Student number__________ Grader number___________ Biol110-Cell Biology Spring 2010 Problem Set#1 ANSWER KEY  What gives cells their shape? (2 pts) Why do cells adopt different shapes? (1 pt) For example, why are neurons large and branched (1 pt) and why are lymphocytes (B and T cells) small? (1 pt) Answer: Cells are shaped by an internal cytoskeleton (1 pt), or by an external cell wall (1 pt). They adopt different shapes to specialize for a particular function (1 pt). For example, neurons need to be branched in order to communicate with many cells simultaneously (1 pt) via electrical signals and they are large to reach them over large distances (1 pt). Lymphocytes need to be small to be able to squeeze trough capillaries (1 pt) and/or between epidermal cells lining blood vessels (1 pt).  What two key cellular features distinguish prokaryotes from eukaryotes? (2 pt) Where do archeabacteria usually live (1 pt), and why did it take scientists so long to realize that they were evolutionarily distinct from eukaryotes and prokaryotes? (1 pt)
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