Unit 2: The Cell
Animations
Study Guide
Chapter 7
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.
Material can pass through the plasma membrane without input of energy in a process called
transport.
(passive transport) is the tendency for molecules to
spread
out evenly down their
gradient.
(nonpolar)
molecules
and small molecules like O
2
can pass through the membrane by diffusion;
molecules (except
water
) and large molecules like
glucose
cannot.
Osmosis is the
diffusion
of
across a
membrane, and determines the
of its
environment.
Organisms without cell
must have adaptations for
to maintain water
balance.
Plant cells fare best in
environments.
diffusion is the movement of molecules across the membrane facilitated by
proteins,
the concentration
gradient.
transport, such as
sodium-potassium
, is the movement of molecules
their concentration gradient using energy, which can then be used to move other molecules by
against their concentration gradient without use of
energy.
Review.
Large molecules are tranported into and out of cells by bulk transport mechanisms of
and
.
In
, the cell takes in macromolecules by forming
vesicles
from the plasma membrane via invagination.
In
,
transport
migrate to the plasma membrane, fuse with it, and release their contents.
Review:
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Oct 12, 2009
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