaging 10 nm. The intermediate filaments are much more stable than microtubules and actin fil