surrounded by a protein coat.
A virus is a non-cellular structure consisting of DNA or RNA surrounded
by a protein coat.
1.1.3 1 State that all cells are formed from other cells.
All cells are formed from other cells.
1.1.4 3 Explain three advantages of using light microscopes.
Light microscopes (LMs) were first used by Renaissance scientists, as
Topic: 1 – Cells
Sub-topic: 1.1 – Cell Theory
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well as the microscopes you are likely to use in the laboratory. Visible
light is passed through the specimen and through the glass lenses. Light
microscopes can magnify correctly to about 1000 times the size of the
actual specimen; in which the greater magnification decreases blurriness.
1.1.5 2 Outline the advantages of using electron microscopes.
The electron microscope focuses a beam of electrons through the
specimen. Resolving power is inversely related to the wavelength of
radiation a microscope uses, and electron beams have wavelengths much
shorter than the wavelengths of visible light. Most modern electron
microscopes can theoretically achieve a resolution of about 0.1
nanometers, but the limit for biological structures is generally only two
nanometers. The cell ultrastructure refers to a cell's anatomy as resolved
by an electron microscope.
1.1.6 1 Define organelle.
Organelles are subcellular structures that are too small to be resolved by
the light microscope.
1.1.7 2 Compare the relative sizes of molecules, cell membrane thickness, viruses,
bacteria organelles, and cells, using appropriate SI unites.
Eukaryotic cell 10-100
Nucleus 10-20
Chloroplast 2-10
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Sub-topic: 1.1 – Cell Theory
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Mitochondria 0.5-5
Prokaryotic cell 1-5
HIV virus 100 nm
Ribosome 25nm
Cell membrane 7.5-8 nm thick
DNA strand 2 nm in diameter
Small molecules 1 nm
H atom 0.1 nm
Bacteria 5-.1
1.1.8 2 Calculate linear magnification of drawings.
1 meter= 1000 millimeters (mm)
1 mm= 1000 micrometers (um)
1 um= 1000 nanometers (nm)
1.1.9 3 Explain the importance of the surface to volume ration as a factor limiting
cell size.
Size is a general feature of cell structure that relates to function. The
logistics of carrying out metabolism set limits on the size range of cells.
Bacteria called mycoplasmas are probably the smallest packages with
enough DNA to program metabolism and enough enzymes and other
cellular equipment to carry out the activities necessary for a cell to
sustain itself and reproduce. Metabolic requirements also impose upper
limits on the size increases in size, its volume grows proportionally more
than the other surface area. Area is proportional to a linear dimension
squared, where as volume is proportional to the linear dimension cubed.
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Sub-topic: 1.1 – Cell Theory
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For objects of the same shape, the smaller the object, the greater its ratio
of surface area to volume. There are different kinds of cells: three
dimensional, cuboidal, and thin and flat.
1.1.10 1 State that unicellular organisms carry out all the functions of life.
Unicellular organisms carry out all the functions of life.
1.1.11 3 Explain that all cells in multicellular organisms differentiate to carry out
specialized functions by expressing some of their genes but not others.
The cells of multicellular organisms must continually turn certain genes on
and off in response to signals from their external and internal
environments. Also, gene _expression must be controlled on a long-term
basis for cellular differentiation. Highly specialized cells, such as those of
muscle or nerve tissue, express only a tiny fraction of their genes. A
typical human cell expresses only 3-5% of its genes at any given time.
1.1.12 1 Define tissue, organ, and organ systems.
A Tissue is an integrated group of cells with a common structure and
function. An organ is a specialized center of body function composed of
several different types of tissues. An organ system is a specialized center
of body function composed of several different types of organs.
