• 12 parts
  • Checked October 2026

Diagram of a Human Red Blood Cell, Cut in Half

A detailed diagram of a red blood cell: one cut in half, one hemoglobin molecule, and a frog's cell.

Diagram of a Human Red Blood Cell, Cut in Half

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1 2 3 4 5 6 7 8 9 10 11 12
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Write the name of each numbered part.Answer key

  1. Cell membrane
  2. Hemoglobin
  3. Rim
  4. Center
  5. Heme
  6. Iron atom
  7. Alpha chain
  8. Beta chain
  9. Oxygen molecule
  10. Nucleus
  11. Frog red blood cell
  12. Human red blood cell

Drawn for this site on 2026-10-01 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: every kind of blood cell on a smear

All 12 parts on the diagram

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The cell 4

  1. Cell membrane The thin sack that holds the hemoglobin in.
  2. Hemoglobin The protein that fills the cell and carries oxygen.
  3. Rim The thick outer edge of the disc.
  4. Center The thin middle, dished in on both sides.

Hemoglobin 5

  1. Heme A flat ring that holds iron. Each chain carries one.
  2. Iron atom Sits at the center of each heme. It binds oxygen.
  3. Alpha chain One of the two alpha-globin chains of the molecule.
  4. Beta chain One of the two beta-globin chains of the molecule.
  5. Oxygen molecule Two oxygen atoms, held on the iron of one heme.

Frog cell 3

  1. Nucleus A frog's red blood cell keeps its nucleus.
  2. Frog red blood cell Large and oval, with a nucleus in the middle.
  3. Human red blood cell Smaller and round, with no nucleus.

How this list was compiled: Every name checked on 2026-10-02 and kept only where two of these use it. (1) Wikipedia, Red blood cell and Hemoglobin, text only, https://en.wikipedia.org/wiki/Red_blood_cell and https://en.wikipedia.org/wiki/Hemoglobin : a biconcave disk, sunk in the center, dumbbell-shaped in cross section, with a rim on its edge; no nucleus in the mature human cell; a plasma membrane as the sack, the cytoplasm rich in hemoglobin; mammal red cells without nuclei and smaller than those of most other vertebrates; hemoglobin of four subunits, two alpha and two beta, each with a heme group whose iron atom can bind one oxygen molecule. (2) Gray's Anatomy (1918), The Blood, https://www.bartleby.com/107/134.html : circular disks, biconcave in profile, with no nucleus and a central part; the hemoglobin held within an envelope or membrane. (3) MedlinePlus Genetics (US National Library of Medicine), HBB gene, https://medlineplus.gov/genetics/gene/hbb/ : four protein subunits, two of beta-globin and two of alpha-globin, each bound to an iron-containing heme; the iron in the center of each heme can bind one oxygen molecule. (4) University of Rochester Medical Center, What Are Red Blood Cells?, https://www.urmc.rochester.edu/encyclopedia/content?ContentID=34&ContentTypeID=160 : round with a flattish, indented center; hemoglobin is the protein inside. (5) James Tyson, An Introduction to the Study of Practical Histology (1873), https://archive.org/details/61220700R.nlm.nih.gov : the nucleated oval corpuscles of the frog; the center and the periphery of the human disk. (6) William Narramore, Preliminary Physiology (1910), https://archive.org/details/b28053874 : in the frog's blood the red corpuscles are large, oval, nucleated cells. (7) L. B. Arey, The Normal Shape of the Mammalian Red Blood Corpuscle, The American Journal of Anatomy, volume 22 (1917), https://archive.org/details/americanjournalo22wist : the thin center and the thick rim of the disk. (8) RCSB Protein Data Bank, PDB-101, Molecule of the Month: Hemoglobin, https://pdb101.rcsb.org/motm/41 : four protein chains, two alpha and two beta, each with a ring-like heme group that holds an iron atom; oxygen binds to the iron atoms. (9) National Heart, Lung, and Blood Institute (NIH), https://www.nhlbi.nih.gov/health/thalassemia/causes : hemoglobin is made of two kinds of protein chains, called alpha globin and beta globin. Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work

How it works

This diagram of a human red blood cell shows one whole cell and one cut in half. Two more views open a hemoglobin molecule and set a frog's cell beside the human one. Read the names, then press Quiz me.

Read the full guide

Inside a red blood cell diagram

In this human red blood cell diagram labeled from the outside in, the cell is a round disc with a thick rim and a thin center, dished on both sides. A cell membrane wraps it, and hemoglobin fills it. The mature cell has no nucleus.

Hemoglobin and the frog

The second view turns the hemoglobin red blood cell diagram into one molecule: four chains, two alpha and two beta. Each holds a heme, and the iron at its center can bind one oxygen molecule. The third view is a frog blood cell diagram beside the human cell: the frog's cell is large and oval and keeps its nucleus.

  • Erythrocyte is the textbook word for a red blood cell. The quiz accepts it.
  • The lobes show which chain is which, not the real fold of the protein.

Questions and answers

Does a human red blood cell have a nucleus?

No. A mature human red blood cell has no nucleus. It loses the nucleus as it develops, which leaves more room for hemoglobin.

What shape is a red blood cell?

A biconcave disc: round, flat and dished in on both sides, so the center is thin and the rim is thick. Cut in half, it has the outline of a dumbbell.

What is hemoglobin made of?

Four protein chains, in adults usually two alpha and two beta. Each chain holds a heme, and the iron at the center of each heme can bind one oxygen molecule.

How is a frog's red blood cell different from a human one?

A frog's red blood cell is large and oval, and it has a nucleus. A human red blood cell is smaller and round, and it has no nucleus.

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