Cell Transport
Chapter 3
Sections 3-5
Cell Transport
4 main types:
1.
2.
3.
4.
Diffusion (type of passive transport)
Osmosis (type of passive transport)
Facilitated Diffusion (type of passive transport)
Active Transport (requires energy)
***Passive Transport means no energy is required.
1. Diffusion- Movement of materials from areas of
high concentration to areas of low concentration
1. All living cells have a liquid interior
(cytoplasm) and are surrounded by liquid
2. Diffusion causes many
substances to move across
cell membrane but does not
require the cell to use energy
(called passive transport)
3. Equilibrium- when conc. of
molecules are equal on both
sides of membrane
2. Osmosis- Diffusion of water molecules through
selectively permeable membrane; does not
require energy (passive transport)
• Most membranes are selectively permeable
(some materials can pass across membrane
and others cannot) like “sieve”
Effects of osmosis on cell
• Isotonic- solution that has an equal concentration of
dissolved particles; “equilibrium”; cells are normal
• Hypotonic- solution that has a lower concentration of
dissolved particles; "below strength”; (cell swells)
• Hypertonic- solution that has a higher concentration
of dissolved particles; “above strength” ;(cell shrinks)
hypotonic solution
hypertonic solution
Isotonic solution
3. Facilitated diffusion- diffusion of molecules assisted
by protein channels that pierce a cell membrane.
Ions, sugars, and salts are too big to fit through cell
membrane. Must use protein channel to slide
through.
•
Does not require
addition of energy
(passive transport)
4. Active Transport- movement of molecules and ions
against a concentration difference (from low to high)
1. Requires input of energy
2. Small molecules “pumped” across
membrane (e.g. Na+ and K+ ions)
3. Large amounts of
material transported
through movements
of the cell
membrane
2 Examples of Active Transport:
1. Endocytosis- uptake of liquids or large molecules into
a cell by inward folding of the cell membrane
Pinocytosis- “cell drinking”
Phagocytosis- “cell eating”
2. Exocytosis- release of substances out a cell by
the fusion of a vesicle with the cell membrane.
Removes large amounts of material from a cell.
Unicellular Organisms- single celled organisms
1. Perform all life functions (grow, respond to
environment, reproduce, etc.)
2. Unicellular organisms dominate life on Earth
Multicellular Organisms- organisms made
of more than one cell
• Cell specialization- cells in multicellular
organisms are specialized/differentiated to
perform particular functions within the organism
•Cells are interdependent and do not live on
their own
Levels of Organization Review
1. Cells- smallest unit of life (ex. Nerve, muscle, bone)
2.
3.
4.
5.
Tissues- group of similar cells that perform particular function
Organs- groups of tissues working together. (ex. Muscle,
stomach, etc.)
Organ System- group of organs that work together (ex.
Muscular, skeletal, circulatory, etc.)
Organism- living thing