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What is a cell?
A cell is the smallest unit of life.
The cell theory states:
● All living things are made up of
cells
● Cells are the basic units of
structure and function in living things
● New cells are produced from
existing cells
CELL THEORY
1. The basic unit of life is the cell. (Hooke)
• In 1665, an English scientist
named Robert Hooke made
an improved microscope and
viewed thin slices of cork
viewing plant cell walls
• Hooke named what he saw
"cells"
CELL THEORY
2. All living things are made of 1 or more cells.
• Matthias Schleiden (botanist studying plants)
• Theodore Schwann (zoologist studying
animals) stated that all living things were
made of cells
Schwann
Schleiden
CELL THEORY
3. All cells divide & come from old cells. (Virchow)
Virchow
The different shapes of cells reflect
their different functions.
• The long extensions that
reach out in various
directions from the nerve
cell allows the cell to
send and receive nerve
impulses(messages)
• The flat, plate-like shape
of skin cells suits their
function of covering and
protecting the surface of
the body.
What limits cell size?
• Small cells can exchange
substances(oxygen, nutrients, and carbon
dioxide) more readily than larger cells
because small objects have a higher
surface area to volume ratio.
• So, the cells divide!
There are 2 kinds of cells:
•
Eukaryotes – Have
a nucleus
•
• Examples of
Examples of
prokaryotes are
eukaryotes are
bacteria
plants, animals,
fungus, and protists
•
More complicated
• Prokaryotes – Do
NOT have a nucleus
• Smaller than
eukaryotes
• Less complicated
Prokaryotic Cells
• No ______________
• No _________________________
• Examples: Bacteria
• Prokaryotic cells include the following
features:
– Smaller in size
– DNA in a nucleoid region
– Cell membrane
– Ribosomes
– Cell wall of peptidoglycan
Eukaryotic Cells
•
•
•
•
Have _____________________
Have _______________
Larger than Prokaryotic Cells
Examples:
– animal cells,
– plant cells,
– fungi cells and
– protist cells
Cells have specialized structures to
carry out functions. These are called
organelles.
Cell Organelles:
• Nucleus – command
center of the cell.
Contains the cell’s
genetic material in the
form of DNA. ONLY
FOUND IN
EUKARYOTES
• Cytoplasm – the “gel”
material inside the cell
membrane but not in
the nucleus. The
organelles live inside
the cytoplasm.
Cell Organelles:
•
Endoplasmic Recticulum (ER) – makes lipids, proteins and
other materials that are exported (taken out) of the cell.
•
Rough ER – part of the ER that makes proteins.
-Called “rough” because ribosomes are attached to the
surface and makes it look bumpy.
•
Smooth ER – part of the ER that makes lipids and
contains enzymes. Also plays a role in the detoxification
of drugs. Ex.) Liver cells play a key role in detoxifying
drugs, so they contain large amounts of Smooth ER.
-Called “smooth” because ribosomes are not attached to
the surface.
Cell Organelles:
• Ribosomes – small
particles of RNA and
protein found
throughout the
cytoplasm. They
produce proteins by
following instructions
that come from the
nucleus.
Cell Organelles:
•
Golgi Apparatus–
modifies, sorts and
packages the
proteins that come
from the Rough ER
and either stores
them or ships them
out of the cell.
• Lysosome – removes
waste from the cell.
Cell Organelles
• Vacuoles –
saclike
structures used
to store
materials such
as water, salts,
proteins, and
carbohydrates.
Cell Organelles
• Mitochondria –
converts food into
energy that the cell
can use. They are
the power centers of
the cell.
• Cytoskeleton –
supports the cell and
helps to maintain the
shape.
Cell Organelles
• Cell membrane –
regulates what
enters and leaves the
cell and also provides
protection and
support.
• Centriole-located near
the nucleus and helps
organize cell
division. Not found
in plant cells.
Cell Organelles
• Nuclear membranesurrounds the nucleus
and allows material to
move in and out of the
nucleus.
• Nucleolus- within the
nucleus, where the
assembly (making) of
ribosomes begin.
Cell Organelles:
• Chloroplasts – ONLY
FOUND IN PLANT
CELLS
- captures energy
from sunlight and
converts it into chemical
energy in plant cells.
• Cell Wall – ONLY
FOUND IN PLANT
CELLS
- provides support
and protection for the
plant cell.
• Peroxisomes—absorb nutrients, digest
fatty acids, and alcohol
-breakdown toxic hydrogen peroxide to
water