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Unit 3 - Cells
I. Cytology - The study of cells
A. Cell Theory
1. Cells are the basic unit of structural units
of all plants and animals.
2. Cells are the smallest functioning units of
life.
3. Cells are produced by the division of preexisting cells.
4. Each cell maintains homeostasis.
B. Ways we visualize cells:
1. Light microscopes – 1000X, thin sections
2. Electron microscopes – 1oo,oooX
a. Transmission – very thin sections, show detail
of internal cellular structures
b. Scanning = 3-D, surface, plasma membrane
C. The typical cell – The cell membrane separates:
1. Extracellular (Interstitial) fluid – Watery
medium surrounding the cell
2. Cytoplasm – cell contents made up of:
a. CYTOSOL – fluid inside
b. ORGANELLES – “little organs”, structures
that perform specific functions
D. Membrane Transport - Selectively permeable
Allows some materials to pass, prevents others
(based on size, electrical charge, molecular shape,
lipid solubility, or combination.)
http://www.wisconline.com/objects/index_tj.asp?objID=AP11
01
1. PASSIVE - Move ions or molecules without an
energy input, through the lipid portion
of the membrane or through a channel
protein.
a. Diffusion - Net movement from an area of high
concentration (many collisions) to an
area of low concentration (few collisions)
CONCENTRATION GRADIENT
http://www.
wisconline.com/o
bjects/index_
tj.asp?objID=
AP1903
EX: Osmosis - Diffusion of water across a
selectively permeable membrane
toward a solution that has the
highest solute concentration
(due to substances dissolved, etc.
in solution)
Osmotic pressure – the amount of pressure
required to stop osmosis across a membrane.
http://www.accreteil.fr/biotechnologies/doc_osmosi
s.htm
*ISOTONIC - “equal tension” – equlibrium exists, no net
movement into or out of the cell., 0.9%
NaCl = isotonic for RBC
*HYPOTONIC - “below” – solute concentration is
higher inside the cell, water moves into
the cell. Cell may swell, rupture.
RBC = HEMOLYSIS
*HYPERTONIC - “above” – solute concentration is
higher outside the cell, water moves
out and the cell shrivels.
RBC = CRENATION
http://www.tvdsb.on.ca/westmin/science/sbi3a1
/Cells/Osmosis.htm
b. Facilitated Diffusion - Large and lipid soluble
substances move across the
membrane with the help of
carrier proteins.
Glucose and Aquaporins
c. Filtration - Use of gravity or mechanical pressure
to move substances across a selectively
permeable membrane
Capillaries, kidneys
http://www.wisconline.com/objects/index_tj.asp?objID=AP11103
2. ACTIVE TRANSPORT - Cell requires energy in the
form of ATP to move
substances across a membrane
against the concentration
gradient
EX: Cytosis – Vesicular transport
a. Endocytosis - Large particles/molecules are
surrounded by plasma membrane
and brought into the cell.
http://programs.northlandcollege.edu/biology/Biol
ogy1111/animations/transport1.html
PHAGOCYTOSIS –
Projections of cytoplasm
surround and engulf
cell, “cell eating”.
PINOCYTOSIS – engulfed
material is liquid – a droplet
of liquid is attracted to the
membrane surface which
folds inward and forms a
pinocytic vesicle.
RECEPTOR-MEDIATED –
recognition sites that attach
to specific molecules such as
hormones, nutrients,
antibodies,
neurotransomitters
b. Exocytosis – elimination of undigestible particles.
http://www.stolaf.edu/people/giannini/flas
hanimat/cellstructures/phagocitosis.swf
E. Protein Synthesis - Cells are protein factories – produce
a large # of proteins, some
structural, others regulatory
(hormones), antibodies, enzymes
1. The genetic code - DNA – Holds the instructions
(genes) to produce a protein.
a. Made up of nucleotides that are in turn
made up of a nitrogen base, phosphate, and
deoxyribose sugar.
b. Located in the nucleus of eukaryotic cells,
cannot leave
c. Double-stranded molecule that is kept together
by H-bonds between complementary base pairs.
2. Transcription - Instructions are copied from DNA.
a. From double-stranded
DNA, which cannot leave
the nucleus, the protein
instructions are copied as
complementary base pairs
into single-stranded
messenger RNA (mRNA).
b. The mRNA leaves the
nucleus through the
nuclear pores to reach
protein factories –
WHICH ORGANELLE?
WHERE LOCATED?
http://wwwclass.unl.edu/biochem/gp2/m_biol
ogy/animation/gene/gene_a2.html
3. Translation - mRNA provides the template for a protein
to be made.
a. mRNA attaches to the small subunit of a ribosome
(one protein is made per ribosome) and the large
subunit then attaches.
b. tRNA (transfer RNA) brings the specific amino acid
(20 different) with the complementary triplet code
(anticodon) to mRNA (tRNA – UAC, mRNA – AUG)
c. The next tRNA brings
another amino acid to the
next mRNA codon and
these amino acids are
joined by a peptide bond.
a.
d.
b. & c.
d. Amino acids are attached
one-by-one until the
protein is formed – this
process is stopped by a
“stop codon”.
e. The protein is released
from the ribosome.
http://wwwclass.unl.edu/biochem/gp2/m_biology/animation/gene
/gene_a3.html
GENE – A group of nucleotides on a DNA molecule that
serves as a set of instructions for a protein. Average
100 nucleotide pairs in length.
F. Cell Cycle – Somatic cells
1. Why? Heal wounds, growth, surface area to
volume, limited capability of nucleus
2. Two divisions:
a. Nuclear
b. Cytokinesis
3. Phases - Nuclear
a. Interphase Nondividing
period (90%
a.
c.
of cycle),
b.
separated
into three
phases = G1,
S, G2.
During S
DNA is
replicated.
b. Prophase
-chromatin
shortens into
chromosomes
-nuclear membrane begins to disappear
-centrosomes move to poles
c. Prometaphase -Spindle fibers attach to centromeres
d. Metaphasechromosomes
line up on the d.
equatorial
plate
e.
f.
e. Anaphase
-duplicated
halves of
each
chromosome
separate and
move to
opposite
poles
f. Telophase -Nuclear membrane reforms
-Chromosomes re-condense into
chromatin
4. Cytokinesis -
Division of the cytoplasm
http://www.cellsalive.com/mitosis.htm
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::53
5::535::/sites/dl/free/0072437316/120073/bio
14.swf::Mitosis%20and%20Cytokinesis
5. Cancer – cells duplicate without control
•Tissue is called tumor, growth, neoplasm
•Oncology – The study of
•Cancerous is called malignant
•Non-cancerous is benign – does not spread to other
parts and may be removed
•Hyperplasia – increase in frequency of cell
division
a. Malignant tumors – duplicate continuously, quickly
and without control
•Hyperplasia
•Metastasis -
Spread to other parts, cancer cells
secrete AMF (autocrine motility
factor) – a protein which allows them
to metastasize – hard to detect and
eliminate
•Often this invasion kills the normal tissues by
starving it out
•Then they invade adjacent tissues and establish
secondary tumors
b. Causes
•CARCINOGEN - Chemical or environmental agent
that causes cancer (60-90% of
human cancers) 90% of all lung
cancers caused by smoking, UV
radiation
•VIRUSES - Mostly in animals
•ONCOGENESIS - Genes found in human cells that
trigger cancerous growth when
inappropriately activated
•ANTIONCOGENESIS
c. Treatment
•Chemotherapy
•Radiation