IB Topic 2.1-2.3

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IB Topic 2.1-2.3

• Prokaryote and Eukaryote Cells

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Cell Theory

• A. There are 3 main points
• 1. All living organisms are composed of cells.
• 2. Cells are the smallest unit of life.
• 3. All cells come from pre-existing cells

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Cell theory history and evidence

• The discovery of cells is linked to technological
  advancements (microscopes)
• B. 1590-Jansen developed the compound microscope
  (it had two lenses)
• C. 1665-Robert Hooke discovered the cell
• 1. Looking at cork
• D. 1675-Leeuwenhoek discovered unicellular
  organisms

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• E. 1838-Mathius Schleiden
• discovered all plants are
• made of cells
• F. 1839-Theodore Schwann
• discovered all animals are
• made of cells
• G. 1855-Rudolph Virchow discovers all organisms
  are made of cells
• organismany living thing

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Characteristics of Life (single cell or
multi-cell)

• 1. Order (organization) from small to large
• -Ex Organelles make up cells.
• Cell make up tissues.
• Tissues make up organs.
• Organs make individuals.
• 2. Metabolism- organisms take in and release
  energy
• 3. Response (to the environment)- response to
  stimuli
• 4. Growth and development- heritable programs of
  DNA direct growth and development (change in
  ones shape during life)
• 5. Homeostasis- organisms have regulatory
  mechanisms to maintain their internal
  environments
• Examples body temperature, blood sugar,
  osmoregulation
• 6. Reproduction- the ability to reproduce ones
  own kind
• 7. Evolutionary adaptation- life evolves as a
  result of interaction between organisms and their
  environment

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Multicellular organisms

• A. Multicellular organisms show emergent
  properties
• B. Emergent properties arise from interaction of
  the components
• - The whole is greater than the parts (Ex a
  heart cannot function without the whole body)
• - A single cell can do nothing on its own, but
  when you put all of the cells together they can
  perform many functions

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Multicellular organisms and differentiation

• A. Multicellular organisms differentiate to carry
  out specialized functions
• B. All cells originated from the same place and
  all carry the genetic information to perform any
  function (your toe cell could have been a brain
  cell)
• C. In each cell there is only a small amount of
  activated genetic material
• Ex All cells have the genes for taste. The
  only cells with activated taste genes are on
  your tongue.

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Stem Cells

• Have ability to reproduce and
• differentiate
• Embryo cells all start out as stem cells
• Valuable for scientific research
• May be able to differentiate stem cells to
  desired cell type
• These may replace damaged cells
• Sources
• Embryonic cells from human blastocysts
• Fetal cells from aborted fetuses
• Umbilical cord stem cells cells from the
  umbilical cord of newborns
• Placenta derived stem cells cells from the
  placenta and amniotic fluid of newborns
• Adult cells from adult tissue (bone marrow,
  fat...)

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• Homework-Outline one therapeutic use of stem
  cells for humans or some other animal.
• DO NOT USE WIKIPEDIA AS YOUR RESOURCE!!
• You may use any government or university website.
  Their websites generally end in .edu or .gov.

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Viewing Cells

• Light microscopes
• See color images
• have a larger field of view
• prepare samples easily
• observe living and non-living material
• We cannot see most cell organelles
• 2. Electron microscopes
• - must be dead and no real colors
• Scanning Electron (SEM)
• - electron beams that bounce off the specimen
• Transmission Electron (TEM)
• - Used electron beams that pass through
  specimen
• (more detail because they have a
  higher resolution)

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Transmission Microscope (guess what these
structures are...)
Scanning Microscope
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Microscope Vocabulary

• 1. Resolution- describes clarity of pictures
• -higher resolution more detailed pictures
• 2. Magnification- makes objects larger
• 3. An increase in magnification may reduce the
  resolution

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Calculating Linear Magnification

• A. The formula-
• Magnification size of image
• size of specimen
• B. Example-the object is magnified by two

This is the magnified image.
This is the original object.
Diameter of the image4cm Diameter of the
specimen2 cm Find the magnification.
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Common SI Unit Conversions

• 1nm (nanometer) 1 x 10-9 m
• 1um (micrometer) 1 x 10-6 m
• 1mm (millimeter) 1 x 10-3 m
• 1cm (centimeter) 1 x 10-2 m
• 1m (meter) 1m
• 1km (kilometer) 1 x 103 m

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Calculating linear magnification

• Take a measurement of the drawing (width or
  length)
• Take this same measurement of the specimen  
• Remember to convert units if needed to
• Place your values into the equation
• Magnification length of drawing / length of
  actual specimen
• You can also calculate the length of the specimen
  if this is unknown length of the drawing /
  magnification.
• VIDEO http//www.youtube.com/watch?vL1d-02yRsRE

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Limitations to Cell Size

• A. Cells cannot grow indefinitely
• B. They reach a maximum size and divide.
• C. Bigger cells are less efficient.
• -They have to transport materials further.
• -The smaller the surface area to volume ratio
  the harder it is for the cell.

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How Big Is A Cell?
OBJECT SIZE
Eukaryotic 10-100 µm
Prokaryotic 1-5 µm
Nucleus 10-20 µm
Chloroplast 2-10 µm
Mitochondrion 0.5-5 µm
Large virus (HIV) 100 nm
Ribosome 25 nm
Cell membrane 7.5 nm
DNA dbl. helix 2 nm
H atom 0.1 nm
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Diagram of a typical prokaryote
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Prokaryote organelles

• 1. Cell wall- gives the cell structure and
  strength (covered by sticky capsule)
• 2. Plasma membrane- separates the internal
  features from the outside environment
• 3. Cytoplasm- holds cells organelles and
• enzymes
• 4. Pili- help the cell hold on to other
• structures and aid in movement
• 5. Flagella- aid in organism movement
• 6. Ribosomes- make protein from mRNA
• 7. Nucleoid- area containing naked DNA
• (ring)
• 8. Slime capsule- a protective barrier
• around the cell (may help shield it from
• antibiotics)

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An electron micrographs of E. coli
For IB you must be able to identify the
structures on a micrograph.
http//www.cellsalive.com/index.htm
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Prokaryote reproduction

• 1. Most prokaryotes divide by binary fission

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Eukaryote Cells
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Eukaryote Information

• 1. All eukaryotes have enclosed nuclei and other
  membrane bound organelles
• 2. Eukaryotes are true cells (eu true)
• 3. Eukaryotic cells are present in protists,
  plants, fungi and animal
• 4. Animal cells have a secretory vesicle
• -It secretes glycoproteins that makeup the
  extracellular matrix
• -The extracellular matrix functions in support,
  adhesion and movement

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Animal Cell Organelles

• Nucleus contains genetic material, controls the
  cell
• Ribosome synthesizes proteins from mRNA.
• Free floating, rough ER, chloroplast and
  mitochondria.
• Rough ER synthesizes proteins to be excreted by
  the cell
• Smooth ER synthesizes lipids and carbs
• Golgi Apparatus modifies, packs and ships via
  vesicles
• Lysosome digestion (enzymes)
• Peroxisome produces and breaks down hydrogen
  peroxide
• Mitochondrion aerobic respiration, converts
  chemical energy into ATP using oxygen

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• A animal cell

Figure 6.9
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Plant Cells

• Organelles found in plants only
• - cell wall
• -provides rigid support for the cells
• -made mostly of cellulose
• -plays important role in turgor (hardening of
  cells by the intake of water)
• -prevents cells from taking in too much water
• - chloroplasts- organelle required for
  photosynthesis
• - vacuole- membrane bound sac used for storage of
  organic compounds

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• A plant cell

CYTOSKELETON
In plant cells but not animal cells Chloroplasts
Central vacuole and tonoplast Cell
wall Plasmodesmata
Figure 6.9
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Summary of differences between eukaryotes and
prokaryotes!
Prokaryotic Cells Eukaryotic cells
small cells (lt 5 mm) larger cells (gt 10 mm)
always unicellular often multicellular
no nucleus or any membrane-bound organelles always have nucleus and other membrane-bound organelles
DNA is circular, without proteins (naked) DNA is linear and associated with proteins to form chromatin (not naked)
ribosomes are small (70S) ribosomes are large (80S)
no cytoskeleton always has a cytoskeleton
cell division is by binary fission cell division is by mitosis or meiosis
reproduction is always asexual reproduction is asexual or sexual