Cytoplasm

Cytoplasm Structure

  • Cytoplasm is a jelly-like substance found between cell membrane and nucleus.
  •  All the cell organelles are embedded in the cytoplasm. It is composed of water, organic and inorganic compounds. 
  • Cytoplasm is one of the essential components of the cell that is present in both plant and animal cells. 
  • Cytoplasm functions by controlling all the metabolic activities taking place within the cell and most of the chemical reactions are carried within it.

 

Endoplasmic reticulum

Endoplasmic reticulum is a network of tiny tubular structures scattered in the cytoplasm. It divides the intracellular space into two distinct compartments, one is luminal (inside ER) and another is extra luminal (outside ER). They function as the transport system of a cell, involved in transporting materials throughout the cell.

Endoplasmic reticulum is divided into two types based on presence and absence of ribosomes.

  • Rough endoplasmic reticulum: The endoplasmic reticulum bearing ribosomes on their surface is called rough endoplasmic reticulum (RER). It is involved in the protein synthesis and secretion. They are extensive and continuous with the outer membrane of the nucleus.
  • Smooth endoplasmic reticulum: The endoplasmic reticulum with the absence of ribosomes on its surface is called smooth endoplasmic reticulum (SER). They are responsible for lipid syntheses. In animal cells, lipid like steroid hormones is synthesized in SER. They are also responsible for detoxifying the cell.

 

Mitochondria

  • Mitochondrion is a double membrane bound cell organelle that are not normally visible under the microscope.
  • This cylindrical or sausage shaped structure is also called the power house of the cell as they are the sites for aerobic respiration of the cell and produce cellular energy in the form of ATP. 
  • The outer membrane and the inner membrane divide its lumen into two compartments i.e., inner compartment called matrix possessing single circular DNA molecule and a few RNA molecules. forming a number of infoldings called cristae and the outer membrane forming the continuous limiting boundary of the organelle.
  • Depending on the shape, size and physiological activity of the cell, the number of mitochondria per cell are variable. 
  • The structure has a diameter of 0.2 to 1µm (average 0.5 µm) and length 1.0 to 4.1 µm.

                                                                                                                            Plastids

Plastids are large and membrane bound organelles that are found in all plants and in euglenoids. They contain some specific pigments that are responsible for imparting specific colours to the plants. On the basis of the type of pigment, plastids can be classified into three types.

  • Chloroplasts: Chloroplasts are double membrane bound cell organelles that contain chlorophyll and carotenoid pigments that are responsible for trapping light energy and this energy is used for the purpose of photosynthesis.

                                                                                                                      Chloroplasts

The inner membrane surrounds a space called stroma. Chlorophyll containing structures called thylakoids are arranged as piles of coins and each pile is called a granum. Thylakoids are connected by flat membranous tubules known as stromal lamella.

  • Chromoplasts: These include carotenoid, fat soluble pigments like carotene, xanthophyll etc. providing characteristic colours like yellow, orange, red, etc. to the plants.
  • Leucoplasts: These types of plastids store nutrients and are colourless. They include amyloplasts storing carbohydrates, leucoplasts storing proteins, and leucoplasts storing oils and fats.

The Golgi Apparatus

  • It is responsible for sorting, modifying, and shipping off the cellular products that come from the rough endoplasmic reticulum (ER), just like a post office.
  • The Golgi apparatus is similar to stacked flattened discs, almost like stacks of oddly shaped pancakes.
  • The Golgi apparatus has two distinct sides with each having a different role. 

Lysosomes

  • An organelle that contains enzymes that break down and digest inessential cellular components, such as a damaged organelle is called the lysosome.
  • Protein products packaged by the Golgi such as digestive enzymes are meant to stay inside the cell in order to break down certain materials.
  • The enzyme-containing vesicles are released by the Golgi, and they may form new lysosomes or fuse with existing lysosomes.

 Vacuoles

  • Vacuoles are generally characterized as storage bubbles of unpredictable shapes which are found in cells.
  • They are liquid-filled organelles enclosed by a film.
  • The vacuole stores the food or a spread of nutrients that a cell might need to survive.
  • In addition, it also stores waste products.
  • The by products are at last tossed out by vacuoles. Thus, the remainder of the cell is shielded from contamination.
  • The animal and plant cells have different sizes and numbers of vacuoles. Compared to animals, plant cells have larger vacuoles.

Related Topic Name

1. About Cell and Cell Theory
2. Cell Membrane and Cell Wall
4. Diffusion and Osmosis