This work set the stage for several centuries of work on animal electricity culminating in our modern notions of the cellular membrane potential and propagating action potentials. In famed experiments like those shown in Figure 2, Luigi Galvani discovered that muscles in dead frogs could be stimulated to twitch by the application of an electrical shock. The mystery of nerve cells went beyond their intriguing morphology as a result of their connection with electrical conduction and muscle action. See Figure 1 for several examples of the drawings made by van Leeuwenhoek as a result of his observations with the early microscope. Already in the early days of microscopy, biological pioneers found these cells a fascinating object of study, with van Leeuwenhoek musing, “Often and not without pleasure, I have observed the structure of the nerves to be composed of very slender vessels of an indescribable fineness, running length-wise to form the nerve”. Nerve cells are among the most recognizable of human cell types, noted not only for their enormous size relative to many of their cellular counterparts, but also for their unique shapes as revealed by their sinuous and elongated structures. The drawing on the left shows a longitudinal view of nerves and the drawing on the right shows a cross-sectional view of a central nerve surrounded by five others (labeled with “G”). How many virions result from a single viral infection?įigure 1: Antoine van Leeuwenhoek’s 1719 drawings of nerve cells in a letter to a friend.How many photons does it take to make a cyanobacterium?.What is the permeability of the cell membrane?.How many ribosomal RNA gene copies are in the genome?.How many chromosome replications occur per generation?.How many cells are there in an organism?.A Quantitative Miscellany – Introduction.What is the error rate in transcription and translation?.What is the mutation rate during genome replication?.How genetically similar are two random people?.How many chromosomes are found in different organisms?.How quickly do different cells in the body replace themselves?.How long do the different stages of the cell cycle take?.How long does it take cells to copy their genomes?.How fast do molecular motors move on cytoskeletal filaments?.What are the rates of cytoskeleton assembly and disassembly?.What is the frequency of rotary molecular motors?.How fast are electrical signals propagated in cells?.How fast do proteasomes degrade proteins?.What is the maturation time for fluorescent proteins?.What is faster, transcription or translation?.What is the turnover time of metabolites?.How many ions pass through an ion channel per second?.What are the rates of membrane transporters?.How does temperature affect rates and affinities?.How many reactions do enzymes carry out each second?.What are the time scales for diffusion in cells?.How does metabolic rate scale with size?.What is the power consumption of a cell?.What is the electric potential difference across membranes?.What is the free energy released upon combustion of sugar?.What is the energy in transfer of a phosphate group?.How much energy is released in ATP hydrolysis?.What are the physical limits for detection by cells?.How much force is applied by cytoskeletal filaments?.What is the entropy cost when two molecules form a complex?.How much energy is carried by photons used in photosynthesis?.What is the energy scale associated with the hydrophobic effect?.What is the thermal energy scale and how is it relevant to biology?.How many rhodopsin molecules are in a rod cell?.What are the absolute numbers of signaling proteins?.What are the copy numbers of transcription factors?.What is the macromolecular composition of the cell?.What are the concentrations of cytoskeletal molecules?.How much cell-to-cell variability exists in protein expression?.What are the most abundant proteins in a cell?.What lipids are most abundant in membranes?.What are the concentrations of free metabolites in cells?.What are the concentrations of different ions in cells?.What is the concentration of bacterial cells in a saturated culture?.What quantities of nutrients need to be supplied in growth media?.What are environmental O2 and CO2 concentrations?.What is the elemental composition of a cell?.Concentrations and Absolute Numbers – Introduction.II: Concentrations and Absolute Numbers.What is the thickness of the cell membrane?.How big are the molecular machines of the central dogma?. Which is bigger, mRNA or the protein it codes for?.How big are biochemical nuts and bolts?.How big is the endoplasmic reticulum of cells?.What is the range of cell sizes and shapes?.
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