Introduction

• Cytoplasm is the jelly-like and semi-fluid structure present in the space between the cell membrane and nucleus.

• 3 Main Functions of the Cytoplasm :

  1. Structural Support and Cell Shape : The cytoplasm, along with the cytoskeleton, helps maintain the cell's shape and provides a framework for organelles to function properly. 

  2. Medium for Cellular Processes : The cytoplasm is where many important cellular activities, like protein synthesis, glycolysis, and cell division, take place. 

  3. Material Transport : Cytoplasmic streaming, a process where the cytoplasm moves around, helps transport nutrients, enzymes, and other substances within the cell, ensuring efficient distribution of resources. 

Structure

• The cytoplasm is often described as a viscous, jelly-like material. It's not entirely fluid, but rather has a consistency that allows for the movement of molecules and organelles.

• The cytoplasm can change from a more fluid state (sol) to a thicker, more gel-like state (gel), depending on the cell's needs.

• The three main parts of the cytoplasm are cytosol, organelles, and cytoplasmic inclusions.

• The main component of the cytosol is water which consists of dissolved ions, proteins, and other small molecules.

• Ions dissolved in the cytosol include K+, Na+, Cl-, Mg2+, Ca2+, and bicarbonate. It also contains amino acids, proteins, and molecules that regulate osmolarity, such as protein kinase C and calmodulin.

• Membrane-bound organelles:

  • Nucleus: The control center of the cell, containing the genetic material (DNA). 

  • Mitochondria: The powerhouses of the cell, responsible for generating energy through cellular respiration. 

  • Endoplasmic reticulum (ER): A network of membranes involved in protein and lipid synthesis, folding, and transport. 

  • Golgi apparatus: Modifies, sorts, and packages proteins and other molecules for transport within or outside the cell. 

  • Lysosomes: Contain enzymes that break down cellular waste and debris. 

  • Vacuoles: Store water, nutrients, and waste products. 

• Non-membrane-bound organelles:

  • Ribosomes: Sites of protein synthesis. 

  • Cytoskeleton: Provides structural support and enables movement within the cell. 

• Other structures:

  • Cell membrane: The outer boundary of the cell, regulating the entry and exit of materials. 

  • Cell wall (in plant cells): Provides support and protection to the cell. 

  • Chloroplasts (in plant cells): Sites of photosynthesis, converting light energy into chemical energy. 

• Cytoplasmic inclusions are non-living, temporary structures within the cytoplasm that accumulate stored nutrients, secretory products, or pigment granules.

• 3 Main Cytoplasmic Inclusions :

  • Glycogen granules : These are the storage form of glucose and are particularly abundant in liver and muscle cells.

  • Lipid droplets : These are spherical structures containing accumulated triglycerides and are found in various tissues, especially fat cells.

  • Pigments : These are colored substances that can be found in various cells, such as melanin in skin and hair cells.