Cell Biology By the Numbers


Course given on fall semester by Ron Milo, teaching fellow: Yinon Bar-On and Ron Sender

Mondays 11:15-13:00 @Belfer auditorium

Course email (to send exercises, suggestions, errors, insights...): cellbiologybythenumbers@gmail.com

Main reading resource: "Cell Biology by the Numbers" book

Vignettes that reveal how numbers serve as a sixth sense to understanding our cells

Course outline

Subject 1 (04/11/19): Quantitative reasoning in molecular and cell biology

Exercise 1 (due by 11/11/19)

A filmed version of the lecture from the class of 2014-15


Subject 2 (11/11/19): Size and mass

Exercise 2 (due by 18/11/19)

Slides from the lecture - photo gallery of sizes in cell biology

A filmed version of the lecture from the class of 2014-15


Subject 3 (18/11/19): Number of cells in the human body

Lecture slides


Subject 4 (25/11/19): Concentration and absolute numbers

Exercise 3 (due by 02/12/19)

Slides from the lecture - photo gallery of concentrations in cell biology

A filmed version of the lecture from the class of 2014-15


Subject 5 (02/12/19): The biomass distribution on Earth

Lecture slides


Subject 6 (09/12/19): Rates and durations

Exercise 4 (due by 16/12/19)

A filmed version of the lecture from the class of 2014-15 


Subject 7 (16/12/19): Energy, food, and humanity

Exercise 5 (due by 23/12/19)

General info on the final assignment 

Guidelines for the final assignment can be found in the following document:

Final course presentation format and execution


Oral presentation

  • 5 minutes with calculation on white board, 2 minute extension for extra aids/features (multi-answer question presented to class, object for demonstration etc.)
  • Pay attention to unit conversions, significant digits, big clear handwriting, keep it simple and elegant.
  • Assignment of dates will be posted soon!


Written vignette

  • 2-3 pages long, with introduction of the question, some background, the calculation, possible outcomes and interesting conclusions.
  • To be submitted (after feedback from class peers) 2 weeks after the oral presentation.


23/12/19  - Send us an email with your chosen subject as 1-2 lines for approval.
06/01/20 - Start of student presentation sessions.

Student presentation schedule

The student presentation schedule can be found in the following document:
  • If you can't make it to the date you are assigned to, please find someone to switch with and notify us of the change.
  • If you prefer a different email to receive feedback and comments to, let us know and we'll update the email address.

Course description and syllabus:

Over the past decades, biology has evolved rapidly from a descriptive, qualitative discipline to a more analytical, data-driven and quantitative one. Our ability to collect numbers that describe the most basic molecular processes within the cell has increased significantly, and simple calculations based on these data can provide important insights and enrich our scientific intuition.

This course is aimed at exposing students to the practice of making back of the envelope calculations (so called Fermi problems) with key numbers in biology, and its useful applications in research. We will learn how to identify the major factors that determine the order of magnitude of the results, when to allow simplification, how to calculate them efficiently, and how to avoid common pitfalls.

The course is composed of weekly lectures on different aspects of quantitative cell biology through many examples of basic (yet often surprising) questions:

- Size and geometry (e.g. What is larger, mRNA or the protein it codes for? How many cells are there in a human?)

- Concentrations and absolute numbers (e.g. What is the elemental and macromolecular composition of a cell? How many virions result from a single viral infection?)

- Energies and Forces (e.g. What is the power consumption of a cell? How much does protein synthesis take out of the entire energy budget of a cell?)

- Rates and durations (e.g. How long does it take cells to copy their genomes? What is faster, transcription or translation? What are the time scales for diffusion in cells?)

- Information and errors (e.g. What is the mutation rate during genome replication? What is the error rate in transcription and translation?)

The last few meetings of the course will be dedicated to presentations of student calculations as a final assignment.

Accompanying texts:

Course book is freely available at: bionumbers

Specific reading material will be given during the course.

* Those who did not take a molecular biology course should read the first few chapters of "Essential Cell Biology", Alberts et al, Garland Science

Other recommended readings (none compulsory, all for enrichment and fun):



Attendance and active participation is required.

50% - Weekly assignments

50% - Final assignment (presentation + written vignette)

Interesting links:

BioNumbers Database

BioNumber of the month

Key numbers in cell biology (with reference links)

Physical Biology of the cell at Caltech - Rob Phillips group

Order of Magnitude Physics course (Prof. Nir Shaviv, in hebrew)