Golgi Apparatus:
The Golgi apparatus, also known as the Golgi complex or Golgi body, is a cellular organelle present in eukaryotic cells. It is responsible for processing, packaging, and distributing macromolecules, such as proteins and lipids, within the cell.

Endoplasmic Reticulum:
The endoplasmic reticulum (ER) is another organelle found in eukaryotic cells. It is a network of membranous structures involved in the synthesis, folding, and transportation of proteins and lipids. The ER is divided into two regions: the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER).

Differences between Golgi Apparatus and Endoplasmic Reticulum:
Although both the Golgi apparatus and endoplasmic reticulum are involved in the processing and transportation of macromolecules, they have distinct structures and functions. Here are some key differences between the two organelles:

1. Structure:
- Golgi Apparatus: It consists of a stack of flattened membranous sacs called cisternae. These cisternae are often arranged in a curved structure resembling a stack of pancakes.
- Endoplasmic Reticulum: It consists of a network of tubules and flattened sacs called cisternae. The ER is interconnected and extends throughout the cytoplasm of the cell.

2. Function:
- Golgi Apparatus: Its main function is to modify, sort, and package proteins and lipids into vesicles for transportation. It receives proteins from the ER and modifies them by adding sugars, lipids, or other molecules.
- Endoplasmic Reticulum: The rough ER (RER) is involved in protein synthesis and folding. It has ribosomes attached to its surface, giving it a rough appearance. The smooth ER (SER) is involved in lipid synthesis, detoxification of drugs, and storage of calcium ions.

3. Transportation:
- Golgi Apparatus: It receives vesicles containing proteins from the ER and modifies them. It then sorts and packages these proteins into new vesicles for transportation to their final destinations within or outside the cell.
- Endoplasmic Reticulum: The RER synthesizes proteins and transports them to the Golgi apparatus for further processing. The SER is involved in the synthesis of lipids and their transportation to other parts of the cell.

In summary, the Golgi apparatus and endoplasmic reticulum are both essential organelles involved in the processing and transportation of macromolecules, but they have distinct structures and functions within the cell. The Golgi apparatus modifies, sorts, and packages proteins and lipids, while the endoplasmic reticulum is involved in protein synthesis, lipid synthesis, and transportation.