8 interactive concept widgets for Cell: The Unit of Life. Drag any slider, change any number, and watch the formula and the answer update live. Built so you understand how each NEET problem actually works, not just the final number.
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Compare every NEET-tested difference between prokaryotic and eukaryotic cells: nucleus, ribosomes, organelles, DNA, mesosome, and more.
Switch between the two cell types to see every difference NEET tests.
| Feature | Prokaryote | Eukaryote |
|---|---|---|
| Nuclear membrane★ | Absent | Present |
| Membrane-bound organelles★ | Absent | Present |
| Ribosome type★ | 70S (50S + 30S) | 80S (60S + 40S) |
| Cell size | 1–10 µm (smaller) | 10–100 µm (larger) |
| DNA form★ | Circular, no histone | Linear, with histones |
| Cell wall | Peptidoglycan (bacteria) | Cellulose (plants) / Absent (animals) |
| Nucleoid / Nucleus★ | Nucleoid (no membrane) | True nucleus |
| Plasmid | Present | Absent (usually) |
| Mesosome★ | Present | Absent |
| Mitosis / Meiosis | Absent (binary fission) | Present |
| Pili / Fimbriae | Present | Absent |
| Examples | Bacteria, Cyanobacteria (BGA) | Plant, Animal, Fungi, Protista cells |
★ = high-frequency NEET comparison point
Prokaryotic examples
Escherichia coli
Gram-negative bacterium, common in gut
Streptococcus
Spherical bacteria (cocci), cause throat infections
Nostoc
Cyanobacterium (blue-green alga), fixes nitrogen
Mycoplasma
Smallest known cell; NO cell wall; PPLO
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Click each membrane component (phospholipid bilayer, integral proteins, peripheral proteins, cholesterol, glycoproteins) to see its structure and NEET significance.
Click each component to learn its structure and NEET importance.
Phospholipid bilayer
Two layers of phospholipid molecules. Each molecule has a hydrophilic (water-loving) head and two hydrophobic (water-fearing) fatty acid tails. The heads face outward (toward water); the tails face inward (away from water). This creates a stable bilayer.
NEET focus: The bilayer arrangement (heads out, tails in) is responsible for the "fluid" nature of the membrane. Phospholipids can move laterally within each layer.
Key facts for NEET
•
Proposed by Singer and Nicolson in 1972
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"Fluid" = phospholipids move laterally within each layer
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"Mosaic" = proteins scattered like tiles in a mosaic
•
Earlier model: Danielli-Davson sandwich model (1935): protein-lipid-protein
•
Membrane thickness: approximately 7.5–10 nm
•
Selectively permeable: small nonpolar molecules (O2, CO2) pass freely; ions and large polar molecules need transport proteins
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Switch between plant and animal cells, then click any organelle to see its structure, function, and NEET focus. Covers nucleus, mitochondria, ER, Golgi, chloroplast, vacuole, centriole, and more.
Switch cell type, then click any organelle to see its structure, function and NEET focus.
NucleusPlant + Animal
FUNCTION
Controls cell activities. Contains hereditary information (DNA). Site of DNA replication and RNA transcription.
STRUCTURE
Nuclear envelope (double membrane, nuclear pores), nucleoplasm, chromatin (euchromatin + heterochromatin), nucleolus (rRNA synthesis).
NEET focus: Mature RBCs (erythrocytes) in mammals: NO nucleus. Nucleolus disappears during cell division. Euchromatin = light staining, active; heterochromatin = dark, inactive.
Plant cell has but animal cell lacks:
Cell wall, chloroplasts, large central vacuole, plasmodesmata, plastids
Animal cell has but plant cell lacks:
Centrioles, lysosomes (generally), small/absent vacuoles
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Follow the flow: RER synthesizes proteins, vesicles go to Golgi, Golgi modifies and sorts, trans face releases lysosomes and secretory vesicles. Understand what is and is not part of the system.
Click each station to understand how proteins and lipids travel through the endomembrane network.
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Rough ER (RER)
Rough ER has ribosomes attached to its cytoplasmic face, giving it a "rough" texture under electron microscopy. It synthesizes proteins that will be secreted from the cell, inserted into the plasma membrane, or targeted to the Golgi apparatus or lysosomes. Proteins enter the ER lumen as they are synthesized (cotranslational translocation) and undergo initial folding and glycosylation.
NEET focus: RER = ribosomes on surface + protein synthesis. Ribosomes on RER are 80S. Outer nuclear envelope membrane is continuous with RER. "Rough" because of ribosomes.
NOT part of endomembrane system:
Mitochondria:
Has own DNA and 70S ribosomes; semi-autonomous. Origin: endosymbiotic.
Chloroplast:
Has own DNA and 70S ribosomes; semi-autonomous. Origin: endosymbiotic.
Peroxisomes:
Not derived from ER or Golgi; originate by division of pre-existing peroxisomes.
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Explore internal structure of both organelles (cristae vs thylakoids, matrix vs stroma, F0-F1 particles vs photosystems) and compare them side-by-side.
Compare both organelles and explore their internal structures. Both are semi-autonomous and have 70S ribosomes.
Mitochondria structure: click any part
Side-by-side comparison
| Feature | Mitochondria | Chloroplast |
|---|---|---|
| Found in | All eukaryotic cells (plant + animal) | Plant cells and algae only |
| Function | ATP synthesis (cellular respiration) | Photosynthesis |
| Inner membrane feature | Cristae (infoldings) | Thylakoids stacked into grana |
| Internal fluid | Matrix (inside inner membrane) | Stroma (around thylakoids) |
| Key enzyme complex | F0-F1 ATPase on inner membrane | Photosystems I and II in thylakoid |
| DNA type | Circular (naked, no histone) | Circular (naked, no histone) |
| Ribosome type | 70S (50S + 30S) | 70S (50S + 30S) |
| Autonomous? | Semi-autonomous | Semi-autonomous |
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See the exact subunit composition of 70S and 80S ribosomes, where each type is found, and why Svedberg units are not additive.
Switch between 70S and 80S to see subunit composition, locations, and why Svedberg units are not additive.
50S
30S
= 70S
Large subunit: 50S
rRNA: 23S + 5S
Proteins: ~34
Small subunit: 30S
rRNA: 16S
Proteins: ~21
70S ribosome: key facts
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Found in: prokaryotes (bacteria), mitochondria, chloroplasts
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Large subunit: 50S (contains 23S rRNA + 5S rRNA + ~34 proteins)
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Small subunit: 30S (contains 16S rRNA + ~21 proteins)
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50 + 30 = 70S (NOT 80): S units are not additive
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Antibiotics that target 70S: streptomycin, erythromycin, chloramphenicol
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This is why antibiotics kill bacteria but NOT our cells (our cytoplasmic ribosomes are 80S)
Where each type is found:
Why S units are NOT additive:
Svedberg units (S) measure the sedimentation rate in a centrifuge. The rate depends on mass, shape, AND density. When two subunits combine, the resulting particle has a different shape and hydrodynamic properties, so its S value is NOT the sum of the two subunits. That is why 50S + 30S = 70S (not 80S), and 60S + 40S = 80S (not 100S).
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Click each nuclear component in the diagram to learn its structure (double membrane, nuclear pores, nucleolus rRNA synthesis, euchromatin vs heterochromatin) and NEET importance.
Click each nuclear component to explore its structure and NEET significance.
Nuclear envelope
The nuclear envelope consists of two concentric unit membranes separated by a perinuclear space (10-50 nm wide). The outer membrane faces the cytoplasm and is continuous with the rough ER membrane (studded with ribosomes). The inner membrane faces the nucleus. Together they form a double-layered boundary around the nucleus.
NEET focus: Nuclear envelope = double membrane. Outer membrane is continuous with RER. This means the perinuclear space is continuous with the ER lumen. Absent in prokaryotes.
Cells with no nucleus (enucleate):
Mature mammalian RBC (red blood cell):
No nucleus, no mitochondria
Sieve tube elements (phloem):
Lose nucleus at maturity; alive but enucleate
Prokaryotic cells (bacteria):
No nucleus: genetic material in nucleoid
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Scored quiz covering all cell topics: ribosome types, fluid mosaic model, endomembrane system, organelle identification, chromatin, centrioles, and nucleus.
Question 1 of 12 · Topic: Ribosome
The 50S + 30S subunits combine to form a ribosome of:
A.
80S
B.
70S
C.
100S
D.
60S
0 answered
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