Chapter
7
Animations
Art
Unit 2: The Cell
Membrane Structure and Function
Review
The plasma membrane is a "fluid mosaic" made of
with a mosaic of
embedded
in it, and exhibits
permeability.
Membranes contain amphipathic
, containing both hydrophobic and hydrophilic
regions,
and form a
, with
embedded
proteins.
(nonpolar)
molecules
and small molecules like O
2
can pass through the membrane by diffusion;
molecules (except
water
) and large molecules like
glucose
cannot.
(passive transport) is the tendency for molecules to
spread
out evenly down their
gradient.
is the
diffusion
of
across a
membrane, and is affected by the concentration gradient of dissolved substances, or
.
In
environments where solute concentration is the
as it is inside the cell, there is no net water movement.
In
environments where solute concentration is
than it is inside the cell, water tends to move
the cell.
In
environments where solute concentration is
than it is inside the cell, water tends to move
the
cell.
Organisms without cell
must have adaptations for
to maintain water
balance
in
hypotonic
and
hypertonic
environments.
Plant cells fare best in
environments.
diffusion is the movement of molecules across the membrane facilitated by
proteins,
the concentration
gradient.
proteins
provide corridors that allow a specific molecule or ion to cross the membrane.
proteins
undergo a change in shape that translocates the solute-binding site across the membrane.
transport, such as
sodium-potassium
, is the movement of molecules
their concentration gradient using energy, usually in the form of
.
Review.
Large proteins cross the membrane by
transport mechanisms.
In
. The cell takes in macromolecules by forming new
from the plasma membrane via invagination.
In
(cell
eating
), large particles are engulfed by
into a vacuole, and are
digested
in the
.
In
(cell
drinking
), small droplets of fluid are "gulped" into
.
In
,
transport
migrate to the plasma membrane, fuse with it, and release their contents.
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