Download 3.1 Cell Theory - Perry Local Schools

3.1
3.3 Cell Theory
3.3 KEY CONCEPT The cell membrane is a barrier that
separates a cell from the external environment.
3.1
3.3 Cell Theory
Cell membranes are composed of two phospholipid
layers.
3.1
3.3 Cell Theory
Cell membranes are composed of two phospholipid
layers.
• The cell membrane has two major functions.
– forms a boundary between inside and outside of the
cell
– controls passage of materials
cell membrane
inside cell
outside cell
3.1
3.3 Cell Theory
Cell membranes are composed of two phospholipid
layers.
• The cell membrane is selectively permeable.
Some molecules can cross the membrane
while others cannot.
3.1
3.3 Cell Theory
Cell membranes are composed of two phospholipid
layers.
• The cell membrane is selectively permeable.
Some molecules can cross the membrane
while others cannot.
3.1
3.4 Cell Theory
3.4 KEY CONCEPT Materials move across membranes
because of concentration differences.
3.1
3.4 Cell Theory
Molecules move in RANDOM STRAIGHT line until they run
into another particle and are deflected
Movement continues until they reach equilibrium
equal concentration throughout the space
Movement never STOPS – maintains equilibrium
Concentration, Temperature, & Pressure affect rates of
diffusion
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
• Molecules diffuse down a
concentration gradient.
• From High to Low concentration
3.1
3.4 Cell Theory
Passive transport does not require energy input from a
cell.
• Diffusion
•3 types of diffusion
1. Osmosis
2. Facilitated Diffusion
3. Diffusion Through Ion
Channels
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Osmosis is the diffusion of water molecules
across a semipermeable membrane.
Water
•
Most important compound in
living organisms
Polar
•
molecule with an unequal
distribution of charge
Hydrogen Bond
•
•
•
attraction of opposite charges
forms a weak bond
forms between water molecules
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Adhesion – attraction between unlike
substances
Cohesion – attraction between like
substances
Surface Tension – caused from
cohesion
Capillarity – Due to adhesion &
cohesion water is pulled up through
tiny tubes
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Requires more heat to increase its T than
do most other common liquids
Loses a lot of heat when it cools
Due to the hydrogen bonds
Insulator that helps maintain a steady
environment when conditions fluctuate
(homeostasis)
3.1 Cell Theory
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Solution = A mixture in which a solute is dissolved
evenly in a solvent
Solute – What gets dissolved
Solvent – What does the dissolving
Water is the universal solvent
Because its polar
• Has an unequal distribution of charge
• Dissolves both positive and negative solutes
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Diffusion and osmosis are types of passive transport.
• There are three types of solutions.
• isotonic
•
hypertonic
•
hypotonic
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Hypotonic
Concentration of dissolved substances (solute) is lower
in the solution outside the cell than inside the cell
Water moves through the membrane into the cell
Cell swells
Cytolysis – cell bursts (animal cells)
Turgor Pressure – plant cells
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Hypertonic
Concentration of dissolved substances outside the cell
is higher than inside the cell
Water flows out of cell
Plant cells – loss of turgor pressure – Plasmolysis –
wilting
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Isotonic
concentration of solute in solution is the same outside
as inside the cell – equilibrium
Water diffuses at the same rate in and out of the cell
Maintaining equilibrium - homeostasis
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Some molecules can only diffuse through transport
proteins.
• Some molecules cannot easily diffuse across the cell
membrane.
• Facilitated diffusion is
diffusion through channel
proteins.
• High to low concentration
3.4
Diffusion
and Osmosis
3.1 Cell
Theory
Diffusion through Ion Channels
Na+ sodium
K+ potassium
Ca2+ calcium
Cl- chloride
(not soluble in lipids)
Ion channels allow ions to diffuse into and out of cell
Ion channels are either open all the time or gates which
open in response to stimuli
1. stretching of cell membrane
2. electrical signals
3. chemical signals
3.5
Active
Transport
3.1 Cell
Theory
3.5 KEY CONCEPT Cells use energy to transport
materials that cannot diffuse across a membrane.
3.5
Active
Transport
3.1 Cell
Theory
Active transport requires energy input from a cell
and enables a cell to move a substance against its
concentration gradient.
• Active transport is
powered by chemical
energy (ATP).
• Active transport occurs
through transport protein
pumps (carrier proteins)
• Na-K pump
• Cells use active transport
to maintain homeostasis.
3.5
Active
Transport
3.1 Cell
Theory
A cell can import and export large materials or large
amounts of material in vesicles during the
processes of endocytosis and exocytosis.
• Cells use energy to transport material in vesicles.
• Endocytosis is the process of
taking material into the cell.
• Phagocytosis – endocytosis
of solid particles.
• Pinocytosis – endocytosis of
liquids
3.5
Active
Transport
3.1 Cell
Theory
A cell can import and export large materials or large
amounts of material in vesicles during the
processes of endocytosis and exocytosis.
• Cells use energy to transport material in vesicles.
• Exocytosis is the process of
expelling material from the
cell.