Do Now –
How do you think
things get in and out
of a cell membrane?
The cell theory states:
1. All living things are composed of cells.
2. Cells are the basic unit of structure and function
in living things.
3. All cells arise from pre-existing cells.
The cell theory is a widely accepted explanation of
the relationship between cells and living things.
It holds true for all living things, no matter how big
or small, or how simple or complex.
BUT…..
Recent discoveries have led
scientists to identify several
exceptions to the cell theory.
EXCEPTION #1
Mitochondria and chloroplasts, which are cell parts,
contain genetic material (DNA) and can duplicate
themselves inside living cells.
EXCEPTION #2
A virus is not a cell.
A virus can reproduce inside a living host cell,
but outside the cell, it shows no sign of life.
flu virus
EXCEPTION #3
The first living cells on earth must have
developed from non-cellular material.
What are the ORGANELLES
Cells contain a variety
of small structures
that perform specific
functions.
PROKARYOTIC CELLS
do not contain any
membrane-bound internal organelles.
EUKARYOTIC CELLS
contain many different
membrane-bound internal organelles.
Plant cells and animal cells have some differences
in the organelles they contain.
PLASMA MEMBRANE
The cell membrane, or PLASMA MEMBRANE,
surrounds the cell and separates the cell contents
from the environment.
plasma membrane
A living cell disposes of waste products and
exchanges materials and with its environment
across its cell membrane.
The membrane is made of a double lipid layer
in which large protein molecules float.
LIPIDS
PROTEINS
http://www.youtube.com/watch?v=PnhcjEjvbrw
The cell membrane is
SEMI-PERMEABLE.
Some substances can pass
through it,
while others cannot.
The membrane
regulates the passage
of materials into and
out of the cell.
The CELL MEMBRANE PROTEINS perform
a variety of functions.
TRANSPORTERS
These proteins help to carry
materials through the
plasma membrane.
Otherwise, transport
across the membrane is
often impossible or too
difficult to support life.
ANCHORS
These proteins help to physically support
cells and keep them connected together.
RECEPTORS
These proteins pick up
signals from other cells and
relay the message to the inside.
ENZYMES
These proteins control the
chemical reactions that occur
inside the cell.