MODULE 3 | Transport Mechanisms through Membranes Flashcards
is
generally not permeable to
proteins, nucleic acids, and
other molecules needed for
the structure and function of
the cell
Plasma membrane
• is the net movement of molecules and ions across a
membrane from higher to lower concentration
(down a concentration gradient)
PASSIVE TRANSPORT
• does not require metabolic energy
PASSIVE TRANSPORT
Examples/types of passive transport:
a) DIFFUSION
b) OSMOSIS
c) FACILITATED DIFFUSION
Solutes, such as ions or molecules, tend to
move from an area of higher concentration of
a solute to an area of lower concentration of
that same solute in solution.
Diffusion
•This movement occurs as a result of the
random and constant motion characteristic of
all molecules, and is independent from the
motion of other molecules.
Diffusion
is the diffusion of water across a
selectively permeable membrane, such as
the cell membrane, from a region of higher
water concentration to the area of lower
water concentration
Osmosis
is the diffusion of solutes through channel
proteins in the plasma membrane. Water can
pass freely through the plasma membrane
without the aid of specialized proteins.
FACILITATED DIFFUSION
• The movement of substances across the cell membrane
from regions of lower concentration to those of higher
concentration against a concentration gradient.
ACTIVE TRANSPORT
Requires metabolic energy
ACTIVE TRANSPORT
Active Transport is achieved through:
a) Protein Pumps
b) Vesicular Transport
1. Endocytosis
2. Exocytosis
Transport
proteins in the plasma membrane
transfer solutes such as small ions
(Na+, K+, Cl-, H+), amino acids,
and monosaccharides.
Protein Pumps
Vesicles or other bodies in
the cytoplasm move macromolecules or large particles
across the plasma membrane.
VESICULAR TRANSPORT
•Types of vesicular transport
•Endocytosis
•Exocytosis
is the uptake of material through
the cell membrane by the formation of a vesicle.
Endocytosis
is often used for
endocytosis when solid particles are
ingested.
Phagocytosis
is distinguished from
phagocytosis in that much smaller
vesicles are formed, and they
contain liquid rather than particles.
Pinocytosis
2 types of endocytosis
- Phagocytosis
- Pinocytosis
membrane-bound
sacs called secretory vesicles
accumulate materials for release
from the cell.
Exocytosis
a genetic disorder
that occurs at a rate of approximately
1 per 2000 births.
•The diagnosis is based on the
following signs:
•recurrent respiratory diseases and
• high levels of unabsorbed fats in
the stool.
Cystic Fibrosis
It is the results from an abnormality in Cl−
channels.
Cystic Fibrosis
•Water returns from tissue fluid to blood
capillaries because the protein
concentration of blood plasma is higher than
the protein concentration of tissue fluid
Edema
When the plasma
glucose concentration is abnormally
low the rate of transport of glucose
into brain cells may be too slow for
the metabolic needs of the brain
Hypoglycemia