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Cell Types
Cell Theory
• Every living organism is made of one
or more cells
• The smallest organisms are made of
single cells while multicellular
organisms are made of many cells
• All cells arise from pre-existing cells
Cell Function Limits Cell Size
• most cells are small, ranging from 1 to 100
micrometers in diameter
• cells need to exchange nutrients and wastes with
the environment
• no part of the cell can be far away from the
external environment
• surface area to volume ratios must be kept rather
large
All Cells Share Common Features
• a plasma membrane encloses all cells and
regulates material flow in and out of the cell
• cytoplasm is the fluid interior where a cell’s
metabolic reactions occur (cytosol)
• DNA (deoxyribonucleic acid) is the hereditary
blueprint and RNA (ribonucleic acid) copies
DNA for protein production (universal genetic
code)
Two Basic Cell Types
Prokaryotic Cells (bacteria)
• DNA is in the form of circular loops and is free in the
cytoplasm
• cells contain no internal membranes and no organelles
except for ribosomes
Eukaryotic Cells (protists, fungi, animals, plants)
• DNA is linear, bound with histone proteins in structures
called chromosomes and housed in a central structure
called a nucleus
• cells contain complex internal membrane systems and
specialized organelles
‘Naked ring of DNA’
X
1 µm
Spherical (cocci)
2 µm
Rod-shaped (bacilli)
5 µm
Spiral
Making Scientific Illustrations
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Draw only on white, unlined paper.
One drawing per page. Draw large – but not off the edge of the
page.
Draw only in pencil.
Do not shade or color your drawings. Stay focused on FORM.
Use clean, unbroken lines. No artsy sketching.
Have a title, magnification, and appropriate labeling on each
drawing.
Draw only biological structures! Do not draw air bubbles, dust,
debris, and other irrelevant objects just because you see them.
Pay attention to detail. Draw less, draw big (fill the space),
draw carefully.