Transcript homeostasis and cell transport

HOMEOSTASIS
AND CELL
TRANSPORT
Chapter 5
Biology I
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
Passive Transport
*Cell membranes help organisms maintain homeostasis
by controlling what substances enter or leave the cell
*passive transport: substances pass across the cell
membrane without any input of energy by the cell
 Diffusion: the movement of molecules from an area of
higher concentration to an area of lower concentration
 Concentration gradient: the difference in the
concentration of molecules across a distance
Passive transport 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
Osmosis- water molecules diffuse across a cell
membrane from an area of higher concentration
to an area of lower concentration
 Passive transport of water
 Direction of Osmosis…
 …depends on the concentration of solutes on both sides of
the membrane
 hypotonic: solutes lower outside, water moves in
 hypertonic: solutes higher outside, water moves out
 isotonic: solutes equal on both sides, water moves
equally in and out
THE NEXT SLIDE ILLUSTRATES THIS…
How cells deal with osmosis
Contractile vacuoles:
organelles that
remove water
 Occurs in
organisms that
live in hypotonic
solutions
(example:
paramecia)
 Requires the use
of energy
 Some cells pump solutes out, changing the
flow of water
 Animal cells and most plant cells live in
hypotonic solutions
 Tugor pressure: the pressure water exerts
against the cell wall- occurs in a hypotonic
solution
 Plasmolysis: the cell shrinks away from the
cell wall in a hypertonic solution (example:
plants wilting)
 Some cells can’t compensate
for changes in the solute
concentration of their
environment (example: red
blood cells will eventually
burst)
 Cytolysis: the bursting of cells
A type of passive transport…
Facilitated diffusion- the transport of
substances through a cell membrane along a
concentration gradient with the aid of carrier
proteins
Example: glucose- molecule too big to cross freely
Diffusion through ion channels
Ion channels: a complex of protein molecules in a
cell membrane that form a pore through which ions
can pass
Examples: sodium (Na+), potassium (K+), calcium
(Ca2+), and chloride (Cl-)
Active Transport- the movement of chemical
substances, usually across the cell membrane,
against a concentration gradient; requires
cells to use energy
Cell membrane pumps
Sodium-potassium pump: a carrier protein that uses
ATP to actively transport sodium ions out of a cell and
potassium ions into the cell
Movement in Vesicles (used when molecules
are too large or needed in large quantities)
Endocytosis: the
process by which cells
ingest external fluid,
macromolecules, and
large particles,
including other cells
vesicle: a small
cavity or sac that
contains materials
in a eukaryotic cell
pinocytosis: a type of endocytosis that
involves the transport of solutes or
fluids
phagocytosis: a type of endocytosis that involves
the movement of large particles or whole cells
Many unicellular organisms feed this way
Phagocytes: a cell that ingests and destroys
foreign matter or microorganisms
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
Cells use exocytosis
to release large
molecules, wastes,
or toxins