Download Unit 4 Cell Structure, Cell Processes, Cell Reproduction

Unit 4
Cell Structure, Cell Processes,
Cell Reproduction, and
Homeostasis
Mrs. Stahl
AP Biology
How cells first came about!
• http://ed.ted.com/lessons/the-wackyhistory-of-cell-theory
Robert Hooke
• 1665
• First to identify cells by observing cork
from the bark of an oak tree.
Anton Van Leewenhoek
• 1674
• Described living things and observed them in
greater detail
• Discovered bacteria (we didn’t call them that
yet) and called them “animalcules” because
they resembles little animals moving about.
Matthias Schleiden
• 1838
• Found that plants are made of cells
Theodore Schwann
• 1839
• All living things are made of cells
Rudolf Virchow
• 1855
• Proposed that cells come from pre-existing cells
Three Major Principles of the Cell Theory
• 1. All organisms are made of one or
more cells, and the life processes of
metabolism and heredity occur within
these cells.
• 2.All existing cells come from preexisting cells
• 3. Cells are the basic unit of life
Cell Size
• Cells are small so that they can diffuse (go from
areas high concentration to low concentration
until equilibrium is met) easily throughout the
body = MAINTAIN HOMEOSTASIS
• Rate of diffusion is determined by:
– 1. Amount of surface area available
– 2. Temperature
– 3. Concentration Gradient
– 4. Distance
• As the cell increases in size, the rate of diffusion
will also increase. Therefore, smaller cells will
move in and out of the cell quicker.
• The larger the cell the more it requires- takes
longer for diffusion to occur due to it having to
synthesize all of the macromolecules inside of
it, transport energy, and regulate metabolic
waste.
Why are they so small?
Surface Area to Volume Ratio
• Small so that they can maximize surface area on
the outside so that nutrients (oxygen) can enter
and waste (carbon dioxide) can leave.
• If they are too small the organelles won’t fit. For
this reason they could never be infinitely small.
• Surface area-to volume ratio: As a cell’s size
increases, its volume increases more rapidly than
its surface area.
Further Explanation
Substances going in
Cell where chemical
reactions take place
(Volume)
Draw
into
your
notes!
Waste products being
released
• When a cell increases in size the chemical
reactions increase, which means more
substances need to be taken in so that the
reactions can be fueled and more waste
products will be released.
• Each cell can only take in so much due to its
surface area.
• When a cell increases in size the surface area
doesn’t increase the same as its volume.
• When a cell increases in size the ratio of the
cells surface : volume ratio decrease.
Example
• Cube 1= 1 cm.
• Cube 2= 3 cm.
• What is the surface area to volume ratio of each?
– Formulas:
SA= 6a2
Volume= a3
• For cube 1: SA= 6 X 12 = 6 cm2 , V=13 = 1cm2
– Ratio= 6:1
• Cube 2: SA= 6 X 32 = 54 cm2 , V= 33 = 27 cm2
– Ratio = 2:1
What happened in Cube 2
that the ratio decreased?
What happens when SA : V ratio gets
too small?
1. Substances can’t enter fast enough
2. Waste products leave slowly and can
accumulate in the cell
3. Cell can’t maintain homeostasis because it is
not able to lose heat fast enough
Extra Resources
• http://www.youtube.com/watch?v=wuXSEO
KNxN8
• http://www.bozemanscience.com/014environmental-matter-exchange/
How do we see cells?
• Assignment- You are to write a minimum of
three, maximum of five, page paper (MLA
format), with a minimum of three citations
about microscopes and the different kinds. You
should include:
– Why we can’t see cells
– Light, Compound, and Electron: Scanning and
Transmission
– The uses of stains and why they are beneficial
– Due December 8th and 9th
Four features that ALL cells have
• 1. A nucleus or nucleoid- where DNA is stored
• 2. Cytoplasm- jellylike substance that cushions and
protects all of the organelles. Also aids in
transporting nutrients such as amino acids, sugars,
and proteins.
– Cytosol- solution in the cytoplasm that is full of organic
compounds and ions
• 3. Ribosomes- synthesize (make) proteins
• 4. Plasma or Cell Membrane- selectively permeable
membrane made up of a phospholipid bilayer which
picks and chooses what is allowed into the cell.
Nerve Cells
http://www.pinterest.com/pin/32088216071181270/
White blood
cell engulfing a
bacteria cell
and spewing
out the
remnants
http://www.nature.com/naturejobs/2013/130
815/images/nj7462-367a-i1.0.jpg
Inside the
chloroplast of a
plant cell
http://io9.com/photos-of-the-amazing-andgruesome-world-under-a-micros-1291328130
Eyelashes!
http://www.ebaumsworld.com/pictures/view/83877873/
Bacteria on
the tongue
http://www.ebaumsworld.com/pictures/view/
83877873/
Artery and
blood cells
http://www.ebaumsworld.com/pictures/view/
83877873/
Clump of sperm
tails in the
testes
http://www.ebaumsworld.com/pictures/view/
83877873/
Staphylococcus
bacteria in the
trachea
http://www.sciencephoto.com/media/12812/
enlarge
Liver cell
http://www.sciencephoto.com/media/310232
/enlarge
Lung Cells
http://images.sciencesource.com/preview/149
17208/SQ7335.html
Prokaryotic VS.
Eukaryotic
Prokaryotic Cells
– No nucleus or membrane bound organelles
– DNA is suspended in the cytoplasm and circular
– Single celled and chemical reactions aren’t compartmentalized,
instead they operate as a single unit
– Cell Wall and cell membrane
– MreB protein which is a homologue of actin= these fibers run
perpendicular, giving the bacteria cell a rod shape. When MreB is
removed , the cells are spherical
– Evolved 3.5 bya
– Two main domains: Bacteria or Archaea
• Divided into groups based on their need for oxygen:
– Obligate anaerobes- cannot survive in the presence of oxygen.
– Obligate aerobe- needs oxygen to survive
– Facultative aerobe- can survive whether or not oxygen is
present.
Roles of Prokaryotic Cells
• Harvest light via photosynthesis
• Decomposers- break down dead organisms
and recycle the nutrients back into the
ecosystem
• Some do cause diseases
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Cell wall
Bacterial
chromosome
Capsule
0.5 µm
Flagella
(a) A typical
rod-shaped
bacterium
(b) A thin section through
the bacterium Bacillus
coagulans (TEM)
Structure of a Prokaryote
Cytoplasm
Cell
membrane
Pili
Cell Wall
www.biologyjunction.com
DNA
Ribosomes
Flagella
Draw
in
notes!
Functions
• Pili- help prokaryotes stick to the surfaces
• Flagellum- tail like structure used for movement.
• Plasmid- small piece of DNA that replicates separately
from the main chromosome.
• DNA- shaped in a loop or circle and is located in the
cytoplasm.
• Cytoplasm- jellylike substance that surrounds
molecules and organelles in a cell
• Cell wall- structural support, protection, prevent
excessive uptake or loss of water
• Cell membrane- controls the movement of substances
in and out of the cell.
Peptidoglycan
• Cell wall is composed of it
• Peptidoglycan is a carbohydrate matrix that is
cross linked by short polypeptide units
• Antibiotics such as penicillin and vancomycin,
interfere with the cross link and cause the entire
structure to fall apart by allowing water to rush in
resulting in cell rupture.
• Some disease causing bacteria secrete a jelly-like
protective capsule around them which allows
them to stick to surfaces (teeth, skin, nails, food)
and invade.
Eukaryotic Cells
Websites
Background from www.kidsdiscovery.com