Worksheet for Activity 1: Estimating Sizes
Answers
Answers are indicated in bold green text
The symbol ~ is used to mean "approximately". Answers
slightly larger or smaller than these are equally valid. Remind
students that the point of this exercise is to get in the right ball
park, not to worry about absolute precision!
Image 1
1. Diameter of phage head? ~ 40 nm
2. Length of phage tail? ~ 100 nm
3. Overall size of this virus? ~ 140 nm
Image 2
1. Diameter of sperm tail A? ~ 200 nm
2. Diameter of a single microtubule C? ~ 20 nm
3. How many microtubules are found in the outer doublet
(near B)? nine pairs of 2 microtubules
4. How many microtubules are found in the center of the
tail (near C)? two unpaired microtubules
Image 3
1. How big is one lysozyme molecule? ~ 30 Angstroms
(averaging height and width)
Image 4
1. How long is a Cyclops? ~ 2.5 mm
Image 5
1. Diameter of a picornavirus? ~ 30 nm
2. Is this virus larger, the same size, or smaller than
bacteriophage lambda? slightly smaller (See your
answers to Image 1.)
Image 6
1. How big is an 80S ribosome (red)? ~ 35 nm
2. How big is a 70S ribosome (blue)? ~ 25 nm
Image 7
1. How big is a water molecule? ~ 2 A
2. How big is a hydrogen atom? ~ 1 A
Image 8
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2.
3.
4.
How large is an erythrocyte? ~ 9 µm
How large is a lymphocyte? ~ 10 µm
How large is the nucleus of a lymphocyte? ~ 9 µm
How large is a polymorphonuclear leukocyte? ~ 15 µm
Image 9
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2.
3.
4.
How large is the cell body of a neuron? ~ 25 µm
How large is the nucleus of a neuron? ~ 14 µm
How large is the nucleolus of a neuron? ~ 3 µm
What differences can you observe between a healthy
neuron and one from a patient with Alzheimer's disease?
The diseased neuron contains a large accumulation
of material adjacent to the nucleus (colored orange
in this computer rendition) not found in the normal
neuron. Other information not cited here identifies
this material as amyloid plaque.
Image 10
1. How large is this cell? ~ 30 µm
2. How long is an "average" F-actin filament bundle? ~ 10
µm (not easy to estimate)
3. The large clear circular area in the lower right portion of
the cell is the nucleus, not visible in this particular
technique but clearly outlined by filaments. How large is
the nucleus? ~ 10 µm
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