Download All organisms -living things are made of cells. These cells are like

All organisms -living
things are made of cells.
Cells do the jobs that
keep organisms alive.
Cells
Cells are the smallest
part of a living thing.
These cells are like
tiny building
blocks.
Discovery of Cells
• The invention of the lens
• Robert Hooke (1665): observed a
thin slice of cork (dead plant cells)
with a microscope. He described
what he observed as “little boxes”
(cells).
Discovery of Cells
• Antonie van Leeuwenhoek (1675) Dutch tradesman
and scientist was the first person to observe living cells.
Handcrafted microscope
The Cell Theory
• Who developed the cell theory?
– Matthias Schleiden (1838): concluded
that all plants are composed of cells
– Theodor Schwann (1839): concluded
that all animals are composed of cells
– Rudolph Virchow (1855): determined
that cells come only from other cells
Cell Theory
• All living things composed of cells
• Cells are the basic unit of structure
and function in living things
• New cells are produced from
existing cells
Microscopes
• Magnification: refers to the microscope’s
power to increase an object’s apparent size
• Resolution: refers to the microscope’s
power to show detail clearly
Observing Cells
• Light microscope
– Can observe living cells in true color
– Magnification of up to ~1000x
– Resolution ~ 0.2 microns – 0.5 microns
Observing Cells
• Electron Microscopes
– Preparation needed kills the cells
– Images are black and white – may be colorized
– Magnification up to ~100,000 times
2D or 3D images
Blood cells
Cell Diversity- Size
Smallest Cells: Bacterium 2-10 micro meters
Biggest Cells:
Ostrich egg
6 inches long, 5 inches wide, 3 pounds
Longest Cells:
Giraffe nerve cell is up to 2 m
Cell Diversity- Shape
• Cells differ widely in shape.
• Most cells are roughly cuboidal
or spherical.
Cell Diversity- Internal Organization
• Nucleus: contains DNA which directs the activity of the cell
• Organelle: a cell component that performs specific functions
in the cell
• Eukaryotes: cells that contain a nucleus and membranebound organelles
• Prokaryotes: cells that lack nuclei and membrane-bound
organelles
Why Are Cells So Small?
• Cells need sufficient surface area to allow
adequate transport of nutrients in and wastes out.
• As cell volume increases, so does the need for
the transporting of nutrients and wastes.
Why Are Cells So Small?
• However, as cell volume increases the surface
area of the cell does not expand as quickly.
– If the cell’s volume gets too large it cannot
transport enough wastes out or nutrients in.
• Thus, surface area limits cell volume/size.
Why Are Cells So Small?
• Strategies for increasing surface area, so
cell can be larger:
– “Frilly” edged…….
– Long and narrow…..
• Round cells will always be small.
Cell:
• Organisms that do not have a distinct nucleus—
prokaryotic (PRO = NO)
Ex: bacteria
• Organisms with cells that have true nucleus and
organelles—eukaryotic (EU = TRUE)
Ex: plants, animals, fungi
Nucleus—control center of the cell
Double membrane that surrounds the nucleus—
nuclear membrane
• Hereditary information inside the nucleus—
chromatin (DNA)