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Cells
 All
cells have two
characteristics in
common


Surrounded by a cell
membrane
At some point contain
DNA
 Two

Types
Prokaryotic and
Eukaryotic
Prokaryotes

Generally smaller and
simpler
 Genetic material is
not contained in a
nucleus
 Grow, reproduce,
respond to the
environment
 Example: Bacteria
Eukaryotes





Generally larger and more
complex
Contain dozens of structures
and internal membranes
Highly specialized cells
Genetic material is contained
in a nucleus
May be single celled
organisms, or part of a large
multi-cellular organism
Diversity of Cellular Life

Unicellular Organisms



Made of a single cell
Majority of life on
Earth
Multi-cellular
Organisms


Made of many cells
Depend on
cooperation and
communication among
specialized cells
 Cell
specialization: cells
develop in different
ways to perform
different tasks


Animal cells: red blood
cells (transport oxygen),
pancreas (protein
production), muscle cells
(movement)
Plant cells: guard cells
(regulate exchange in
leaves)
Levels of Organization

Individual Cells

Tissues



Organs


Cells grouped together
A group of similar cells that perform a particular
function
Tissues work together
Organ Systems

Group of organs that work together to perform a
specific function
Osmosis and Diffusion
Chapter 7.3
Cell Boundaries
 Cell


Thin flexible barrier that surrounds a cell
Regulates what enters and leaves the cell,
provides protection and support
 Cell


Membrane
Wall
Strong supporting layer around the cell
membrane
Gives protection and support to a plant cell
Cell Membrane Structure

Made of two layers
(lipid bilayer)


Gives cell membranes
a flexible structure that
forms a strong barrier
Contains protein and
carbohydrate
molecules

Helps materials cross
the membrane

Found outside
the cell
membrane
(plants)


Main function to
provide support
and protection
Allows water,
oxygen, carbon
dioxide to pass
through
 Made from
carbohydrates
and protein
Cell Wall
Structure

Movement of
dissolved molecules
from one side of cell
membrane to another
 Particles move from
an area where they
are more
concentrated to an
area where they are
less concentrated
 Substances diffuse
across a membrane
without the cell using
any energy
Diffusion

Diffusion of water
across a selectively
permeable
membrane

Most membranes
selectively
permeable
• some substances
can pass through
and others cannot
• Water passes easily
across most
membranes
Osmosis
Osmosis

How Osmosis
works…

Water will move
across the membrane
until equilibrium is
reached
• Moves from high to low
concentration

Osmotic pressure:
pressure on the
hypertonic side of a
selectively permeable
membrane

Hypertonic: side of
the membrane with
more molecules;
“above strength”
 Hypotonic: the side of
the membrane with
less molecules;
“below strength”
 Isotonic:
concentrations the
same on both sides of
the membrane; “same
strength”
Solutions
Facilitated Diffusion

Cell membrane has
certain channels
(proteins) that make it
easy for certain
molecules to cross
the membrane

Will only occur if there
is a higher
concentration on one
side of the membrane
Active Transport

Small molecules and ions are carried across
membranes by proteins


Endocytosis


Requires energy, cells use majority of their energy for
transport
Process of taking material into the cell by folding of
cell membrane
Exocytosis

Membrane of vacuole fuses with cell membrane
forcing contents out of cell