Biology Topic 2 Review
Syllabus Statements
• 2.1.1 – outline cell theory
• 1.1.2 – State that a virus is a non-cellular structure consisting of DNA
or RNA surrounded by a protein coat
• 1.1.3 – State that all cells are formed from other cells
• 1.1.4: Explain three advantages of using light microscopes
• 1.1.5: Outline the advantages of using electron microscopes
• 1.1.6: Define organelle
• 1.1.7: Compare the relative sizes of molecules, cell membrane
thickness, viruses, bacteria, organelles & cells. Use appropriate SI
units.
• 1.1.8: Calculate the linear magnification of drawings
• 1.1.9: Explain the importance of the surface area to volume ratio as
a factor limiting cell size.
• 1.1.10: State that unicellular organisms carry out all of the functions
of life
• 1.1.11: Explain that cells in multicellular organisms differentiate to
carry out specialized functions by expressing some of their genes but
not others
• 1.1.12: Define tissue, organ, organ system
Cell Theory
•
Three principles based on different
studies
1.
2.
3.
•
All organisms made of cells
Cells are the basic unit of life
Cells come from other preexisting cells
BUT… All cells aren’t created equal
Evidence of Cell theory
• 1 – many organisms studied and found to
consist of cells
– Work of schleiden and schwann started this
– Are some questionable cases – hyphae in fungi,
muscle fibers, some tissues like bone
• 2 – Nothing smaller than cells can “survive”
when isolated
• 3 – experiments show that spontaneous
generation is impossible
– Only evidence for cells forming from cell division
Unicellular organisms
• Like amoeba, euglena etc. are made of just one
cell
• They do everything necessary to be called alive
– Metabolism, homeostasis, response, growth,
reproduction, and nutrition or energy use
Multicellular organisms
• Have many cells
• Allows compartmentalization of function =
specialization
• Multicellular Organisms therefore have
emergent properties where they can do
more than the sum of their parts
• Take life in general being the sum of a
bunch of non living chemical reactions
To have different cells do different
things you need differentiation
• So cells develop along different pathways or
differentiate
• This means different cells express different
genes
• Remember that every cell in an organism has all
the same DNA, only some cells express different
genes within that genome
• Once the developmental pathway of a cell is
started then it is usually fixed
So which cells can differentiate?
• Stem cells – can self renew and
differentiate
• Human embryos are almost all stem cells
• Some still found in different human tissues
like skin, liver bone marrow
• Those only used for limited repair
Therapeutic use of stem cells
• Area of rapid development – many uses exist
• Cord blood from umbilical cord contains
hematopoietic stem cells – can become any
blood cell type
• Test the blood and remaining fluid
• Used to treat some leukemias – chemo to kill the
cells that over produce white blood cells then
introduce cord blood to blood stream of patient
• Stem cells establish themselves in the marrow
and replace defective cells
Possible fates of cord blood stem
cells
So how big are all these cells
we’re talking about?
How small are we talking?
Viruses = 100 nm
Bacteria = 1 um
Organelles = up to 10 um
cells = up to 100 um
Chick egg = 5 cm
Nerve/muscle cells in leg = 1 m
Human height > 1 m
Can you
calculate
cells size
off of a
micrograph
?
1. If given a scale bar
•
•
•
Measure the scale bar in centimeters
Measure the desired aspect of the cell in cm
Set up and solve a proportion –
•
Scale (um) / scale measure (cm) = actual size (um) /
measured size (cm)
2. If given the magnification
•
•
•
Measure desired aspect of cell in cm
Convert your measurement to um (multiply by
10,000)
Divide by magnification to get actual size
•
(image size / actual size ) = magnification
Importance of the Surface area to Volume
Ratio or why are cells so small
The larger the cell, the harder it is to communicate
from one part to the other; more difficult to move
substances through diffusion.
As cell size increases, volume increases as a
cubic function. Chemical reaction rate is a
function of volume. Transport of necessary
materials is a function of surface area increasing
as a squared function.
1.2 Prokaryotic Cells
• 1.2.1: Draw a generalized Prokaryotic cell
– Include; cell wall, plasma membrane, mesosome,
cytoplasm, ribosomes, & nucleoid (region containing
naked DNA)
• 1.2.2: State one function for each of the following:
cell wall, plasma membrane, mesosome,
cytoplasm, ribosomes, & nucleoid (region
containing naked DNA
• 1.2.3: State that prokaryotes show a wide range of
metabolic activity including photosynthesis,
fermentation, nitrogen fixation
Prokaryotes
• Lack membrane-enclosed organelles
• DNA is not associated with protein,
chromosome is frequently circular and
double stranded
• Hereditary material is located in nucleoid
region; no membrane separates DNA from
the rest of the cell.
Functions
• Cell wall = Rigid, protective layer
• Plasma membrane = Regulates materials entering
cell
• Mesosome = folding of plasma membrane,
functions in respiration
• Cytoplasm = semifluid matrix of sugars, amino
acids, proteins that the cell uses to carry out
everyday activities
• Ribosomes = protein synthesis, 70s in prokaryotes
• Nucleoid (region containing naked DNA) = genetic
information of the cell
Identify structures on an e coli
electron micrograph
When prokaryotes
divide they do so by
the process of binary
fission
1.3 Eukaryotic Cells
• 1.3.1: Draw a diagram to show the ultrastructure of
a generalized animal cell as seen in an
electromicrograph
– Include ribosomes, rough ER, lysosome, Golgi apparatus,
mitochondrion, nucleus
• 1.3.2: State one function of each of the following
organelles: ribosomes, rough ER, lysosome, Golgi
apparatus, mitochondrion, nucleus
• 1.3.3: Compare prokaryotic & eukaryotic cells
• 1.3.4: Describe three differences between plant
and animal cells
• 1.3.5:State the composition and function of the plant
cell wall
Animal Cells
Function
• Ribosomes = 80s, protein assembly
• Rough ER = secretory protein & membrane
synthesis, forms vessicles
• Lysosomes = Digest all major classes of
macromolecules, Autopathy, Apoptosis
• Golgi apparatus = Center of manufacturing,
warehousing, sorting, and shipping
• Mitochondrion = Cellular respiration
• Nucleus = contains genetic info
• Chloroplast = Photosynthesis
Identify structures on
a micrograph of liver
cells
Prokaryoties vs. Eukaryotes
• Prokaryotes
(All are Prokaryotae)
1. Very small (1-10 um)
2. No nucleus (nucleoid –
naked DNA in central
area)
3. No membrane bound
organelles – like
mitochondria
4. Have cell walls
5. 70s ribosome
•
1.
2.
3.
4.
5.
Eukaryotes
(all other kingdoms)
Larger (10-100um)
Protein asociated DNA
in chromosomes in
nucleus
Many M.B.O. like
mitochondria
Plants & some fungi
have cell walls
80s ribosome
What are some differences
between plant and animal cells?
Plant Cells
Animal Cells
Roles of extracellular components
•
•
•
•
Plant Cells
Functions to protect plant cells, maintain their
shape and prevent excess water intake.
Taken together helps support plants against
gravity
Animal Cells
Animal cells secrete glycoproteins to form the
extracellular matrix
Functions in support, adhesion, movement
1.5 Cell Division
• 1.5.1: State that cell division involves interphase, mitosis &
cytokinesis
• 1.5.2: State that interphase is an active period in the life of a
cell when many biochemical reactions occur, as well as the
transcription and replication of DNA
• 1.5.3: Describe the events that occur in the 4 phases of
mitosis (prophase, metaphase, anaphase, telophase)
• 1.5.4: Explain how mitosis produces two genetically identical
nuclei
• 1.5.5: Outline the difference in mitosis and cytokinesis
between plants and animals
• 1.5.6: State that growth, tissue repair, and sexual
reproduction involve mitosis
• 1.5.7: State that tumors (cancers) are the result of
uncontrolled cell division and that these can occur in any
organ
Why cells divide
•
Cell division functions in reproduction,
growth and repair.
• unicellular organisms: the division of one
cell to form two reproduces an entire
organism. – asexual reproduction
Mitosis allows:
a) Growth
b) Development from fertilized egg
c) Replacement of dead and damaged cells
The Cell Cycle (process of cell
division)
Interphase
a) 90% of cell cycle
b) A period of intense biochemical activity during
which the cell grows and copies it
chromosomes in preparation for cell division.
c) Consists of three periods:
G1 phase: first growth phase
S phase: synthesis of DNA; chromosomes
replicate
G2 phase: 2nd growth phase
Prophase
• In nucleus, nucleoli disappear
• Chromatin fibers condense into discrete
chromosomes composed of 2 chromatids which
are identical; joined at centromere.
• In cytoplasm: mitotic spindle forms from
cytoskeleton microtubules between 2
centrosomes.
• Centrosomes move apart caused by lengthening
of microtubules.
• Nuclear envelope fragments
2. Metaphase
• Centrosomes positioned at opposite poles
of cell.
• Chromosomes move to metaphase plate,
long axis is at right angle to spindle axis.
• Centromeres of all chromosomes aligned
on the metaphase plate.
• Kinetochores of sister chromatids face
opposite poles.
Anaphase
• Characterized by movement. Begins with paired
centromeres of each chromosome move apart.
• Sister chromatids split apart into separate
chromosomes and move to opposite poles of the
cell.
• Movement is centromere first.
• Kinetochore microtubules shorten at kinetochore
end.
• Poles of cell move father apart (elongation of
cell).
• At end of anaphase, 2 poles have identical
collections of chromosomes.
5. Telophase
•
•
•
•
•
Nonkinetochore microtubules elongate the cell
Daughter nuclei begin to form at 2 poles
Nuclear envelopes form around chromosomes.
Nucleoli reappear
Chromatin fiber of each chromosome uncoils
and chromosomes become less distinct.
• Cytokinesis begins – 2 separate daughter cells.
Result = 2 Identical daughter cells
• Interphase  DNA duplicates
• Chromosomes form with 2 identical
chromatids joined at the centromere
• Metaphase  chromosomes line up on
metaphase plate, kinetchore of each
chromatid facing opposite poles
• Anaphase  separates identical chromatids
(now chromosomes) into new daughter cells
• By replication and organized division of
genetic material the result is 2 identical
daughter cells
6. Cytokinesis: division of the
cytoplasm. Begins in telophase.
Animal Cells
• Occurs as cleavage. Cleavage furrow forms
as a shallow groove in the cell surface near the
old metaphase plate.
• A contractile ring of actin microfilaments forms
on the cytoplasmic side of the furrow. It
contracts until it pinches parent cell in 2.
• Remaining mitotic spindle breaks and 2 cells
are completely separate.
Cytokinesis: Plant cells
In plant cells, cytokinesis occurs by cell plate
formation across the parent cell’s midline (old
metaphase plate).
a) Golgi-derived vesicles move along
microtubules to the cell’s center, where they
fuse into a disc-like cell plate.
b) Additional vesicles fuse around the edge of the
plate and fuse with existing parent cell’s
plasma membrane.
c) A new cell wall forms as cellulose is deposited
between the 2 membranes of the cell plate.
Cytokinesis: Animal vs. Plant
Cancer cells are abnormal
• Cancer cells do not exhibit density
dependent inhibition.
• Cancer: alteration in genes that control
cell division; cancer cells do not respond
normally to controls on cell division.
• Cancer cells divide excessively, invade
other tissues (metastasis) and, if
unchecked can kill the whole organism.