Cells
Discovery of the Cell
We could not have discovered
the cell without the invention
of the microscope in the 17th
century
Robert Hooke (1635-1703)
1. Used a microscope to examine
cork, trees carrots, and ferns.
2. He saw little boxes that he
compared to the rooms that
monks live in: cells.
Anton van Leeuwenhoek
was the first person to observe live cells.
The Cell Theory:



All living things are composed of one or more cells
Cells are the basic unit of structure and function of all
living organisms
Cells come from other cells
Cell Diversity
Size

A nerve cell can extend all the ways down
a giraffe’s leg.

Most cells are not visible without a
microscope
Shape
•
•
cells have a variety
of shapes
Nerve cells have long
extensions, skin cells
are flat, and white
blood cells can
change their shape
Internal Organization
– Eukaryotic cells contain organelles that can
be compared to our organs.
– All cells have a cell membrane and genetic
information called DNA (called chromosomes
when compacted)
Prokaryotic vs. Eukaryotic
–
Prokaryotic cells: have a membrane
and DNA only. THEY HAVE NO
nucleus or organelles. EXAMPLE:
Bacteria
–
Eukaryotic cells: have a membrane,
DNA, and organelles. EXAMPLE:
plant, animal, fungi, and protist
cells
Parts of all cells


Cell membrane: surrounds and protects
the cell and selectively allows nutrients
in and waste out
(present in prokaryotes and eukaryotes)
Chromosomes
Compact DNA
 present in prokaryotes and eukaryotes

Organelles
Found
in
Eukaryotic Cells
only!
Nucleus
Stores hereditary information called DNA.
Synthesizes (makes) RNA and ribosomes.
Mitochondria

Transfers energy from organic compounds
to ATP (energy)
Muscle cell
Tumor cell
Ribosomes
Organizes the synthesis of proteins
 found in cytoplasm and on Rough ER

Endoplasmic Reticulum
prepares proteins for export
 Rough-packages proteins

Smooth-makes steroids
Golgi Apparatus

Processes and packages substances
made by cell.
Lysosome

digests waste (old molecules, organelles,
and foreign substance)
Cilia
short hair-like structures on the outside of
the cell present in large numbers that
assist in movement.
 Example: in respiratory system to keep
out foreign particles

Flagella
long hair-like structures that whip back
and forth to propel the cell forward.
 Example: sperm cell

PLANT CELLS ONLY
Cell Wall

supports and protects (plant cells only)
Chloroplast

use energy from the sun and convert it
into energy. (plant cells only)