Student Notes on Homeostasis
Biology
*All living things must maintain a
conditions
regardless of
Homeostasis: the process of maintaining
environment, a
to change
Important terms to know:
Solute: substance being
quantity)
and
in the cell’s
in another substance (often the lesser
Solvent: substance that
another substance
Ex. Koolaid, Which is the solute and which the solvent?
Mixture vs. Compound
Compound:
be easily separated by
methods
The chemical/physical properties are totally different than the properties of the parts
NaCl
Na-very
, whitish, Cl-
, green gas
We know this compound as
.
H2O2
H2- explosive gas, O2-flammable gas
We know this compound as
Mixture:
.
be easily separated by
methods
The chemical/physical properties remain the same
Types:
1. Solution: two or more
is
evenly
*
in a single phase, does not
out, it
molecules are smaller than in the
ex.
2. Suspension:
larger than
will
over time, unless the mixture is constantly stirred or agitated
out
ex.
separated
water-mud settles when not
3. Colloid: particles of
and
*small
, particles can be
are mainly the same size,
remain
ex. types of emulsionsmoke, fog-liquid in gas
,
Each of these mixtures is in our body:
Solution:
Suspension:
Colloid:
Major part of cells that maintain homeostasis:
1. Plasma Membrane:
a. Function:
of
out-too much can be harmful
Cells need nutrients-
between cell and its environment, allows steady
to come into the cell and excess
,
,
b. Selective permeability: allows some
in and
others
out
c. Structure:
phospholipid bilayer: two layers of
back to back
glycerol, fatty acids, phosphate
Nonpolar:
Polar:
, no charge
can dissolve other substances
(like dissolves like so
Water is
cell)
Fatty acids
Hydrophobic: water
Hydrophilic: water
can only dissolve
, so it can interact with
water (face
)
(facing outside of the
of cell membrane)
d. Fluid mosaic model: membrane is
a pattern on the membrane surface
, proteins
Transport proteins: allow needed
or
move through the membrane, movement of substances in a mixture
to
Processes used to maintain homeostasis:
1. Diffusion: net movement of
concentration to an area of
from an area of
concentration until it reaches equilibrium
-results due to the
movement of particles, a slow process
3 Key factors of diffusion
1. concentration: more
, more rapid
2. Temperature: increase in temp.
molecules and then
up the movement of
3. Pressure: increase in
and
, accelerate molecule
Goal of cell is to have:
Dynamic Equilibrium:
and out of the cell, but no
movement of molecules,
concentration change
Concentration gradient: difference in
across space
2. Osmosis: diffusion of
-water flows to side of cell with
*water continues to
on both sides of the membrane
rate in
across a semi-permeable membrane
water, where water
is low
until it is in
3 types of solutions, osmosis in cells
1. Isotonic solution: The
of
inside and
outside the cell are the same, so water moves in and out of the cell at the same
*
and
of the cell are normal, do not
experience osmosis, water concentration is the same in and out of the cell
2. Hypotonic: solute concentration is
concentration or amount is lower
the cell
outside the cell, water
the cell so water moves
*
and
pressure increases, can cause
of cell swells beyond normal
Result: animal cells can
, plant cells become
pressure
3. Hypertonic: solute concentration outside the cell is
cell, so
concentration or amount is
cell, so water moves
of the cell
*size of cell decrease for animal cells, causes
Result: animal cell
shrinks, plant
due to
than in the
outside the
,
in plant cell
Turgor pressure vs. plasmolysis vs. cytolysis
Turgor pressure: in
cells, when water moves
the pressure
and makes cell rigid
Plasmolysis: water
cell and cell
Cytolysis: cells take in
cells
much water and
cell
, only in
Water regulation in organisms
1. Single celled: most found in
and
environments,
*Want to avoid bursting, have
that act as a pump and remove water by contracting
2. Higher level animals: cells in a
environment, no water
Small portion of cells in the brain shrink and cause
salt
in
*Cells in
environment drink too much
, low
*Small patch of cells in brain when they
trigger
and cause kidney tubules to open up and produce more
Passive transport: no
the membrane
Ex.
is needed to move the
across
and
Facilitated diffusion: passive transport of
-Moves sugars and amino acids
Active transport:
of
with the help of
through a