Download Homeostasis and Transport Notes

Biology
Homeostasis and Cellular Transport
Homeostasis
• Literally means, “
inner balance”
• Keeping internal
conditions within
healthy limits
• It applies to things
like body
temperature and
blood pressure
Feedback Loops or Homeostatic
Mechanisms
Cellular Transport
• Cellular transport
describes how
substances cross the
cell membrane.
• As you remember, the
cell membrane controls
what goes in and out of
the cell.
Phospholipids
• The cell membrane is
made mostly of
phospholipids
• They have a hydrophilic
head and hydrophobic
tail
• Hydrophilic means
water loving
• Hydrophobic means
water fearing
Phospholipid Bilayer
• The cell membrane is
made of two layers of
phospholipids
• It also contains some
proteins
• The hydrophilic heads
face the cytoplasm and
extracellular fluid,
while the tails face
inward
Types of Transport
• Passive Transport –
Substances cross the
membrane without the
use of energy (ATP is
the most used energy
molecule in the human
body)
• Active Transport –
Substances cross the
membrane through the
use of energy, or ATP
Passive Transport
• Diffusion - The movement of substances
from an area of high concentration to an area
of low concentration
Passive Transport Cont’d
• Facilitated Diffusion – Diffusion that takes
place using a membrane protein.
• They can open and close when needed.
Osmosis
• The diffusion of water.
Equilibrium
• After diffusion or osmosis has taken place and
there is an equal concentration of substances.
Passive Transport Summary
• Passive transport usually moves things:
1. That are small
2. From high to low concentration
3. That are lipid soluble
4. Without using ATP
Active Transport
• Movement of substances across the cell
membrane that requires the use of ATP
(energy).
Types of Active Transport
• Protein Pumps – A membrane protein and ATP
are used to pump substances against their
concentration gradient across into or out of
the cell.
• Example - Na/K ATP pump
://www.brookscole.com/chemistry_d/templates/student_resources/shared_resou
rces/animations/ion_pump/ionpump.html
Exocytosis and Endocytosis
• Special vacuoles called vesicles, and ATP are
used to add and remove substances from the
cell.
• http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::
535::/sites/dl/free/0072437316/120068/bio02.s
wf::Endocytosis and Exocytosis
Exocytosis
• Substances in a vesicle are forced through the
membrane using ATP and released in the
fluid surrounding the cell.
Endocytosis
• Phagocytosis – “Cell eating,” cells use ATP
and a vesicle to ingest solid molecules
• Pinocytosis – “Cell drinking,” cells use ATP
and a vesicle to ingest liquids
Receptor Mediated Endocytosis
• Cells ingest molecules using ATP after they
bond to special receptor proteins on the cell’s
surface.
Active Transport Summary
• Active transport can move things in a wide
variety of ways, but certain situations must
use active transport:
1. Moving large molecules
2. Moving from low to high concentration
3. Moving things that are not lipid soluble
4. All situations must use ATP
Tonicity
Cells will react differently when placed into
solutions with varying concentrations of
substances, an idea known as tonicity.
Isotonic Solutions
• Equal concentration
of substances inside
the cell and outside.
• The size of the cell
does not change.
Hypertonic Solutions
• Concentration of
substances is greater
outside the cell than
inside.
• The cell shrinks as a
result.
Hypotonic Solution
• Concentration of
substances is greater
inside the cell than
outside.
• The cell swells as a
result.
• If the concentration is
great enough, the cell
will burst (aka lysis).
Comparison of Human Blood Cells