1. Cells

2. Overview of the cellular basis of life

3. Cells are the structural units of all living
things.
The principle of complementarity states
that the biochemical activities of cells are
determined and made possible by the
specific subcellular structures of cells.

4. The generalized or composite cell has
three major regions - the nucleus, the
cytoplasm, and plasma membrane.

6. The plasma membrane:
Functions

7. Membrane transport
Interstitial fluid is an extracellular fluid
derived from blood, and baths the cells.
The plasma membrane is a selectively
permeable barrier, which allows some
substances to pass while excluding
others.

10. Passive processes cause substances to
penetrate the membrane without any
energy input from the cell, while in active
processes the cell provides ATP to drive
the transport mechanism.

12. Diffusion is the tendency of molecules or
ions to scatter evenly throughout the
environment.
Molecules tend to move away from areas
of high concentration, and toward areas
of low concentration, along their
concentration gradient.

14. The diffusion of a solvent (water) though
a selectively permeable membrane is
called osmosis.
The total concentration of all solute
particles in a solution is referred to as the
solution’s osmolarity.

17. Hydrostatic pressure is the back pressure
exerted by water against the membrane.
Tonicity is the ability of a solution to
change the tone or shape of cells by
altering their internal water volume.
Solutions with concentrations equal to
those found in cells are isotonic.

18. Solutions that have a higher
concentration of solutes than the cell are
hypertonic.
Solutions that are more dilute than cells
are called hypotonic.

19. In facilitated diffusion, molecules
combine with protein carrier molecules in
the plasma membrane and are released
into the cytoplasm.

21. Filtration is the process by which water
and solutes are forced through a
membrane or capillary wall by
hydrostatic pressure. The molecules
move along a pressure gradient instead of
a concentration gradient.

22. Active transport (solute pumping) is
similar to facilitated diffusion, except that
solute pumps move solutes against their
concentration gradient by coupling with
ATP.

24. If two transported substances are moved
in the same direction, the system is a
symport system.
If the the substances cross the membrane
in opposite directions, the system is an
antiport system.

25. In primary active transport, the energy is
provided directly by hydrolysis of ATP.
In secondary active transport, the
transport is driven indirectly by passive
ion gradients.
An example of a primary active transport
system is the sodium/potassium pump.

27. In phagocytosis, part of the plasma
membrane and cytoplasm protrude and
flow around some relatively large or solid
material, forming a vesicle called a
phagosome.
Most phagocytes move by means of
amoeboid motion.

31. In pinocytosis, the plasma membrane
surrounds a droplet of extracellular fluid.
Receptor-mediated endocytosis uses
proteins that bind only with certain
substances.

33. Generation and maintenance of a
resting membrane potential
A membrane potential is an electrical
voltage across the plasma membrane,
resulting from a separation of oppositely
charged ions.
All cells exhibit a resting membrane
potential of approximately -20 to -200
mV. Therefore, all cells are polarized.

35. The greater outward diffusion of
potassium (than inward diffusion of
sodium) leads to a charge separation at
the membrane (inside negative). This
charge separation is maintained by the
operation of the sodium-potassium pump.

36. Ions diffuse according to electrochemical
gradients, which takes into account the
effect of both electrical and chemical
forces.

37. Cell-environment interactions
Cell adhesion molecules (CAMs) are
composed of glycoproteins that anchor
cells to molecules in the extracellular
space, propel the cells past one another,
and recruit white blood cells to
traumatized tissue.

38. Membrane receptors are proteins and
glycoproteins that serve as binding sites.
Signaling chemicals that bind specifically
to membrane receptors are called ligands.

39. G protein-linked receptors use G proteins
as a relay to activate or inactivate a
membrane-bound enzyme of ion channel.
The intracellular chemical signals are
known as second messengers.
Ionic calcium and cyclic AMP are two
important second messengers, which
usually activate protein kinase enzymes.