2.1 the transport of substances across the cell Flashcards
passive transport.
Processes that enable substances to move in and out of
cells without an input of energy from the cell
concentration gradient
a difference
in concentration
between one side of
a membrane and the
other
difusion
the net
movement of ions or
molecules from an area
of higher concentration
to an area of lower
concentration
Factors that affect the rate of
di!usion include
1-Molecule size: the larger a molecule is, the more difficult it is for it to diffuse across a membrane. As a result, the rate of diffusion decreases with molecule size.
2-Molecule polarity: Although small polar molecules can cross membranes, their rates of diffusion are generally lower than those of non-polar molecules of the same size.
3-Molecule or ion charge: In general, charged molecules and ions cannot diffuse across a cell membrane.
4-Temperature and pressure also affect the rate of di!usion.
osmosis
the movement of water
from an area of
higher concentration
to an area of lower
concentration, across
a semi-permeable
membrane
what is the osmatic
isotonic
the solution with the lower
concentration of solute
hypotonic (hypo = “less than”).
concentrations, the solution with the higher
concentration is
hypertonic (hyper = “more than”).
When two solutions have the same osmotic
concentration,
they are isotonic (iso = “equal”).
what is the osmatic
hypertonic
what is the osmatic
hypotonic
what is the osmatic
hypotonic
what is the osmatic
hypertonic
facilitated diffusion
the transport of ions
or molecules across
a membrane by
means of a membrane
protein along the
concentration gradient
for that ion or molecule
An ATP
molecule is derived from
an adenosine nucleotide, but it has a triple phosphate group
instead of a single phosphate group. the hydrolysis of the end phosphate group from an
ATP molecule releases energy,
ion pumps are
carrier proteins that use ATP to “pump” ions from one side of a membrane to the other, against a concentration gradient. One of the most well-studied examples is
the sodium- potassium pump. “is system transports sodium ions out of the cell while transporting potassium ions into the cell.
Secondary Active Transport
Ion pumps create a charge and concentration difference across cell membranes, forming an electrochemical gradient that stores energy. Secondary active transport harnesses this gradient to move molecules or ions across the membrane
phagocytosis
If the material the cell takes in is made up of discrete particles, such as an organism or some other fragment of organic matter, the process is called phagocytosis (which literally means “cell-eating”).
pinocytosis
If the material the cell takes in is liquid, the process is called
pinocytosis (which literally means “cell-drinking”).
Receptor-mediated endocytosis
Receptor-mediated endocytosis uses special receptor proteins on a portion of the cell membrane called coated pits. These receptors bind to specific molecules outside the cell. As the pit folds inward, it forms a vesicle containing the bound molecules. The cell can then use or digest the vesicle’s contents, and the receptors may be reused by the cell membrane.
