Chapter 3 Cells and Tissues
I. Cells – basic unit of life
 made up of mostly carbon,
oxygen, hydrogen, and nitrogen.
 trace elements important 
iron, sodium, potassium, calcium,
iodine
 electrolytes- carry an electrical
charge
 Ex: (sodium and potassium)
 Contain large amounts of water
 Interstitual fluid – cells are
constantly bathed in this.
 Many sizes 2Мm  3ft
(1meter), many shapes (disc,
threadlike, cube-like)
A. Anatomy of the Cell – these
characteristics common to all
cells.
1. Three regions – nucleus,
cytoplasm, plasma membrane
a. nucleus- control centercontains genes in DNA. DNA
is instructions for building the
whole body. (Specifically
proteins). DNA is necessary
for reproduction. ** Cell will
die without nucleus.
Nucleus has three regions:
1. nuclear membrane – double
membrane (nuclear
envelope) – fluid filled
space between layers. –
fused regions create
nuclear pores.
2. Nucleoli – in nucleus –
where ribosomes are
assembled.
3. Chromatin – DNA and
proteins combined when cell
is not replicating. (looks
like bumpy threads) –when
cell is dividing – chromatin
condenses and coils to form
chromosomes.
b. plasma membrane – or cell
membrane – barrier separating
cell from outside world.
Composed of two lipid layers
w/protein. Glycoproteins –
“sugar proteins” – determine
blood type; act as receptors.
pg 66 Fig 3.3.
1. Specialization of the
plasma membrane
a. microville – tiny fingerlike projections –
increase surface area.
b. Tight junctions –
adjacent plasma
membranes are fused
together. Ex: in small
intestines, prevents
digestive enzymes from
entering blood stream.
c. Desmosomes – adhesion
junctions, prevent cells
from pulling apart. (skin
cells)
d.Gap junctions- allow
communication between
cells. (nutrients and
ions pass directly from
cell to cell.) Cells
connected by hollow
cylinders. Pg 66 Fig 3.3
c. Cytoplasm – cell material
outside nucleus and inside
plasma membrane.
 three major elements of
cytoplasm
cytosol(cytoplasm), organelles,
and inclusions.
1. cytosol- semitransparent
fluid which suspends other
elements. Nutrients and
solutes dissolved in cytosol.
2. Organelles – specialized
structures in the cell that
have specific functions.
3. Inclusions – stored
nutrients or cell products.
(crystals, mucus, melanin,
and fat droplets)
d. cytoplasmic organelles –
“little organs”
1. ribosomes – made of
proteins and ribosomal
RNA. Tiny round dark
bodies. Site of protein
synthesis. Some float free
in cytoplasm, some
attached to rough
endoplasmic reticulum.
2. Endoplasmic reticulum –
(ER) – “network with in the
cell” - system of fluid
filled cisterns (canals).
Provides a network of
channels for carrying
substances.
a. rough ER – ribosome on
surface.
b. Smooth ER –
cholesterol synthesis
and breakdown; fat
metabolism.
3. Golgi apparatus – (golgi
body) – stack of flattened
membranous sacs –
function to modify and ship
proteins. Proteins bulge in
ends of golgi  ends pinch
off forming secretory
vesicles.
4. Lysosomes – formed from
golgi. Membrane bags
containing powerful
enzymes. Function 
digest worn out or unusable
cell structures. Found in
abundance in white blood
cells. “suicide sacs” can
rupture and destroy cell.
5. Peroxisomes – sacs that
contain oxidase enzymes –
function  detoxify
harmful substances. Do
not bud from golgi.
6. Mitochondria – wall
consists of double
membrane (two plasma
membranes). Outer
membrane smooth; inner
membrane has shelf like
protrusions called cristae.
*ATP molecules are
formed here.
7. Cytoskeleton – internal
framework that
determines cell shape; made up of :
a. intermediate fibers –
help form desmosomes.
b. Microfilaments –
involved in cell motility
c. Microtubules –
determine overall shape
of cell and distribution
of organelles.
8. Centrioles – made up of
microtubules- they direct
the spindles during cell
division.
9. Cilia – whip-like cellular
extensions that move
substances along cell
surface.
10. Flagella – long whip-like
extension. Used to propel
the cell.
II. Cell Physiology
A. Membrane transport
1. solution – homogeneous
mixture of two or more
components. Ex: seawater
a. solvent – substances in
largest amount
b. solutes – substances in
smaller amount.
2. Water is known as the
universal solvent.
3. Intracellular fluid –
nucleoplasm and cytosol –
contains gases, nutrients,
salts and dissolved water.
4. Interstitual fluid – fluid
that continuously bathes
exterior of cells. –mixture
of amino acids, sugars, fat,
vitamins, hormones, salts,
wastes, etc. – every cell
must extract the exact
amount of the substances it
needs and rejects the rest.
5. Selective permeability – a
barrier allows some
substances to pass through
it while excluding others.
6. Transport is either
passive or active.
a. passive – substances are
passed across the
membrane w/o energy
from the cell.
b. Active – cell provides ATP
that drives the transport
process.
B. Passive Transport
1. diffusion – process by
which molecules tend to
scatter themselves
throughout the available
space.
a. molecules move down
their concentration
gradient.
b. Plasma membrane is a
barrier to diffusion.
Molecules move passively
through if:
1. small enough to pass
through pores
2. can dissolve in the
fatty portion of the
membrane. This is
considered simple
diffusion.
c. osmosis – diffusion of
water across a selectively
permeable membrane.
d.Facilitative diffusion –
larger molecules can not
fit through pores, use a
carrier protein.