Anton van Leeuwenhoek (1632-1723) was the first to
adapt lenses to the study of living organisms.
He discovered microorganisms.
1665 – Robert Hooke
Observed chambers, dead plant
cells, in cork.
• Coined the term "cells” in 1665.
1833 - Robert Brown
• Studied the nucleus. Do all living cells
have a nucleus?
Human Cheek Cell
1838 - M.J. Schleiden
Discovered plants are
made of cells.
Elodea….Typical Plant Cell
1839 - T. Schwann
animals are made of
1855 - Rudolph Virchow
• “Omnis cellula e cellula”
“All cells are from other
researching cancer cells.
The Cell Theory
1. All living organisms are composed of one or more cells.
2. Cells are organisms' basic units of structure and function.
3. Cells come only from pre-existing cells.
How do you measure cells?
Cells are measured using “microns”.
A micron is another casual name for a
Note: 1.0 µ m = one millionth of a meter
What limits the size of a cell?
• Cell volume to surface area ratios favor
small size... an efficient amount of
materials must enter and leave the cell.
• Nucleus’ ability to control the cell is
limited by the size of the cell.
The Cell Membrane
AKA: Plasma Membrane
• Separates the cell from the
• Is “semi-permeable”…… regulates
the movement of materials in/out of
• ALL cells have a plasma membrane
• The Cytoplasm is an Area (not stuff)
between the plasma membrane and
the nuclear envelope. The cytoplasm
contains the cytosol, nucleus (if
present) and cell organelles.
• Semi-fluid portion of the cytoplasm (the
gooey stuff inside the cell)….
Composed mostly of water, nutrients.
• Most conspicuous organelle.
• usually spherical, but can be lobed or
irregular in shape.
• Typically found near the center of a
eukaryotic cell…..prokaryotes do not have a
• Control center for the cell.
• Contains the genetic instructions.
… the outer boundary of the
nucleus which gives the
shape to the nucleus.
• Dark area in the nucleus.
• 0 - 4 per nucleus.
• Storage area for ribosomes.
• DNA and Protein in a “loose” format
(stringy form of DNA) Will eventually
form the cell’s chromosomes. The DNA
holds the cell’s genetic information.
• Found in the nucleus of eukaryotes and
in the center region of prokaryotes.
The Cell Organelle
• Term means "small organ” Formed
body in a cell with a specialized
• Keeps various enzymes separated in
(bags of enzymes)
• Structure: made up of protein and RNA
• No membrane.
• Function: site of protein synthesis.
• Free in the cytosol…..make proteins for
use in cytosol.
• Attached to the Endoplasmic
Reticulum….. make proteins that are
exported from the cell.
• Often referred to as ER.
• Stacks of flattened stacks involved in
the production and transportation of
proteins, sugars, fats,…..etc
especially in cells
that export these
the cell. In liver
cells, the smooth
ER breaks down
toxins and drugs.
AKA Golgi bodies or Golgi Complex
• Structure: flattened sacs arranged in a
stack. (looks like a stack of Pita bread)
• 3 to 20 per cell.
• The Golgi Apparatus package and modify
proteins and lipids into vesicles (small,
spherical shaped sacs that bud from the
Golgi apparatus). The vesicles often merge
with the plasma membrane to release
contents to the outside of the cell.
• Vesicles from the Golgi apparatus
that contain digestive enzymes.
They breakdown food, cellular
debris and foreign invaders such
• Assist with cell death.
• Not present in plant cells.
• Organelles that breakdown various
substances. During digestion
0xygen is produced and combines
with H2O to form Hydrogen
Peroxide…. a toxin. Peroxisomes
break down Hydrogen Peroxide.
• Function: Site of Cellular Respiration – Cellular
Respiration is the release of energy from food to
form ATP…. All cells use ATP as their energy
• “Powerhouse” of the cell.
• Found in the cytosol.
• Have their own DNA. Can reproduce themselves.
• Function: Site of Photosynthesis - chloroplasts
use of light energy to make food, sugars, from
carbon dioxide and water.
• Contain the green pigment chlorophyll.
• Found in the Cytosol
• Have their own DNA. Can reproduce themselves.
Function: store plant pigments such as
chlorophyll (green) and carotene (orange, red).
• Found in plants only.
• Classified (named) by color….example:
• “Chloro” means green, therefore a
chloroplast is a green plastid that stores
• “Leuco” means white, therefore
Leucoplasts (AKA Amyloplasts) are
white plastids that store starch.
• Network of protein fibers and in the cytoplasm.
• Give Cells structure and shape.
• Involved in Cell movement.
• Cytoskeleton is composed of 2 different types of
fibers, which are organized in deceasing
Maintenance of cell shape.
Hold organelles in place.
• Responsible for Muscle contractions.
• Cytoplasmic streaming in plants, like
• Maintenance and changes in a cell’s shape.
Cilia and Flagella
Classified by their lengths and numbers
• Function - to move cells or to sweep
materials past a cell.
• Cilia - short, but numerous.
• Flagella - long, but few (usually only one).
• Usually one pair per cell, located close
to the nucleus.
• Found in animal cells only.
• Help in cell division.
• Same structure as a centriole.
• Found at the base of the cilia and
Plant Cell Walls
• All plant cells have a Primary Cell Wall.
• Some cells will develop a Secondary Cell
• Plant cell walls are made of cellulose
( a polysaccharide made of β -glucose).
• Fungi cell walls are made of chitin (a
• Function as the cell's exoskeleton for support and
• Thin layer rich in pectin (used to make
jelly) found between adjacent plant
• Glues cells together.
Vacuoles and Vesicles
Fluid-filled, membrane-bound bodies
3 Types of Vacuoles and Vesicles
• Food vacuoles
• Central water vacuoles
• Contractile vacuoles
The function of the vacuole depends
on the organism.
single-cell organisms …….“Food” vacuoles
store newly ingested food until the
lysosomes can digest it.
• “Contractile” vacuoles pump out excess
Comparing Plant Cells and
Have cell walls,
chloroplasts, and a
central water vacuole…
animal cells do not!!
Have lysosomes and
cells do not!!