Nucleus — Science definition
Defined in 4 courses:
- The compartment holding almost all of a eukaryotic cell's DNA; it stores and issues instructions rather than building anything. (Life Science & Scientific Inquiry)
- The dense, positively charged center of an atom, containing the protons and neutrons. (Physical Science: Matter, Forces & Energy)
- The membrane-bound organelle that stores a eukaryotic cell's DNA and directs its activities. (Life Science: Biology)
- The tiny, dense, positively charged core of an atom that holds the protons and neutrons and nearly all of its mass. (Physical Science: Chemistry)
Where it is taught
- Cell Structures & Organelles — Cells, Transport & Cellular Energy, Life Science & Scientific Inquiry, Grade 7
- Atomic Structure — Properties of Matter, Physical Science: Matter, Forces & Energy, Grade 8
- Prokaryotic & Eukaryotic Cells & Their Organelles — Cells, Membranes & Exchange, Life Science: Biology, Grade 10
- Atomic Models & Subatomic Particles — Atoms, Electrons & Periodicity, Physical Science: Chemistry, Grade 11
In use
The largest organelle in most of your cells is the nucleus, and it is where almost all the cell's DNA is kept — the long molecule that carries the instructions for building proteins.
Cell Structures & Organelles
Its nucleus, the very small central region, contains positively charged protons and, for most isotopes, electrically neutral neutrons.
Atomic Structure
A prokaryote — every bacterium and archaeon — lacks a membrane-bound nucleus and the typical eukaryotic organelle system.
Prokaryotic & Eukaryotic Cells & Their Organelles
Questions using nucleus
Problem 1
Answer and explanation
No. Ribosomes build proteins using cellular instructions; the nucleus stores much genetic information in a typical eukaryotic cell.
Problem 2
Answer and explanation
Yes. Ribosomes can use cellular instructions without an enclosed nucleus; the arrangement differs from the typical eukaryotic-cell model.
Response criteria
- Explain the relevant biological process accurately.
- Use the supplied evidence and show calculation steps with units where needed.
- Connect a labeled model or mechanism with the claim.
- State an assumption, evidence limitation, or useful next observation.
Problem 3
Hints
Ribosomes alone do not distinguish these types.
Answer and explanation
Eukaryotic; these membrane-bound structures support that classification.
Taught alongside
- organelle
- cytoplasm
- ribosome
- mitochondrion
- atom
- proton
- neutron
- electron
- atomic number
- mass number
- isotope
- ion
- model
- evidence