What jobs do the major organelles do in a eukaryotic cell?

Think of a eukaryotic cell as a set of work areas, not as a tiny factory with every part in every cell. Here is a plain-language reference:

1. Nucleus: Holds the cell’s DNA and directs the making of ribosomes and proteins. [S1] [S3]
2. Ribosomes: Build proteins. Some are associated with the rough endoplasmic reticulum; others are not. [S1] [S2]
3. Mitochondria: Carry out cellular respiration, which helps produce ATP, a form of usable cellular energy. [S1]
4. Endoplasmic reticulum (ER): Rough ER is involved in modifying proteins; the ER also makes lipids. Smooth ER can store calcium ions. [S2]
5. Golgi apparatus: Sorts, tags, packages, and distributes proteins and lipids. [S2]
6. Vesicles and vacuoles: Membrane-bound compartments used for storage and transport. Some plant vacuoles also break down large molecules. [S1] [S3]
7. Chloroplasts: Carry out photosynthesis in plant cells. [S1]

These are broad roles, not a complete inventory of everything each organelle does.

For a simple example, imagine a protein that is made on a ribosome associated with rough ER and then sent elsewhere in the cell. The rough ER can modify proteins and send them onward in transport vesicles. The Golgi sorts, tags, and packages proteins, and vesicles can carry materials between places. [S2]

Route to remember:

Ribosome → rough ER → transport vesicle → Golgi → vesicle → destination

This is a learning diagram, not a promise that every protein follows that exact route. The sources describe general functions; they do not establish the route, destination, or steps for every protein in every cell. Also, smooth ER has different highlighted jobs: making lipids and storing calcium ions. [S2]

That’s a good distinction to make. In the comparison described by OpenStax, plant cells have chloroplasts, a cell wall, and a large central vacuole, while animal cells do not. The same text notes that most plant cells lack the centrosomes and lysosomes it describes for animal cells. [S3]

For this guide’s organelles, the clearest difference is chloroplasts: they occur in plant cells, not animal cells or prokaryotes, in the broad comparison. [S1] The sources give general textbook comparisons, not an exhaustive list of every cell type or every exception. So treat “plant” and “animal” as useful starting categories, not a guarantee that all cells within a category are identical.

Try sorting the organelles by the question each one helps answer:

• Where is the DNA, and where is the synthesis of ribosomes and proteins directed? Nucleus. [S1] [S3]
• Where are proteins built? Ribosomes.
• What helps supply usable energy? Mitochondria, through cellular respiration and ATP production. [S1]
• What processes or distributes proteins and lipids? ER and Golgi, with different roles in that pathway. [S2]
• What stores or transports materials? Vesicles and vacuoles. [S1]
• What carries out photosynthesis in plant cells? Chloroplasts. [S1]

A useful self-test is to cover the names and explain each job in your own words. If a question asks about a particular cell, check its type before assuming it contains every structure on the list.