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Cell Transport
Cell Transport
• movement of materials (CO2, O2, H2O,
glucose, proteins, etc) into or out of cell via
cell membrane
2 Types of Cell Transport
1. Active Transport- requires energy
2. Passive Transport- No energy required
Why is Cell Transport Important?
• Homeostasis- maintaining a steady state
• Metabolism- chemical reactions that
convert “food” into energy
Helps cells achieve equilibrium- when
concentrations of molecules of a
substance are the same everywhere
Brownian Motion
• All matter is made up of atoms or
molecules and these particles are
constantly moving. These atoms move in
a straight line until they collide with
another atom or some barrier then they
reflect and move in a straight line until they
collide with something else. This
movement of atoms and molecules is
called Brownian motion.
3 Types of Passive Transport
1. Diffusion
2. Osmosis
3. Facilitated Diffusion
1. Diffusion
• movement of molecules from areas of
higher concentration to areas of lower
concentration
• requires no energy expenditure by cell
Key components of cell that
function in cell transport
• Cell membrane- phospholipids bilayer
• Cytoplasm- aqueous solution that contains
materials
• Mitochondria- powerhouse of cell
(glucose ATP)
• RBC- carries protein hemoglobin that
transports oxygen and carbon dioxide to
and from cells
Example of Cellular Diffusion
Review
• Solution= Solute + Solvent
• Solute
• Solvent
Ex: Sugar water
Salt water
3 Prefixes for SOLUTES
• Hypo = Low
hypoglycemic
Ex: Hypothermia,
• Hyper = High
hyperglycemic
Ex: Hyperactive,
• Iso = Equal
Solution Types
1. Hypotonic Solution- concentration of
solute molecules outside the cell is lower
than the concentration in cytosol (water
moves into cell until equilibrium is
reached)
Solution Types
2. Hypertonic Solution- concentration of
solute molecules outside the cell is higher
than the concentration in cytosol (water
moves out of cell until equilibrium is
reached)
• water tends to diffuse from hypo- to
hypertonic solutions
Solution Types
3. Isotonic Solution- concentration of solute
molecules outside and inside the cell are
equal ( water moves in and out of cell but
at equal rates)
2. Osmosis
• process by which water molecules diffuse
across a cell membrane from an area of
higher concentration to an area of lower
concentration
• Requires no energy expenditure by cell 
Passive Transport
Extreme Osmosis
•
Concentration gradient is so far from
equilibrium that even after moving water
or solutes, equilibrium still will not be
reached, and this may result in DEATH
of cell
1. Crenation- dehydration of an animal cell
2. Plasmolysis- dehydration of a plant cell
3. Cytolysis- cell bursting, usually occurs in
animal cells
Plant Cells and Osmosis
• Plant cells- usually in a hypotonic
environment
• Water moves into cell via osmosis
• Cell expands until it presses against cell
wall, creating a pressure called turgor
pressure
3. Facilitated Diffusion
• Proteins embedded in cell membrane help
molecules that can’t move across membrane
rapidly enough, into or out of cell
• Carrier proteins are specific for one type of
molecule
• Protein changes shape protecting molecule from
hydrophobic interior of membrane, then releases
molecule on other side
Ion Channels
• similar to carrier proteins, but are specific
for certain ions
• Examples of ions: Na+, Cl-, K+, Ca+2
• These ions are important for many cell
functions, but are not soluble in lipids so
need to pass through these ion channels
• Some channels are always open, others
close
Active Transport
• movement of materials up concentration
gradient from areas of lower concentration
to areas of higher concentration
• requires cells to use energy
• works like proteins in facilitated diffusion
(bind to specific molecule, changes shape
to protect, and releases molecule on other
side)
• Ex: Sodium/Potassium Pump
• Many animal cells need higher Sodium
concentration outside of cell and higher
Potassium concentration inside cell
• Splits molecule of ATP to change shape of
protein to allow this
2 Types of Active Transport
1. Endocytosis-process by which cells
ingest external fluid, macromolecules,
and large particles, including other cells
•
enclosed by portion of cell that folds in
on itself creating a pouch called a vesicle
2 Types of Endocytosis
A. Pinocytosis- “cell drinking” –involves
transport of solutes or fluids
B. Phagocytosis- “cell eating” –movement
of large molecules or whole cells into a
cell
*animal cells ingest bacteria and destroy
them via phagocytosis
• 2. Exocytosis-vesicles in cytoplasm fuse
with cell membrane releasing contents into
external environment
• *Remember this is how proteins leave cell
• Nervous and endocrine systems use
exocytosis to release small molecules that
control activities of other cells