Cell Structure
Discovery of the Cell
Scientists did not start using simple compound
microscopes until the mid 1600’s.
 Robert Hooke used an early compound microscope to
look at slices of cork.

http://www.smithlifescience.com/cork2.GIF


Hooke named the ‘seemingly empty’ chambers ‘cells.’
Around the same time, Anton von Leeuwenhoek was
using a single-lens microscope to observe unicellular
organisms in pond water for the first time.
Cell Theory
Additional observations of cells in other
living things led scientists to 3 basic
conclusions, known as the cell theory.
 Cell Theory states:

– All living things are composed of cells.
– Cells are the basic units of structure and
function in living things.
– New cells are produced from existing cells.
There are two categories of cells……

Prokaryotes
– No nucleus
– Few organelles
(no membranebound
organelles)
– Small in size
http://www.cod.edu/people/faculty/fancher/ProkaryoticCell.jpg
– Ex: Bacteria

Eukaryotes
– Nucleus
– Many membranebound organelles
– Large in size
– Ex: Humans, plants,
fungi, etc.
http://www.cod.edu/people/faculty/fancher/EukaryoticCell.jpg
Cell Structure
All cells, both prokaryotes and eukaryotes,
have DNA and a cell membrane.
 Cells also contain organelles – specialized
structures within the cell that perform
certain tasks.
 These organelles float around in the cell’s
cytoplasm, which is mostly made of water.

Prokaryotes…….they’re simple.

Prokaryotes only have a
few basic structures:
– DNA
– Cell/plasma membrane
– Cell wall
– Ribosomes
– Some use structures like pili,
cilia, and flagellum to move
in aquatic environments.
 ….but
they come in
many varieties.
http://scienceblogs.com/clock/2006/11/cell_structure.php
Eukaryotes are more complex.
Eukaryotes can be multicellular or
unicellular.
 Eukaryotes contain many organelles…….

Cell Organelles?
Cell (plasma) membrane

Regulates what enters and leaves the cell.
Nucleus

Controls most cell processes and contains nearly all of
the cell’s DNA
Ribosomes

assemble proteins.
– Some are free floating
while others are
attached to the
endoplasmic
reticulum.
Endoplasmic Reticulum (ER)

There are two types:
– Rough – chemically
modifies proteins that are
produced by the ribosomes
on its surface.
– Smooth – contains
specialized enzymes and
makes lipid components for
the cell membrane.
Golgi apparatus

Sorts, modifies, and packages proteins and other
materials from the ER for storage or secretion
from the cell.
Lysosomes and peroxisomes


Lysosomes contain enzymes that are specialized to
digest lipids, carbs, proteins so they can be reused
Peroxisomes contain enzymes that are specialized to
digest toxic substances
Cytoskeleton
http://scienceblogs.com/clock/2006/11/cell_structure.php

A network of protein filaments (microtubules
and microfilaments) that help the cell move and
maintain its shape
Mitochondria

Provides the cell with usable chemical energy
– It is the site of cellular respiration.
Mitochondria Cont.

Contains many folds which increase
surface area for cellular respiration
reactions
How are Cells different?
http://staff.tuhsd.k12.az.us/gfoster/standard/BCELL1_files/image005.jpg
http://scienceblogs.com/clock/2006/11/cell_structure.php
Plant cells have special features…..

Plants contain:
– Chloroplasts – create and store usable
energy through the process of
photosynthesis.
– Cell wall – provides the cell with rigid
structure.
– No Lysosomes
– One large vacuole – used for the storage of
water and some other materials
 Animal cells usually have many small vacuoles
Plant Cell
Animal Cell
http://micro.magnet.fsu.edu/cells/chloroplasts/images/chloroplastsfigure1.jpg
http://en.citizendium.org/images/c/c7/MitochondriaSMALL2.jpg