Download homeostasis and cell transport

HOMEOSTASIS
AND CELL
TRANSPORT
Chapter 5
Biology II
Vocabulary- Chapter 5 (23 words)
Passive transport
facilitated diffusion
Diffusion
carrier protein
Concentration gradient
ion channels
Equilibrium
phagocyte
Osmosis
exocytosis
Hypotonic
pinocytosis
Hypertonic
phagocytosis
Isotonic
endocytosis
Contractile vacuole
vesicle
Turgor pressure
active transport
Plasmolysis
sodium-potassium pump
cytolysis
A. Passive Transport
*Cell membranes help organisms maintain homeostasis
by controlling what substances enter or leave the cell
*passive transport: substances that pass across the cell
membrane without any input of energy by the cell
1. Diffusion: the movement of molecules from an area of
higher concentration to an area of lower concentration
a. Concentration gradient: the difference in the
concentration of molecules across a distance
c.
d.
e.
f.
b. Driven entirely by the molecule’s
kinetic energy- molecules in constant
motion
Equilibrium: the concentration of molecules will be the
same throughout the space the molecules occupy
Even at equilibrium, there is still balanced movement
Some membranes allow molecules to pass through,
but not others- if allowed, it will diffuse
Examples: carbon dioxide and oxygen diffuse across
membranes
2. Osmosis- the process by which water
molecules diffuse across a cell membrane from
an area of higher concentration to an area of
lower concentration
a. Passive transport of water
b. Direction of Osmosis
1. depends on the concentration of solutes on both
sides of the membrane
2. hypotonic: solutes lower outside, water moves in
3. hypertonic: solutes higher outside, water moves
out
4. isotonic: solutes equal on both sides, water moves
equally in and out
c. How cells deal with osmosis
1. Contractile vacoules: organelles that remove water
a. Occurs in organisms that live in hypotonic solutions
(example: paramecia)
b. Requires the use of energy
2. Some cells pump solutes out, changing the flow of
water
3. Like animal cells, most plant cells
live in hypotonic solutions
4. Tugor pressure: the pressure water exerts against the
cell wall- occurs in a hypotonic solution
5. Plasmolysis: the cell shrinks away from the cell wall in
a hypertonic solution (example: plants wilting)
6. Some cells can’t compensate for changes in the solute
concentration of their environment (example: red
blood cells)
7. Cytolysis: the bursting of cells
3. Facilitated diffusion- the transport of
substances through a cell membrane along a
concentration gradient with the aid of carrier
proteins
a. A type of passive transport
b. Example: glucose- molecule too big to cross freely
4. Diffusion through ion channels
a. Ion channels: a complex of protein molecules in
a cell membrane that form a pore through
which ions can pass
b. Examples: sodium (Na+), potassium (K+),
calcium (Ca2+), and chloride (Cl-)
B. Active Transport- the movement of chemical
substances, usually across the cell membrane,
against a concentration gradient; requires
cells to use energy
1. Cell membrane pumps
a. Sodium-potassium pump: a carrier protein that
uses ATP to actively transport sodium ions out of a
cell and potassium ions into the cell
2. Movement in Vesicles (used when
molecules are too large or needed in large
quantities)
a. Endocytosis: the
process by which
cells ingest external
fluid,
macromolecules,
and large particles,
including other
cells
1. vesicle: a small
cavity or sac that
contains materials
in a eukaryotic cell
2. pinocytosis: a type of endocytosis
that involves the transport of solutes or
fluids
3. phagocytosis: a type of endocytosis that
involves the movement of large particles or
whole cells
a. Many unicellular organisms feed this way
b. Phagocytes: a cell that ingests and destroys
foreign matter or microorganisms
b. Exocytosis: the process by which a
substance is released from the cell through a
vesicle that transports the substance to the
cell surface and then fuses with membrane to
let the substance out of the cell
1. Cells use to
release large
molecules, wastes,
or toxins