Number of cells in the human body
M
100 kg
N
M =
m
V
1000 – 10,000 µm3
m
10–12 – 10–11 kg
100 kg
10–12 – 10–11 kg
= 1013 – 1014
Number of chromosome replications (r) occurring per generation in humans
1013 – 1014 cells
1016 divisions in lifetime
three idealized scenarios:
binary tree divisions
hybrid scenario
2r = 1016
(log2(10) 3.3)
binary
tree
stage
theoretical number
chromosome
replications
per generation
r 1016
1 kg of stem cells
r 40
r 50
one stem cell divisions
2r = 1012 cells
terminal
differentiation
stage
x 104 giving a total of 1016 cells
r 40 + 104 104
How many rRNA genes are needed?
200,000 ribosomes
cell cycle 100 min 6000 s
Vpolymerase
footprint
40 bases
10–20
bases
s
30
ribosomes
s
dozens of
gene repeats
needed
max
rRNA
production ≤ 1 s
rate
Leakage time scale through membrane (rapid if small molecule is uncharged—e.g., glycerol)
concentration cout
permeability
volume V
concentration cin
flux =
number
area × s
total amount lost = p × (cin–cout) × A
area
A
flux
leakage time scale, τ
τ=
number of molecules inside
amount lost each second
=
V × cin
=
p × A × (cin–cout)
cin × 4 πr 3
3
r
=
3p
cin × p × 4πr 2
assume
cout = 0
for glycerol in E. coli
bacterial cell size
r
3p
10–6 m
1
×
3 4x10–8 m
s
glycerol permeability
10 s
so if the similar glyceraldehyde used in glycolysis was
not phosphorylated it would rapidly leak from cell
total
area
Number of photons needed to make a cyanobacterium
volume
1 µm3
CO2 + H2O + n x h ν
1010 carbon atoms per cyanobacterium
1011
n
photons
cyanobacterium
CH2O + O2
10 photons per carbon atom
Fraction of cell volume occupied by bursting virions
total virions fraction of host cell volume =
D
Bx d
B = burst size
e.g.:
SIV in T cell
T phage in E. coli
D (µm)
10
1
d (µm)
0.1
0.05
d3 x B
D3
B
50,000
200
fraction
5%
2%
bone marrow cells 2.4%
hepatocytes 0.8%
adipocytes 0.2%
lymphocytes 1.6%
platelets 4.7%
erythrocytes, 84%
26±3×1012 of 31±6×1012
total human cell count
epidermal
cells 0.4%
dermal
fibroblasts 0.6%
bronchial
endothelial
cells 0.5%
vascular
endothelial
cells 1.9%
muscle cells other respiratory
0.0003% 2% interstitial cells 0.4%
(A)
(B)
number of fat cells
(×109 cells)
obese
80
60
40
lean
20
0
0
10
20
30
40
age (years)
50
60
fat cell volume (fL)
1,200,000
1,000,000
800,000
600,000
400,000
200,000
0
0
20
40
60
80
body fat mass (kg)
100
120
zygote
germline
gut
pharynx and neurons
muscle
time
epidermis
vulva
somatic gonad
early
(B)
origin
middle
late
terminus
frequency of rRNA genes (%)
(A)
(C)
60
origin
40
E. coli
K–12
20
terminus
0
location
on genome
nucleoli
microtubules
nucleus
≈10 µm
HCO3– glycerol
sucrose
glucose
Cl–
+
+
Na K
fructose
–5
10
–3
10
increasing permeability
tryptophan
10
–1
10
1
H 2O
urea
indole
10
3
NH3
10
CO2
O2
5
permeability coefficient (nm/s)
(A)
(B)
20 nm
empty capsids following infection
nascent viruses
1 µm
organism
nematode C. elegans
D. melanogaster
Arabidopsis thaliana
mouse
human
number of chromosome
replications leading to:
male sperm
female ovum/ovule
8
34–39
10
36
62
40–1000
[age range 15–50]
25
23
BNID
105572
103523
106749
105576
105574,
105585
organism
human
D. melanogaster
C. elegans
C. elegans
C. elegans
stage in life cycle or organ
adult
embryo cycle 14
adult male (somatic)
adult hermaphrodite (somatic)
hatched larvae
estimated cell count
3.7±0.8×1013
6000 (nuclei)
1031
959
558
BNID
109716
106463
100582
100581
101366
virus
host cell used
influenza A & B
influenza A
HIV
SIV (model for HIV)
chicken egg cells
MDCK cell line
H. sapiens memory T cells
R. macaque T cells
prokaryotic host
cyanomyovirus S-PM2
podovirus P60
cyanomyovirus MA-LMM01
bacteriophage S1
bacteriophage S3
phi EF24C
bacteriophage Lambda
bacteriophage T1 to T7
bacteriophage MS2
Synechococcus WH7803
Synechococcus WH7803
M. aeruginosa
Stenotrophomonas sp.
Stenotrophomonas sp.
E. faecalis
E. coli
E. coli
E. coli
burst size
BNID
multicellular host
500–1000
1000–10,000
1000–3000
40,000–60,000
101590
101605
105872
102377
40
80
50–120
80
100
100
150
100–300
5000–10,000
104841
104842
103247
104855
104852
104857
105025
105870
109050