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Cell Structure and
Function
Robert Hook
• 1665 - Hook used a primitive microscope to
view cork. What he saw (cell walls) he
described as “cells” because they looked like
rooms in a monastery.
The Cell Theory (1835-1855)
Schleiden, Schwann, and Virchow
1. All living things are composed of cells.
2. Cells are the basic units of structure and
function in living things.
3. New cells are produced from existing cells.
Two categories of cells
• Eukaryotes (eu “true”; karyon “nucleus”) are
cells that have a nucleus.
• Prokaryotes (pro “before”) do not contain
nuclei.
• Nucleus – large membrane-enclosed structure
that contains the cell’s genetic material in the
form of DNA.
Comparison
Prokaryotes
• Smaller and simpler than eukaryotes
• Genetic material not contained in nucleus
• Carry out activities associated with living
things: grow, reproduce, respond to
environment and some move
• Example: bacteria
Eukaryotes
• Contain a nucleus in which their genetic
material is separated from the rest of the cell.
• Can be unicellular: amoeba, protozoa
• Can be multicellular: animals, plants, fungi
• Contain organelles – “little organs”
2 Parts of Eukaryotic Cell
• Nucleus and the cytoplasm
• Cytoplasm is the portion of the cell outside
the nucleus.
Nucleus
• Contains almost all DNA and with it the coded
instructions for making proteins and other
important molecules.
• Surrounded by nuclear envelope (double
membrane) dotted with nuclear pores; allows
movement of info into & out of nucleus
• Contains chromatin (granular material) – consists
of DNA bound to protein; cell divisions, forms
chromosomes: genetic info passed on
Ribosomes
• Formed in the nucleolus (small region of
nucleus)
• Very small dotlike structures
• Make proteins
Vacuoles
• Round membrane storage sac for holding
food, water, or waste
Mitochondria
• Double membrane structures, where cellular
respiration (the break down of sugar) occurs
to release energy
Chloroplast
• Double membrane structure, where
photosynthesis takes place (making of
carbohydrates or sugars), contains green
pigment called chlorophyll
Cell Membrane
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aka Plasma Membrane
Thin, flexible barrier that surrounds the cell
Regulates which molecules enter and leave
Provides protection and support
Cell Wall
• Rigid structure around cell, outside of cell
membrane
• Provides support and protection
• Plant cells: mostly cellulose