Cells

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Cells

• Cell Theory, Prokaryotes, and Eukaryotes

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Cell Theory

• Living organisms are composed of cells.
• Cells are the smallest unit of life.
• Cells come from pre-existing cells.

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Cell Theory

• Discuss the evidence for the cell theory
• Simple, get some broth, pour it in two flasks,
  boil both, leave one uncovered, and seal the
  other
• What do you think will happen?

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Cell Theory
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Cell Theory

• Unicellular organisms carry out all the
• functions of life.
• Metabolism
• Response
• Homeostasis
• Growth
• Reproduction

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Characteristics of Cells

• Metabolism the complete set of chemical
  reactions in a living organism
• Response a change of internal or external
  behavior based upon environmental stimulus
• Homeostasis the ability to regulate the
  internal environment of an organism

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Characteristics of Cells

• Growth an organism captures and stores energy
  from the environment (food), at a faster rate
  than it uses the captured energy (released as
  heat)
• Reproduction new individual organisms are
  produced, can be sexual or asexual

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Give an example...

• The human body is in homeostasis, name three
  aspects of the body that must be regulated and
  maintained at a constant level.
• Blood sugar levels
• Temperature
• Oxygen
• Blood and extracellular fluid pH

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Cell Theory

• Compare the relative sizes of molecules, cell
• membrane thickness, viruses, bacteria,
• organelles and cells, using the appropriate
• SI unit.
• What does SI stand for?
• What types of units are considered SI?
• Put the above structures in order from smallest
  to largest, guess what size they might be, using
  SI units.

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Levels of Complexity

• Appreciation of relative size is required, such
  as
• molecules (1 nm)
• thickness of membranes (10 nm)
• viruses (100 nm),
• bacteria (1 µm)
• organelles (up to 10 µm)
• most cells (up to 100 µm)
• MTVBOC

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Cell Theory

• Calculate the linear magnification of drawings
  and the actual size of specimens in images of
  known magnification.
• Magnification could be stated (for example, 250)
  or indicated by means of a scale bar.

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What is the Magnification of This Picture?
1 µm
10 cm
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How Long are These Bacteria?
50 mm
50k X
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Determination of Actual Size

• Actual Size Measured Size
• Magnification
• Actual Size 50mm (50x10-3m or 0.05m)
• 50,000 (5x104)
• Actual Size 1µm (1x10-6m)

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Cell Theory

• Explain the importance of the surface area
• to volume ratio as a factor limiting cell size.
• The rate of heat production/waste
  production/resource consumption of a cell is a
  function of its volume, whereas the rate of
  exchange of materials and energy (heat) is a
  function of its surface area.

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Surface Area Limits Cell Size

• The boundary of every cell acts as a barrier that
  allows sufficient passage of oxygen, nutrients,
  and waste to service the entire volume of the
  cell.
• Volume increase more rapidly than surface area as
  cells grow
• The rate of exchange with the environment is
  inadequate in a cell with a very large cytoplasm

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Surface Area vs. Volume

• radius of a cell is 1mm
• surface area is about 13mm2
• volume will be about 4mm3
• radius is increased to 10mm 10x increase
• surface area is about 1300mm2 100x increase
• volume will be about 4000mm3 1000x increase

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Cell Surface Area to Volume Ratio
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Cell Theory

• Multicellular organisms show emergent properties.
• Emergent properties arise from the interaction of
  component parts the whole is greater than the
  sum of its parts.
• Can you think of something else with emergent
  properties?
• Did you think of computers? Some other technology?

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Cell Theory

• Cells in multicellular organisms differentiate to
  carry out specialized functions by expressing
  some of their genes but not others.
• Even though every cell has the same DNA code, not
  every gene is being used at the same time
• Different cells use different genes

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Cell Differentiation
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Cell Theory

• Stem cells retain the capacity to divide and have
  the ability to differentiate along different
  pathways.
• Stem cells have not yet decided what type of
  specialized cells they will be.
• Kind of like students before the find careers.
• So how do cells decide?

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How Stem Cells Decide

• All participants will begin seated at a table or
  lab bench
• If you are within arms reach of a member of the
  opposite sex, then stand up and put your stool
  under the table.
• If you are standing and wearing pants, then take
  five steps in any direction.
• If you took a shower this morning, then switch
  places with the nearest person to you.
• If you are full IB, then put your right hand on
  top of your head.
• If the person nearest you has their hand on their
  head, then put your left hand on your stomach.
• If you have a hand on your head on your stomach,
  then pat your head and rub your stomach in a
  circular motion. Do not stop.
• If you are still sitting, spin in a circle, click
  your heals together three times, and say,
  theres no place like home.

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Cell Theory

• Outline one therapeutic use of stem cells.
• This is an area of rapid development. In 2005,
  stem cells were used to restore the insulation
  tissue of neurons in laboratory rats, resulting
  in subsequent improvements in their mobility.
• Stem Cell Video

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Prokaryotes

• Simple, single celled organisms

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Prokaryotic Structure

• Cell wall rigid structure surrounding cell,
  made of proteins
• Plasma membrane lipid bi-layer enclosing the
  cytoplasm
• Ribosomes site of protein synthesis, type 70s
• Pilli used for attachment
• Flagella used for locomotion in some bacteria
• Nucleoid region containing DNA
• Cytoplasm interior of cell

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Prokaryote Genome

• Prokaryotes do not have a nucleus
• The DNA exists as a single circular chromosome
• It does not have histone proteins, and is known
  as naked DNA
• The region where the circular DNA strand is found
  is called the nucleoid

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Prokaryotes

• Draw and label a diagram of the ultrastructure of
  Escherichia coli (E. coli) as an example of a
  prokaryote.
• The diagram should show the cell wall, plasma
  membrane, cytoplasm, pili, flagella, ribosomes
  and nucleoid (region containing naked DNA).
• See page 98 of your textbook.

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Prokaryotes
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Prokaryotes

• You should be a able to identify structures in
  electron micrographs of E. coli.

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Review

• What a factor limits cell size?
• Why?

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Prokaryotes

• Binary fission is used by most prokaryotes for
  asexual reproduction.
• This process replicates the original, or mother,
  cell, to produce two identical daughter cells.

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Binary Fission

1. The fission process begins when the DNA of the
   mother cell is replicated and joins into a
   circular structure, pair by pair.
2. Each circular DNA strand then attaches to the
   plasma membrane.
3. Near the site of attachment, the cell elongates
   and causes the two duplicated chromosomes to
   separate.
4. At this point, the plasma membrane invaginates,
   or pinches inward toward the middle of the cell.
5. When it reaches the middle, the cell splits into
   two daughter cells.

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Binary Fission
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Binary Fission
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Eukaryotes

• Complex Cells with Organelles

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Eukaryotes

• Draw and label a diagram of the ultrastructure of
  a liver cell as an example of an animal cell.
• The diagram should show free ribosomes, rough
  endoplasmic reticulum (rER), lysosome, Golgi
  apparatus, mitochondrion and nucleus.
• See page 100 of your textbook

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Eukaryotes Cell Parts

• Plasma membrane
• Nucleus
• Nuclear envelope
• Nucleolus
• Ribosomes

• Endoplasmic Reticulum
• Golgi Apparatus
• Vesicles
• Lysosomes
• Mitochondria
• Centrioles

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Plasma Membrane

• Phospholipid bi-layer that surrounds cell
• Functions to separate internal cell environment
  (cytoplasm) from exterior environment
• Selectively Permeable allows specific
  substances to cross membranes but not others
• Contains various types of membrane proteins

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Plasma Membrane
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Nucleus

• Location of genetic material (DNA chromosomes)
• Consists of nuclear envelope, chromatin (DNA),
  nucleolus, and nuclear pores
• Functions to separate DNA from the rest of the
  cell

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Nuclear Envelope

• Double membrane surrounding nucleus
• Nuclear pores allow entry and exit of molecules
  between nucleus and cytoplasm
• Continuous with rough endoplasmic reticulum

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Nuclear Pores
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Nucleolus

• Located within nucleus
• Site of ribosome production and assembly

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Ribosomes

• Composed of two subunits
• Created in nucleolus
• Located in cytoplasm or RER
• Functions in synthesis of proteins

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Ribosomes

• Composed of multiple proteins and ribosomal RNA
  (rRNA)
• 80s

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Endomembrane System

• Membranous organelles function to
  compartmentalize cellular reactions in isolated
  locations
• Includes RER, the Golgi, lysosomes, vacuoles,
  vesicles, mitochondria, and cholorplasts

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Rough Endoplasmic Reticulum

• Studded with ribosomes on outer surface
• Site of protein synthesis for
• hydrolytic enzymes destined for lysosomes
• membrane proteins channel and receptor proteins
• secretory proteins proteins going outside the
  cell
• Continuous with nuclear envelope
• Vast complex of channels
• Inside is called the lumen

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Vesicles

• Lipid bi-layer spheres
• Used to transport proteins throughout the cell
• Transported along cytoskeleton microtubules

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Golgi Apparatus

• Receives vesicles from ER
• Modifies, packages, and transports molecules to
  final destination
• Cis face toward ER
• Trans face toward plasma membrane

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Lysosomes

• Storage vesicles containing hydrolytic
  (digestive) enzymes
• Enzymes used to breakdown food or damaged
  organelles

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Protein Trafficking

• Proteins destined for specific cellular locations
  such as the plasma membrane or lysosomes are
  synthesized at the RER
• Vesicles transport proteins to Golgi apparatus
• From Golgi apparatus proteins are sent, via
  vesicles, to specified cellular location

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Mitochondria

• Location of cellular respiration (making ATP from
  glucose)
• Parts include
• Double membrane
• Intermembrane space
• Cristae
• Matrix
• DNA
• 70s ribosomes

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Cytoskeleton

• A series of protein tubes and filaments create an
  internal skeleton within cells
• Functions in cell shape, cell division,
  locomotion, and vesicle transport

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Extracellular Matrix

• Animal cells secrete glycoproteins that form the
  extracellular matrix
• This functions in support, adhesion and movement.

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Eukaryotes

• Identify structures in electron micrographs of
  liver cells.

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Plant Cells

• Plant cells are eukaryotes with additional
  modifications
• Chloroplasts
• Cell walls
• Central vacuoles
• Plasmodesmata
• No centrioles

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Generalized Plant Cell
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Chloroplasts

• Location of photosynthesis
• Photosynthesis the transfer of light energy
  into the chemical bonds of glucose
• Parts include
• Thylakoid
• Grana
• Stroma
• DNA
• 70s ribosomes

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Cell wall

• maintains cell shape
• prevents excessive water uptake
• holds the whole plant up against the force of
  gravity
• Composed of the polysaccharide cellulose

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Central Vacuole

• Used for storage of starch
• Filled with water, functions in maintaining cell
  pressure

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Plasmodesmata

• Pores connecting adjacent plant cells
• Allow free movement of molecules between cells

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Eukaryotes

• State four differences between plant and
• animal cells.
• Plants have chloroplasts, animals dont
• Plants have cell walls, animals dont
• Plants have large central vacuole, animals dont
• Plants have plasmodesmata, animals dont

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Animal and Plant Cell Comparison
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Eukaryotes

• Compare prokaryotic and eukaryotic cells.
• 3 Differences should include
• naked DNA versus DNA associated with proteins
• DNA in cytoplasm versus DNA enclosed in a nuclear
  envelope
• no mitochondria versus mitochondria
• 70S versus 80S ribosomes
• eukaryotic cells have internal membranes that
  compartmentalize their functions

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Inner Life of the Cell

• No narration 3min
• With narration 8min