🔬 Cell Biology
The structure and function of the basic unit of life.
Cell Biology has 52 topics on LearnViz, graded from Beginner to Advanced. Pick a topic below to read its explanation, examples, FAQs and related links.
What is Cell Biology?
Cell biology explains the smallest unit of life. Every organism is built from cells, and the parts inside them (the membrane, nucleus, mitochondria and ribosomes) decide what a cell can do. Learning how these parts work together is the foundation for almost every other area of biology.
Beginner topics (17)
Cell Theory
States that all living things are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.
🔬 Cell BiologyProkaryotic Cell
A simple cell with no membrane-bound nucleus; its DNA lies in a nucleoid region, as in bacteria and archaea.
🔬 Cell BiologyEukaryotic Cell
A complex cell with a true nucleus and membrane-bound organelles, found in animals, plants, fungi and protists.
🔬 Cell BiologyPlasma Membrane
The thin, selectively permeable phospholipid boundary that separates the inside of a cell from its surroundings.
🔬 Cell BiologyNucleus
The control centre of a eukaryotic cell, enclosed by a double membrane and containing the chromosomes.
🔬 Cell BiologyCytoplasm
The jelly-like fluid and suspended structures between the plasma membrane and nucleus where many reactions occur.
🔬 Cell BiologyMitochondrion
The organelle that produces most of the cell's ATP through aerobic respiration, often called the powerhouse.
🔬 Cell BiologyRibosome
A small particle of RNA and protein that assembles amino acids into polypeptides during translation.
🔬 Cell BiologyEndoplasmic Reticulum
A network of membrane tubes and sacs; the rough form makes proteins and the smooth form makes lipids.
🔬 Cell BiologyGolgi Apparatus
A stack of flattened membranes that modifies, sorts and packages proteins and lipids for secretion or delivery.
🔬 Cell BiologyLysosome
A vesicle filled with digestive enzymes that breaks down worn-out organelles, food particles and invaders.
🔬 Cell BiologyChloroplast
The green plant organelle containing chlorophyll where light energy is converted to chemical energy in photosynthesis.
🔬 Cell BiologyCell Wall
A rigid outer layer outside the plasma membrane in plants, fungi and bacteria that gives shape and protection.
🔬 Cell BiologyVacuole
A fluid-filled organelle that stores water and nutrients; very large and central in mature plant cells.
🔬 Cell BiologyCytoskeleton
A network of protein filaments that maintains cell shape, anchors organelles and enables movement.
🔬 Cell BiologyCell Size and Surface Area
Cells stay small because a high surface-area-to-volume ratio allows efficient exchange of materials with the environment.
🔬 Cell BiologyMicroscopy Basics
Light microscopes magnify living cells up to about 1000 times, while electron microscopes reveal fine internal detail.
🔬 Cell BiologyIntermediate topics (20)
Phospholipid Bilayer
Two layers of amphipathic lipids with hydrophilic heads outward and hydrophobic tails inward, forming the membrane core.
🔬 Cell BiologyFluid Mosaic Model
Describes the membrane as a flexible fluid bilayer in which proteins float and move laterally like a mosaic.
🔬 Cell BiologySimple Diffusion
Passive movement of small nonpolar molecules down their concentration gradient directly across the membrane.
🔬 Cell BiologyFacilitated Diffusion
Passive transport of ions and polar molecules down a gradient through channel or carrier proteins.
🔬 Cell BiologyOsmosis
The diffusion of water across a selectively permeable membrane from lower to higher solute concentration.
🔬 Cell BiologyActive Transport
Movement of substances against their gradient using energy, usually ATP, via carrier proteins called pumps.
🔬 Cell BiologySodium-Potassium Pump
An ATPase that moves three Na+ out and two K+ into the cell per ATP, maintaining the membrane potential.
🔬 Cell BiologyEndocytosis
The uptake of materials by folding the plasma membrane inward to form a vesicle inside the cell.
🔬 Cell BiologyExocytosis
Vesicles fuse with the plasma membrane to release their contents outside the cell.
🔬 Cell BiologyTonicity
Describes how an external solution affects cell volume: hypotonic causes swelling, hypertonic causes shrinking.
🔬 Cell BiologyCell Cycle
The ordered sequence of growth, DNA replication and division: G1, S, G2 and the mitotic phase.
🔬 Cell BiologyMitosis
Nuclear division that produces two genetically identical daughter nuclei with the same chromosome number as the parent.
🔬 Cell BiologyMeiosis
Two rounds of division that halve chromosome number to form genetically varied haploid gametes.
🔬 Cell BiologyCytokinesis
Division of the cytoplasm after nuclear division, by a cleavage furrow in animals or a cell plate in plants.
🔬 Cell BiologyCell Junctions
Tight junctions, desmosomes and gap junctions that seal, anchor or connect neighbouring animal cells.
🔬 Cell BiologyExtracellular Matrix
A network of collagen and glycoproteins outside animal cells that provides support and cell signalling cues.
🔬 Cell BiologyCell Signalling
Cells detect extracellular ligands with receptors and convert them into responses through signal transduction pathways.
🔬 Cell BiologyEndosymbiotic Theory
Proposes that mitochondria and chloroplasts arose from engulfed bacteria that became permanent cell residents.
🔬 Cell BiologyCell Differentiation
The process by which unspecialised cells switch on particular genes to become specialised cell types.
🔬 Cell BiologyStem Cells
Undifferentiated cells capable of self-renewal and of developing into specialised cell types.
🔬 Cell BiologyAdvanced topics (15)
Cyclin-Dependent Kinases
Enzymes activated by cyclins that phosphorylate target proteins to drive progression through cell cycle checkpoints.
🔬 Cell BiologyCell Cycle Checkpoints
Control points at G1/S, G2/M and metaphase that halt the cycle until DNA and spindle attachments are correct.
🔬 Cell BiologyApoptosis
Programmed cell death carried out by caspase enzymes, removing damaged or unneeded cells without inflammation.
🔬 Cell BiologyAutophagy
A recycling pathway in which cytoplasmic components are enclosed in autophagosomes and degraded by lysosomes.
🔬 Cell BiologyNuclear Pore Complex
A large protein assembly that gates the nuclear envelope, controlling traffic of RNA and proteins via importins.
🔬 Cell BiologySignal Recognition Particle
A ribonucleoprotein that guides ribosomes making secretory proteins to the endoplasmic reticulum membrane.
🔬 Cell BiologyVesicle Trafficking
Coat proteins and SNARE complexes sort, bud and fuse vesicles to move cargo between membrane compartments.
🔬 Cell BiologyReceptor Tyrosine Kinases
Surface receptors that dimerise on ligand binding and autophosphorylate, triggering cascades like the Ras-MAPK pathway.
🔬 Cell BiologyG Protein-Coupled Receptors
Seven-transmembrane receptors that activate G proteins to generate second messengers such as cAMP.
🔬 Cell BiologySecond Messengers
Small intracellular molecules such as cAMP, IP3 and Ca2+ that amplify and spread signals from receptors.
🔬 Cell BiologyMicrotubule Dynamics
Alternating growth and rapid shrinkage called dynamic instability lets tubulin polymers explore space and build the spindle.
🔬 Cell BiologyMotor Proteins
Kinesin, dynein and myosin convert ATP energy into directed movement along microtubules or actin filaments.
🔬 Cell BiologyCell Migration
Crawling movement driven by actin polymerisation at the leading edge, adhesion turnover and rear contraction.
🔬 Cell BiologyCancer Cell Biology
Mutations in oncogenes and tumour suppressors disrupt cycle control, apoptosis and adhesion, producing uncontrolled growth.
🔬 Cell BiologyTelomeres and Senescence
Shortening of chromosome end caps with each division eventually triggers permanent growth arrest called senescence.
🔬 Cell BiologyUse cases
- Medicine: Many diseases, from some cancers to mitochondrial disorders, begin with a fault in one cell component.
- Biotechnology: Cell culture and cell structure knowledge are used to make vaccines, insulin and other therapeutic proteins.
- Exam revision: Labelled diagrams of organelles and the cell cycle are among the most common questions in school and first-year university biology.
- Microscopy: Knowing what each organelle looks like helps you identify structures on stained slides and electron micrographs.
Frequently asked questions
How many topics are covered in Cell Biology?
Cell Biology has 52 topics on LearnViz: 17 Beginner, 20 Intermediate and 15 Advanced. Each one has its own page with an explanation, use cases, FAQs and related topics.
Where should a beginner start in Cell Biology?
Start with the Beginner topics, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell. Once those terms feel familiar, move on to the Intermediate topics.
What are the most advanced topics in Cell Biology?
The Advanced level includes Cyclin-Dependent Kinases, Cell Cycle Checkpoints, Apoptosis, Autophagy, Nuclear Pore Complex. Read the Beginner and Intermediate topics first, because the Advanced ones build on them.
Can I test my knowledge of Cell Biology?
Yes. The Cell Biology quiz asks questions generated from the topic explanations, and the timed tests on LearnViz cover the same material.
Do all cells have a nucleus?
No. Prokaryotes such as bacteria have no nucleus; their DNA sits in a region called the nucleoid. Mature mammalian red blood cells also lose their nucleus.
What is the easiest way to remember organelle functions?
Give each organelle one job: mitochondria make ATP, ribosomes make proteins and the Golgi apparatus packages them. Drawing a labelled cell from memory is a strong self-test.
How are plant cells different from animal cells?
Plant cells have a cell wall, chloroplasts and a large central vacuole, and most lack centrioles. Animal cells have none of the first three features and do have centrioles.